bluuebunny/crossref_metadata_2025 huggingface dataset:
Injection-Time Effects on Falloff Responses From Composite Reservoirs
Authors: Ambastha A. K. , Ramey H. J.
Published: December 2007

An analytical solution for a radial, composite reservoir is used to establish dimensionless injection time based on the front radius as a correlating parameter for falloff responses of all front radii. Effects of short injection time on the accuracy of methods used to estimate swept volume (or front radius) are discussed. If injection-time effects are ignored, the pseudo-steady-state method may overestimate swept volume by an order of magnitude. For short injection times, model selection (a two- vs. three-region model) for type-curve matching can be difficult. Finally, a correlation is presented for the magnitude of injection time to analyze falloff data with an injectivity type curve.
Single-Trip Tubing-Conveyed Perforating, Production Testing, and Pressure-Buildup Testing in Nonflowing Wells
Authors: Barnes J. A. , Snider P. M. , Swafford C. V.
Published: December 2007

This paper describes tools and procedures for tubing-conveyed perforating (TCP) and subsequent production testing of a well with a reverse-flow jet pump with a specially designed blanking sleeve. A downhole shut-in pressure buildup is also obtained and all equipment is pressure-actuated, eliminating the use of wireline.
Analysis of Pressure-Transient Data From Underbalanced Perforating
Authors: Centanni R. J. , Chacon E. A. , Garrett J. C. , Shealy R. A. , Ruiz S. J.
Published: December 2007

Determination of reservoir characteristics from transient pressures created by underbalanced perforating can enable an operator to decide whether a well is commercially productive before permanent completion. Several techniques exist to analyze such data. In this work, closed-chamber testing and log-log- and Cartesian-plotted short producing times are used to analyze data collected from a multiwell project in the Gulf of Mexico. Pressure data were obtained from underbalanced perforating and backsurge-washing treatments. Results of these analyses compared favorably with buildup tests performed after the wells were completed.
Quicklook Prestimulation Well Test
Authors: Ahmed U. , Husband F. J. , Tariq S.
Published: December 2007

In this paper, we present a technique that allows one to perform a short-term well test. The short duration of the test results in reasonably good estimates of formation permeability, skin factor, and reservoir pressure. The technique, referred to as "Quicklook, " requires pressure measurement at the surface and downhole. After perforating, the formation is subjected to an instantaneous-rate drawdown or injection for a couple minutes. The instantaneous-rate period is followed by a shut-in period of sufficient duration to achieve the desired radius of investigation. Three interpretation plots are made to perform the analysis: a derivative type plot for flow-regime identification and type-curve analysis, a specialized plot [rate-convolved Homer (RCH) analysis] for certain flow parameter calculations, and a system-verification plot. A desirable feature of the technique is that the testing and perforating can be performed during the same trip. Two field examples from low-permeability wells illustrate the technique and data interpretation.
A Reservoir Model for Wireline Formation Testing
Authors: Yildiz Turhan , Langlinais Julius
Published: December 2007

A 3D analytical model has been developed to improve the analysis of the transient pressure response of a reservoir to wireline formation testing (WFT). The mathematical model was used to evaluate the validity of current interpretation techniques and to investigate the sensitivity of transient pressure behavior to wet/bore parameters.

Introduction

WFT is an openhole-logging technique where data are used to determine initial reservoir pressure; vertical pressure distribution along an open hole, fluid contacts, and formation permeability. Formation permeability is deduced from the pressure behavior observed during the test.1–8 WFT pressure data are typically noisy, and interpretation is based on simplified flow configurations; thus, until now, only a qualitative estimate of formation permeability from WFT data has been possible.

WFT consists of one or two drawdown periods and a buildup period. A WFT tool typically has a probe, a pressure gauge, and one or two pretest chambers. Fig. 1 gives a schematic of the WFT tool. The test is performed after the packer on the tool squeezes the mudcake out and properly isolates the formation. The probe is inserted into the formation through the mudcake, and formation fluid is withdrawn until the first chamber is full; the second chamber, when present, is filled at a higher flow rate. Then, the fluid withdrawal is stopped.

During the drawdown and subsequent buildup periods, the pressure at the probe is recorded by a pressure transducer. Fig. 2 illustrates the flow-rate schedule and the expected pressure behavior at the probe for a WFT tool.

