MWD / Formation evaluation

Advances in MWD and formation evaluation for 2003

Developments include wireline, memory and while-drilling logging methods; mud hydrocarbon measurements and cuttings permeability; wireline test tools; a core logger; and service company web sites

 David Patrick Murphy, Shell Technology EP, Houston

 Recent advances in formation evaluation can improve the quality and increase the quantity of formation data, and reduce costs while making operations more efficient. Twenty-nine examples of these advances and related tools discussed here cover: 

•  Wireline logging – Imaging logs, slim HPHT platform, NMR, formation resistivity and electrokinetic logs
•  Memory logging – Through bit logging
•  MWD – Telemetry, hostile environment platform, NMR, acoustic, porosity, formation resistivity and caliper logs
•  Mud logging – GCMS mud hydrocarbon measurement and cuttings permeability
•  Testing – Wireline formation tests
•  Coring and analyses – Core logger
•  General – Service company web sites and NMR fluid properties. 

  WIRELINE LOGS

 Wireline logs typically provide more formation evaluation wellbore data for lower cost than other tools, except when rig costs are high. Seven applications are discussed here.

 Imaging. Two new resistivity borehole- wall- imaging logs have been introduced. Precision Drilling Computalog’s High Resolution Micro Imager (HMI) is designed for water-based muds.¹ It is fully combinable with the company’s other tools. HMI is rated at 350° and 20,000 psi and can be run in hole sizes of 6 to 20 in. When run in the standard mode, it has six pads, each containing 25 buttons. It can also be run in the Dual-HMI mode with 12 pads, each containing 25 buttons. 

 Baker Atlas’ EARTH Imager is designed to provide high-resolution images in oil-based muds.² It has six pads, each with eight sensors. Circumferential coverage for one logging pass is 64.9% in an 8-in. hole. Additional coverage can be obtained if the tool rotates during a second logging pass, Fig. 1. EARTH Imager can provide resistivity images in formations ranging from 0.2 to 10,000 ohm-m. High resolution R_xo curves can be generated with 1.5% accuracy over the range of 1 to 2,000 ohm-m. The tool is rated at 350° F and 20,000 psi, and can be run in hole sizes of 6 to 21 in. Maximum logging speed is 600 ft/hr. 

Fig. 1. Two separate passes of the Baker Atlas oil-based mud micro-resistivity EARTH Imager over a 3-m interval, with excellent repeatability shown between main and repeat runs.2 Mechanical layering is indicated by fractures terminating on bedding surface as indicated (XX and YY). Both images are statically normalized. The enlarged image is dynamically normalized with both passes displayed.

 Slim HPHT logs. Schlumberger’s SlimXtreme slimhole HPHT well logging platform is designed to log hole sizes as small as 3-7/8 in.³ It is rated at 500°F and 30,000 psi for continuous logging times ranging between 5 and 8 hr, depending on the sensor. A single wireline tool string can contain an Array Induction Tool, Litho-Density, Compensated Neutron and Gamma Ray. An integrated accelerometer provides real-time speed corrections for all SlimXtreme measurements. All tools use advanced wireline digital telemetry rated to the same pressure and temperature as the complete platform, and are capable of transmitting data through wireline cables as long as 36,000 ft. An integral electrical cable release capability allows the cable to be freed from the tool string in a controlled manner by application of electrical current if the tool string becomes stuck. The company’s SlimXtreme tools are fully combinable with its Xtreme and SlimAccess systems. 

 NMR. Schlumberger has extensively tested an experimental version of its new-generation NMR wireline logging tool.⁴ It is a multi-frequency, eccentered, gradient-field logging tool. Multiple frequency-acquisition modes allow radial profiling of the near-wellbore formation in a single logging pass, Fig. 2. This tool has increased maximum depth of investigation (DOI) to better probe native fluids and reduce sensitivity to hole rugosity. To date, the deepest DOI investigated by the tool is 6 in. A prepolarizing magnet enables fast logging in long T₁ environments. The developer has incorporated acquisition sequence programmability to allow rapid introduction of new NMR sequences beyond the standard Carr-Purcell-Meiboom-Gill (CPMG) sequence. 

