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Gaia Earth Sciences Limited

Wireline Operations for Drilling Engineers March 2007

Written by Stuart Huyton of Gaia Earth Sciences Limited

Wireline Operations for Drilling Engineers

March 2007

Contents 1

Choice of wireline tools vs. measurements required.......................................................... 1 1.1 Evaluation Services .................................................................................................... 1 1.2 Auxiliary Services ...................................................................................................... 1 2 Logging Equipment & Tool types...................................................................................... 2 2.1 Surface equipment...................................................................................................... 2 2.1.1 Rig-up Equipment .............................................................................................. 2 2.1.2 IDW - Integrated Depth Wheel .......................................................................... 2 2.1.3 CMTD - Cable-Mounted Tension Device.......................................................... 2 2.1.4 Cables ................................................................................................................. 2 2.2 Auxiliary tools............................................................................................................ 2 2.2.1 ACTS-B - Auxiliary Compression Tension Sub................................................ 2 2.2.2 GPIT - General Purpose Inclinometry Tool....................................................... 2 2.2.3 TCC - Telemetry Cartridge ................................................................................ 2 2.2.4 DTC - Digital Telemetry Cartridge.................................................................... 2 2.2.5 EDTC – Enhanced Digital Telemetry Cartridge ................................................ 3 2.2.6 DTA - Downhole Tool bus Adapter................................................................... 3 2.2.7 WXT-A - Wireline Cross-Over Tool ................................................................. 3 2.2.8 Weakpoints......................................................................................................... 3 2.2.9 Wireline Jars....................................................................................................... 3 2.3 Resistivity................................................................................................................... 3 2.3.1 Water-based mud................................................................................................ 3 2.3.2 Oil-based mud .................................................................................................... 4 2.4 Density ....................................................................................................................... 6 2.4.1 LDT - Lithology Density Tool ........................................................................... 6 2.4.2 PEX (HILT) - Platform Express......................................................................... 6 2.4.3 PEX150 .............................................................................................................. 6 2.5 Neutron....................................................................................................................... 6 2.5.1 CNT - Compensated Neutron Tool .................................................................... 7 2.5.2 PEX (HILT) - Platform Express......................................................................... 7 2.5.3 PEX150 .............................................................................................................. 7 2.6 GR/Spectral GR.......................................................................................................... 7 2.6.1 SGT - Scintillation Gamma-Ray Tool ............................................................... 7 2.6.2 PEX (HILT) - Platform Express......................................................................... 7 2.6.3 PEX150 .............................................................................................................. 7 2.6.4 NGT - Natural Gamma-Ray Spectrometry Tool................................................ 7 2.7 Sonic........................................................................................................................... 7 2.7.1 SDT - Sonic Digital Tool ................................................................................... 8 2.7.2 DSLT - Digitizing Sonic Logging Tool ............................................................. 8 2.7.3 DSI (DSST) - Dipole Shear Sonic Tool ............................................................. 8 2.7.4 MSIP (Sonic Scanner) - Modular Sonic Imaging Platform ............................... 8 2.8 Magnetic resonance.................................................................................................... 9 2.8.1 CMR - Combinable Magnetic Resonance Tool ................................................. 9 2.8.2 CMR-200............................................................................................................ 9 2.8.3 CMR-plus ........................................................................................................... 9 2.8.4 MREX - Magnetic Resonance eXpert................................................................ 9 2.9 Imaging/Dipmeter ...................................................................................................... 9 2.9.1 Electric ............................................................................................................. 10 2.9.2 Acoustic............................................................................................................ 10 2.10 Callipers ................................................................................................................... 10

Wireline Operations for Drilling Engineers

March 2007

2.11 Pressures/Sampling .................................................................................................. 11 2.11.1 MDT - Modular Formation Dynamics Tester .................................................. 11 2.11.2 Quicksilver Probe............................................................................................. 12 2.11.3 Cased Hole Dynamics Tester ........................................................................... 12 2.11.4 Pressure eXpress .............................................................................................. 12 2.12 Coring....................................................................................................................... 13 2.12.1 MSCT - Mechanical Sidewall Coring Tool ..................................................... 13 2.12.2 CST - Chronological Sample taker .................................................................. 13 2.13 Seismic ..................................................................................................................... 13 2.13.1 Check shot surveys........................................................................................... 13 2.13.2 Vertical seismic profiles (VSP)........................................................................ 13 2.13.3 Deviated well survey or vertical incidence VSP.............................................. 14 2.13.4 Offset VSP surveys .......................................................................................... 14 2.13.5 Walk-away surveys .......................................................................................... 14 2.13.6 CSI Combinable Seismic Imager ..................................................................... 14 2.13.7 VSI Versatile Seismic Imager .......................................................................... 14 3 Logging modes for each tool type.................................................................................... 15 3.1 Sampling Rate .......................................................................................................... 15 3.1.1 Resistivity, Nuclear .......................................................................................... 15 3.1.2 Sonic................................................................................................................. 15 3.1.3 CMR ................................................................................................................. 15 4 Pros and cons of different tools........................................................................................ 16 5 Tool string combinations and implications ...................................................................... 16 5.1 Wireline Toolstrings................................................................................................. 17 5.1.1 Resistivity-Sonic-Density-Neutron-Gamma ray .............................................. 17 5.1.2 Pressures-Sampling (MDT-single probe)......................................................... 18 5.1.3 Pressures-Sampling (MDT-dual packer).......................................................... 19 5.1.4 CMR Toolstring ............................................................................................... 20 5.1.5 Imaging Toolstring (UBI-OBMI)..................................................................... 21 5.1.6 Seismic Toolstring (VSI) ................................................................................. 22 5.2 TLC Toolstrings ....................................................................................................... 23 5.2.1 UBI-AIT-PPC-OBMI-GPIT-PEX Toolstring .................................................. 23 5.2.2 GR-PPC-DSI-MDT-CMR+-GR Toolstring...................................................... 24 6 Normal logging speeds & ratings..................................................................................... 25 7 Logging modes vs logging speed ..................................................................................... 28 8 Depths............................................................................................................................... 28 8.1 Depth control............................................................................................................ 28 8.2 Driller’s Depth vs Wireline Depth ........................................................................... 29 9 A comparison between Schlumberger and Baker Atlas................................................... 31 10 About the Author.......................................................................................................... 42

Gaia Earth Sciences Limited Wireline Operations for Drilling Engineers

March 2007

The aim of this short course is to provide a basic level of logging knowledge for drilling engineers, in order to improve their understanding of wireline operations, and the implications of different tool types on operating time etc.

1 Choice of wireline tools vs. measurements required Logging runs are normally divided into evaluation runs and auxiliary runs. Evaluation runs acquire the main data types which are required for the petrophysical evaluation and for input to the reservoir model. Auxiliary runs are those used for other purposes such as cement bond logging, stuck pipe operations, cutters, punchers etc.

1.1

Evaluation Services

Petrophysical analysis involves the determination of physical properties of the formation rocks in order to locate and quantify hydrocarbons. Of these properties the ones normally measured are: • • • • •

Natural radioactivity Neutron Porosity Bulk Density Resistivity Sonic properties

To make an evaluation it is necessary to use all of these measurements in order to determine the true or effective porosity, the volume of that porosity occupied by water and the volume occupied by hydrocarbon. All of these are usually acquired during the first logging run, in what is usually described as a supercombo or quad-combo run (resistivity, neutron, density, sonic). Further runs are usually made for the following: • • • • • •

1.2

Formation pressures Formation fluid samples Magnetic resonance logs Images Cores Seismic

Auxiliary Services

Auxiliary services include: • • •

Cement bond Free-point/Back-off Corrosion

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• •

Callipers Magnetic fishing tool

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2 Logging Equipment & Tool types 2.1

Surface equipment

Included here are the ancillary devices and tools which are required for logging operations.