In recent years, considerable effort has been directed to obtaining the formation permeability from WFT data. The use of the WFT pressure data for permeability evaluation was first proposed by Moran and Finklea.6 Later, Stewart and Wittmann7 extended this study.
Characteristic-Time Concept in Hydraulic Fracture Configuration Evolution and Optimization
Authors: Lee T. S. , Advani S. H. , Avasthi J. M.
Published: December 2007

This paper introduces the concept of characteristic time as a measure to separate and to optimize the roles of Griffith surface energy and fracture-fluid dissipation energy during hydraulic fracture evolutions. The analysis reveals two separate sets of solutions that correspond to two distinct time regimes of hydraulic fracture propagation: a dominant fluid dissipation energy and a dominant fracture surface energy regime. Each influence domain is governed by a characteristic time and demarcated by a transition region, where the energy contributions of each are of the same order of magnitude. Verification of the theoretical response trends and the use of the characteristic-time concept as a design tool are also presented.
Flow Characteristics of Hydraulic Fracture Proppants Subjected to Repeated Production Cycles
Authors: Holditch S. A. , Blakeley D. M.
Published: December 2007

When fracture proppants are subjected to cyclic loading, the conductivity of the fracture is reduced. This paper presents laboratory results to quantify the degradation of sand and intermediate-strength proppants (ISP's) as closure stress is loaded cyclically to the proppant. The results imply that, if a deep gas well is opened and then shut in repeatedly, permanent damage to the hydraulic fracture will occur.
Field Application and Benefits of Wellsite Buildup Technology
Authors: Roach M. K.
Published: December 2007

For many rod-pumped wells in the U.S., conventional buildup tests are too costly relative to the apparent potential benefits. Yet with lower oil prices and declining production volumes, the need for such data to optimize recovery is even greater. Mobil has eliminated this dilemma on a number of its fields by turning to the latest in acoustic buildup technology to reduce the cost of these tests.
Assessment of the Mechanical Stability of High-Angle Wells in Block 22/11, Nelson Field Discovery
Authors: Kwakwa K. A. , Batchelor A. S. , Clark R. C.
Published: December 2007

This paper summarizes the theory of using a practically oriented simulator to assess the mechanical stability of a wellbore in a triaxial, linearly elastic stress field. The model can be used to determine the range of mechanically stable well inclinations in a given formation and to produce mud-weight programs tailored to efficient and safe drilling, even in difficult conditions. In the Nelson discovery in Block 22/11 of the North Sea, the model was used to evaluate mechanical instability experienced during drilling of deviated appraisal wells through overpressured Oligocene shale. Simulation results showed that, within a range of drilling-mud densities, wells of any orientation can be drilled through the shale. However, practical considerations of formation heterogeneity, swab and surge pressures, and possible chemical interaction dictate that inclined wells beyond about 65° should not be attempted until more field data are acquired to enhance confidence in the use of the model in Block 22/11.
Fines Migration and Formation Damage: Influence of pH and Ion Exchange
Authors: Vaidya R. N. , Fogler H. S.
Published: December 2007

This paper elucidates the influence of pH and ion exchange on formation damage caused by fines migration. The experimental results affect waterflooding, design of drilling muds, and alkaline flooding. In-situ release of naturally existing fines (generally clays) results from changes in colloidal conditions of the permeating fluid. Such processes can cause extensive formation damage in sandstones, thereby reducing oil production. Our recent studies clearly indicate that the release process is started by a combination of high pH and low salinity. We present experimental results that suggest and confirm the interdependence between changes in salinity, cation exchange, and pH, leading to drastic permeability reductions. These results therefore provide new insight into the phenomenon of formation damage caused by water sensitivity or injection of incompatible brines. We also describe a unified approach to understanding these results and the findings of previous investigators. Predictions obtained from a physicochemical model based on ion exchange and colloidal chemistry agree well with experimental observations. The effect of different cations on formation damage also was investigated. This study can be extended to predict migration of bacteria and other particulates that cause formation damage.
Migration of Particles to a Hole Wall in a Drilling Well
Authors: Walker Richard E.
Published: December 2007

The rate at which a particle will migrate from the rotating drill pipe to the hole wall was calculated as functions of the mud properties, pipe rotational speed, and hole size. The information can be used to estimate the relative carrying capacity of one mud compared to another Then the changes that need to be made when a hole. is not cleaning can be determined. An adaptive control process for field use is suggested

Two major simplifying assumptions are that axial flow does not influence the liquid viscosity and that the viscous resistance to particle movement in the radial direction is proportional to the particle's velocity. The calculations assume a power model liquid, spherical cuttings, and concentric pipe in a round hole. A concept of "theoretical zones" where the calculations are valid interspersed with areas where the particles are uniformly redistributed, is used to relate the simplified theory to actual hole conditions.

