bluuebunny/crossref_metadata_2025 huggingface dataset:
Insight Into Sulfate in High-Salinity Producers and Selection of Scale Inhibitor
Authors: Hamouda Aly A.
Published: December 2007

Several squeeze treatments in the Ekofisk field have tested various squeeze parameters, such as the overflush volume and the displacement means to maximize the scale squeeze life time, to prevent the formation of downhole scale cost-effectively. Scale may form when incompatible waters are mixed or the physicochemical parameters of the fluid (temperature, pressure, and chemical composition) change. This paper presents experience gained from treatment of high-salinity produced water on the Tor platform (2/4E) in the Norwegian sector of the North Sea, which has a total-dissolved-solids (TDS) content of about 200, 000 mg/L, compared with the typical average of about 70, 000 mg/L in some other Ekofisk fields. The high-salinity water requires extra care for predicting the scaling tendency, inhibiting scale formation, and preventing upsets in the downstream production facilities, like the oily-water treatment system. The high content of calcium and iron ions present in the produced water makes it even more difficult to treat. Because the scale inhibitor selected is nearly always a compromise, no one single laboratory test can determine the best scale inhibitor. This paper, however, discusses an approach for examining the sulfate-scale-inhibition efficiency with a reference to field experience for both down-hole and topside treatments.
Portable Piston Gas Prover for Field Calibration of Flowmeters
Authors: Ting V. C. , Haipine J. C.
Published: December 2007

This paper describes a newly developed, unique piston-gas-prover system and its advantages for on-site gas flowmeter calibration to improve measurement accuracy. The gas prover was tested at a natural gas flow calibration facility and at the Colorado Engineering Experimental Station Inc. (CEESI) to demonstrate its measurement performance, repeatability, and accuracy. The piston prover, with a design similar to that of an existing piston liquid prover, is bidirectional and uses a special piston to move gas through a calibrated section of known volume. It is constructed to perform on-site calibration of such flowmeters as gas turbine or orifice meters at operating conditions. The unit can easily be set up in series with a field meter for calibration. Less than 4 in. of water pressure drop is required to operate the piston through the calibrated section.

In the evaluation tests, a master turbine meter was calibrated on unprocessed natural gas. Test results show turbine pulse-count repeatability to be ±0.05%. The accuracy of the piston prover was also checked in series with an air calibration system at CEESI. This study showed that on-site calibration of a gas metering device can be conducted successfully with a portable piston-gas-prover system to improve flow measurement accuracy.
Cone Breakthrough Time for Horizontal Wells
Authors: Papatzacos Paul , Herring T. R. , Martinsen Rune , Skjaeveland S. M.
Published: December 2007

Recovery from an oil zone underlying a gas cap, overlying an aquifer, or sandwiched between gas and water can be improved by repressing the coning problem through horizontal-well drainage. Literature methods to predict coning behavior are limited to steady-state flow conditions and determination of the critical rate. The results in this paper are based on new semianalytical solutions for time development of a gas or water cone and of simultaneous gas and water cones in an anisotropic infinite reservoir with a horizontal well placed in the oil column. The solutions are derived by a moving-boundary method with gravity equilibrium assumed in the cones. For the gas-cone case, the semianalytical results are presented as a single dimensionless curve (time to breakthrough vs. rate) and as a simple analytical expression for dimensionless rates > ⅓. For the simultaneous gas- and water-cone case, the results are given in two dimensionless sets of curves: one for the optimum vertical well placement and one for the corresponding time to breakthrough, both as functions of rate with the density contrast as a parameter. The validity of the results has been extensively tested by a general numerical simulation model. Sample calculations with reservoir data from the Troll field and comparison with test data from the Helder field demonstrate how the theory can be used to estimate the time to cone breakthrough and its sensitivity to the uncertainties in reservoir parameters.
A Procedure to Shut Off High-Pressure Water Flows During Primary Cementing
Authors: Mitchell Richard K. , Salvo Gregory S.
Published: December 2007

Shutting off high-pressure water flows and achieving good cement bonding during primary cementing has long been a problem experienced by operators. Corrosion, casing leaks, excessive water production, and contamination of freshwater aquifers have led to costly workover operations throughout the oil field, especially within the Permian Basin. Remedial cementing jobs are often expensive and unsuccessful when primary cementing techniques fail. Therefore, a cost-effective, engineered method for cementing off these water flows was developed. This paper describes the cementing techniques, well-control criteria, well preparation, and data evaluation. Use of new and existing cementing practices provided the flexibility necessary to handle variable well conditions. Preplanning, evaluation of produced waters, compatibility studies, and proper slurry design helped to eliminate poor cement jobs in many areas. If one works closely with service and rig personnel, the procedure can be accomplished quite effectively, even on wells in which unexpected water flows are encountered. Examples of the procedure are documented with proven field results under variable conditions.
Two-Phase Compressibility Factors for Retrograde Gases
Authors: Rayes D. G. , Piper L. D. , McCain W. D. , Poston S. W.
Published: December 2007