2.1.1 Rig-up Equipment This consists of the sheave wheels, tie-down chain, spade and WMC line. This load-bearing equipment is subject to regular inspections and certification. The WMC line is usually part of the rig equipment. Note: Schlumberger have recently down-rated some items of rig-up equipment and some units so it may not be possible to pull up to the normal 50% working load of the logging cable. In order to fully utilise the maximum pull on the cable it important to have fully rated rig-up equipment and to have the logging unit properly certified as well. This can make the difference between pulling out of the hole and a fishing job!

2.1.2 IDW - Integrated Depth Wheel This is the primary depth measuring device. It is mounted on the cable just in front of the drum. There are two independent measuring wheels. It must be calibrated every 6 months and the wheels checked for wear.

2.1.3 CMTD - Cable-Mounted Tension Device This measures cable tension at surface. It is mounted just behind the IDW. It should be calibrated every 6 months.

2.1.4 Cables There are many types of logging cable depending on the application. The cable for openhole logging has twin armour and seven electrical conductors. The armour is used as a ground or earth connection. Schlumberger cables do not generally have magnetic marks on them these days whereas Baker Atlas ones should have.

2.2

Auxiliary tools

2.2.1 ACTS-B - Auxiliary Compression Tension Sub This measures the tension or compression between upper and lower heads of the tool. It is run with most modern tools and is essential for running logs on drill-pipe.

2.2.2 GPIT - General Purpose Inclinometry Tool This provides directional information: deviation, azimuth and relative bearing. (Usually an indication of the angle of rotation of the tool from its high side.)

2.2.3 TCC - Telemetry Cartridge This is the older CTS, Cable Telemetry System, telemetry cartridge, used to send tool signals up the cable. It uses the DTB, Downhole Tool Bus.

2.2.4 DTC - Digital Telemetry Cartridge This is a newer DTS, Digital Telemetry System, cartridge. It uses the FTB Fast Tool Bus.

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2.2.5 EDTC – Enhanced Digital Telemetry Cartridge This is the latest telemetry cartridge and is required for some of the newer tools as it gives a higher bandwidth.

2.2.6 DTA - Downhole Tool bus Adapter This is used to convert between two different telemetry systems so that older tools can be combined with newer ones (think of it as a slip road onto a motorway).

2.2.7 WXT-A - Wireline Cross-Over Tool This is the downhole switch which is used to switch between two different toolstrings run together. This allows longer, more complex strings to be run together but sequentially. It is useful for reducing operation time for TLC runs.

2.2.8 Weakpoints Weakpoints are located in the logging cable head and allow disconnection of the cable if tools become stuck. There are two types of weakpoint: fixed rating and electrically actuated. Weakpoints with a fixed rating must be carefully chosen so that they may be safely broken (using draw-works) with the toolstring at TD without exceeding the safe working load of the cable. Electrically actuated weakpoints can not be used with some toolstrings.

2.2.9 Wireline Jars Hydraulic wireline jars are routinely run by Baker Atlas but not by Schlumberger. They can be a valuable addition to a wireline toolstring and have saved many a fishing job.

2.3

Resistivity

2.3.1 Water-based mud

2.3.1.1 Laterolog Laterologs are used primarily for determining the resistivity (Rt) of the virgin formation. They can only be used in conductive mud. Older tools need a bridle (or stiff bridle for TLC).

2.3.1.2 DLT - Dual Laterolog Also DST Dual Laterolog and MSFL Tool, which has a 4-arm calliper at its base and has a tendency to get stuck; not advised for first RIH in bad hole. This is an old tool which is not commonly run any more; however, it may still be around in some places. The Dual Laterolog Tool (DLT) provides deep and shallow resistivity measurements, LLD and LLS. The DST (dual laterolog micro spherically focused tool) is a DLT that includes an SRS (micro spherically focused resistivity sonde), giving a very shallow measurement MSFL (micro spherically focused log)

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2.3.1.3 HALS - High Resolution Azimuthal Laterolog Sonde Part of PEX. The HALS provides deep and shallow resistivity, mud resistivity and azimuthal resistivity readings. It is a bottom-only tool and not very common these days.

2.3.1.4 HRLA - High-Resolution Laterolog Array Tool This tool is through-wired and requires no bridle. It provides five independent, actively focused, depth and resolution matched measurements that are useful in thinly bedded and deeply invaded formations.

2.3.1.5 ARI - Azimuthal Resistivity Imager Also called ALAT Azimuthal Laterolog Tool. This tool combines the standard DLT measurements with a 12-channel azimuthal resistivity image and a high resolution deep resistivity measurement.

2.3.1.6 MCFL - Micro-Cylindrically Focused Log Part of PEX. The MCFL provides a microresistivity measurement in conductive muds which provides the resistivity of the invaded zone. (If run in oil-based mud in combination with a CMR, the MCFL should have a dummy pad installed to reduce noise.)

2.3.1.7 SP - Spontaneous Potential This is a measurement of electrical potential (voltage) produced by the interaction of formation water, conductive drilling fluid and shales.

2.3.2 Oil-based mud Induction tools are used to measure resistivity in oil-based mud systems, but there are many cases when it is okay to run an induction tool in Water Based Mud, see the chart below. On a recent job in North Africa the wrong tool type was sent to the rig and bad resistivity data was acquired, it is one of the most basic questions to ask when planning for a job.

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2.3.2.1 DIT - Dual Induction Tool This is an older tool which is not commonly run but may still be around in some locations. It provides an Induction Deep (ID) and Induction Medium (IM) resistivities with fixed focuses. It can also provide an SFL Spherically Focused Log and SP measurement if run in water-based mud.

2.3.2.2 AIT - Array Induction Imager Tool This gives five basic log resistivity curves with a median radial depth of investigation of 10, 20, 30, 60, and 90 inches and vertical resolution of 1, 2 & 4 feet. It uses vertical and radial adaptive focus. The AIT-H needs much less rathole than the AIT-B, it is run at the base of the PEX and is not through wired. The AIT-B/C is through wired but is significantly longer. SP and mud resistivity can also be measured.

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2.4

March 2007

Density

2.4.1 LDT - Lithology Density Tool This gives direct measurements of formation lithology and density. It uses a Caesium 137 gamma ray source and several detectors, mounted on a pad with a one-armed calliper.

2.4.2 PEX (HILT) - Platform Express Also known as the Highly Integrated Logging Tool. The PEX tool is only applicable for use in wells which are neither hot nor deep as it has a limited temperature and pressure rating (125 degC (260 degF), 10k psi). It uses a Caesium 137 gamma ray source and several detectors, mounted on a pad with a one-armed calliper.

2.4.3 PEX150 This is a PEX tool rated to 150 degC (300 degF), 15k psi.

2.5

Neutron

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2.5.1 CNT - Compensated Neutron Tool This measures the neutron porosity (hydrogen nucleus) using a 16-Ci Americium Beryllium neutron source and two thermal neutron detectors. It must be run eccentered.

2.5.2 PEX (HILT) - Platform Express Also known as the Highly Integrated Logging Tool. The HGNS, Highly-integrated Gammaray Neutron Sonde, is the part of the PEX which contains the neutron and gamma-ray measurements. It uses the same 16-Ci Americium Beryllium neutron source as the CNT with two thermal neutron detectors. It must be run eccentered.

