bluuebunny/crossref_metadata_2025 huggingface dataset:
Improvements in Physical-Property Models Used in Micellar/Polymer Flooding
Authors: Camifleri D. , Fil A. , Pope G. A. , Rouse B. A. , Sepehrnoori K.
Published: December 2007

This is one of three companion papers describing a micellar/polymer or chemical flood simulator and comparing its results to experimental data. Various physical-property models required by chemical flood simulators have been improved and others developed. The most significant development is the use of pseudophases to model phase behavior. The method allows representation of four pseudocomponents. This is made possible by assuming that alcohol is distributed among the other three pseudocomponents, thus forming three pseudophases that are assumed to be in thermodynamic equilibrium. Another improvement relates to the ion-exchange model. Cations are considered to exchange with both surfactant micelles and clays. The model assumes the exchange to be entirely a result of electrostatic association. A model for treating physical dispersion coefficients as a function of saturations has been added. The model is based on experimental evidence and is purely empirical.
Determination of Interstitial Chloride in Shales and Consolidated Rocks by a Precision Leaching Technique
Authors: Manheim F. T. , Peck E. E. , Lane C. M.
Published: December 2007

We have devised a technique for determining chloride in interstitial water of consolidated rocks. Samples of rocks ranging from 5 to 10 g are crushed and sieved under controlled conditions and then ground with distilled water to submicron size in a closed mechanical mill. After ultra-centrifugation, chloride content is determined by coulo-metric titration. The chloride concentrations and total pore-water concentrations, obtained earlier from the same samples by low-temperature vacuum desiccation, are used to arrive at the "original" pore-water chloride concentrations by a simple iteration procedure.

Interstitial chlorinity results obtained from Cretaceous and Jurassic strata in the Gulf of Mexico coastal areas ranged from 20 to 100 g/kg CI with reproducibility approaching ±1 %. We have also applied the technique to igneous and metamorphic bedrocks as well as ocean basalts containing 1 % water or less. Chloride values ranging from 6.7 to 20 g/kg with a reproducibility of about 5% were obtained.
Cerro Prieto Case History: Use of Wireline Logs to Characterize a Geothermal Reservoir
Authors: Halfman S. E. , Lippmann M. J. , Gilreath J. A.
Published: December 2007

The Cerro Prieto geothermal field is located in Baja California, Mexico, in the Salton Trough–a rift basin filled mainly with Colorado River sediments. A comprehensive wireline log analysis was undertaken as part of a multidisciplinary study of this geothermal system. It established (1) the physical properties of the various sedimentary units; (2) the depositional environment and hydrothermal alteration of the units; (3) the location, attitude, and displacement of faults; and (4) the subsurface circulation of the geothermal fluids.

Presented are the methodology that was used and the application of the results to further exploration and development of this high-temperature geothermal resource.
A Laboratory Study of Wilmington Tar Zone CO2 Injection Project
Authors: Sankur V. , Creek J. L. , DiJulio S. S. , Emanuel A. S.
Published: December 2007

We conducted a laboratory study of heavy-oil recovery by CO2 injection to support-the Wilmington, CA tar zone CO2 injection project operated by Long Beach Oil Development Co. The study comprised (1) phase behavior of Wilmington tar zone reservoir oil and CO2, and (2) phase behavior of the oil and the refinery gas used for the field project, (3) viscosity measurements of oil/gas mixtures, (4) reservoir- condition displacements of oil by CO2 and by refinery gas, (5) equation-of-state characterization of phase behavior, and (6) computer simulation of gas/oil displacements.

Saturation pressures'and swelling factors were measured for oil/gas mixtures, which showed that N2 is substantially less soluble in oil than is CO2. Viscosity measurements show that the viscosity reduction is a function of pressure and of the total gas dissolved in the oil.

Four reservoir-condition corefloods showed that the recovery efficiency of CO2 is higher than that of the refinery gas for continuous or low WAG injection, and the recovery efficiency of the refinery gas at 1:1 WAG is about twice that of continuous injection. The corefloods were modeled with a finite-difference compositional simulator. Predictions agree with the experimental results.
Evaluation of Flow Characteristics of Perforations Including Nonlinear Effects With the Finite-Element Method
Authors: Tariq Syed M.
Published: December 2007

This study presents results of finite-element modeling of steady-state flow in perforated natural completions. Use of a mesh chosen carefully by grid sensitivity analysis permits evaluation of flow with more precision than that achieved by previous investigators. Also, for the first time, flow characteristics of perforated completions are evaluated with the non-Darcy effect resulting from converging flow around the perforation taken into account. The results indicate (1) confirmation of Locke's results qualitatively but 5 to 10% overprediction by the nomograph, (2) the importance of angular phasing between adjacent perforations, (3) the uncertainty in generally accepted severe permeability impairment in the compacted zone, and (4) a significant reduction in productivity owing to a non-Darcy effect around the perforation for high-rate gas wells.
Response of Wells Producing Layered Reservoirs: Unequal Fracture Length
Authors: Camacho-V. R. G. , Raghavan R. , Reynolds A. C.
Published: December 2007

The response of fractured wells producing noncommunicating layered reservoirs is the focus of this work. The conductivity of the fracture is assumed to be finite. The fracture length is assumed to vary from layer to layer. Two modes of production—constant wellbore pressure and constant rate—are considered.