Fig. 2. Radial profile logs form Schlumberger’s new-generation NMR wireline logging tool in a Schlumberger test well.4 Tracks 1 and 2 show gamma ray and induction logs; Tracks 3 and 4 are porosity and free fluid volumes. T2 distributions from four depths of investigation are shown on the right.

 Formation resistivity in high-angle wells. During the mid-1960s, Pierre Grimaldi discovered an induction log measurement technique that could give conductivity measurements independent of shoulder beds and approximately independent of relative dip angle. Schlumberger has applied Grimaldi’s unpublished technique in a new processing approach for its AIT-family of multiarray induction logs.⁵ The computations require only a small change to the standard AIT processing, which will allow Grimaldi logs to be displayed in real time at the wellsite. The DOI of Grimaldi-processed logs is quite shallow, but has a well-defined radial response. In cases where invasion is not too deep, the logs can give a dip-independent estimate of true formation resistivity without producing the often-seen, high-angle bed boundary horns or spikes, and without need for computer-intensive processing. 

 Faster cased-hole resistivity. Cased-hole resistivity log measurements are performed in stationary mode to obtain acceptable quality readings. Schlumberger’s second-generation, cased-hole resistivity log, CHFR-Plus, incorporates an improved measurement principle which halves station acquisition time, effectively doubling logging speed up to 240 ft/hr.⁶ The improved measurement principle is a single-step measurement of the formation leakage current based on error cancellation rather than error compensation, eliminating need for making a separate casing resistance compensation measurement, while keeping the same or better precision and accuracy. Field tests have shown cased-hole resistivities matching previously run openhole resistivities over the 1 to 100 ohm-m range, which is the typical range limitation of cased-hole resistivity measurements. CHFR-Plus can be run in casing OD sizes ranging from 4-1/2 to 9-5/8 in. It is rated to 300°F and 15,000 psi. 

 Electrokinetic logging. Groundflow Ltd. has developed a new logging system called Electrokinetic logging (EKL).⁷ Field testing in two boreholes has shown promise in estimating soil and rock permeability. The EKL sonde emits acoustic waves (sound energy) and measures electrical potentials. The electrical response is mostly associated with water/ground interface at the borehole wall. Charge separation occurs when water flows in permeable formation in response to the applied sound pressure field. Permeability and other fluid properties are obtained by observing the electrical potentials at two frequencies. The potentials are very weak, a few microvolts, and the sonde uses patented technology to extract useful signals in an inherently noisy environment. Further work will be needed to refine and calibrate elastic parameters used in EKL processing and to determine EKL’s scope and applicability. 

  MEMORY LOGS

 Slimhole memory openhole logging tools are available using several types of conveyance, one of which is discussed here. 

 Through Bit Logging. Reeves Compact openhole memory tools have been successfully run using Shell’s Through Bit Logging (TBL) conveyance.⁸ TBL involves drilling with a special bit which contains a center insert allowing deployment of logging tools, Fig. 3. Memory logging tools are lowered or pumped down on slick line and hang out of the bottom of the drillstring through the insert. The slick line is detached and retrieved. Logging is performed in memory while the bit is tripped to surface. TBL is designed to be a low-cost and low-risk well logging method. 

Fig. 3. Through Bit Logging bit, complete with drilling insert in place, is shown after logging and tripping out of hole.8 Note how cutters on insert and outer bit line up.

  MWD

 Measurement while drilling formation evaluation tool suites are providing additional measurements, more accurate versions of existing measurements, and new deployment/telemetry options. Thirteen new tools/systems are described below. 