2.5.3 PEX150 This is a PEX tool rated to 150 degC (300 degF), 15k psi.

2.6

GR/Spectral GR

2.6.1 SGT - Scintillation Gamma-Ray Tool Measures natural gamma-ray activity in the borehole

2.6.2 PEX (HILT) - Platform Express Also known as the Highly Integrated Logging Tool. Part of HGNS. Measures natural gamma-ray activity in the borehole.

2.6.3 PEX150 This is a PEX tool rated to 150 degC (300 degF), 15k psi.

2.6.4 NGT - Natural Gamma-Ray Spectrometry Tool The NGT measures the natural gamma-rays and analyses the spectrum to estimate the individual contributions of uranium, thorium and potassium to the total gamma-ray signal. This can help to identify the clay type and sand can be identified as radioactive.

2.7

Sonic

Records acoustic data for the following applications: • • • • • •

Porosity Lithology identification Synthetic seismograms Formation mechanical properties Formation correlations Cement bond quality

Sonic tools are used to measure the propagation time of Compressional, Shear and Stonely waves. These are different modes of sound waves that propagate in the borehole and formation. The main measurement is called DT, delta-T, and is a measure of the time taken for each wave to reach the receiver. (Note that DT is measured in µs/ft so it is actually a “slowness”) Gaia Earth Sciences Ltd

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All sonic tools should be run centred whenever possible (unless in very large hole) and never bare.

2.7.1 SDT - Sonic Digital Tool This is an older tool using CTS telemetry which might still be around. It uses a monopole (symmetric) transmitter.

2.7.2 DSLT - Digitizing Sonic Logging Tool This is a cartridge for running conventional sonic sondes under the newer DTS telemetry. It uses a monopole (symmetric) transmitter.

2.7.3 DSI (DSST) - Dipole Shear Sonic Tool This records sonic waveform data from both monopole (symmetric) and dipole (directional) transmitter sources. The dipole transmitter allows the measurement of shear waves in formations that are slower than the mud. The monopole transmitter is used to measure compressional DT, dipole propagation for determination of shear DT, and low-frequency monopole acoustics for acquisition of the Stoneley borehole mode waveforms.

2.7.4 MSIP (Sonic Scanner) - Modular Sonic Imaging Platform This provides a range of advanced axial, azimuthal and radial measurements. Typical depths of investigation equal two to three times the borehole diameter: • Borehole-compensated monopole with long and short spacings • Cross dipole • Cement evaluation

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2.8

March 2007

Magnetic resonance

The CMR enables the measurement of important reservoir parameters not measured by conventional logs: permeability, producible fluid type and irreducible water saturation. Applications of CMR logs include: • • • • • •

Lithology-independent porosity. Pore-size distribution for reservoir rock quality. Bound and free-fluid volumes. Identification of thin, permeable beds in laminated reservoirs. Hydrocarbon identification. Hydrocarbon pore volume for reserve calculations.

CMR tools work by manipulating the hydrogen nuclei contained in fluid molecules: either water or hydrocarbon. This is the same principle as MR scanners used in hospitals. They are affected by the presence of metallic debris in the borehole and so ditch magnets should be in place during drilling and circulating prior to running CMRs. These tools must be run eccentered, often with weights on wireline since the magnet sticks to the casing and can cause problems RIH.

2.8.1 CMR - Combinable Magnetic Resonance Tool This is an older tool with a very low logging speed of 100 to 600 feet per hour. It also requires manual tuning.

2.8.2 CMR-200 This is a newer tool than CMR but also has some limitations.

2.8.3 CMR-plus This tool has auto-tuning which is used after initial tuning sets up the correct frequencies. It can also be logged at a much faster speed because it has a longer pre-polarisation magnet than previous tools.

2.8.4 MREX - Magnetic Resonance eXpert This is the latest CMR tool. It provides multiple depths of investigation ranging from 1.5 to 4 inches in one pass.

The tool is about twice the length of the older CMRs.

2.9

Imaging/Dipmeter

These tools are used for: • • • • • •

Structural geology Sedimentary features Rock texture Complement to coring and formation tester programs Geomechanics Reservoir characterization

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2.9.1 Electric

2.9.1.1 FMI - Formation MicroImager This tool only works in conductive muds. It has four pads mounted on a four-arm calliper and 192 micro resistivity buttons.

2.9.1.2 OBMI - Oil-Base MicroImager This tool only works in non-conductive muds. It has four pads mounted on a four-arm calliper.

2.9.2 Acoustic

2.9.2.1 UBI - Ultrasonic Borehole Imager The UBI consists of a rotating acoustic transducer. The size of the transducer must be matched to the hole size. On the way down the transducer is flipped to measure fluid properties against a plate at known distance. The transducer must be flipped back to face the borehole wall in order to start logging. There is a mud weight limitation with these tools and there is sometimes difficulty in starting rotation at TD after flipping the transducer. Large holes can also be a problem due to viscous forces acting on the larger subs.

2.10

Callipers

Various tools have mechanical callipers and these are either 1-arm or 4-arm. They can be used to calculate integrated hole volume for use in cement calculations, however, the integrated volumes usually use only a single calliper. The 4-arms tools provide measurements of 2 diameters. • • • •

PEX – single arm. FMI – 4-arm. OBMI – 4-arm. PPC – Powered Positioning Calliper, 4-arm.

In addition to mechanical callipers and acoustic calliper can also be obtained by the UBI in open hole (or USIT in cased hole).

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2.11

March 2007

Pressures/Sampling

2.11.1

MDT - Modular Formation Dynamics Tester

The MDT is used for: • • • • •

Pressure measurement Fluid contacts and zone analysis Permeability estimation Depletion measurement Fluid sampling

It consists of some of the following modules: • • • • • • • • • • • •

MRPC - Electrical power cartridge MRHY - Hydraulic power module MRPS - Single probe module MRSC - Conventional sample chamber modules MRMS - Multi-sample module MRPO - Pumpout module MRFA - Optical fluid analyzer module MRPD - Multi-probe module MRCF - Flow control module MRPA - Dual packer module LFA - Live fluid analyser CFA - Compositional fluid analyser

The pressure readings are made with Strain and quartz gauges. Pre-tests (pressure readings) are used for fluid gradients. Samples may be taken as follows: • • •

PVT samples - MPSR Modular PVT Sample Receptacle Single-phase samples - SPMC Single-Phase Multi Sample Chamber Large volume chambers - 1 gallon, 2 ¾ gallon.

Samples are taken at suitable points which have been identified during making pre-tests. In order to get as clean (or contamination-free) sample as possible, the pump-out module is used to pump fluid from the formation into the borehole. As this takes place, the contamination levels can be monitored using one of the optical analysers: LFA or CFA. It may take a considerable time for the fluid to clean-up sufficiently to take a sample. This depends on the formation characteristics. A mini-DST or mini-frac can be made with the dual packer module. An example of an MDT formation pressure plot is given next.

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MDT Formation Pressure Plot 6850.0

6900.0

Depth (tvdss)

6950.0 Gas Oil Water

7000.0

7050.0

Grad 1 Grad 2 Grad 3 Grad 4

7100.0

7150.0

7200.0 2940

2960

2980

3000

3020

3040

3060

3080

3100

3120

3140

Pressure (psia)

2.11.2

Quicksilver Probe

This tool uses a concentric probe assembly and needs two pump-out modules to be run. The outer probe pumps out filtrate-contaminated fluid whilst the centre probe samples pure reservoir fluid. The fluid properties for both parts of the probe are monitored to control the independent pumping systems. This is being called “focused sampling” and it is claimed that its use can decrease the sampling time by an order of magnitude – the price reflects this.