The two-phase compressibility factor should be used in material-balance calculations for rich-gas-condensate systems. This paper presents a correlation for estimating this factor from field data. The correlation, which is based on 67 fluid-depletion studies with C7+ concentrations ≥4 mol% also applies to rich gases with large amounts of CO2, H2S, and N2. The correlation gives an average error of 3.66% but may result in larger errors for some rich gases.
Numerical Evaluation of Single-Slug, WAG, and Hybrid CO2 Injection Processes, Dollarhide Devonian Unit, Andrews County, Texas
Authors: Lin E. C. , Poole E. S.
Published: December 2007

This paper summarizes a numerical evaluation of the effectiveness of applying the conventional single-slug and water-alternating-gas (WAG) CO2 injection processes and an innovative hybrid process at the Dollarhide Devonian Unit, Andrews County, TX. The hybrid process consists of the injection of an initial slug of CO2 followed by WAG CO2 and water injection. The study shows that a properly designed hybrid injection process may have the potential to improve CO2 flood oil recovery.
Converting Wells in a Mature West Texas Field for CO2 Injection
Authors: Power Michael T. , Leicht Monte A. , Barnett Kerney L.
Published: December 2007

This paper deals with the planning, special equipment considerations, and operations necessary to convert 163 water injection wells to CO2 injectors that will function through at least the end of the century. The paper is divided into two parts: planning and engineering (wellhead, packer, and tubular selection) and procedural operation highlights (fishing, openhole cleanout, casing evaluation and repair, stimulation, liner running, wellhead replacement, packer setting, and the reworking of tubulars). A case-history approach was used to analyze the success or failure of the various methods and techniques used in this project. All 165 wells were converted as of March 29, 1989.
CO2 -Foam Fracturing With Methanol Successfully Stimulates Canyon Gas Sand
Authors: Craft J. R. , Waddell S. P. , McFatridge D. G.
Published: December 2007

Successful stimulation using CO2 foam with methanol has revived the economically marginal Canyon gas-sand reservoir of Sterling County, TX. Field experience in the Conger (Penn) field demonstrated that CO2 foam (1) lessened the water required in the fluid and (2) provided a gas assist to help remove water and lower interfacial tension (IFT). The low pH of the fluid, combined with additional clay stabilization, iron control, and enhanced water recovery additives, proved helpful in initial well response and subsequent performances. Since the CO2-foam fracture treatments were administered, production from Sterling County Canyon gas sands met or surpassed initial rates, even though formation pressure in the field declined 33.2%.

Stimulation is essential for commercial production in these sands. However, water blockage, caused by stimulation, was encountered in designing an effective completion technique for a tight formation with reduced bottomhole pressure (BHP). Production in tight, low-pressure gas wells can be completely blocked if formation pressure does not exceed the capillary pressure increase caused by injected fracture fluid. Original stimulation techniques consisted mainly of gelled-water fracture treatments containing 65, 000 lbm of 20/40-mesh sand with a maximum concentration of 2½ lbm/gal. In many cases, several weeks of swabbing were required to ensure continuous flow. After the fracture treatments, about 40% water recovery was realized throughout the field. This paper discusses CO2-foam fracture treatments and job design and presents case histories from several Conger (Penn) field CO2-foam fracture treatments.
Effect of Solvent Viscosity on Miscible Flooding
Authors: O'Steen B. L. , Huang E. T. S.
Published: December 2007

This paper presents experimental results for tertiary miscible displacements in strongly water-wet Berea cores. Floods with both continuous solvent and simultaneous solvent/water injection were studied at ambient conditions. Three solvent/oil systems are compared: heptane (0.4 cp) displacing mineral oil (6 cp), tagged heptane displacing heptane, and tagged mineral oil displacing an equal-viscosity mineral oil (6 cp). Saturation profiles from microwave absorption measurements and production histories are presented. The experimental results show that the manner in which residual oil is mobilized and propagated depends on solvent/water injection ratio, oleic/water-phase viscosity ratio, and fractional-flow hysteresis.
A Mathematical Model of In-Situ Gelation of Polyacrylamide by a Redox Process
Authors: Todd B. J. , Willhite G. P. , Green D. W.
Published: December 2007

Recent displacement data conclusively show that the initial permeability reduction during in-situ gelation processes does not result from a bulk gelation of the injected fluid. This paper presents a filtration-based model that correctly accounts for all physical phenomena occurring during in-situ gelation displacements.
Use of Pulsed-Neutron Capture Logs To Identiffy Steam Breakthrough
Authors: Masse P. J. , Gosney T. C. , Long D. L.
Published: December 2007

Identification of steam-breakthrough zones in a stacked sand/shale sequence with variable lateral continuity is difficult. Such identification, however, would allow the modification of field operations to enhance recovery through improved vertical sweep and heat injection. Twenty pulsed-neutron capture (PNC) logs were run to identify the steam-breakthrough zone(s) in a seven-pattern area of Mobil's Middle Expansion (MIDX) Steamflood Project in the South Belridge field. These PNC data were combined with data from recent replacement wells and a detailed geologic analysis. Evaluation of this combined information allowed identification of potential steam-breakthrough zone(s), and operations were modified to reduce and eliminate steam breakthrough.
Removal of Oil, Grease, and Suspended Solids From Produced Water With Ceramic Crossflow Microfiltration
Authors: Chen A. S. C. , Flynn J. T. , Cook R. G. , Casaday A. L.
Published: December 2007