 EM telemetry. Electromagnetic (EM) telemetry is evolving as an alternative to mud pulse telemetry for MWD/LWD data transmission to surface. There are some limitations with respect to the types of formations (not too conductive nor too resistive) through which EM signals can pass. EM telemetry rates are comparable to mud-pulse-telemetry rates. However, EM telemetry can be used for underbalanced drilling with air, foam, or aerated muds, which preclude the use of mud pulse telemetry. Three new EM telemetry systems have recently been documented: 

•  Precision Drilling Computalog’s Extended-Range Electromagnetic (EM) MWD system ⁹
•  Schlumberger’s E-pulse electromagnetic telemetry ¹⁰
•  Halliburton Sperry-Sun’s electromagnetic MWD.¹¹

 Direct Telemetry. GrantPrideco’s Intellipipe drill pipe communication system is a very high-speed telemetry link through drill pipe between downhole MWD/LWD tools and surface.¹² Data is transmitted across each pipe connection using a non-contacting coupler requiring no specific orientation, Fig. 4. Every 1,000 ft along the drillstring, amplification joints are used to boost the signal. Transmission rates can be as high as 1,000,000 bits/sec, compared to traditional mud pulse and newer EM telemetry rates of 1 to 10 bits/sec. Bi-directional communication enables instructions to be sent to downhole tools from surface. Intellipipe was developed in cooperation with the US Department of Energy. 

Fig. 4. GrantPrideco Intellipipe can provide high speed MWD/LWD telemetry12 to/from the surface even in underbalanced drilling situations.

 Hostile-environment MWD. Precision Drilling Computalog has introduced its HEL MWD system, rated to operate reliably at downhole pressures up to 30,000 psi and temperatures up to 180°C, while surviving to 200°C.¹³ HEL comprises the following tools and sensors: 

•  Integrated Directional Sonde
•  High Temperature Azimuthal Gamma Ray
•  Environmental Severity Measurement
•  Borehole/Annular Pressure. 

 The HEL system has undergone extensive field testing in Mexico and the US and has been run successfully in wells with mud weights up to 19 ppg and temperatures exceeding 170°C. 

 NMR. Schlumberger has field tested a new LWD NMR tool designed to acquire T₂ data.¹⁴ The tool contains a motion sensor package to identify detrimental drilling motion conditions. Those results are available, in real time, to permit corrective actions while the well is drilled, or to identify zones where a repeat reaming pass is necessary for better data quality. The magnetic field of the tool is axially symmetric. Therefore, a correction calculation can be applied to raw MWD magnetometer directional survey measurements, making it possible to add the NMR tool anywhere in the bottomhole assembly. 

 Acoustic shear velocities. Monopole acoustic tools are not able to acquire shear acoustic velocity information in slow formations, especially in the soft sediments of deepwater reservoirs. In wireline logging, dipole acoustic tools are used to acquire shear acoustic velocities in slow formations. Baker Hughes INTEQ has constructed and field tested an LWD multipole acoustic tool which allows the acquisition of acoustic velocities in monopole, dipole and quadrupole modes.¹⁵ 

 The company’s published results indicate that its LWD dipole tool, unlike its wireline counterpart, is not suitable for direct shear-velocity measurement in slow formations because: 1) there is a severe tool-wave contamination, and 2) the formation flexural-wave velocity differs significantly from the formation shear velocity. The LWD quadrupole wave is believed to be the best candidate for the shear measurement because: 1) the tool quadrupole wave is absent when operating in the low-frequency range, and 2) the quadrupole wave in a slow formation travels at formation shear velocity at low frequencies. In fast formations, the formation shear velocity can be measured from the second mode of the quadrupole wave, provided there is sufficient signal-to-noise ratio for measuring this wave mode during drilling. 

 Sonic in large holes. Sperry Sun has developed a 9.5-in. version of its Bi-modal AcousTic (BAT) sonic tool for acquiring acoustic velocity data in large holes.¹⁶ The tool is designed with two opposed transmitters capable of firing strong signals at multiple frequencies, and dual, seven-element receiver arrays for high signal/noise ratio in soft, highly-attenuating formations. The tool is mechanically compatible with larger bottomhole assemblies used to drill large-diameter surface holes, while providing compressional slowness (D t_c ) data in boreholes ranging from 14-3/4- to 26-in. diameter.