2.11.3

Cased Hole Dynamics Tester

This can be used for multiple pressure testing and sampling in cased wells. It does require good cement. Sequence: • drills through casing and into the formation • perform multiple pre-tests and take samples • plugs the hole made in the casing

2.11.4

Pressure eXpress

This is a new tool which provides only pressure and fluid mobility measurements during the first logging run i.e. it can be combined with PEX etc.. It can make pre-test measurements very quickly because it uses a dynamically controlled pressure pretest system with precise control of volume and drawdown rates in a wide mobility range. A pressure limit can also be set as necessary.

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2.12

March 2007

Coring

2.12.1

MSCT - Mechanical Sidewall Coring Tool

This tool cuts cylindrical cores from the formation wall, stores them sequentially and returns them to the surface for analysis. The cores are 0.91 inches in diameter and 2.0 inches long. 50 cores can be recovered but with optional configurations for recovering 75 or 20. Applications include: • • • • • • • •

Lithology analysis Secondary porosity analysis Porosity and permeability determination Confirmation of hydrocarbon shows Determination of clay content Determination of grain density Lithology determination Detection of fracture occurrence

The MSCT requires a lot of power, either from the rig, or a standalone powerpack. This needs to be determined before mobilisation.

2.12.2

CST - Chronological Sample taker

Core Sample Taker or Sidewall Coring Tool This is a percussive coring gun which used gunpowder to fire 30 bullets per gun. Two guns can be combined to give 60 shots per run. Correct choice of the explosives and hardware is essential with this tool. Schlumberger’s tool still needs full radio silence. Applications include: • • • • • • •

Porosity measurement Permeability estimate Lithology identification Grain size, density, and shape indication Hydrocarbon identification Oil, gas, and water volume estimates Micro palaeontology.

2.13

Seismic

Seismic surveys are used for the following:

2.13.1

Check shot surveys

First break travel time information.

2.13.2

Vertical seismic profiles (VSP)

Additional reflection data from below the receiver position.

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2.13.3

March 2007

Deviated well survey or vertical incidence VSP

The source is maintained over the receiver position.

2.13.4

Offset VSP surveys

Imaging of reflectors away from the borehole.

2.13.5

Walk-away surveys

Multi-source positions with a limited number of receiver positions or array settings. These are the main types of tools in use:

2.13.6

CSI Combinable Seismic Imager

3-axis sensors Up to 4 tools in combination

2.13.7

VSI Versatile Seismic Imager

3-axis sensors Up to 40 shuttles

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3 Logging modes for each tool type 3.1

Sampling Rate

Most logging tools which make continuous readings are sampled so that the data is measured only at these sample points. Normal sampling is every 6 inches. Hi-resolution sampling is at a higher frequency that this and varies depending on the particular tool. In addition to the sampling rate, different tools can also work with different vertical resolutions. These are very much dependent on the individual tool and some of these are summarised below.

3.1.1 Resistivity, Nuclear Vertical resolution Density Neutron GR Induction Laterolog

Standard resolution 18 inches 12 inches 12 inches 48 inches 18 inches

Hi-resolution 2, 8 inches 2 inches 12, 24 inches 8 inches

3.1.2 Sonic There are many different modes for sonic logging especially for the newer tools. As a rule of thumb, the more modes that are required, the slower will be the logging speed. • • • •

Compressional Shear Stoneley Monopole/Dipole

Vertical resolution Compressional DT Shear DT

2 ft 8 to 10 ft or 10 to 12 ft; 2 ft

3.1.3 CMR The CMR uses the following main modes: • • •

Bound fluid Enhanced precision Stations

Vertical resolution Static Dynamic (high-resolution mode) Dynamic (standard mode): Dynamic (fast mode):

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Vertical resolution 6 inches 9 inches 18 inches 30 inches

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4 Pros and cons of different tools Logging tools are chosen depending on a number of factors to do with the logging environment and the logging modes required. Some older tools may be available which can make the same measurements as more modern equivalents but usually at a cost in terms of a reduced logging speed. Factors affecting tool choice: • • • • • •

Temperature, pressure Logging modes required Logging speeds PEX vs LDT-CNT CMR+ vs CMR200 NGT-D vs NGT-C

The main thing which decides the most suitable tool required is the data requirement of the petrophysicist. Environmental factors may limit the choice of tool especially in HPHT wells where the extreme tools may not be able to provide the same measurements.

5 Tool string combinations and implications Toolstring combinations are fairly flexible these days with modern telemetry systems; however, there are some combinations that should be avoided. There are at least three telemetry systems in use with different tools. These are (from newest): FTB (fast tool bus), DTB (downhole tool bus) and analogue. Analogue tools are now fairly old but include tools like the mechanical coring tool, MSCT. It is possible to combine FTB and DTB tools by using a telemetry adaptor, DTA. It is also possible to run tools together but run them sequentially by using a downhole switch. This is useful with pipe conveyed logging (PCL or TLC) as it allows non-compatible tools to be run together but logged in turn. Other factors which affect the combinability of tools are: • •

Presence of through wires Length & weight of tools vs depth of well

CMR tools are sometimes problematic and consideration should be given to running these alone or isolated sequentially with a switch.

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5.1

March 2007

Wireline Toolstrings

5.1.1 Resistivity-Sonic-Density-Neutron-Gamma ray

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5.1.2 Pressures-Sampling (MDT-single probe)

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5.1.3 Pressures-Sampling (MDT-dual packer)

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5.1.4 CMR Toolstring

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5.1.5 Imaging Toolstring (UBI-OBMI)

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5.1.6 Seismic Toolstring (VSI)

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5.2

March 2007

TLC Toolstrings

5.2.1 UBI-AIT-PPC-OBMI-GPIT-PEX Toolstring

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5.2.2 GR-PPC-DSI-MDT-CMR+-GR Toolstring

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6 Normal logging speeds & ratings Schlumberger

T degF

P Kpsi

Speed Ft/hr

Baker Atlas

T degF

P Kpsi

Speed Ft/hr

350

20

all

TTRM NAUTILUSTTRM

350 500

20 30

all all

Resistivity Water-based mud DLT

350

20

5000

DLL

350

20

48006000

DLT-E, DST-E MSFL SP HALS MCFL HRLA

350 350 n.a. 260 260 350

20 20

MLL SP

350 n.a.

20 n.a.

3000 5000

10 10 20

TBRT HDLL

350 350

20 20

3000 18006000

ALAT

350

20

5000 3600 5000 3600 3600 18005000 18005000

Oil-based mud DIT SFL

350 350

20 20

5000 5000

DPIL, DIEL HDIL

20 20

AIT

350

20

5000

NAUTILUS-HDIL

350 350400 500

6000 18006000 18006000

Density LDT PEX PEX150

350 260 300

20 10 15

1800 3600 3600

ZDL FOCUS-ZDL NAUTILUS-CDL (compensated density)