Results of studies of two onshore and two offshore pilot plants that use ceramic crossflow microfiltration (CCFM) to separate oil, grease, and suspended solids from produced water are discussed. The method is capable of producing permeate quality with <5 mg/L (detection limit) of dispersed oil and grease and <1 mg/L of suspended solids.
OILMUD: A Microcomputer Program for Predicting Oil-Based Mud Densities and Static Pressures
Authors: Peters E. J. , Chenevert M. E. , Alhamadah A. M.
Published: December 2007

OILMUD* is a program for predicting the densities and hydrostatic pressures in oil-based mud columns at high pressures and temperatures. The program uses multiple-linear-regression analysis on experimental data to calculate the densities and static pres sures for diesel-oil-based mud and for four less-toxic mineral-oil-based muds. This menu-driven, easy-to-use program runs on an IBM personal computer and compatible systems. It can be used by a drilling engineer to estimate downhole densities and pressures during drilling on the basis of surface measurements or to plan the mud program for a new well.
Heat and Mass Transport in Steam-Drive Processes
Authors: Mandl G. , Volek C.W.
Published: December 2007

Steam-injection tests in the field have shown that heat transport into theoil/water region, ahead of the steam zone, may have a significant effect on theproduction process. Earlier theoretical work on reservoir heating by hot-fluidinjection can be used to describe the growth of the steam zone, but only ifheat transport from steam zone into oil/water region is neglected. It thereforebecame necessary to re-examine and extend the earlier theory.

It was found that this theory ceases to be consistent with the physicalmodel of the process at a certain critical time, which depends on reservoirthickness, temperature, and quality of the steam. The critical time marks animportant change in the heat flow across the condensation front:

(Equation)

On the basis of the new equation, an approximate description for the steam-zonegrowth is developed by making use of upper and lower bounds for the exactsolution of the problem. The boundary conditions for heat and mass flow insidethe oil/water region are established, and a simple method of determining thesaturation at the downstream side of the condensation front is presented.

Experimental results show that the theory gives an accurate description ofsteam-zone expansion before the critical time. At times near critical time, andalso after critical time, experimental data show theoretical steam-zone volumesto be high, Even so, the accuracy of the calculated steam-zone volumes issufficient for practical purposes.

Theory of Steam-Zone Growth

Introduction

The engineering evaluation of steam-drive processes is based mainly on amathematical description of reservoir heating by hot fluid injection presentedseveral years ago by Marx and Langenheim. This theory can be used to determinethe growth of the steam zone, provided the flow of heat from the steam zoneinto the liquid zone ahead of the condensation front (Fig. 1) is neglected.

Since we must expect, however, that heat transport into and inside theliquid region (the region between condensation front and production wells) willaffect both the water/oil flow and the growth of the steam zone, it isnecessary to re-examine and to generalize the Marx and Langenheim theory asapplied to steam drive, which will hereafter be termed the "old"theory. Observations made in several field tests emphasize the need to studythe heat flow across the condensation front (CF). On several occasions it wasdiscovered that heat was transported in the liquid zone far ahead of theadvancing CF, resulting in an early breakthrough of warm water.
Application of X-Ray CT Scanning To Determine Gas/Water Relative Permeabilities
Authors: MacAllister Donald J. , Miller Kenneth C. , Graham Stephan K. , Yang Chung-Tien
Published: December 2007

Three-phase oil/water and gas/water experiments were performed to investigate the dependence of relative permeability on wettability. Quantitative fluid saturations were determined with an X-ray computer-aided tomography (CT) scanner. Oil, water, and gas distributions generated in 3D were found, in some cases, to be highly nonuniform and dependent on experimental conditions. Results indicate that some traditional thinking about measuring relative permeability may be in error and merits further investigation.
Field Examples of Electrical Resistivity Changes During Steamflooding
Authors: Mansure A. J. , Meldau R. F. , Weyland H. V.
Published: December 2007

An essential part of using electrical geodiagnostic techniques to map thermal recovery processes is understanding the relationship between the process and the formation resistivity. This paper shows how the relationships used to interpret electrical well logs can be used to understand steamflood resistivity changes. Examples are presented of data from steamfloods in fields with different reservoir characteristics. Included is a typical heavy-oil steamflood (Kern River field) and a steamflood where fresh water is used for the steam generator feedwater (Elk Hills field). Because of differences in reservoir characteristics, changes in resistivity vary from reservoir to reservoir. The information presented include well logs taken before and after steamflooding and petrophysical measurements sufficient to determine the factors that controlled the resistivity changes in each field.
Shear-Wave Porosity Logging in Sands
Authors: Medlin W. L. , Alhllall K. A.
Published: December 2007