 Centralization is not required, and the tool is compatible with bi-centered bits. Therefore, it can be used to provide porosity and pore pressure information in applications where bi-centered bits preclude the acquisition of acceptable-quality LWD neutron porosity and density data. The 9.5-in. BAT is combinable with similar-sized directional, gamma ray, resistivity and annular pressure sensors to facilitate both drilling and formation evaluation applications in real time in large boreholes. 

 Porosity logs. Density and neutron are the most-used LWD porosity logs. LWD density logs are very susceptible to standoff-based errors. Most new LWD density tools minimize standoff-based error effects by using some variation of a binning approach for data acquisition. The binning approach basic concept is to divide the borehole circumference into several bins and compute bulk density and photoelectric effect by using data from bins where the density sensors are closest to the borehole wall (least standoff). Since a binning approach captures data from around the borehole circumference, the information can be processed in such a way as to provide a borehole image of porosity changes (from bulk density) or lithology changes (from photoelectric effect). Three new LWD density-neutron tools have recently been documented: 

•  Precision Drilling Computalog’s new porosity logging system¹⁷
•  Sperry-Sun’s Compensated Thermal Neutron (CTN) and Azimuthal Litho Density (ALD) ¹¹
•  Baker Hughes INTEQ’s ADVANTAGE Porosity Logging Service (APLS).¹⁸

 Multi-frequency resistivity. Precision Drilling Computalog has developed a 4-3/4-in. slimhole LWD propagation resistivity tool called the Multi-Frequency Resistivity Tool (MFR).¹⁹ The slimhole MFR is designed to operate in borehole pressure of up to 30,000 psi and flowrates of 400 gpm without sustaining damage to the tool or electronics. MFR operates at both 2 MHz and 400 kHz at antenna-receiver spacings of 20, 30 and 46 in. Phase and attenuation measurements at each transmitter-receiver pair result in 48 absolute measurements, which are combined to produce 12 compensated resistivity measurements at different radial distances from the borehole. Their compensated antenna and electronics designs result in reported phase and attenuation accuracy specs of +/-0.25 mmhos and +/-0.5 mmhos respectively. Deepest DOI is obtained using 400 kHz attenuation measurements made at a 46-in. antenna-receiver. 

 Caliper. Schlumberger has proposed an integrated LWD caliper derived from neutron, density and ultrasonic azimuthal LWD data.²⁰ Each individual caliper measurement has a specific applicability range and all are affected by acquisition and environmental parameters in different ways, making them somewhat cumbersome to quality control and use. Schlumberger’s method automatically rates the different calipers according to acquisition and environmental parameters (mud characteristics, tool motion, formation properties, etc.) and combines them depth-by-depth according to their respective confidence factors. The resulting integrated at-drilling-time caliper should be more accurate and robust than any of the individual calipers. This integrated caliper approach could be extended to include any new caliper types that become available in the future. 

  MUD LOGGING

 Mud logging provides nearly real-time information concerning lithology, rock properties, hydrocarbon presence and hydrocarbon properties. Three French organizations have developed two relevant systems. 

 GCMS. Geoservices has field tested a new wellsite system for drilling-mud gas measurement of hydrocarbon gases and vapors from C₁ to C₈, including BTX (Benzene-Toluene-Xylenes), non-hydrocarbon gases (CO₂) and sour gases (H₂S) using a gas chromatograph/mass spectrometer (GCMS) analyzer.²¹ A new-generation, heated gas trap and transfer line resulted from research carried out by Geoservices and Institut Français du Pétrole (IFP). To extract hydrocarbons up to C₈ from the drilling mud, the mud is heated before extraction. By doing this, heavy components usually found in the liquid state at ambient conditions can also be extracted. To transport the extracted sample with minimal loss, a new transfer line has been designed. With this new line, absorption of paraffinic or aromatic hydrocarbons – a known problem with standard transfer lines – is reported to be negligible. Further, specific couplings have been developed: 1) between extractor and transfer line, and 2) between transfer line and analyzer. These minimize transit time and avoid any condensation in the line; sample transport is performed under specific pressure and temperature conditions. 