Introduction

This theoretical study was conducted to improve the understanding of hole cleaning and how various drilling conditions and muds influence the ability to lift cuttings to the surface. The primary object of the study was to see how fast a particle might move from the drill pipe to the hole wall and how factors of drilling and liquid properties influence the rate of radial movement. The rate of movement may be important as the centrifugal force set up by the rotating drill pipe tends to force the particle toward the hole wall, an area of low vertical mud velocity and, therefore, poor lifting.
Correlations of Mud Rheological Properties With Cuttings-Transport Performance in Directional Drilling
Authors: Becker T. E. , Azar J. J. , Okrajnl S. S.
Published: December 2007

An experimental study comparing the effects of mud rheological parameters on annular drill-cuttings buildup was conducted in a large-scale flow section. Rheological parameters examined were mud yield point (YP); plastic viscosity (PV); YP/PV ratio; power-law exponent; consistency index; Fann™ V-G Meter dial readings at 600, 300, 200, 100, 6, and 3 rev/min; effective viscosity (calculated by the power-law derivation); and initial and 10-minute gel strengths. Fifteen bentonite/polymer water-based muds were used, ranging from water to a mud with YP and PV values of 20 lbf/100 ft2 and 40 cp [19.6 Pa and 0.04 Pa·s], respectively. For each mud, flow tests were run at annular velocities from 120 to 240 ft/min [37 to 73 m/min] and hole angles from 30 to 90° from vertical. The effective drilling rate for all tests was 50 ft/hr [15 m/h]. Altogether, 180 tests are analyzed.

When data were correlated with annular cuttings volume in steady-state flow, the best fit was obtained with low-shear-rate parameters. These parameters include the 6- and 3-rev/min dial readings and initial gel strength. Correlation coefficients for these were often from 0.9 to 0.95. For hole angles ≤45° (from vertical), increasing values of these parameters improved cuttings removal (i.e., reduced cuttings volume). The same was observed at angles near horizontal, but only in the laminar flow regime. Cuttings volumes were always smaller in the turbulent regime during near-horizontal flow.
New Friction Correlation for Cements From Pipe and Rotational-Viscometer Data
Authors: Shah Subhash N. , Sutton David L.
Published: December 2007

This paper presents the results of 24 discrete slurries tested on a pipe flow loop while data were taken simultaneously with a flow-through rotational viscometer. Each slurry was pumped through four different pipe sizes at rates from low laminar to high turbulent flow regimes. Test slurries varied from very thixotropic to highly dispersed and from lightweight to dense.

Analysis of pipe-flow data showed a correlation best described by a Bingham-plastic model. Standard flow properties calculated from the rotational-viscometer data were correlated to flow properties derived from the pipe-flow data. These results could be used to calculate pipe pressure losses with improved accuracy.

Correlations for estimating friction losses of cement slurries in laminar and turbulent flow regimes and for predicting laminar/turbulent transition were developed. Results of these correlations are compared with the findings of previous investigators. An example illustrates the use of these correlations.
Application of Probabilistic Reliability Methods to Tubular Designs
Authors: Payne Mike L. , Swanson John D.
Published: December 2007

Standard tubular design methods are based on a specific margin (i.e., "safety factor") between the maximum anticipated field load and the published rating of the tubular. This technique minimizes the risk of failure but promotes overdesign because of the conservativeness in the tubular rating and in the assumed high-load case. To quantify the safety of a particular design, we developed a new method that accounts for the variation of field loadings and tubular performance. Probability distributions for load and capacity are developed on the basis of assumed field-load histories and actual test results on tubular performance. Reliability design methods, originally used in civil engineering, are used to combine these distributions and to quantify the probability of failure. Results show that current design factors do not provide an effective reliability measurement. As a result of these limitations, true-cost/reliability decisions on designs cannot be made with conventional techniques. If reliability is quantified with the proposed method, decisions can be made that properly balance economics, safety, and uncertainty. This paper should assist engineers who need alternative design approaches and managers interested in a better understanding of how existing tubular design methods relate to risk exposure and optimal costs.
Drill-Bit Diagnosis With Neural Networks
Authors: Arehart R. A.
Published: December 2007

A neural network was constructed to determine the grade (state of wear) of a drill bit while it is drilling. With a three-layer neural network and back-propagation as the learning algorithm, the system was trained with laboratory data collected using bits of known grades drilling through known lithologies. The inputs to the neural network were rate of penetration (ROP), weight on bit (WOB), torque (T), revolutions per minute (RPM), and hydraulic horsepower per square inch (HSI). The network was tested on synthetic formations of various bed thicknesses constructed from the test data.
Bit Whirl—A New Theory of PDC Bit Failure
Authors: Brett J. Ford , Warron Thomas M. , Bohr Suzanne M.
Published: December 2007

This paper presents the results of a study showing that the most harmful polycrystalline-diamond-compact (PDC) bit vibrations can be attributed to a phenomenon called "bit whirl." During whirl, the instantaneous center of rotation moves around the face of the bit, and the bit whirls backward around the hole. Cutters on a whirling bit can move sideways, backward, and much faster than those on a true rotating bit. The impact loads associated with this motion cause PDC cutters to chip, which, in turn, accelerates wear. Laboratory and field results show the detrimental effects of whirl on PDC bit rate of penetration (ROP) and life.
Eliminating the Rugosity Effect From Compensated Density Logs by Geometrical Response Matching
Authors: Flaum Charles , Holenka J. M. , Case C. R.
Published: December 2007

A theoretical and experimental effort to understand the effects of borehole rugosity on individual detector responses yielded an improved method of processing compensated density logs. Historically, the spine/ribs technique for obtaining borehole and mudcake compensation of dual-detector, gamma-gamma density logs has been very successful as long as the borehole and other environmental effects vary slowly with depth and the interest is limited to vertical features broader than several feet. With the increased interest in higher vertical resolution, a more detailed analysis of the effect of such quickly varying environmental effects as rugosity was required.