In the first part, the fractures are assumed to communicate only at the wellbore. The results given in this section are intended to provide engineers with analytical capabilities to examine responses in wells where the layers that have been stimulated are separated by considerable distances. Procedures to interpret the results of pressure buildup and/or production tests (drawdown responses) in terms of layer properties are presented. Criteria to ensure maximum productivity are specified. The second part examines well responses when the fractures are in communication at points other than the wellbore. All other things being identical, we show that communication between fractures increases productivity.
Nonlinear Inversion of Pressure-Transient Data
Authors: Hanson Jonathan M.
Published: December 2007

Analysis of pressure-transient data is typically carried out with graphical methods that include type-curve, semilog, and log analyses. When sparse and/or noisy data are available, interpretation of pressure transients by graphical means can be difficult. Nonlinear inversion coupled with statistical methods allows model uniqueness and reservoir parameter uncertainty to be quantified under these conditions.
Pressure Core Measurements in Tight Sandstone Lenses During the Multiwell Experiment
Authors: Sattler A. R. , Heckes A. A. , Clark J. A.
Published: December 2007

A pressure-coring operation was performed in two tight sandstone lenses of the Mesaverde group during the drilling of one well of DOE's Multiwell Experiment (MWX). The goals were (1) to obtain accurate water saturation data; (2) to measure the amount and composition of gas on a foot-by-foot basis; and (3) to recover fluids for water-chemistry analysis. This application of pressure coring had not been tried before; it was felt to be a novel approach for accurate water-saturation measurements in tight sandstone core.

Several changes to usual pressure-coring procedures were adopted, including the development of an organic, noninvasive coring fluid compatible with the oil-based drilling fluid used to help preserve the original water saturation. The pressure-core assembly was modified so that gas samples could be taken directly from the inner barrel and would allow the capture of any gas not trapped during the process; however, none was found. Three 15-ft [4.6-m] -long pressure-core barrels were taken from two sandstone lenses 20 and 30 ft [6.1 and 9.2 m] thick.

Water-saturation data were obtained on the pressure core by both Dean-Stark distillation and vacuum-oven drying. The analyses of all recovered core suggest that water-extraction procedures should be carried on for a long time and that the Dean-Stark procedure may not be the water-extraction procedure of choice for tight sandstone core. The failure of one core barrel to hold pressure turned out to provide a bonus, because identical analyses were made on pressurized and unpressurized core from the same sandstone. These analyses showed no appreciable water-saturation difference on rock with the same porosities. No fluid was recovered during thawing alone; the rock was too tight. Gas was obtained in the pressure-coring process and measured on a foot-by-foot basis.
A Combination Air and Fluid Drilling Technique for Zones of Lost Circulation in the Black Warrior Basin
Authors: Graves S. L. , Niederhofer J. D. , Beavers W. M.
Published: December 2007

Structural geologic information available for the coal-bearing formations in the Black Warrior basin documents the occurrence of numerous fault and fracture zones. A combination air/fluid drilling technique may be advantageous to coalbed-methane operations in this and other areas with similar hydrologie and geologic conditions. We successfully used this technique recently on coalbed-methane wells in Tuscaloosa County, AL.
Model Investigation of Wellbore Pressure Distribution in Stem-Induced Fracturing
Authors: Fourney W. L. , Holloway D. C. , Simha K. R. Y.
Published: December 2007

This paper describes model testing conducted to investigate pressure variations along the length of a wellbore between a decoupled bottom charge and the stem. Tests were conducted in three-dimensional models made from thick plexiglass sheets that contained small decoupled explosive charges in the bottom of the borehole. Charge sizes varied from 75 to 200 mg, and the open borehole length between the top of the charge and the stem ranged from three to seven times the charge length. Both top and bottom charge initiations were investigated. Multiple pressure transducers were used along the borehore, and pressure/time distributions were determined at several locations.

An additional series of tests is described in which the borehole geometry was altered by varying the diameter of an orifice plate placed in the wellbore. The use of this orifice plate was demonstrated to be effective in controlling the increase rate of the pressure pulse at the stem location.
Success in Prevention of Casing Failures Opposite Salts, Little Knife Field, North Dakota
Authors: Rike E. A. , Bryant G. A. , Williams S. D.
Published: December 2007

We became aware in early 1981 of a severe problem with casing failures opposite salts in the Little Knife field. A concerted engineering effort was initiated to isolate and to remedy the cause of failures. With the use of a relaxed invert-oil-emulsion drilling fluid and properly designed cementing programs, the problem has been arrested. In the 26 wells drilled in the Little Knife field since initiation of this drilling program, there have been no instances of casing failure.
Type Curves for Finite Radial and Linear Gas-Flow Systems: Constant-Terminal-Pressure Case
Authors: Carter Robert D.
Published: December 2007