 Cuttings permeability. Institut Français Du Pétrole (IFP) and Institut de Méchanique des Fluides de Toulouse (IMFT) have presented an original method for measuring drill cutting permeability without any specific lab conditioning such as cleaning, coating, etc.²² A volume of about 100 cc of cuttings is placed in a pressure vessel. The cell is then filled with a viscous oil. Oil invasion into the cuttings always traps a certain amount of gas. When a pulse of pressure is applied on the cell, the oil enters into the cuttings due to gas compressibility. Permeability is then derived from the dynamic of the oil invasion by using a simple model. 

 The proposed method does not require specific conditioning, it is easy to handle and provides consistent results in the classical range of reservoir permeability, i.e., up to 2,000 md for 3 – 5-mm cuttings, up to 200 md for 2 – 3-mm cuttings, and up to 50 md for 1 – 2 mm cuttings. Due to its simplicity and consistency, this method could be used in the field to evaluate reservoir permeability in nearly real time during drilling. 

 Although the proposed methodology is not designed to estimate porosity, tests show that a reasonable porosity estimate is obtained in most cases, except when assumption of gas saturation at initial pressure (25%) is not appropriate. This study is part of a larger project devoted to the petrophysical characterization of reservoirs from cuttings measurements (porosity, residual saturation, capillary pressure). 

Fig. 5. Precision Drilling Computalog Flow Rate Tester (FRT) with dual packer section.23

  WIRELINE TESTING

 Formation testing provides pressure, fluid and other information. Three examples of available new technologies are presented. 

 Dual-packer wireline tester. Precision Drilling Computalog has introduced its Flow Rate Tester (FRT), an H₂S-rated wireline test tool with dual packer section, Fig. 5.²³ FRT can be used in openhole and cased hole (when pre-perforated). Packer spacing can be set between 18 in. and 20 ft. Packer element diameters can be chosen in sizes from 4.5 to 7 in. allowing FRT to be run in openhole sizes of 6-1/4 to 8-3/4 in. and casing from 5-1/2 to 9-5/8 in. Fluid identification is done using resistivity, capacitance and pump characteristics. FRT is rated to 15,000 psi and 302°F. 

 Live-fluid analyzer. Schlumberger has used optics for downhole fluid identification in its Modular Formation Dynamics Tester (MDT) for more than a decade. The new Live Fluid Analyzer (LFA)²⁴ module for MDT utilizes new downhole optical techniques to analyze fluids as they flow through the wireline test tool. LFA builds on and improves existing optical fluid analysis with its ability to detect and measure dissolved methane in live fluids. Oils of different types can be differentiated based on both their methane content and color. 

 Replacing production tests. Shell has published information for using wireline formation tests to replace production tests.²⁵ These techniques have been applied successfully in multibillion-dollar deepwater investments without regrets. The techniques are Shell’s Intellectual Property; however, they will be licensed and made available to some wireline contractors for commercial use by the rest of the industry. The techniques go beyond simply obtaining pressures and samples, and shed light on rock and fluid properties such as: formation effective permeability, static reservoir temperature and reservoir fluid PVT properties (GOR, API gravity, molecular weight, viscosity, compressibility, saturation pressures and FVF). 

 These measurements can be made in real time downhole, without the fluid sample ever reaching the surface. In addition, analysis can be performed downhole to check for compositional grading or variable fluid types in the formation that could be masked during conventional production tests. Accuracy of these techniques is contingent on making measurements on a clean uncontaminated formation fluid sample. Shell has used analysis of near-infrared (NIR) spectrum data to consistently recover samples with low levels of contamination. With knowledge of pertinent PVT properties, permeability and pressures, flowrates can be predicted successfully from wireline tests and thus substitute for production tests. Wireline tests cannot substitute for production tests to estimate reservoir extent. 