We investigated the correlation between porosity and shear-wave velocity from acoustic logs in cored sand intervals. Data were collected in 13 wells with >5, 000 ft of core representing worldwide locations. Core porosities ranged from 0.02 to 0.38 at depths between 2, 400 and 11, 600 ft. Shear-wave velocities were obtained with Mobil's dipole logging tool, and porosities were obtained from standard core analysis. Our correlation data were obtained by averaging porosities and shear-wave travel times over intervals ≥4 ft, the approximate resolution of our shear-wave tool. We excluded intervals in which the porosity or shear-wave travel time varied widely. We find a linear correlation between porosity and shear-wave travel time, provided we exclude clay-bonded sands such as those found along the U.S. gulf coast. The corelation coefficient is 0.91, about the same as that for compressional-wave data in the same intervals. These results are consistent with shear-wave data reported for ultrasonic laboratory measurements. Further comparison of our data with ultrasonic measurements shows evidence of dispersion effects. The velocity of shear waves is more sensitive than that of compressional waves to porosity and is insensitive to gas effects. Also, shear-wave logs, unlike compressional-wave logs, can be obtained through casing with the dipole tool, regardless of cement-bond quality. These advantages make shear-wave logging attractive for evaluating porosity in old wells where porosity logs were never run or were of poor quality. The method fails in slow formations because the shear-wave arrival falls behind a strong tube-wave arrival generated by the bender tool in cased wells. Other applications of shear-wave logging also are discussed.
Characterization of Core-Scale Heterogeneities Using Laboratory Pressure Transients
Authors: Kamath Jalram , Boyer R. E. , Nakagawa F. M.
Published: December 2007

We constructed a novel, state-of-the-art laboratory setup that captures several hundred pressure readings per second to study the response of cores to pressure disturbances. We used our new experimental setup to measure accurately and rapidly permeability of homogeneous cores, matrix and fractured properties of a fractured rock, and the individual segment properties of a butted core sample.
Effects of Propagating Fractures on Pressure-Transient Injection and Falloff Data
Authors: Larsen Leif , Bratvold Reidar B.
Published: December 2007

Methods are presented to generate isothermal and nonisothermal pressure-transient data for injection and falloff periods affected by a propagating or closing fracture. Both changing and stationary fracture properties can be handled along with stationary and moving temperature and saturation profiles (which are based on Buckley-Leverett-type computations). The approach is based on general analytical solutions for the Laplace-transformed pressure in multizone elliptic systems under constant-rate production. It extends earlier results on flow in single- and two-zone elliptic systems. Rate distributions along fractures and rate transients when the wellbore pressure is kept constant can also be obtained.
Evaluation of Fracture Asymmetry of Finite-Conductivity Fractured Wells
Authors: Rodríguez Fernando , Cinco-Ley Heber , Samaniego-V. Fernando
Published: December 2007

This paper presents a graphical technique to evaluate asymmetry of hydraulically fractured wells. This technique is based on a new analytical solution for the pressure behavior of a finite-conductivity, asymmetrically fractured well during the pseudolinear flow period and the known bilinear flow solution. A semianalytical solution for transient flow toward finite-conductivity, asymmetrically fractured wells producing at constant rate is also presented. This solution was used with the analytical solution to analyze the pseudolinear flow pressure behavior.

An expression relating dimensionless fracture conductivity, CfD, and asymmetry factor, a, with a parameter calculated from analysis of well-test data, βa, was developed by combining the pseudolinear and bilinear flow solutions; a graph of a vs. βa with CfD as a parameter is then constructed. The parameters βa and CfD are calculated as follows: βa=0.309 mbf2/(bLfmLf) and CfD=2.944 mLfm/mbf2, with mbf as the slope of the bilinear Δp-vs.-t¼ straight line, mLf and bLf as the slope and intercept of the pseudolinear Δp-vs.-t½ straight line, respectively, and m as the slope of the semilog Δp-vs.-log t straight line obtained during the pseudoradial flow period. Correlations developed apply indistinctly to oil and gas wells. Published field data were reanalyzed with the technique presented here and asymmetry was detected.
Impact of Fluid Displacement Effects on Log-Inject-Log Tests
Authors: Pathak Prabodh
Published: December 2007

This paper evaluates the accuracy of log-inject-log (LIL) tests, analyzes the fluid-displacement behavior around the wellbore, discusses the transient behavior of pulsed-neutron-capture (PNC) logs before steady state is reached, and establishes the conditions under which LIL tests work best. This paper shows that both completion and reservoir properties affect the accuracy of LIL tests.
An Improved Method To Predict Future IPR Curves
Authors: Klins M. A. , Clark J. W.
Published: December 2007

This paper presents a significantly improved yet simple method to predict future oilwell deliverability and inflow performance relationship (IPR) curves. For the 21 reservoirs studied, current empirical techniques overpredicted future performance by 117%, while the new approach reduced the average error to only 9%. This new method, when coupled with nodal analysis, could affect equipment sizing, investment planning, and property sales economics significantly because it provides more realistic predictions.
Compositional Simulation and Performance Analysis of the Prudhoe Bay Miscible Gas Project
Authors: McGuire P. L. , Moritz A. L.
Published: December 2007