350 260 500

20 10 30

1800 3600 1800

Neutron CNT PEX PEX150 HGNS

400 260 300 260

20 10 15 10

1800 3600 3600 3600

CN FOCUS-CN NAUTILUS-CN

350 260 500

20 10 30

1800 3600 1800

GR/Spectral GR SGT PEX

350 260

25 10

GR FOCUS-GR

350 260

20 10

1800 3600

PEX150

300

15

NGT

300

20

DSL

350

20

1800

HNGS

300

20

1800 18003600 18003600 9001800 18003600

Auxiliary ACTS-B CMTD Cables

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March 2007

T degF

P Kpsi

Speed Ft/hr

Baker Atlas

T degF

P Kpsi

Speed Ft/hr

Sonic SDT

350

20

DSLT-B/H

350

20

DSI

350

20

MSIP

350

20

18003600 18003600 9001800 6003600

DAL

350

20

3600

MAC/XMAC

350

20

FOCUS-DAL

260

10

9001680 3600

Magnetic resonance CMR

350

20

3001800 3001800 3001800

MREX

350

20

1801800

CMR-200

350

20

CMR-plus

350

20

Imaging/Dipmeter Electric FMI

350

20

9001800 1800

STAR

350

20

EI

350

20

6003000 1800

OBMI Acoustic UBI

350

20

350

20

4501200

CBIL

400

20

750

Callipers 1-arm, 4-arm

350

20

1,3,6 Arm

350

20

PEX FMI

260 350

10 20

FOCUS-2 axis STAR

260 350

10 20

OBMI

350

20

18003600 3600 9001800 1800

EI

350

20

UBI

350

20

CBIL

400

20

PPC

350

20

4501200 1800

18003600 3600 6003000 6003000 750

Pressures/Sampling MDT MRPC MRHY MRPS MRSC MRMS MRPO MRFA MRPD MRCF MRPA LFA CFA CHDT Pressure eXpress

400 400 400 400 400 400 400 400 350 400 350 400 400 350 300

20 20 20 20 20 20 20 20 15 20 20 20 20 20 20

n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a.

RCI RCI-EB RCI-CB RCI-MB FMT-Tanks RCI-WA RCI-RB RCI-IB n.a. RCI-BB RCI-DP RCI-IB RCI-IB

350 350 350 350 350 350 350 350

20 20 20 20 20 20 20 20

n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a.

350 350 350 350

20 20 20 20

n.a. n.a. n.a. n.a.

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Wireline Operations for Drilling Engineers Coring MSCT CST

350 450

20 20

Gaia Earth Sciences Ltd

March 2007

n.a. n.a.

RCOR SWC

350 450

20 20

n.a. n.a.

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7 Logging modes vs logging speed Logging modes make a significant difference to logging speeds. Despite the advent of toolstrings like Platform Express, PEX, which claim to be able to log at up to 3600 feet per hour, many other factors usually combine to reduce the logging speed. Resistivity tools, which do not have any pad contact with the formation, can be logged almost at any speed. Radioactive tools require slower speeds because of the statistical nature of radiation, source strength and detector sensitivity. Therefore, the increase of logging speed for PEX over older tools has a lot to do with the design of the tools and the advances in software processing to extract better measurements. Other factors which influence logging speed are the telemetry rate to surface through the cable and the processing power of the PCs in the logging unit. Some units may have older PCs which could mean a slower logging speed for some of the newer tools. Some other tools will cause reduced logging speed depending on the operating modes. The DSI can work in many different modes and reduce logging speed to 800 feet per hour if run in all of them. CMR tools can also have reduced logging speed depending on the modes and the environment. Some older versions of tools can require reduced logging speeds when compared to the newer versions. This particularly applies to NGT-C vs NGT-D and CMR vs CMR+ or CMR200. However, it is important to determine the exact data requirements before allocating the tool and only then can an estimate of logging speed be made for each run.

8 Depths 8.1

Depth control

Absolute depth control (first run-in-hole procedure) is usually followed on the first wireline run in the hole. Schlumberger depth control relies on the accuracy1 of the measuring wheel system called the IDW2. There are two independent measuring wheels, each with a depth encoder. The second wheel provides a back-up and allows measurement of wheel slippage. On the first run down in the well, the depth measured by the IDW is considered to be absolute. The only corrections necessary are those associated with the calibration of the depth wheels, the type of cable being used and (on a semi-submersible) the tide. The rig-up length is checked at surface and then at the casing shoe. Any significant change (i.e. > 0.5 ft) in rig-up length is used to correct the depth at the casing shoe.

1 2

2 ft per 10,000 feet. IDW = Integrated Depth Wheel Gaia Earth Sciences Ltd

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The difference between the depth wheels is constantly checked by the software and an alert issued if this is excessive. It should be less than 5ft per 10,000 ft. The tidal variation is also taken into account and any significant variations between starting the run and reaching TD are used to correct the depth before logging. In open-hole a down-log is made. At TD this is compared with the uncorrected up-log to calculate the depth (stretch) correction to be added. Typical depth control parameters: IDW calibrated on: Wheel corrections: Rig-up length at surface Rig-up length at shoe Difference Depth correction due to tide Depth correction at TD (up/down-log comparison)

11th February 2006 -7, -6 88.81 m 89.2 m 0.39 m + 0.2 m + 4.5

Baker Atlas depth control relies on the use of magnetic marks on the cable and stretch corrections obtained from charts. Also, although the Baker Atlas depth measuring system has two wheels, only one of them is used for depth input into the acquisition system. In order to ensure that slippage is acceptable, the position of the magnetic marks must be continuously monitored throughout the logging run.

8.2

Driller’s Depth vs Wireline Depth

The difference between driller's depth and wireline depth always provokes debate especially at the time that the well is drilled. However, there is always a discrepancy and this is due to the way in which the "depths" are measured. Driller's depth is calculated by strapping the pipe at surface. The calculation of wireline depth is more complicated. Wireline depth is measured using a depth wheel system at the surface. This measures the length of the logging cable as it passes between two wheels. The cable tension is highest at surface so this is where the maximum stretch occurs. As the tools are run into the well, the wireline depth wheels measure absolute depth with an accuracy of 2 feet per 10,000 feet. As this is a mechanical system, it is not perfect and, there will always be some slippage between the two depth wheels. Normally this should not exceed 5 feet every 10,000 feet. This value is constantly monitored by software and an alarm sounds if the slippage exceeds the permissible level. If it does, the engineer must investigate why. The wheels are periodically checked for wear and the whole system is calibrated regularly. The only other things that can affect the depth are the changing tide or a change in the block height by the driller. The change in tide is known from the tide tables and any change in block height is checked for by measuring the length of the cable on surface (from logging unit to rotary table (called the rig-up length)). This is measured just after activating the wave motion compensator and just before entering open hole. On reaching TD, the toolstring changes direction and the cable tension at surface increases due to the increased friction on the cable. Thus the cable at surface between the measuring wheels is now longer than when running in and so the depths all appear shallower and it is necessary to apply a correction. The amount of this correction is the difference between the

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wireline depth on the way down (which is taken as absolute) and the depth on the way up with any tidal changes or changes in rig-up length taken into account. The difference between the up and down tension can be considerable, especially in deviated or S-shaped wells. It is possible to calculate the theoretical change in depth between up and down using the different tensions, the length of the cable and the stretch coefficient. This calculation doesn't work especially well in deviated wells but it can be used as a guide to check that the up-log/down-log difference is within the expected range. The depth system described here is for Schlumberger only. Baker Atlas do not rely on the measuring wheel accuracy (they only use one) and their depth control relies on the use of magnetic marks on the cable and corrections applied from stretch charts.

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9 A comparison between Schlumberger and Baker Atlas The tools and equipment supplied by Schlumberger and Baker Atlas are fairly similar in terms of the measurements made and the tool configurations. The table below gives a comparison between the two. Schlumberger Auxiliary ACTS-B Auxiliary Compression Tension Sub

tension or compression between upper and lower heads of the tool GPIT General Purpose Inclinometry Tool IDW Integrated Depth Wheel

Baker Atlas TTRM Cable Head Tension, Mud Resistivity, Downhole temperature sub. Note that when run with the FOCUS (new quad combo) it includes an accelerometer as well. Run at the top of the string, normally above the Wireline JARS, which Schlumberger do not use. ORIT Digital orientation tool. Dual Depth Wheels, one mechanical, one electronic. Primary measurement employs magnetic marks every 25M or 100FT.