  CORING AND ANALYSES

 Coring and analysis provide information directly obtained from formation sediments. 

 Core logger. The latest version of Geotek’s Multi-Sensor Core Logger (MSCL) provides a large number of measurements on core passed across the core logger at scan rates of up to 12 m/hr, Fig. 6.²⁶ Primary MSCL measurement sensors are: 

•  Ultrasonic transducers to measure compressional acoustic velocity
•  Gamma ray source and detector for measuring gamma ray attenuation, providing density/porosity information
•  Magnetic susceptibility sensor to determine the amount of magnetically susceptible material present
•  Electrical resistivity sensor to estimate core electrical resistivity using a non-contacting method.

Fig. 6. Latest version of Geotec’s MSCL Core Logger25 can record total and spectral natural gamma ray, non-contact resistivity, magnetic susceptibility, compressional acoustic velocity, core diameter, gamma ray attenuation (providing density/porosity values), core images and temperature (not shown).

 Two secondary measurement sensors enable measurements to be corrected for changes in core diameter and temperature: 

•  Core diameter is measured using a pair of displacement transducers connected to spring-loaded compressional wave transducers, enabling compressional wave velocity and density to be corrected for changes in core diameter. 
•  Temperature is measured using a platinum resistance thermometer, and can be used to correct for temperature changes that may occur during the logging process. It can also be used to make compressional acoustic velocity corrections. 

 Additional sensors such as total and spectral natural gamma ray and core imaging can be added to the system in a modular fashion.

  GENERAL

 Service company web sites can provide valuable references. NMR fluid properties are used in interpretation of results from NMR logging tools, lab core/fluid spectrometers and downhole fluid spectrometers. 

 Service company web sites. The three major well logging service companies have opened expanded web sites for their customers: Baker Hughes’ www.bakerhughesdirect.com, Halliburton’s www.myhalliburton.com, and Schlumberger’s www.connect.slb.com. These sites contain significant volumes of reference materials such as log interpretation charts, tool specs, technical papers, publications and educational/marketing material. Customers of these service companies can register online to set up an account and password for site access. 

 NMR fluid properties. Rice University has published results of experiments to characterize NMR response of light and heavy hydrocarbons at reservoir conditions.²⁷ With respect to light ends, it was found that linear correlations between relaxation time and viscosity/temperature and diffusivity for pure higher alkanes do not hold for pure ethane and propane. From the results, Rice has developed a mixing rule for multi-component gas mixtures which agree with experimental results. Light oils have identical T₁ and T₂ relaxation time distributions. However, heavy or asphaltene crude oils have different T₁ and T₂, with the ratio increasing with viscosity, asphaltene content and acquisition parameters. 

  ACKNOWLEDGMENT

 The author would like to thank Shell Technology Exploration and Production for permission to publish this article. And he gratefully appreciates technical details and insight provided by companies whose technology is discussed in this article.

  LITERATURE CITED

 1 Precision Drilling, Computalog High Resolution Micro Imager, Brochure CP-011.2/202.5M, 002.

 2 Lofts, J., et al, “A new micro-resistivity imaging device for use in oil-based mud,” Paper II, Transactions, SPWLA 43rd Annual Symposium, June 2002.

 3 Schlumberger, SlimXtreme, www.slb.com, October 2002.

 4 Heaton, N., et al., “Applications of a new-generation NMR wireline logging tool,” Paper SPE 77400, Transactions, SPE Annual Technical Conference and Exhibition, September 2002.

 5 Barber, T., et al., “An analytical method for producing multiarray induction logs that are free of dip effect,” Paper SPE 77713, Transactions, SPE Annual Technical Conference and Exhibition, September 2002.

 6 Benimeli, D., et al., “A new technique for faster resistivity measurements in cased holes,” Paper Y, Transactions, SPWLA 43rd Annual Symposium, June 2002.

 7 Kobayashi, G., et al., “Development of a practical EKL (electrokinetic logging) system,” Paper H, Transactions, SPWLA 43rd Annual Symposium, June 2002.