This paper presents gas-prpduction-rate results in type curve form for finite radial and linear flow systems produced at a constant terminal (bottomhole) pressure. These results can be used in the analysis of acfual gas and oil rate/time data to estimate reservoir size and to infer reservoir shape. The type curves are based on dimensionless variables that are a generalized form of those presented previously.1,2 In addition, an approximate drawdown parameter is presented. Example applications that demonstrate the applicability of the type curves to a variety of reservoir configurations are given. The Appendix contains derivations of the dimensionless variables and the drawdown parameter.
A New Jet Perforating Charge Eliminates Carrot Plugging
Authors: Robinson R.L. , De Frank Pete , Hatfield R.F.
Published: December 2007

Introduction

Production equal to or greater than open-hole completions is possible through perforated completions if the flow paths throughout the perforations are free of obstructions. Previous investigations have indicated that, in some cases, maximum productivity is not obtained due to plugging of the perforations with debris from the wellbore fluid and/or debris from the perforating process. Control of wellbore fluid and proper well completion techniques are very important in the elimination of perforation plugging. Selection of properly designed perforating equipment also is quite important for maximum well productivity.

Studies made with the use of the perforation flow laboratory, in which perforating tests are run under simulated well conditions, have shown that perforation plugging occasionally occurs. Plugs in perforations result from various causes. One of the contributors to plugging that can be controlled by the perforating device is the slug or carrot resulting from jet perforating. This condition has undergone extensive study, and previous developments have resulted in a decrease in carrot size-but not in complete elimination. It was felt that, if a method of completely eliminating the carrot could be found (with charge performance equal or better than previously obtained), a significant contribution would have been made. Such a charge has been developed and is reviewed in this paper.

Theoretical Considerations of Carrot Elimination

There are several popular theories of how a shaped charge jet is formed. One of these is the hydrodynamic theory, wherein the liner is treated as a fluid under the impact of the explosive forces. Another is the spalling theory, where the interaction of shock waves in the liner causes small particles to be torn from the inner surface of the liner and projected at high velocity toward a common focal line to form the jet. It is not unreasonable to assume that both of these theories may be partially correct. For purposes of our discussion, it is simpler to use the second theory.
A Ternary, Two-Phase, Mathematical Model of Oil Recovery With Surfactant Systems
Authors: Thomas Charles P. , Fleming Paul D. , Winter William K.
Published: December 2007

A mathematical model describing one-dimensional (1D), isothermal flow of a ternary, two-phase surfactant system in isotropic porous media is presented along with numerical solutions of special cases. These solutions exhibit oil recovery profiles similar to those observed in laboratory tests of oil displacement by surfactant systems in cores. The model includes the effects of surfactant transfer between aqueous and hydrocarbon phases and both reversible and irreversible surfactant adsorption by the porous medium. The effects of capillary pressure and diffusion are ignored, however. The model is based on relative permeability concepts and employs a family of relative permeability curves that incorporate the effects of surfactant concentration on interfacial tension (IFT), the viscosity of the phases, and the volumetric flow rate.

A numerical procedure was developed that results in two finite difference equations that are accurate to second order in the timestep size and first order in the spacestep size and allows explicit calculation of phase saturations and surfactant concentrations as a function of space and time variables. Numerical dispersion (truncation error) present in the two equations tends to mimic the neglected effects of capillary pressure and diffusion. The effective diffusion constants associated with this effect are proportional to the spacestep size.
New Developments in Induction and Sonic Logging
Authors: Tixier M.P. , Alger R.P. , Tanguy D.R.
Published: December 2007

In the combination induction-electrical log used at present in the field, the induction logging tool is appropriate for the investigation of moderately invaded formations. A new induction sonde with a radius and investigation about twice as large has been developed recently for the case of deep invasion. It has very nearly the same vertical resolution as the present sonde so that thin beds are defined as accurately as before. The characteristics of the new tool are described, the corresponding interpretation charts are given and field examples are discussed.

The design of the sonic logging tool has been modified to improve the calibration and the reliability. The fact that porosity can be accurately recorded by means of the sonic log has prompted new interpretation. procedures for saturation estimation, wherein the data concerning the various permeable beds in a given well are correlated.

One approach consists of plotting transit time vs true resistivity, with an appropriate scale. With this approach, saturations can be estimated conveniently even in cases where formation water resistivity is not well known.

In another approach, a comparison is made of the values of the formation waters computed from the resistivity and sonic logs. Using the concept of continuity, this procedure makes possible a quick determination of zones of saturation in shaly sands and/or in case of appreciable variations of formation salinities with depth.

It has been found that the comparison of porosity from the sonic log with the apparent porosity computed from a short-investigation resistivity log may reveal, in many cases, the presence of residual oil and thus detect potentially productive formations; this procedure is valuable when the true formation resistivity and the resistivity of the formation water are in doubt.