A laboratory setup simulating the effect of rugosity on Schlumberger Litho-DensitySM tools (LDT) was used to study vertical response functions. These functions were used to derive matching filters, enabling a significant improvement in the compensated log response in the presence of rugosity. The data served as a benchmark for the Monte Carlo models used to generate synthetic density logs in the presence of more complex rugosity patterns. The results show that proper matching of the two detector responses before application of conventional compensation methods can eliminate rugosity effects without degrading the measurement's vertical resolution. The accuracy of the results is as good as that obtained in a parallel mudcake or standoff with the conventional method. Application to both field and synthetic logs confirmed the validity of these results.
Fracturing Oil Shale With Electricity
Authors: Melton Noel M. , Cross Theodore S.
Published: December 2007

Laboratory studies to evaluate the use of electricity for fracturing various grades of Colorado oil shale were started in 1964. Breakdown voltages varied greatly from one grade of shale to another, ranging from a minimum of 300 v to a maximum of 15,000 v. With few exceptions, the shale samples were readily fractured at relatively low current levels. On the basis of encouraging results obtained in the laboratory, experiments were expanded to field tests to study electrical characteristics of oil shale when subjected to overburden pressure. These tests generally confirmed the laboratory experiments. Fracturing was accomplished at all electrode spacings used. The spacings varied from 3 to 129 ft. Based upon results obtained in these field experiments, additional fracturing tests were conducted in four shallow wells drilled in an oil shale formation. Some new permeable zones were created between wells. The induced permeability was improved by detonating two conventional nitroglycerin wellbore shots in one of the wells.

Introduction

Before an in situ retorting process can function, it is necessary to develop techniques to increase the permeability of the oil shale formation. Induced fracturing, the best method of increasing the effective permeability of oil-shale deposits, may be accomplished by hydraulic pressure, high explosives, high-voltage electricity or combinations of two or more of these. This article discusses the laboratory experiments and preliminary field tests being made to study high-voltage electricity as a method of fracturing oil shale. Fracturing is the first phase of the electrocarbonization process and is the phase with which this investigation is primarily concerned. Several investigators have studied the electrocarbonization process as applied in coal, petroleum and oil shale formations, but none has reported making field tests in Green River oil shale.
An Investigation of the Recovery of the Bradford Crude by Steam Injection
Authors: Ozen A.S. , Ali S.M. Farouq
Published: December 2007

Laboratory tests indicate that steam injected at relatively low pressures is effective in recovering oil from previously waterflooded porous media. They also indicate that the relative effect of an increase in temperature on oil recovery is much more pronounced at higher than at lower temperatures.

Introduction

In spite of the recently growing interest in continuous steam injection as an oil recovery technique, very few laboratory investigations of steam drive or steamflooding have been reported. The pioneering work of Willman et al. provided much useful information on the mechanism of a steamflood. More recently, Baker 2 has described results of similar studies conducted in a laminar flow model. While actual field tests will decide the effectiveness of a steamflood in a given area, laboratory studies, nevertheless, provide information that can be used to calculate the maximum oil recovery obtainable under a given set of conditions.

The present investigation was designed basically to obtain information on the response of a fight crude oil (Bradford crude, 450 API gravity) to a steamflood in a previously waterflooded reservoir. (Many reservoirs in the Appalachian area are in this category, and could possibly give a third yield of oil by a steamflood.) Moreover, an attempt was made to ascertain the role of heat losses in laboratory studies of steam injection. Few previously published works have considered this effect.

Steamflooding has been tested in the Appalachian oil fields. In spite of the several early failures, attributed to poor engineering and a lack of basic information on the crude oils involved, steamflooding has been successful in recovering large quantities of oil, as evidenced by steamfloods currently in progress. The results of the present investigation support this view.

Experimental Apparatus

A schematic diagram of the experimental apparatus used in this study - for the case of the consolidated core, Core No. 1 (see Table 1 ) -is shown in Fig. 1. The core was mounted in a Viton rubber sleeve, the ends of which were clamped to steel end plates provided with suitable connections and O-ring seals. The whole assembly was placed within a high- pressure casing, containing a nonvolatile oil. It was possible to heat the oil - and hence the core assembly - to any desired temperature by means of thermostatically controlled circular heater segments mounted on the outside of the casing. The oil within the casing could be kept at a constant pressure, regardless of the temperature, by means of a pressure regulator pressurized by a hydraulic accumulator and a pressure switch. If the casing pressure should increase above the preset pressure, the regulator could allow some of the oil to leak out of the casing. On the other hand, if the casing pressure should decrease below the set point, the pressure switch could turn on a pump, which would pump oil into the casing until the desired pressure was attained.