A pseudocomponent method was developed to use fully compositional reservoir simulation results in the interpretation of separator gas samples. This interpretation provided insight into actual EOR performance by quantifying solvent breakthrough and production rates. Field examples of various reservoir mechanisms affecting the efficiency of Prudhoe Bay EOR are examined.
Activities of the API Committee on Standardization of Tubular Goods
Authors: Bartlett L. E. , Kohut Q. B. , Dabkowski D. S. , McGill Randy
Published: December 2007

This paper outlines the organization of API Committee 5, the Committee on Standardization of Tubular Goods, and discusses the methods used in the standardization process. It also presents several examples of recent changes in standards and current activities in research and regular committee business.
Characterization of the Evolution of Cementing Materials After Aging Under Severe Bottomhole Conditions
Authors: Degouy Didier , Martin Madeleine
Published: December 2007

This paper describes a characterization of the evolution of some cementing materials that are currently used (cements) or are potentially usable (thermosetting resins) after they have been cured and aged under high pressure and high temperature. Specially designed testing equipment to simulate downhole conditions is shown. Variations in material characteristics were studied with standard methods (compressive strength and water permeability measurements) and physical analysis methods [scanner tomography, electronic microprobe, and scanning electronic microscope (SEM)]. The results show how aging influences the relationships between local structure and composition of materials and macroscopic properties.
Completion and Testing of the 242°C BHST Well Dinjevac-1
Authors: Uroda Pavle , Rogoz Luka , Sinovcevic Zeljko , Kovac Darko
Published: December 2007

Well Dinjevac-1 (Di-1), located 120 km northeast of Zagreb, Croatia, was drilled in 1982 to a total depth (TD) of 5502 m. Mud logs, electrical logs, and drillstem tests (DST' s) in the Miocene section of the Pannonian basin indicated hydrocarbon saturation, extremely high temperatures, and relatively high pressures. These Miocene sediments are characterized as compact, low-permeability sandstones. In 1988, the abandoned cement plugs were drilled out and a bottomhole static temperature (BHST) of 242°C was measured. Temperature was the critical factor in the design of the completion and testing method. In spite of some minor quality-control and operational problems, five zones were tested successfully, providing all the relevant information about the reservoirs and the formation fluids. The operation incorporated a one-trip, hydraulically set, high-temperature, high-differential packer with a polished-bore receptacle and tubing-conveyed perforating guns with large, deep-penetrating charges. This paper describes the completion and testing objectives, considerations, operations, and results under probably the hottest completion conditions ever encountered.
Effects of Equipment Layout and Venting Geometry on the Consequences of Gas Explosions
Authors: Simmonds S. A. , Tam V. H. Y.
Published: December 2007

The layout of equipment and vents on offshore platforms determines the consequences of gas explosions. Computer simulations of gas explosions inside offshore modules illustrate this concept. Simple methods (e.g., extension of the Cubbage and Simmonds model) only use blockage parameters and are not suitable for applications to offshore platforms.
Improving Quality Control of Directional Survey Data With Continuous Inertial Navigation
Authors: Stephenson Mark A. , Wilson Harry
Published: December 2007

Continuous inertial navigation systems (INS) for high-accuracy surveying canbe used to enhance quality control of survey data significantly. This papershows how to use the unique capabilities of these systems while retainingcompatibility with widely accepted quality-control methods. A system now in usein the North Sea provides concrete examples.
Independent Load Support in an 18¾-in., 15, 000-psi Subsea Wellhead
Authors: Cowan W. S.
Published: December 2007

Previous-generation subsea wellhead equipment was conceived as an extension of well-known surface wellhead equipment. Contemporary performance criteria for subsea wellhead equipment require new technology from the designer/manufacturer. This paper describes the role of a single design concept, independent load support, in addressing these criteria and illustrates the resulting configuration of a severe-service subsea wellhead system.
Geostatistical Modeling of Gridblock Permeabilities for 3D Reservoir Simulators
Authors: Dimitrakopoulos Roussos , Desbarats A. J.
Published: December 2007

A geostatistical method is presented to determine the absolute horizontal and vertical effective permeabilities at the reservoir block scale from core support-scale values required for 3D reservoir flow simulations. The key element of the geostatistical model is the definition of block support-scale permeabilities as the spatial power average of core-support values over the volume of a reservoir gridblock. Block support-scale permeabilities are then found to be a function of the permeability variogram, the averaging volume, and a power-averaging constant, which is derived separately for horizontal and vertical flow with a numerical approach. The application of the proposed method requires that core-support values be available within each reservoir block. These values are generated with the technique of conditional simulation. This technique provides simulated values reproducing the actual core data at sampled locations and their statistical properties. The approach developed for the determination of permeability input to full-field simulators is demonstrated by an application to the Crystal Viking field "H" pool in Alberta.
An Efficient Algorithm for Computation of Well Responses in Commingled Reservoirs
Authors: Spath Jeffrey B. , Ozkan Erdal , Raghavan Rajagopal
Published: December 2007