Introduction

During the past year, the efficiency of log interpretation has been vastly improved. The improvements have largely resulted from the introduction of a deep-investigation induction device and from the application of new interpretation techniques that utilize sonic vs resistivity readings. Since the new interpretation techniques depend, in part, upon good values of true formation resistivity, the new induction log will be discussed under Part I. The sonic interpretation techniques will be studied under Part II.
Development of a Fluorimetric Method for Detection of Pay Zones During Drilling With Invert Muds
Authors: Connell D. L. , Coates J. A. , Frost D. A.
Published: December 2007

An examination of possible pay-zone detection techniques was prompted by the introduction of low-toxicity oil muds. Infrared (IR) spectroscopy, thin-layer chromatography (TLC), and fluorimetry are shown to be applicable. Fluorimetry is preferred for its better sensitivity and ease of use offshore. We examine the requirements for use of the technique in the field.
A Study of Mineral/Alkali Reactions
Authors: Mohnot S. M. , Bae J. H. , Foley W. L
Published: December 2007

A study of the reaction of alkaline chemicals with minerals constituting reservoir rock is presented. Static tests were conducted with high concentrations of NaOH and orthosilicate solutions and minerals (montmorillonite, kaolinite, illite, and quartz sand). The reaction time varied from 10 minutes to 2 months. Solutions were analyzed for hydroxide, Si, and Al, and solids were analyzed by X-ray diffraction (XRD) and other spectroscopic techniques. The loss of useful alkalinity was the highest with kaolinite and the least with quartz sand for high alkali concentration (5 wt%) or temperature (180°F [82 °C]). A detailed study of kaolinite/alkali reaction kinetics and quartz/alkali equilibrium is presented.
Optimal Spacing for Casing Centralizers
Authors: Lee H. K. , Smith U. C. , Tighe R. E.
Published: December 2007

In the placement of centralizers on casing, it is necessary to integrate information on hole trajectory, casing properties, and centralizer performance. This paper summarizes the basic theory and algorithms for optimizing centralizer spacing based on these considerations. The algorithm predicts the wall forces in a three-dimensional (3D) borehole.

Although centralizer placement is important in all wells, it is especially important for highly deviated boreholes and deep, heavy strings. With the detailed approach described here, centralizer placement design gives the operator greater confidence in the prediction of minimum standoff distance for these types of wells.

Some examples of field applications are presented. Also, cementing results from field wells support the conclusion that good cement placement is obtained when adequate centralizers are used.
Pressure Falloff Behavior in Vertically Fractured Wells: Non-Newtonian Power-Law Fluids
Authors: Vongvuthipornchai S. , Raghavan R.
Published: December 2007

This paper examines pressure falloff behavior in fractured wells after the injection of a non-Newtonian power-law fluid. Results are presented in a form suitable for field application. Responses at wells intercepting infinite-conductivity and uniform-flux fractures are considered. Procedures to identify flow regimes are discussed. The solutions presented here are new and to the best of our knowledge are not available in the literature. The consequences of neglecting the non-Newtonian characteristics of the injected fluid are examined.

Although the main objective of our work is to examine pressure falloff behavior at fractured wells, we also examine responses at unfractured wells. This part of our study examines the validity of using the superposition principle to analyze pressure falloff data. (The pressure distribution for this problem is governed by a nonlinear partial-differential equation.) If the solutions given in the literature are used, then correction factors are needed to analyze pressure falloff data. The results of this phase of our work can also be used to analyze data in fractured wells provided that pseudoradial flow conditions exist.
Gas Well Test Analysis: Use of Normalized Pseudovariables
Authors: Meunier D. F. , Kabir C. S. , Wittmann M. J.
Published: December 2007

Pressure data from gas wells are normally analyzed by use of pseudopressure, which is a transformation of measured pressure. When tests are associated with large pressure changes accompanied by a severe wellbore storage effect, such as in tight reservoirs, use is made of pseudopressure and pseudotime transforms. The purpose of the pseudovariables is to linearize "effectively" the governing diffusivity equation so that proper test interpretation can be made.

In this study, normalized pseudovariables or transforms are introduced. Use of these new pseudovariables produces results identical to those obtained with the conventional pseudovariables. However, the proposed pseudovariables offer some distinct practical advantages. For example, units of pressure and time are retained, thus giving a physical "feel" for the pseudovariable definitions. Other features include use of liquid equations for solving the gas flow problems—i.e., constants of the working equations remain unchanged.

This study also proposes two methods for estimating the rate-dependent skin, together with permeability, mechanical skin, and well deliverability. The first method involves logarithmic convolution of pressure with flow rate, both measured downhole, by use of a radial model. A trial-and-error approach is used to obtain the rate-dependent skin on a convolution plot. The second method requires a transient flow-after-flow test of short duration; a standard graphic technique allows the estimation of the desired reservoir parameters.