Simpler experimental set-ups were employed for Cores 2 and 3.

JPT

P. 692ˆ
Oil Recovery by Gravity Drainage Into Horizontal Wells Compared With Recovery From Vertical Wells
Authors: Dykstra Herman , Dickinson Wade
Published: December 2007

Gravity drainage is a significant factor in many EOR projects, particularly those involving steam stimulation and extended recovery from depleted reservoirs. This paper compares the effect of dip, reservoir thickness, oil mobility, and well spacing on production from horizontal vs. vertical wells. Total production from vertical and horizontal wells as a function of time also is compared. The basic physical concept involved in this study is the constriction coefficient. For a horizontal well, the constriction coefficient is larger than that for a vertical well at the start of drainage but that difference decreases with time.
Analytical and Numerical Solution of Oil Recovery From Fractured Reservoirs With Empirical Transfer Functions
Authors: Kazemi Hossein , Gilman J. R. , Elsharkawy A. M.
Published: December 2007

An analytical and a numerical solution to Buckley-Leverett flow in a ID fractured porous rock is given. An empirical matrix/fracture transfer function was used. The numerical solution is fast and is adaptable to 3D field problems. The limitations of empirical transfer functions are discussed.
A Computer Technique for Analyzing Pumping Well Performance
Authors: Patton L. Douglas
Published: December 2007

A computerized analytical technique for investigating sucker rod pumping well performance develops load-position values (dynagraphs) at the pump, at desired points in the rod string and at the polished rod through use of a mathematical model of the sucker rod installation. Using the load-position diagrams of the pump, junction points and polished rod, quantitative deductions may be made regarding the mechanical condition and performance of the down-hole equipment (rod string, pump, tubing anchor, etc.) and the physical properties of the well itself (pump submergence, gas interference, fluid pound, etc.). Analysis of subsurface dynagraphs from several cave histories is discussed.

Introduction

Production men have recognized for years that a more complete knowledge of rod pumping performance would suggest means of lowering lifting costs, making more appropriate installation designs and increasing the proportion of oil economically recoverable by rod pumping.

It was this need for knowledge that led to intensive studies from 1927 to 1943. During those years the polished rod dynamometer (1927), the bottom-hole pressure bomb (1929), the pump dynagraph (1936) and the sonic fluid-level sounder (1936) were developed. During that time many engineers used those tools to develop the theories on which our present knowledge of sucker rod pumping is based.

Contributions made since 1943, in an effort to correlate data obtained from the various instruments, are mostly elaborations and refinements of the basic principles established during the preceding period. A notable exception is the Gibbs-Neely mathematical technique that analyzes pumping well performance with a digital computer. In effect, the technique yields all the information derived from these mechanical devices but has the added advantage of requiring only one series of measurements taken and recorded at the polished rod.
Experimental Investigation of Hydrate Formation and Dissociation in Consolidated Porous Media
Authors: Youslf M. H. , Sloan E. D.
Published: December 2007

This paper describes the first uniform formation of natural gas hydrates in Berea sandstone cores by use of a flow system. The hydrate formation was monitored by pressure drop and changes in electric resistance along three cores of three different permeabilities. Formation procedures, such as annealing to ensure uniformity, and the effects of surfaces on equilibria are discussed. Hydrates were dissociated through depressurization, as is done for gas recovery from the Messoyakha hydrate reservoir in the USSR. During the dissociation, two types of rate behavior were observed as functions of the displacement of the dissociation pressure from the equilibrium value. Conclusions and implications for the production of natural gases from hydrate deposits are discussed.
Deploying Mainframe Technical Applications on the PC
Authors: Glynn C. J.
Published: December 2007

Numerous engineering applications on the corporate mainframe network running VM/CMS have been redesigned and deployed on PC’s running DOS. The majority of these applications apply to operations engineering and include calculating fluid properties, multiphase flow pressure drops, and optimum designs for both downhole and surface equipment. The redesign effort focused on the user interface with only minor changes being made to the calculation routines. The PC version of the applications execute faster, at a lower cost per execution, and require less support and training than the corresponding mainframe version.
PC and Mainframe Computer-Graphics Techniques Applied to Volumetric Evaluation of a Mature Oil Field
Authors: Newell K. David , Schoeling Lanny G. , Wong Jan-Chung
Published: December 2007

Mapping and volumetric analysis of large reservoirs are important steps in evaluating mature oil fields for secondary and tertiary development. This paper describes how a research group mapped and conducted an extensive volumetric analysis on the Zenith pool, a large, mature oil field in central Kansas, with a Data General MV20000 minicomputer with Surface III™ mapping software and a PC with Surfer™ and spreadsheet software.