CMTD Cable-Mounted Tension Device

Cable tension sensor – Sheave mounted

Cables Swivels SAH-E/F – removes tool rotation from cable torque

Swivels SWVL – removes tool rotation from cable torque

Resistivity Water-based mud Laterolog Laterologs are used primarily for determining the resistivity (Rt) of the virgin formation. Their operating domain is restricted to conductive muds and invasion: Rt>Rxo DLT

Laterolog Ditto

DLL – Dual laterolog tool. Dual Laterolog instruments are electrode tools designed to produce reliable formation resistivity measurements in boreholes containing saline drilling fluids. They operate by "focusing" a survey current into the formation. Dual Laterolog instruments are superior to induction instruments in high resistivity (>100 ohm-m) formations and/or well-bores with drilling fluids more conductive than the in-situ formation waters. No such tool in BA. Must combine MLL/TBRT for similar combo.

DLT-E, DST-E Dual Laterolog and MSFL Tool The Dual Laterolog Tool (DLT) provides both deep and shallow resistivity measurements, LLD and LLS. The DST (dual laterolog micro spherically focused tool) is a DLT that includes

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Wireline Operations for Drilling Engineers an SRS (micro spherically focused resistivity sonde), giving a very shallow measurement MSFL (micro spherically focused log) SP

March 2007

SP

HALS High Resolution Azimuthal Laterolog Sonde deep and shallow resistivity mud resistivity azimuthal resistivity MCFL Micro-Cylindrically Focused Log Part of PEX

Microresistivity measurement

HRLA High-Resolution Laterolog Array Tool

Gaia Earth Sciences Ltd

ML. The Minilog is a pad device that measures resistivity at two shallow, but different, depths of investigation. This allows the identification of mudcake, and therefore permeable formations. TBRT. The Thin-Bed Resistivity (TBRT) instrument provides high vertical resolution previously associated only with micro-resistivity devices, yet it has a depth of investigation in the range of 13 to 21 in. (330 to 533 mm). As a result, under ideal shallow invasion conditions, the TBRT service can be used to measure formation resistivities in beds less than 2 in. (51 mm) in thickness. Even when invasion is deeper, TBRT provides an excellent indication of hydrocarbons in thin beds, and is the best choice for bed identification when thin bed processing is done to enhance the resolution of standard resistivity tools. MLL. The Micro Laterolog is a focused pad device that measures the resistivity of the invaded zone near the borehole. It is designed to work best when the resistivity of the flushed zone is much greater than that of the mudcake, a situation where the Minilog performs poorly. When used in conjunction with deeper reading resistivity measurements, the MLL can provide a good indication of movable hydrocarbons PROX. The Micro-Proximity Log is a focused pad device that measures the resistivity of the invaded zone near the borehole. It has a deeper depth of investigation and larger vertical resolution than the Microlaterolog, and is designed to work best in fresh drilling muds with thicker mudcakes, a situation where the Microlaterolog performs poorly. When used in conjunction with deeper reading resistivity measurements, the PROX can provide a good indication of movable hydrocarbons in these conditions. HDLL (direct competitor to HRLA) The HighDefinition Lateral Log (HDLL) service, a newgeneration array-type galvanic measurement logging service, provides formation resistivities at multiple depths of investigation in conductive, water-based drilling mud systems. The combination of the HDLL system’s highvertical resolution and deep-investigating measurements with inversion processing provides a detailed analysis of formation

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March 2007 resistivity (Rt), flushed zone resistivity (Rxo), and depth of invasion. These measurements provide more accurate formation resistivity data than conventional systems in thinly bedded hydrocarbon-bearing reservoirs and in the presence of deep drilling fluid invasion. Using HDLL data results in a better reservoir description, more accurate water saturation (Sw) determination, and a detailed evaluation of the drilling fluid invasion profile

ALAT Azimuthal Laterolog Tool azimuthal resistivity device. It combines the standard DLT measurements with a 12channel azimuthal resistivity image and a high resolution deep resistivity measurement. SP Oil-based mud Induction

No similar tool in B.A. ALAT’s are hardly used these days anyway. SP Induction

DIT-E

Dual Induction Tool-E

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DPIL. The Dual Phase Induction Log measures formation conductivity with three different depths of investigation. These measurements can be used to determine the conductivity of the undisturbed formation, even in the presence of deep invasion. The DPIL also measures the spontaneous potential (SP), which can be used to aid lithology determination. DIEL. The Dual Induction-Focused Log provides data from four measurements performed simultaneously. These include resistivity curves made by a deep investigation induction, a medium investigation induction, and a shallow investigation focused device. Also, a spontaneous potential measurement is made to aid in lithology identification. The three resistivity measurements are combined to provide a quantitative correction for the effects of the invaded zone and, consequently, a more accurate value for the resistivity of the undisturbed formation, Rt. The Dual InductionFocused Log is applicable in all wells drilled with low salinity or non-conductive drilling fluids. It has particular application in medium to low porosity formations where mud filtrate invasion is common. Measuring the effects of such invasion increases the accuracy of the formation evaluation. In suitable conditions, the response of the induction curves can be enhanced to give vertical resolution down to 3 ft (0.91 m).

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Induction Deep (ID) and Induction Medium (IM)

SFL Spherically Focused Log (current and voltage) SP AIT Array Induction Imager Tool

Five basic log resistivity curves with a median radial depth of investigation of 10, 20, 30, 60, and 90 in vertical resolution of 1, 2 & 4 ft adaptive focus, both vertically and radially SP Mud resistivity Density LDT Lithology Density Tool direct measurements of formation lithology and density

Gamma ray source – Caesium 137 several detectors, mounted on a pad one-armed calliper PEX (HILT) Platform Express

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March 2007

IEL. The Induction Electrolog resistivity log is for medium porosity formations drilled with low salinity muds. It is also applicable in holes drilled with non-conductive fluids and air. Induction readings approximate true resistivity where bed thickness is greater than 5 ft (1.524 m) and the diameter of invasion is less than 40 in. (1016 mm). Curves presented are the gamma ray, spontaneous potential, short normal, and the induction resistivity. SP sub needs to be included. HDIL/FOCUS-HDIL (direct competitor to AIT/PEX-AIT) The High-Definition Induction Log (HDIL) service, a full-spectrum array-type induction logging service, provides formation resistivities at multiple depths of investigation in freshwater- and oil-based drilling mud systems. The combination of the HDIL system’s high-vertical resolution and deepinvestigating measurements with inversion Processing, provides a detailed analysis of formation resistivity (Rt), flushed zone resistivity (Rxo) and depth of invasion. The FOCUS-HDIL is the PEX equivalent of an AITH. 6 depths of investigation, 10”-120”. 1, 2, 4 ft vertical resolution. SP

ZDL. The Compensated Z-Densilog service provides both formation bulk density and the photoelectric absorption index (Pe) data. These measurements allow evaluation of complex formations determining lithology and porosity in such formations. Gamma ray source – Caesium 137 Dual detectors, mounted on a pad one-armed calliper FOCUS (direct competitor to PEX TLD) densilog. Baker Atlas has introduced FOCUS, the latest in high efficiency premium open hole logging systems. All downhole instruments have been redesigned, incorporating advanced downhole sensor technology into shorter, lighter, more reliable logging instruments that are capable of providing formation evaluation measurements with the same precision and accuracy as the industry's highest quality sensors at up to twice the speed of conventional triple-combo and quad combo