An algorithm to compute pressure distributions in commingled reservoirs that are produced by complex, completion systems is described. We show that single-layer solutions for systems of interest can be readily combined to obtain pressure distributions in commingled reservoirs for combinations of rock types. Completion schemes and outer-boundary conditions for each layer may be different. Theoretical claims are substantiated by considering example applications.
Gas-Lift Technology Applied to Dewatering of Coalbed Methane Wells in the Black Warrior Basin
Authors: Johnson Kenneth J. , Coats Alan , Marinello Stephen A.
Published: December 2007

Coalbed methane (CBM) wells usually are dewatered with sucker rod or progressive cavity pumps to reduce wellbore water levels, although not without problems. This paper describes high-volume artificial-lift technology that incorporates specifically designed gas-lift methods to dewater Black Warrior CBM wells. Gas lift provides improved well maintenance and production optimization by the use of conventional wireline service methods.
Fibrous Illite Controls Productivity in Frontier Gas Sandstones, Moxa Arch, Wyoming
Authors: Luffel Donald L. , Herrington Karen L. , Harrison Charles W.
Published: December 2007

Core, log, and well-test analyses from two wells recently completed in the Frontier sandstone in the Moxa Arch area of Wyoming revealed that fibrous illite severely reduced gas productivity. In this study area, presence of fibrous illite currently cannot be predicted and effects can be recognized only through laboratory tests on preserved cores.
Applications of Oxygen Activation for Injection and Production Profiling in the Kuparuk River Field
Authors: Scott Hugh D. , Pearson C. Mark , Renke Steve M. , McKeon Donald C. , Meisenhelder Jeff P.
Published: December 2007

A new time-dependent method of oxygen-activation logging, now being used in the Kuparuk River field on the North Slope of Alaska, provides critical data for waterflood performance evaluation, assessment of ultimate recovery, and evaluation of potential for infill drilling and EOR projects without the use of radioactive tracer materials.
Reservoir Description by Well-Test Analysis by Use of Cyclic Flow-Rate Variation
Authors: Rosa A. J. , Horne R. N.
Published: December 2007

This work investigates the possibility of characterizing the permeability distribution in areally heterogeneous reservoirs through the interpretation of pressure response to cyclic flow-rate variations.

We formulated a mathematical model for the pressure behavior caused by sinusoidal flow rates in reservoirs with continuously and smoothly varying radial-permeability distributions. The solution is obtained by the application of a regular perturbation analysis, and a correlation between the radius of cyclic influence and the frequency of a sinusoidal flow rate is developed. The analytical perturbation solution allows a qualitative assessment of the effects of areal reservoir heterogeneities on the pressure response either at the active well or at an observation well.

Because the perturbation method results in only an approximate solution, we propose a quantitative method to describe the permeability distribution based on the fully correct multicomposite radial reservoir model. The permeability in each zone of the equivalent reservoir is estimated by using a nonlinear regression procedure.

The frequency correlation may be used to design pulse-test flowrate schedules so that an optimum result can be achieved in terms of parameter estimation. We investigated several factors affecting the quality and the uncertainty in the estimated permeability distribution, along with examples including a variety of geometric and permeability distribution configurations. These factors include the type of test (constant-rate drawdown or pulse test) and reservoir configuration. In particular, we found the frequency of flow-rate changes and the point in the system at which to measure and interpret the pressure data to be important.
A Multiple-Depth-of-Investigation Electromagnetic Wave Resistivity Sensor: Theory, Experiment, and Field Test Results
Authors: Bittar Michael S. , Rodney Paul F. , Mack Steve G. , Bartel Roger P.
Published: December 2007

This paper presents theoretical, experimental, and field results for a multiple-depth-of-investigation, measurement-while-drilling (MWD), electromagnetic wave resistivity (EW) sensor. The sensor has four different transmitter/receiver antenna spacings with a phase difference and amplitude ratio at each spacing. The resultant logs provide information on the resistivity radial profile and an accurate Rt evaluation. Comparisons of field logs with wireline logs and with theoretical and experimental results show that this type of sensor can offer an extra-shallow, shallow, medium, and deep investigation depth under most logging conditions.
Use of Succinoglycan Biopolymer for Gravel Packing
Authors: Sanz Guillermo Pastor , Gunningham Michael C. , Lau Hon Chung , Samuel Allan J.
Published: December 2007

This paper presents the results of laboratory experiments and field trials on a polysaccharide biopolymer, succinoglycan, for use in gravel packing. This biopolymer causes minimal formation damage and has unique rheological properties that combine high shear-thinning behavior with temperature-induced viscosity breakback; thus, it can be used without breakers.
Reservoir Description Through Pulse Testing in a Mature Field
Authors: Braisted David M. , Spengler Richard M. , Youie Ralph A.
Published: December 2007