A step-by-step procedure was developed to generate structure, isopach, and porosity maps for the five main reservoirs in the field. Lotus 123™ spreadsheets were developed to compile locations, formation tops, and other critical data for more than 500 wells. These data were sent to the minicomputer to generate contour maps depicting structure, isopachs, and porosities with output directed to an electrostatic color plotter. Grid-to-grid manipulation and cross multiplication of these contour maps allowed construction of a porosity-foot map for each reservoir. The final contour maps incorporated the effects of oil/water contact (OWC) with a porosity cutoff determined from porosity/permeability crossplots. Integration of the porosity-foot maps facilitated volumetric and spatial comparison with historic production data.

PC-derived crossplots were used to determine distribution and ranges of data that were in turn depicted as color-coded ranges on maps. Oil production and oil recovery per quarter section, initial production potential, and completion date for each well were mapped with this technique.

The main advantages of the mainframe were computational speed and high-quality graphics. However, complementary analysis with PC-based contour-mapping software provided similar results and served as an independent check for each mapping step.
PDC-Bit Performance Under Simulated Borehole Conditions
Authors: Andersen E. E. , Azar J. J.
Published: December 2007

Laboratory drilling tests were used to investigate the effects of pressure on polycrystalline-diamond-compact (PDC) drill-bit performance. Catoosa shale core samples were drilled with PDC and roller-cone bits at up to 1, 750-psi confining pressure. All tests were conducted in a controlled environment with a full-scale laboratory drilling system. Test results indicate, that under similar operating conditions, increases in confining pressure reduce PDC-bit performance as much as or more than conventional-rock-bit performance. Specific energy calculations indicate that a combination of rock strength, chip hold-down, and bit balling may have reduced performance. Quantifying the degree to which pressure reduces PDC-bit performance will help researchers interpret test results and improve bit designs and will help drilling engineers run PDC bits more effectively in the field.
Inhibition of Gas Hydrates in Water-Based Drilling Muds
Authors: Kotkoskie T. S. , Al-Ubaidi Basil , Wildeman T. R. , Sloan E. D.
Published: December 2007

A series of thermodynamic experiments were run on 16 simulated drilling muds and associated test fluids to improve the understanding of the equilibrium conditions for hydrate formation in water-based drilling fluids. Results indicated that, to a first approximation, the salt and glycerol contents of water in mud dominated hydrate formation. Other mud additives, such as bentonite, barite, and polymers, collectively promoted hydrate formation to a lesser degree.
Sources of Mercury and Cadmium in Offshore Drilling Discharges
Authors: Candler J. E. , Leuterman A. J. J. , Wong S-Y. L. , Stephens M. P.
Published: December 2007

In 1988, the U.S. Environmental Protection Agency (EPA) proposed regulations that would set limits of 1.5 mg/kg mercury and 2.5 mg/kg cadmium for drilling-waste discharges. To determine potential sources of cadmium and mercury in drilling-waste discharges, samples of barite (barium sulfite), formation cores, and commercially available pipe-dope samples were analyzed for total and extractable levels of cadmium and mercury. From this analysis, most of the cadmium and mercury in drilling-fluid discharges are not available to the environment. The contribution of heavy metals from drilled formation solids is not known before drilling. End-of-pipe discharge limits on metals may compel drilling operators to assume that their wastes could fail the discharge limitation and thus ship all drilling wastes to shore.
Effect of Variable Saturation Exponent on the Evaluation of Hydrocarbon Saturation
Authors: Worthington Paul F. , Pallatt Nadla
Published: December 2007

Petrophysical measurements on effectively clean, desaturated core plugs from different fields have shown that the assumption of a constant saturation exponent for a given sample frequently is violated, although the conventional bilogarithmic distribution of resistivity-index/water-saturation data is often approximately linear. These variations in saturation exponent are attributed to the effects of pore geometry, in particular the nonuniform distribution of electrolyte within a heterogeneous pore system as desaturation progresses. The data indicate that, if unrecognized, a variable saturation exponent can induce errors of more than 10 saturation units (s.u.) in the petrophysical evaluation of water saturation. Procedures are outlined for the identification of those physicochemical reservoir conditions that can give rise to a variable saturation exponent and for accommodating these variations in reservoir evaluation.
Computer File Format Standards
Authors: Thrasher T. S.
Published: December 2007