 8 Runia, J., “A next step in the wireless logging staircase: the (world first) successful trial of Through Bit Logging (TBL) in NAM, Dutch Petrophysical Society, http://www.tg.mp.tudelft.nl/ dps/p0102/DPS%201201.pdf, December 2001.

 9 Weisbeck, D., et al., “Case history of first use of extended-range EM MWD in offshore, underbalanced drilling,” Paper IADC/SPE 74461, IADC/SPE Drilling Conference, February 2002. 

 10 Schlumberger, E-Pulse, www.slb.com, December 2002. 

 11 Halliburton, MWD/LWD Services, www.myhalliburton.com, December 2002.

 12 GrantPrideco, Intellipipe, http://www.intellipipe.com, January 2003.

 13 Precision Drilling, “Precision Drilling Corporation launches revolutionary MWD system for deepwater and hostile environment logging,” http://www.precisiondrilling.com/investors/press.htm, September 2002.

 14 Morley, J., et al., “Field testing of a new nuclear magnetic resonance logging-while-drilling tool,” Paper SPE 77477, Transactions, SPE Annual Technical Conference and Exhibition, September 2002. 

 15 Tang, X., et al., “Shear-velocity measurement in the logging-while-drilling environment: Modeling and field evaluations,” Paper RR, Transactions, SPWLA 43rd Annual Symposium, June 2002.

 16 Market, J., et al., “LWD sonic logging in large diameter surface holes,” Paper 77480, Transactions, SPE Annual Technical Conference and Exhibition, September 2002.

 17 Mickael, M., et al., “Standoff compensation and hole size correction of a new LWD density/neutron logging system,” Paper SPE 77478, Transactions, SPE Annual Technical Conference and Exhibition, September 2002. 

 18 Baker Hughes INTEQ, ADVANTAGE Porosity Logging Service, www.bakerhughes.com,2001.

 19 Mack, S., et al., “The design, response and field test results of a new slim hole LWD multiple frequency resistivity propagation tool,” Paper SPE 77483, Transactions, SPE Annual Technical Conference and Exhibition, September 2002. 

 20 Ortenzi, L., et al., “An integrated caliper from neutron, density and ultrasonic azimuthal LWD data,” Paper SPE 77479, Transactions, SPE Annual Technical Conference and Exhibition, September 2002.

 21 Breviere, J., et al., “Gas chromatography-mass spectrometry (GCMS)-a new wellsite tool for continuous C1-C8 gas measurement in drilling mud-including original gas extractor and gas line concepts. First results and potential,” Paper J, Transactions, SPWLA 43rd Annual Symposium, June 2002. 

 22 Egermann, P., “A fast and direct method of permeability measurements on drill cuttings,” Paper SPE 77563, Transactions, SPE Annual Technical Conference and Exhibition, September 2002. 

 23 Precision Drilling, Computalog Flow Rate Evaluation-Formation testing, Brochure CP-021.5M,2002.

 24 Schlumberger, LFA Live Fluid Analyzer, www.slb.com, October 2002. 

 25 Hashem, M. and G. Ugueto, “Wireline formation testers: Uses beyond pressures and fluid samples – a viable replacement of production tests,” Paper XX, Transactions, SPWLA 43rd Annual Symposium, June 2002.

 26 Geotek Limited, Multi-Sensor Core Logger, www.geotek.co.uk, November 2000. 

 27 Zhang, Y., et al, “Oil and gas NMR properties: The light and heavy ends,” Paper HHH, Transactions, SPWLA 43rd Annual Symposium, June 2002.

THE AUTHORS
	David Patrick Murphy is Senior Staff Petrophysical Engineer for Shell Technology EP, Geoscience and Integrated Services, Field Studies team. He is also formation evaluation lecturer for the University of Houston graduate program in petroleum engineering. Mr. Murphy is a licensed professional engineer in Texas, Oklahoma, Louisiana and California.