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Gamma ray source – Caesium 137 several detectors, mounted on a pad one-armed calliper Neutron CNT Compensated Neutron Tool

March 2007 logging tool strings. The logging system consists of the four standard major open hole measurements (resistivity, density, neutron, acoustic), plus auxiliary services. The FOCUS also has a two axis calliper for borehole geometry alongside the ZDL calliper. Gamma ray source – Caesium 137 Dual detectors, mounted on a pad one-armed calliper

16-Ci Americium Beryllium neutron source. two thermal neutron detectors must be eccentered

CN/FOCUS-CN (direct competitor to CNL/PEX CNL) Neutron logs are primarily used for identification of porous formations and for the estimation of porosity. Often, it is possible to distinguish gas zones from oil or water zones by the comparison of a neutron log with another porosity log or with information from core analysis. Combination of the Neutron log with Z-Density (or Densilog) or Acoustilog survey provides accurate porosity values, shale content, and lithological information 16-Ci Americium Beryllium neutron source. two thermal neutron detectors must be eccentered

PEX (HILT) Platform Express Highly Integrated Logging Tool

FOCUS. As per comments above for FOCUS densilog.

HGNS Highly-integrated Gamma-ray Neutron Sonde neutron and gamma-ray measurements 16-Ci Americium Beryllium neutron source. two thermal neutron detectors must be eccentered

16-Ci Americium Beryllium neutron source. two thermal neutron detectors must be eccentered

GR/Spectral GR SGT Scintillation Gamma-Ray Tool

Measures natural gamma-ray activity in the borehole

GR – Gamma ray Tool. The Gamma Ray logging instrument measures the natural radioactivity of the formation and usually correlates with the SP Curve. The instrument has analog and digital varieties providing combination with all instrument combinations, including downhole seismic applications. The Gamma Ray instrument can be run in any liquid or air filled hole, either cased or uncased. In cased hole, a Casing Collar Log (CCL) can also be recorded simultaneously. ditto

PEX (HILT) Platform Express Highly Integrated Logging Tool Part of HGNS Measures natural gamma-ray activity in the borehole

FOCUS, as above (quad combo solution)

NGT Natural Gamma-Ray Spectrometry Tool Latest version is called the HGNS and can be logged at 3600FT/HR. There are Many OLD

DSL. The Digital Spectralog™ (and combined Digital Gamma Ray) service differs from a standard gamma ray instrument - which

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ditto

35 of 42

Wireline Operations for Drilling Engineers versions of NGT in the field, some of which are restricted to 900FT/HR.

Measures the gamma-ray spectrum that occurs naturally in the formation to estimate the individual contributions of uranium, thorium and potassium to the total gamma-ray signal. Sonic SDT Sonic Digital Tool

monopole (symmetric) transmitter DSLT-B/H

March 2007 records total gamma rays as a function of depth - in that it also measures the discrete energy of each gamma ray detected. By separating the total gamma ray signal into its components, the Digital Spectralog can assist customers in locating fracture zones, identifying the lithology of subsurface formations, measuring bed thickness, correlating zones of interest between wells, and making qualitative estimates of formation permeability. Ditto.

AL The Borehole Compensated Acoustilog service presents measurement data on the velocity of sound in formations penetrated by the wellbore. The time interval between the arrival of the acoustic pulses at finite-spaced receivers in the instrument is measured and recorded in units of microseconds per foot (or microseconds per meter). Porosity can be calculated when the value of the acoustic travel time of the formation matrix is known. Signature or VDL waveform presentations are optional. Good correlation, particularly in low porosity formations, and minimizing borehole effects in rugose holes characterize the BHC Acoustilog. Monopole, can be Long spacing, also known as ACL, for large diameter boreholes. DAL. The Digital Array Acoustilogs (a.k.a. DAC) logging system acquires high-resolution, full-wave acoustic data. This system uses two low-frequency transmitters and an array of 12 downhole receivers to record compressional, shear, and Stoneley waveforms simultaneously in both open and cased wellbores. Waveform amplitude, slowness, and arrival time (delta t) Processing of the raw data can be incorporated into advanced log analysis programs to evaluate fractures, sand production, and rock properties. One of the primary advantages of waveform correlation is its insensitivity to cycle skipping, making it particularly effective in gas-saturated, rugose, and washed out boreholes. In addition to openhole applications, the Digital Array Acoustilog instrument may be used for through-casing acoustic logging and cement bond evaluation.

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Digitizing Sonic Logging Tool cartridge for running conventional sonic sondes SLS-D(C), SLS-E(W) and SLS-F(Z) under DTS telemetry

monopole (symmetric) transmitter

DSI DSST Dipole Shear Sonic Tool

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March 2007

MAC. The Multipole Array Acoustilog (MAC) logging system integrates a monopole acoustic array with a dipole array, ensuring the complete acquisition of compressional and shear data in both slow and fast formations in a single logging pass. Each array has eight receivers designed to measure a specific type of signal, and each is configured with highpowered transmitters, improving data quality in both openhole and through-casing applications. The MAC raw data are processed to obtain waveform amplitude, slowness, and arrival time. These data are incorporated into advanced log analysis programs to evaluate fractures and lithology, fluid content, and rock properties. Synthetic seismograms can be constructed for correlating with surface-seismic data and calibrating velocity check-shot surveys. FOCUS- DAL. Digital Acoustic Log. Monopole array acoustic - Accurate Compressional Slowness (∆t) using depth derived borehole compensation (DDBHC). Run as part of the FOCUS quad combo. XMAC/XMAC Elite. XMAC Elite (direct competitor to DSI) increases exploration, drilling and production program value with improved formation evaluation, seismic correlation and geomechanics information accuracy. The XMAC ELITE (Cross Multipole Array Acoustilog Elite) service is a fullwave monopole, dipole and cross dipole instrument. The tool was developed through technology transfers and licensing agreements from Mobil (source technology) and Shell (receiver technology). The hybrid tool is accepted as the benchmark for acquiring quality compressional and shear measurements over a broad range of borehole environments. The XMAC ELITE service provides the best quality monopole and dipole measurements in unconsolidated formations (Delta T greater than 350usec/ft.) where other tools have had difficulties performing. An additional capability comes from cross dipole measurements for accurate determination of azimuthal anisotropy.

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Magnetic resonance The CMR enables the measurement of important reservoir parameters not measured by conventional logs: permeability, producible fluid type and irreducible water saturation.

CMR Combinable Magnetic Resonance Tool CMR-200 CMR-plus Imaging/Dipmeter Structural geology Sedimentary features Rock texture Complement to coring and formation tester programs Geomechanics Reservoir characterization Electric FMI Formation MicroImager

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March 2007

MREX. The MR Explorer (MREX) service, the latest-generation magnetic resonance openhole wireline logging tool, delivers the benefits of previous nuclear magnetic resonance (NMR) systems while acquiring data more quickly and providing high-quality results in almost any borehole environment. The answers provided by the MREX service reduce uncertainty when evaluating reservoirs and identify hydrocarbon-bearing intervals for maximizing recovery. The MREX service can make significant contributions during well and formation evaluation, reservoir description, reserve determination, producibility estimation, fluids characterization, and completion design. MREX (direct competitor to CMR) Magnetic Resonance eXpert Multiple depths of investigation.