The Pressure Transient Testing Technical Program Committee for the 1990 SPE Annual Technical Conference and Exhibition established a subcommittee in 1988 to investigate computer file standards for well-test data, type-curve libraries, and subroutine calls for program algorithms. This paper proposes a format standard for well-test data on floppy disks. The proposed format is adopted from the Canadian Well Logging Soc.’s (CWLS’s) Floppy Disk Committee for log data. The format, known as LAS (Log ASCII Standard), provides a data-file specification so that PC users have a flexible file format to store and retrieve large amounts of electronic instrument data from floppy disk quickly. Using this standard will give analysts direct access to the data they need for graphical analysis and computer-aided interpretation techniques. The LAS standard gives well-test service companies and operators a common floppy disk file structure to support the growing number of PC users who use PC-based pressure-transient analysis (PTA) programs.
Compatibility of Resin-Coated Proppants With Crosslinked Fracturing Fluids
Authors: Nimerick K. H. , McConnell S. B. , Samuelson M. L.
Published: December 2007

This paper describes the additive interaction and/or compatibility of various resin-coated proppants (RCP's) with low-, neutral-, and high-pH water-based fracturing fluids. Solutions are provided for those fluids exhibiting compatibility problems with RCP's.
Comprehensive Simulation of Horizontal-Well Performance
Authors: Economides Michael J. , Deimbacher Franz X. , Brand Clemens W. , Heinemann Zoltan E.
Published: December 2007

The simulation of the performance of a horizontal well has generated certain new and important challenges. These include the partial penetration of the well in the horizontal direction within the allocated drainage area, the positioning of the well between the vertical boundaries, the distance from the parallel horizontal boundaries, and the permeability anisotropy. In addition, there are special problems in the simulation of the response of fractures (natural and induced) in regard to their contact with the well (longitudinal or transverse), their conductivity, and the conductivity distribution along the fracture.

We developed new numerical techniques to facilitate the simulation of these diverse problems. We use a locally refined perpendicular bisection grid to describe the horizontal (or deviated) wellbore. The grid is strictly orthogonal for the anisotropic case, and wellbore blocks are almost regular octagonal prisms. The transition to the coarse Cartesian grid is also orthogonal. The fully implicit formulation ensures the stability of the numerical solution. Our results are found to be in excellent agreement with published analytical or semianalytical approximations. In addition, the results offer flexibility that is not possible with analytical solutions. The grid system used is particularly amenable to handling practical problems with real reservoir geometries and configurations.

This paper presents a comprehensive numerical simulation of problems associated with horizontal wells, including the arbitrary positioning of the well within a fully anisotropic medium. Hydraulic or natural fracmres that intersect the well in the longitudinal or transverse direction are simulated for both infinite and finite conductivities.
The TLWP Cathodic Protection System
Authors: Evans Sheldon
Published: December 2007

This paper details the subsea corrosion protection system of the tension leg well platform (TLWP), which comprises coatings and cathodic protection (CP). Postinstallation surveys reveal potentials of at least 150 mV more protective than the minimum potential required for protection. The TLWP protection system weighs 434, 000 lbm less than the conventional CP design, with 286, 000 lbm less on the floating portion of the TLWP.
Field Experience With an SRB Rapid Detection Test Kit
Authors: Horacek G. L.
Published: December 2007

This paper reports field experience with a new rapid method to detect and count sulfate-reducing bacteria (SRB) accurately. Test results are available in 15 minutes, compared with the 3 to 4 weeks required with traditional culture methods. This new test method detects SRB that grow poorly or not at all on culture media and gives superior results with such solids samples as biofilms, soils, and sludge.
Effect of Foams Used During Carbonate Acidizing
Authors: Bernadiner M. G. , Thompson K. E. , Fogler H. S.
Published: December 2007

Although acidization has been used successfully for many years to increase the productivity of petroleum wells in carbonate formations, demands on the performance and application of the acidizing process are increasing. This study investigated a method of in-situ foam generation that allows deeper wormhole penetration yet uses less acid than conventional methods. The dissolution patterns were imaged with neutron radiography, which provided an in-depth understanding of the effects of foam and other critical parameters. Results show that foam is effective in promoting efficient stimulation, even at low acid injection rates.
Waterflooding a Highly Stratified Reservoir
Authors: Warner Gary E.
Published: December 2007

This paper presents a review and analysis of a highly stratified Burbank sand waterflooding project in Osage County, Okla. Permeability values in this reservoir range from less than 0.1 md to nearly 3 darcys, and 90 percent of the permeability capacity is contained in approximately 26 percent of the reservoir volume.

To date, the project has recovered 103 bbl/flood-acre-ft since waterflood initiation, which represents 50 percent of the total preflood cumulative and 12 percent of the original stock-tank oil in place (OSTOIP). The outstanding feature of this project has been the economical recovery of a sizable quantity of oil at water-oil ratios higher than those normally considered prohibitive. Nearly 70 percent of the recovery to date has been achieved at water-cut values greater than 95 percent.

An ultimate waterflood recovery of 18 bbl/flood-acre-ft or 67 percent of the preflood recovery and 16 percent of the OSTOIP, is predicted. The ultimate primary and Secondary recovery will be 302 bbl/acre-ft and approximately 40 percent of the OSTOIP.