Once the reservoir parameters are estimated with either method, the absolute open-flow potential (AOFP) of a well can be established by assuming a reservoir radius because the AOFP is relatively insensitive to this assumption.
Drilling Techniques Improve Success in Drilling and Casing Deep Overthrust Belt Salt
Authors: Unger K. W. , Howard D. C.
Published: December 2007

One of the most challenging drilling problems encountered in the Western Overthrust belt occurs in the deep Jurassic Preuss salt. A history of lost holes caused by stuck drillstrings, stuck casing, and collapsed casing plagues operators in the Wyoming/Utah Overthrust belt. An ongoing engineering study is being conducted to identify the problem salt-drilling areas and to solve the associated drilling and casing-collapse problems.

In the first part of this study, completed in June 1983, salt-drilling problems were studied in the Anschutz Ranch East field. Problem intervals within the salt section were identified, and unique salt-drilling techniques were developed. As a result of implementation of the salt-drilling techniques, salt-drilling success in Anschutz Ranch East has improved substantially.

Included in this study are an evaluation and recommendations for mud systems, bottomhole assemblies (BHA's), drilling parameters, and caliper logging through the salt interval. Casing collapse caused by nonuniform loading is discussed, and preventive measures are recommended.
Review of PDC Bits Run With Invert-Emulsion Oil Mud in Shallow South Texas Wells
Authors: McClelland G. M.
Published: December 2007

This paper examines 56 polycrystalline-diamond-compact (PDC) bit runs, discusses the evolution of the PDC bit, and recommends guidelines for selecting the most economical bit design for shallow south Texas wells drilled with invert-emulsion oil mud. From March 1981 to April 1984, our South Texas Div. Drilling documented 88 PDC bit runs with invert-emulsion oil mud in shallow south Texas wells. These PDC bits primarily drilled soft Frio formations of sand and shale to less than 12,000 ft [3660 m] total depth (TD). Throughout this time, PDC bit design continually improved, providing progressively greater time and cost savings. Field data indicated that improvements in bit material, body design, cutter placement, and operating procedures have increased rates of penetration (ROP's) and bit life, thus decreasing drilling costs.
Three-Parameter Modification of the Peng-Robinson Equation of State To Improve Volumetric Predictions
Authors: Jhaveri Bharat S. , Youngren Gary K.
Published: December 2007

The Péneloux-Rauzy-Fréze (PRF) method of improving volumetric predictions by introducing a third parameter into a two-parameter equation of state (EOS) is applied to the Peng-Robinson EOS (PR-EOS). The modified PR-EOS is evaluated for application to hydrocarbon fluids. A method is developed for characterizing the third parameter for the heptanes-plus fractions. The usefulness of the modified PR-EOS in improving volumetric predictions is illustrated by applying the equation to several crude-oil and gas-condensate systems from the literature.
Behavior of Oil Muds During Drilling Operations
Authors: Galate J. W. , Mitchell R. F.
Published: December 2007

This paper presents an analysis of the behavior of diesel-oil-based muds with an advanced thermal and hydraulic wellbore mathematical simulator. Recent diesel-oil-mud rheological correlations have been incorporated into the model to account for viscosity and density variations of oil mud with temperature and pressure. As rheological correlations are developed for other oil-based muds, such as mineral-oil-based muds, they can also be incorporated into the model.

A specific deep-well application of the model illustrates the behavior of oil-based muds and shows the differences between water-based mud and oil-mud local fluid densities during drilling, circulating, and static conditions. Temperature and density profiles are presented for various operating conditions to show that modeling improves the understanding of oil-mud behavior downhole.
Decline-Curve Analysis Using type Curves—Case Histories
Authors: Fetkovich M. J. , Vienot M. E. , Bradley M. D. , Kiesow U. G.
Published: December 2007

Case-history studies demonstrate methods of analyzing rate-time data to determine reservoir variables and to predict future production, Constant-wellbore-pressure analysis techniques use existing qdD-tdD type curves and new qdD-tdD type curves from actual field data.
Utility of Motor-Speed Measurements in Pumping-Well Analysis and Control
Authors: Gibbs S. G.
Published: December 2007

This paper describes how motor speed can be used to deduce operating conditions in rod-pumped wells. Through the use of motor performance data, speed can be used to infer gearbox torque, unit balance, motor load, qualitative dynamometer cards, and power consumption. Pumpoff control and continuous monitoring are also applications of the methods discussed.
Two Bottom-Hole Pressure Instruments Providing Automatic Surface Recording
Authors: Kolb R.H.
Published: December 2007

Introduction

A long term project at Shell Development Co.'s Exploration and Production Research Laboratory has been the improvement of the accuracy and the ease of BHP measurements. As a result of these efforts, two complete and separate systems have now been built for the automatic logging of BHP variations. The first of these is a small-diameter instrument suitable for running through production tubing on a single-conductor well cable. During the development of this instrument, as much emphasis was placed on providing a high degree of usable sensitivity and repeatable accuracy as on obtaining the advantages of surface recording. The second system combines the benefits of automatic, unattended recording with the convenience of a permanently installed Maihak BHP transmitter.