Pulse testing was used in the Fortescue field to clarify reservoir geometries and fluid communication pathways. The high communication levels demonstrated in the test data required a nonstandard analysis of the pressure responses. In addition, proper attention to test planning, data acquisition, and data processing allowed valuable insights into reservoir limits. Most of the structural implications derived from the pulse tests have been supported subsequently by a recent 3D seismic survey of the area. The results and insights gained from these tests are being incorporated into a full-field simulation model of the Fortescue field, which is an integral part of a continuing depletion field study.
Complexities in the Analysis of Pressure-Transient Response in Faulted Naturally Fractured Reservoirs
Authors: Khachatoorian Robert , Ershaghi Iraj , Shikari Yusuf
Published: December 2007

Pressure-transient modeling for bulk testing of naturally fractured systems requires consideration of the effect of no-flow barriers on the pressure response. This study shows that, depending on the distance to the fault and under certain reservoir conditions, the presence of a linear barrier can affect the duration and the nature of the transition interval and estimation of interporosity parameters and reservoir transmissivities.

Typical semilog plots for naturally fractured reservoirs (NFR's) may not be observed unless the fault is at a large distance away from the test well. In most cases, a double reflection is predicted—i.e., fracture response and the total system response. A correlation is developed to estimate the distance to the fault from the early fault reflection data. A critical wellbore storage constant can also be identified above which the detection of the fault becomes impractical.
Application of Risk Analysis Methods to Subsurface Well Collisions
Authors: Thorogood J. L. , Hogg T. W. , Williamson H. S.
Published: December 2007

Subsurface separation criteria have evolved empirically over the years. They still are based largely on untested assumptions about safety factors, comfort values, and survey tool accuracy. A mathematical analysis of the probability of collision combined with a decision tree describing the consequences provides a method of risk evaluation. The mathematics can be simplified under certain special assumptions, allowing key features of the problem to be illustrated. A flow chart of the directional-drilling tolerance setting procedure shows how the methods described can be used in daily well-planning operations.
Fatigue Testing of Drillpipe
Authors: Grondin G. Y. , Kulak G. L.
Published: December 2007

Twenty-nine tests in air and 27 tests in a 3.5% NaCl solution were conducted to test the fatigue strength of Grade E 4.5-in.-OD, 16.6-lbm/ft [114-mm-OD, 24.7-kg/m] drillpipe. The effects of stress range, mean stress, corrosion, and upset geometry were tested on the drillpipe body alone and on specimens that included the tool joint, upset, and drillpipe body. Stress range and mean stress effects were significant in noncorrosive and corrosive environments. The effect of upset geometry was minimal on an external upset compared with that on an internal/external upset. Among the specimens that failed, grinding marks on the drillpipe surface, which occurred during inspection at the mill, caused failure of about 60% of the specimens. Grinding created a notch effect and induced a detrimental residual-stress pattern on the pipe surface, which decreased drillpipe fatigue life. API guidelines for cumulative fatigue of Range 2 drillpipe were evaluated in light of these experimental test results and were found to be unsafe for drilling in noncorrosive conditions and possibly too conservative for corrosive conditions.
Azimuthal Resistivity Imaging: A New-Generation Laterolog
Authors: Davies D. H. , Faivre Ollivier , Gounot M- T. , Seeman Bruno , Trouiller J- C. , Benimeli Dominique , Ferreira Antonio , Pittman D. J. , Randrianavony Mahaly , Smits J. W. , Anderson B. I. , Lovell John
Published: December 2007

We describe a new-generation laterolog tool, the azimuthal resistivity imager (ARI). The tool makes deep azimuthal resistivity measurements around the borehole with higher vertical resolution than the Dual Laterolog (DLL). Twelve azimuthal electrodes are incorporated into the DLL electrode array to provide 12 deep, oriented resistivity measurements while retaining the standard deep and shallow laterolog measurements. To allow full correction of the azimuthal resistivities for borehole effect, a shallow auxiliary measurement is incorporated on the azimuthal array. Although the full-coverage azimuthal resistivity image has much lower spatial resolution than borehole microelectrical images, it complements these because of its lower sensitivity to shallow features. Evaluation of heterogeneous and fractured formations, and computation of fracture dip are applications of the tool's imaging capabilities and are discussed and illustrated with log examples. Other log examples cover thin-bed response and corrections for Groningen and borehole effects, including that for eccentering of the tool in the borehole.
Pressure Behavior of Laterally Composite Reservoirs
Authors: Kuchuk F. J. , Habashy Tarek
Published: December 2007

This paper presents a new general method for solving the pressure diffusion equation in laterally composite reservoirs, where rock and fluid properties may change laterally as a function of y in the x − y plane. Composite systems can be encountered as a result of many different types of depositional and tectonic processes. For example, meandering point bar reservoirs may be approximated as lateral composite systems. Reservoirs with edgewater encroachment are another example of such systems.

The new solution method presented is based on the reflection-transmission concept of electromagnetics to solve fluid-flow problems in 3D nonhomogeneous reservoirs, where heterogeneity is in only one (y) direction. A general Green's function for a point source in 3D laterally composite systems is developed by using the reflection-transmission method. The solutions in the Laplace transform domain are then developed from the Green's function for the pressure behavior of specific composite reservoirs. The solution method can also be applied to many different types of wells, such as vertical, fractured, and horizontal in composite reservoirs.