The actual performance is compared with the predicted performance by both the Stiles and the Dykstra-Parsons performance by both the Stiles and the Dykstra-Parsons methods, and applicability of these methods to this particular reservoir is evaluated. The performance of this particular reservoir is evaluated. The performance of this project indicates highly stratified reservoirs can be project indicates highly stratified reservoirs can be successfully and economically waterflooded when either reservoir or economic conditions preclude the use of mechanical and chemical means of mobility control.
Controlled Evaluation of a Surfactant in Secondary Recovery
Authors: Inks C.G. , Lahring R.I.
Published: December 2007

A surfactant waterflood, using a block copolymer of ethylene and propylene oxide (PLURONIC L64*), was started in 1956 in Kansas to determine the commercial feasibility of such a process. The production formation was the Bartlesville sand at a depth of 1,400 ft. Leases in the test area had attained both primary and secondary production peaks, and were on a normal decline when the production peaks, and were on a normal decline when the tests were initiated. The injection wells were taking water at a reasonable pressure and none of the operating conditions were particularly unusual. The leases were selected primarily because of normal operating conditions, and not primarily because of normal operating conditions, and not because of any serious problems demanding remedies. Oil production and water injection data were recorded during the 10-year test period, and their compilation indicates that the surfactant resulted in an increase of about 9 percent in secondary oil production. Other benefits derived from the surfactant injection were lower injection pressure that resulted in reduced power consumption and pressure that resulted in reduced power consumption and reduced erosion of the pumps; and lower calcium scale buildup. These fringe benefits more than offset the cost of the surfactant used.

Introduction

During the past several decades, considerable research has been carried out on secondary recovery of crude oil that remains in the producing formation despite the most efficient, current primary production practices. Methods are constantly sought of increasing recovery of oil, while at the same time improving the economic efficiency of operations.

One method that has received intensive study over the years is the use of a surfactant as a waterflood additive. Laboratory tests show conclusively that dilute solutions of surfactants remove considerably more oil from unconsolidated sand cores than does water alone. The loss of surfactant by adsorption at solid-liquid interfaces has caused serious doubt that surfactants can be used economically as waterflooding additives. This is especially true with anionic and cationic surfactants, and to a lesser extent with nonionic surfactants.

This work was undertaken to determine the effectiveness in increasing oil production by injecting water containing small quantities of a nonionic surfactant. The surfactant selected was PLURONIC L64*, a block copolymer based on ethylene and propylene oxide, having the following structure.
Fire Protection for Hydraulic Pumping Installations
Authors: Alford B.J.
Published: December 2007

A comprehensive study was conducted to determine the possible causes of fires in hydraulic pumping installations possible causes of fires in hydraulic pumping installations and to devise a system that would reduce fire hazards to an economic minimum. The study confirmed that the operating temperature of gas engines is sufficient to ignite a power oil leak spraying on the engine.

The system devised for reducing fires uses a shroud for deflecting leaking oil away from the gas engine, detectors to shut down the system in the event of a leak and piping designed to decrease the possibility of leaks. The system has been applied in the Rocky Mountain area at a cost of approximately $700 per power oil pump. The report gives the reasons for selecting this system and evaluates some of the steps taken.

Introduction

On June 15, 1966, at the Shell Oil Co. Rocky Mountain Div.'s Cabin Creek, Section 8, Hydraulic Pumping Installation, a fire resulted in equipment damages of $86,000 plus the value of deferred production. Two other fires had occurred at similar installations. As a result, a comprehensive study was made to determine the possible causes, and to develop a system to minimize these fire hazards.
New Procedure for Wellbore Flash Calculations
Authors: Litvak M. L.
Published: December 2007

This paper describes a new wellbore flash procedure implemented in a compositional reservoir simulator. It is used for calculations of bottomhole pressure (BHP), surface rates, and fluid compositions of a production well from specified well boundary conditions. Coupled wellbore, well tubing, and surface separator models are considered. The procedure for the solution of the wellbore flash problems with specified production rate at stock-tank conditions and with specified tubing-head pressure is developed.

The new procedure has several advantageous features. Wellbore equations and separator flash equations are solved simultaneously. A new iterative technique is applied for the solution of phase-equilibrium and mass-conservation equations for each stage of a separator battery. Material-balance conditions are satisfied exactly in each iteration. A new rigorous algorithm is developed for the calculation of BHP if tubing-head pressure is specified.

Phase-equilibrium computations in surface separator stages consume a large part of CPU time, required for some large compositional reservoir models (about 50%). In the new procedure, K values are calculated by minimizing Gibbs free energy, and mass-conservation equations are exactly solved in each iteration. This approach provides significant computational improvement (by a factor of four) over previous wellbore flash computations in compositional reservoir simulators with a Cray XMP-416.