The Cable Instrument

For many years the standard instrument for BHP determination has been the wireline-operated Amerada recording pressure gauge or one of several other similar devices. This gauge records on a small clock-driven chart carried within the instrument, and although relatively precise readings from the chart are possible, they are difficult to obtain. Both the maximum recording time and the resolution of the time measurements are limited by chart size, and when a slow clock is required for long tests, the precision of the time measurement is often inadequate. Since it is impossible to determine the data being recorded until the gauge has been returned to the surface, wasted time often results when a test is protracted beyond the necessary time or when it is terminated too soon and must be re-run. Clock stoppage or other malfunctions which would be immediately apparent with surface recording remains undetected with downhole recording; the test is continued for its full term with a consequent loss in production time. As new uses for subsurface pressure data evolved, the shortcomings of the wireline instrument became increasingly apparent, and the concurrent development of a surface-recording pressure gauge and the associated high-pressure well cable service unit was undertaken.
Effect of Aquifer Size on the Performance of Partial Waterdrive Gas Reservoirs
Authors: Al-Hashim H. S. , Bass D. M.
Published: December 2007

Predicting the advancement of a gas/water contact (GWC) in a waterdrive gas reservoir plays an important role in evaluating, forecasting, and analyzing the reservoir performance. This study was conducted to predict the behavior and the rise of the GWC, assuming that it remains horizontal, and to determine its effect on ultimate gas recovery. Several factors control the rise of the GWC. Some of the most important factors are the size of the aquifer, gas production rate, initial reservoir pressure, and formation permeability. These factors account for the abandonment of a number of gas reservoirs at extraordinarily high pressure.

Several methods have been developed for predicting the volume of water influx into a reservoir; the van Everdingen-Hurst method is used in this study. The performance calculated in this study was based on the material-balance equation for gas reservoirs. The gas reservoir pressure was adjusted to the original GWC for the water-influx equation, and the trapped gas in the water-invaded zone was accounted for in the water-invaded region. A constant reservoir permeability of 300 md was used in all calculations. The results showed that when ra/rg≤2, the effect of the aquifer on gas reservoir performance can be neglected. Also, the rate at which the GWC advances is controlled by the aquifer size when ra/rg >2. Finally, regardless of the size of the reservoir, when ra/rg>2, the pressure in the unsteady-state water-influx equation has to be corrected to the original GWC. Failure to do so may result in an error of more than 100% in the cumulative water influx, which in turn could lead to the wrong conclusions regarding the performance of the gas reservoir.
Automatic Determination of Lithology From Well Logs
Authors: Delfiner Pierre , Peyret Olivier , Serra Oberto
Published: December 2007

A procedure combining modern wireline measurements with a lithofacies data base has been developed to produce an automatic lithologic description of the formations crossed by a well.

The database lithofacies are defined from petrographic knowledge and translated in terms of log responses. The assignment of depth levels to a lithofacies is done with the data base and with a discriminant function (Bayesian decision rule). External knowledge can be taken into account by use of artificial intelligence methods. A confidence factor is produced for each result.

Logs currently in the data base are the density, neutron, sonic transit time, gamma ray, photoelectric cross section, and concentrations of thorium, potassium, and uranium. Major lithofacies groups represented in the data base include sandstones, limestones, dolomites, shales, coals, and evaporites. These are subdivided by introducing cement and special minerals and by considering porosity ranges.

The construction of the data base is a critical step. It is largely empirical and requires careful calibration against intervals with well-known lithologies (e.g., from cores). The data base can be tuned to local conditions.

The procedure has been tested in several environments and compared with cores and mud log descriptions. A detailed lithologic column can be produced at the wellsite and used in decision making. The results can also serve as input for further geologic studies of facies and sequences or for quantitative evaluation of formations.
Estimating Reservoir Parameters From the Gas Backpressure Equation
Authors: Brlgham William E.
Published: December 2007

Although Eq. 2 is not quite exact, it is usually accurate enough for engineering purposes.

The question often arises whether Eqs. 1 and 2 can be related to each other. In particular, we would like to know whether the empirical constants C and n in Eq. 1 can be related to the reservoir parameters in Eq. 2. Such a relation is discussed in Ref. 2, but this narrative is not correct. In particular, Eq. 6.74 of that reference and the unnumbered equation at the top of Page 327 are both incorrect. This discussion shows how the constants in Eq. 1 can be related to reservoir parameters.

When one looks at Eq. 2 in detail, one finds that at a low flow rate, a graph of Δp2(Δp2=p¯2−pwf2) vs. qsc will have a slope of 1.0 on log-log paper, while as the flow rate increases, the data curve upward and the slope increases, so that at a high flow rate the slope is 2.0. This behavior is shown in Fig. 1, which is a reproduction of Fig. 6.45 of Ref. 2. Over the usual rather narrow range of well tests (e.g., for about 4 to 20 MMscf/D [0.1 × 106 to 0.57 × 106 std m3/d] in Fig. 1), the curvature is not great and a straight line (Eq. 1) will fit the data nearly as well. Thus it should be possible to relate Eqs. 1 and 2 by determining the conditions under which the slopes are the same. This is the basis used here to relate the constants in Eq. 1 with the reservoir parameters in Eq. 2.
Investment Evaluation by Present-Value Profile
Authors: Wooddy L.D. , Capshaw T.D.
Published: December 2007

Introduction

There is a trend today for business enterprises to be more thorough in their approach toward making capital expenditure decisions. Correspondingly, there has developed a large volume of literature dealing with problems connected with the analysis of capital expenditure proposals or opportunities. Much of the literature describes methods of preparing economic data for analysis; recently, however, there have been many papers on the subject of measuring the worth of the investment opportunity. This paper deals with both areas. It attempts to describe methods useful to the analyst in presenting economic data to management. It is believed that these methods provide optimum utility for decision making. The paper also describes the limitations of the methods and the ways they might be viewed or interpreted by management in various financial positions.