The pressure behavior of a few well-known laterally composite systems are investigated. It is shown that a network of partially communicating faults and fractures in porous medium can be modeled as composite systems. It is also shown that the existing solutions for a partially communicating fault are not valid when the fault permeability is substantially larger than the formation permeability. The derivative plots are presented for selected faulted, fractured, channel, and composite reservoirs as diagnostic tools for well-test interpretation.

It is also shown that if the composite system's permeability varies moderately in the x or y direction, it exhibits a homogeneous system behavior. However, it does not yield the system's average permeability. Furthermore, the composite systems with distributed low-permeability zones behave as if the system has many two no-flow boundaries.
Modeling Changing Storage During a Shut-In Test
Authors: Hasan A. R. , Kabir C. S.
Published: December 2007

Phase redistribution has been observed to occur in oil, gas, and steam-injection wells during a shut-in test. Two empirical approaches—involving exponential and error functions—are currently available to analyze field data. However, these methods do not have any mechanistic basis and may lead to erroneous estimates of reservoir parameters, such as skin. More importantly, these methods cannot be used in a forward mode to predict the reservoir and/or well conditions that would cause changing wellbore storage situations. Such predictions are desirable for deciding on the need for expensive downhole shut-in or flow measurement. Phase redistribution is a consequence of the higher relative velocity of the gas phase in a well's production string after shut-in at the surface. The resulting segregation of phases caused by buoyancy of the gas phase may cause wellbore pressure buildup to be quite different from normally expected response before the onset of the middle-time period. Under one scenario, the bubbles may segregate rapidly to the top of the wellbore leading to an increasing storage situation. Conversely, the bubbles may travel slowly without reaching the top to precipitate a decreasing storage situation. In either event, the commonly used constant-storage model cannot be used for test interpretation. A mechanistic approach, based on the physics of migration of a swarm of bubbles, is developed that explains the changing storage phenomenon by incorporating continually decreasing afterflow from the reservoir after shut-in, the variation of void distribution within the wellbore with depth and time, and the combined effect of afterflow and bubble migration on the wellhead and bottomhole pressures (BHP's). The model is used to develop a simulator, and a few cases are examined to illustrate the simulator's capabilities.
Differentiation of Hydrocarbon Type in Gulf of Mexico Clastic Reservoirs by Inelastic Pulsed Neutron Capture Data
Authors: Scheibal J. R. , Weiland J. L. , Worrell J. M. , Bayer J. E.
Published: December 2007

This paper outlines our results and experiences in hydrocarbon typing Pliocene/Pleistocene turbidite sand reservoirs in two Shell Offshore Inc. Gulf of Mexico fields. While differentiation of hydrocarbon type was important in identifying completion targets for Produce While Drilling (PWD) operations, hydrocarbon typing was extremely difficult. This hydrocarbon typing problem was a result of (1) compositional make-up of both oil and gas, (2) high reservoir pressures encountered (up to 10,000 psi), (3) geological complexity (structural and stratigraphic), (4) the use of oil based mud to drill many wells, and (5) complex mineralogical makeup of the sands.

Because openhole data and routine pulsed neutron capture (PNC) data were often inconclusive, secondary curves presented on PNC logs were extensively examined. The PNC ratio of inelastic short to long spaced data (RIN) was found to be an extremely diagnostic gas indicator, and has been used to further refine and calibrate petrophysical evaluations. These refined evaluations were then incorporated into redesigning a new completion strategy for each well examined.
EOS Modeling and Experimental Observations of Three-Hydrocarbon-Phase Equilibria
Authors: Godbole S. P. , Thele K. J. , Reinbold E. W.
Published: December 2007

An equation-of-state (EOS) fluid characterization has been developed to model three-hydrocarbon-phase equilibria as part of the enriched-gas EOR research program for the Kuparuk hydrocarbon miscible flood on the Alaskan North Slope. Laboratory experiments with Kuparuk reservoir oils and miscible injectants have identified an apparent second equilibrium liquid that is heavier than the original oil and macroscopically reversible. A three-phase EOS fluid characterization was developed to match both two- and three-phase experimental data by use of a modified Peng-Robinson EOS. Experimental observations identified a relationship between the third phase and the oil's pentane-insoluble fraction. The characterization uses a total of 16 components, with the heaviest two approximating the pentane-soluble and pentane-insoluble portions of the C36+ fraction. The properties of these heavy pseudocomponents control the development and behavior of the heavy phase. The EOS fluid characterization was used to study three-phase, enriched-gas-drive displacement mechanisms. For the Kuparuk fluids, a condensing/vaporizing displacement mechanism is predicted in a three-phase environment. Reservoir-condition micromodel displacements were conducted to observe the phase-behavior and displacement mechanisms during Kuparuk enriched-gas displacements. Micromodel observations are consistent with a near-miscible condensing/vaporizing mechanism and qualitatively agree with EOS predictions.