Ditto Ditto Ditto Ditto Ditto Ditto DIP. The High Resolution 4-Arm Diplog instrument is a pad-type lateral device designed to detect changes in formation resistivities. Data are obtained from very shortspaced, focused electrodes, which make contact with the borehole wall. Simultaneous measurements are recorded at each pad electrode system. Each recording is correlated in order to establish dip angles across the borehole. A borehole directional survey and a borehole calliper survey are recorded simultaneously in order to determine the true formation dip. HDIP. The Hexagonal Diplog (HDIP) logging service acquires high-resolution formation dip information using six independent microresistivity sensors. The HDIP data are Processed to calculate and orient the dip and direction of formation features. A tri-axial accelerometer and three magnetometers are employed to determine borehole drift and azimuth and correct for velocity fluctuations of the instrument. Accurate borehole geometry and wellbore volumes are determined from the six independent calliper measurements.

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STAR. (direct competitor to FMI) The STAR Imager service provides high-resolution resistivity formation images in conductive mud systems. The six-arm independently articulated carrier and powered stand-off ensures optimal sensor-to-formation contact even in highly deviated boreholes. Pads with 24-sensors are mounted on each of the six articulated arms, resulting in a total of 144 micro-resistivity measurements, with a vertical and azimuthal resolution of 0.2” (~5 mm).

OBMI Oil-Base MicroImager

Acoustic UBI (Ultrasonic Borehole Imaging) Note: At an early marketing meeting in Paris it was suggested that the new tool should be called BASIL (Borehole Acoustic Imaging Log). Since CBIL (pronounced CYBIL), and BASIL were characters in a British Comedy called Fawlty Towers it was decided to change the name to UBI…

Gaia Earth Sciences Ltd

The resulting high-resolution borehole images can be used to identify geological and borehole features. These include planar features such as bedding, fractures, faults, stratigraphic features such as cross-bedding and ichnofabrics, and the borehole wall features such as breakout and drilling-induced fracturing. Exclusive or in combination with the CBILSM service, identified features are subsequently used in the analysis of structural dip, fracture systems, depositional environments, borehole stability, and net-pay in thinly bedded sequences. The STAR Imager and CBIL instrument's design allows the simultaneous acquisition of both image data sets; they are both also fully combinable with other Baker Atlas logging tools. EI. The new EARTH Imager from Baker Atlas brings the well-understood responses of microresistivity images in wells drilled with nonconductive (commonly referred to as oil-based) muds. This service provides significantly improved vertical resolution and borehole coverage when compared to other available systems. Detailed structural, sedimentological, and petrophysical analysis using image data is now possible in wells drilled with oil-based mud CBIL(direct competitor to UBI) The Circumferential Borehole Imaging Log (CBILSM) service provides high-resolution borehole acoustic images in difficult wellbore conditions, including high-porosity, unconsolidated formations. These images provide valuable insight for making difficult drilling, completion, and production decisions at the wellsite. Full 360º borehole imaging is possible due to an acoustic transducer operating in the pulseecho mode. The transducer rotates to scan the entire circumference of the borehole wall providing sharp images and boundary delineation. The CBIL instrument operates reliably in both water-based and oil-based muds. The lower operating frequency (250 kHz) allows for superior performance in larger holes and heavier muds than other similar 39 of 42

Wireline Operations for Drilling Engineers

Rotating transducer Mud weight limitation Callipers 1-arm, 4-arm

March 2007 devices. Since the CBIL system is an acoustic device that does not require contact with the borehole wall, it is quite effective in horizontal wells. Its small size [3.625 in. (92.1 mm)] allows for operation in slim holes as well as large-diameter holes. Two rotating transducers Ditto. 3-CAL, 4-CAL, 6-CAL. The Calliper Log is a continuous profile of the borehole wall showing variations in borehole diameter. Calliper Logs can be recorded using 2-, 4-, or 6-arm instruments. These measurements and their average accurately define the hole shape and size, especially in deviated and elliptically shaped holes FOCUS STAR EI CBIL

PEX FMI OBMI UBI PPC Pressures/Sampling MDT Modular Formation Dynamics Tester Pressure measurement Permeability estimation Fluid sampling MRPC - Electrical power cartridge MRHY - Hydraulic power module MRPS - Single probe module MRSC - Conventional sample chamber modules MRMS - Multi-sample module MRPO - Pumpout module MRFA - Optical fluid analyzer module MRPD - Multi-probe module MRCF - Flow control module MRPA - Dual packer module LFA - Live fluid analyser CFA - Compositional fluid analyser

RCI. (direct competitor to MDT) Reservoir Characterisation Tool. Ditto Ditto Ditto RCI Electronics Section – EB, Aux Power-OB RCI Hydraulic Power Section - CB RCI Single Packer Section - MB FMT Tanks (e.g. 4 Litre) RCI 6 tank section - WA RCI Pump Section - RB RCI Sampleview - IA n.a. RCI Small pump section - BB RCI Dual Packers RCI Sampleview version IB (methane detector) RCI Sampleview version – IB (as above)

Strain and quartz gauges PVT samples - MPSR Modular PVT Sample Receptacle Single-phase samples - SPMC Single-Phase Multi Sample Chamber Large volume chambers - 1 gallon, 2 ¾ gallon.

4 Litre

Pre-tests for fluid gradients

ditto

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PCT’s SPT’s

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Coring MSCT Mechanical Sidewall Coring Tool

0.91 in. in diameter by 2.0 in. recovers 50 core samples. Optional configurations for recovering 75 core or 20 CST Chronological Sample taker Core Sample Taker or Sidewall Coring Tool

March 2007

RCOR (direct competitor to MSCT). The Rotary Sidewall Coring Tool is a computercontrolled, hydraulically powered coring device for cutting and retrieving multiple sidewall core samples. Ditto 25 core samples available SWC’s (direct competitor to CST’s). Side Wall Cores. The fundamental operating principle of the SWC is relatively simple. A core barrel, which is a hollow cylinder, is shot into the formation by a powder charge ignited by an electric current. The core barrel, containing a formation sample, is retrieved by means of a steel cable attached between the gun and the core barrel. Only one core barrel is fired at a time. A tandem gun can selectively core up to 50 samples on a single run using the 4 in. (101.6 mm) Corgun and up to 44 samples on a single run using the 3 in. (76.2 mm) Corgun. Core barrels are available to sample formations ranging from soft to very hard. The core samples are generally large enough to allow a comprehensive core analysis. Cores range in size from 0.85 in. (21.6 mm) to 0.69 in.

30 bullets per gun Can combine two guns to give 60 shots

Gaia Earth Sciences Ltd

The SP or Gamma Ray curve, run simultaneously with the SWC, provides depth correlation with the primary suite of logs. 25 per gun Can combine to give 50 shots.

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Wireline Operations for Drilling Engineers

March 2007

10 About the Author The author, Stuart Huyton, was born in Scotland and obtained an Honours Bachelor of Science Degree in Electrical & Electronic Engineering at the Heriot-Watt University, Edinburgh. After a short time as a Royal Naval Officer, he joined Schlumberger Wireline as a field engineer in 1981. He worked as a field engineer in Aberdeen, Mexico, Shetland and Denmark. He held numerous technical and managerial roles with Schlumberger Wireline, including Location Manager for Shetland, District Technical Engineer in Aberdeen, Base Manager in Siberia and Operations and Technical Manager for the FSU based in Moscow. Since 1996 he has been an independent consultant based in Scotland offering services to the oil industry.

Stuart Huyton BSc CEng MIET Senior Petrophysicist

Gaia Earth Sciences Limited www.gaia-earth.co.uk

[email protected]

Phayrelands, Cummingston, Elgin, Morayshire, IV30 5XZ, UK Phone: +44 (0)1343-830617 Fax: +44 (0)1343-835854 Mobile: +44 (0)7941-426795

Gaia Earth Sciences Ltd

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