The prosperity of the petroleum industry, perhaps as much or more than any other industry, is dependent on the efficient employment of its capital. This particularly is true in the producing end of the industry because a large part of its assets are continuously being depleted and must be replaced by additional capital expenditures. It has been estimated that capital expenditures for the domestic industry as a whole will exceed $7 billion during 1959, and that drilling and producing investments alone will amount to $4.5 billion. Thus, investments in producing and drilling operations will exceed $12 million daily, on the average. It is readily apparent that management is confronted with a tremendous job in making decisions on a vast number of investment opportunities.

Oil industry executives usually rely upon economic analyses prepared by staff groups, particularly geological and engineering staff groups. The economic analysis normally is based on engineering or geological studies of the particular venture, which are usually highly complicated and contain many assumptions. Assumptions are necessary when certain data are unavailable or for the inclusion of future aspects into the analysis, and these assumptions always result in a degree of risk. Management normally attempts to evaluate risk by understanding the mechanics of the technical study; however, the economic analysis, to be complete, should provide for the measurement of the risk factor as well as the profitability.
Liner Rotation While Cementing: An Operator's Experience in South Texas
Authors: Arceneaux M. A. , Smith R. L.
Published: December 2007

The literature is replete with papers emphasizing the use of pipe movement while cementing to improve the opportunity for a successful primary cement job. Most operators, however, are reluctant to use liner movement, either reciprocation or rotation, while cementing.

This paper reviews experiences with nine rotating liners in south Texas since Dec. 1983. The liner hanger system and procedure used in rotating while cementing is discussed. Mud types and weights, hole sizes vs. bit diameter, cement slurries and volumes, hole deviation, and torque encountered are reviewed. A postanalysis of each job, pressure and differential tests performed, and typical cement bond logs will be presented.

Good primary liner cementing minimizes problems in production and stimulations and reduces cost. Liners were rotated throughout cement displacement on 77% of the jobs, while rotation was initiated on 88%. Liner rotation while cementing has improved the cement jobs and reduced the remedial cement work.
Improved Interpretation of the Inaccessible Pore-Volume Phenomenon
Authors: Gilman J. R. , MacMillan D. J.
Published: December 2007

In laboratory corefloods, polymer solutions used in EOR, such as partially hydrolyzed polyacrylamides (PHPA), often break through at less than 1 PV injected compared to the breakthrough of pure water. The rapid breakthrough is erroneously used to determine the ratio of pores accessible to polymer to total PV (accessible PV). Through numerical simulation and steady-state analysis, we show that the rapid breakthrough of such polymer solutions is not a measure of accessible PV. The only thing that can be inferred from the polymer solution breakthrough time is that polymer solution travels faster than water. Breakthrough time depends on the injected polymer concentration and shear rate.

Our results significantly affect interpretation of polymer flow in porous media. Laboratory-measured polymer bulk properties are not those that should be used in conventional reservoir simulation and pressure-transient test analysis of polymer solutions.

We show two different forms of the same partial differential equation used to describe rapid polymer breakthrough. The finite-difference solutions lead to two different polymer concentrations for each gridblock—a flowing concentration and a bulk (volume-average) concentration. The polymer-concentration-dependent properties required for each formulation must be interpreted correctly.
Application of Preconditioned Conjugate-Gradient-Like Methods in Reservoir Simulation
Authors: Northrup Elizabeth J. , Woo Pang T.
Published: December 2007

Conjugate-gradient-like (CGL) methods were used to solve the matrix equations for several large-field and fine-grid models. The methods used incomplete LU (ILU) or modified incomplete LU (MILU) preconditioning coupled with orthomin acceleration. The CGL methods were applied to the original matrix or to a reduced system from red/black ordering. Test results from a black-oil model with fault throws, a fractured reservoir model, and three steamflood models are given. It was found that the CGL methods are effective for solving the matrix equations. A more powerful preconditioner improves reliability but may require more work. Guidelines for selecting the most effective method are provided.
Controlling Effects in Countercurrent Two-Phase Flow
Authors: Johnston A. J.
Published: December 2007

In many two-phase-flow situations, the prediction of conditions likely to instigate the change in flow regime from stratified to slug is important because this change or "choking" of a pipe may dictate the maximum flow rates possible in that pipe. This paper considers the appropriate parameters in the development of a suitable stability criterion for this transition in countercurrent flow. This criterion is then quantified with the results from an experimental test rig. Finally, a typical two-phase petrochemical situation is examined by use of this stability criterion, and the produced results are compared with previous stratified-flow predictions to identify the controlling effect.
Rapid, High-Temperature, Field Test Method for Evaluation of Geothermal Calcium Carbonate Scale Inhibitors
Authors: Asperger R. G.
Published: December 2007

A new test method is described that allows the rapid field testing of calcium carbonate scale inhibitors at 500° F [260 °C]. The method evolved from use of a full-flow test loop on a well with a mass flow rate of about 1×106 lbm/hr [126 kg/s]. It is a simple, effective way to evaluate the effectiveness of inhibitors under field conditions.

Five commercial formulations were chosen for field evaluation on the basis of nonflowing, laboratory screening tests at 500°F [260°C]. Four of these formulations from different suppliers controlled calcium carbonate scale deposition as measured by the test method. Two of these could dislodge recently deposited scale that had not age-hardened. Performance-profile diagrams, which were measured for these four effective inhibitors, show the concentration interrelationship between brine calcium and inhibitor concentrations at which the formulations will and will not stop scale formation in the test apparatus. With these diagrams, one formulation was chosen for testing on the full-flow brine line. The composition was tested for 6 weeks and showed a dramatic decrease in the sealing occurring at the flow-control valve. This scaling was about to force a shutdown of a major, long-term flow test being done for reservoir economic evaluations. The inhibitor stopped the scaling, and the test was performed without interruption.
Effect of Isolated Vertical Fractures Existing in the Reservoir On Fluid Displacement Response
Authors: Givens J.W. , Crawford Paul B.
Published: December 2007

A potentiometric model study has been made of the effect of vertical fractures existing in the matrix of the reservoir on the flooding or cycling performance. Fractures can have unusual flow characteristics. Fluid entering one side of a fracture can emerge on either the same or opposite side of the fracture, depending on the particular streamline. Fracture orientation has a great influence on the sweep efficiency. However, sustained fluid injection may still permit large areas to be swept.

Introduction

One can find considerable information available in the literature on the effect of fractures originating at the wellbore on sweep efficiencies of waterflooding or gas cycling programs. However, there are few, if any, quantitative data reported in the literature on the effect of vertical or horizontal fractures existing out in the reservoir matrix on secondary recovery performance. Several papers have been presented on the effect of vertical and horizontal fractures on the productivity or conductivity of waterflood and gas injection patterns, but in all cases the fractures initiated at the well and simulated commercial fractures. It is believed that natural fractures may exist out in the reservoir matrix and would effect the displacement performance. The purpose of this report was to study the effect of a few isolated vertical fractures existing out in the reservoir matrix on the performance of waterflood or gas injection patterns.

DESCRIPTION AND EQUIPMENT

Since the potentiometric model was described by Lee it has been widely used to study numerous types of fluid displacement problems. The potentiometric model can be used for fluid displacement studies when the following assumptions are valid:

(a) steady-state conditions exist; (b) the mobility ratio is one; and (c) the capillary and gravitational effects can be neglected.

Five-spot and direct line drive square patterns were studied using a copper strip of the desired length and orientation to simulate a vertical fracture in the reservoir matrix. The 20 x 20-in. model was considered to represent only one element of an infinite array of similar patterns.

DISCUSSION AND RESULTS

FIVE-SPOT PATTERN ONE FRACTURE BETWEEN INJECTION AND PRODUCING WELLS

Fig. 1 shows a quadrant of a five-spot pattern with the vertical fracture existing out in the matrix along a line connecting the injection and producing wells. Length of the fracture was equal to 35.4 per cent of the distance between injection and producing wells. In this particular pattern it is noted that fluid breaks through from the injection well to the producing well when the dimensionless time is equivalent to 26.9. Dimensionless time is defined as volume of fluid injected divided by the volume of displaceable fluid in the pattern expressed as a per cent.

SPEJ

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Biocide Evaluation Against Sessile Xanthan Polymer-Degrading Bacteria
Authors: O'Leary W. B. , Boivin J. W. , Dasinger B. L. , Beck D. , Goldman I. M. , Wernau W. C.
Published: December 2007

This paper supports the use of formaldehyde at economically feasible concentrations as a biocide for EOR processes that use xanthan biopolymer. Its biocidal action against anaerobic sessile xanthan-degrading field organisms was clearly superior to three other biocides tested when 100% kill was used as the criterion for effectiveness.
Automated and Manual Methods for the Determination of Polyacrylamide and Other Anionic Polymers
Authors: Allison J. D. , Wimberly J. W. , Ely T. L.
Published: December 2007

The concentration of Polyacrylamides is determined by precipitation with Hyamine® 1622 Reagent 1 and by measurement of the amount of light scattered by the resulting turbidity. The analysis can be automated as well as adapted for field trials. The effects of anionic surfactants, changes in Polyacrylamide molecular weight, and salinity are discussed.