bluuebunny/crossref_metadata_2025 huggingface dataset:
Obtaining the Minimum Horizontal Stress From Microfracture Test Data: A New Approach Using a Derivative Algorithm
Authors: Jones Colin , Sargeant J. P.
Published: December 2007

This paper presents a new approach to the interpretation of pressure-decline data from microfracture tests. The objective is to determine a representative value for the fracture closure pressure, which we relate to the minimum horizontal stress, σHmin. The method uses a derivative algorithm to identify different flow regimes that may occur during a pressure decline (e.g., wellbore storage and infinite- and fmite-conductivity fracture flow). High-quality data are a prerequisite for this method, but it is simple to use and the necessary computations can be performed easily with modern well-test-analysis software. This method has been applied successfully to data from the North Sea for a number of rock types with permeabilities ranging from effectively zero (claystone) to several darcies (sandstone). Results from different pressure declines for the same interval agree well, and a value often can be quoted for closure pressure to within ±0.5 bar. Several examples are included to demonstrate the advantages of this method. Guidelines for microfracture testing highlight what is important for obtaining test data for this method.
Selection and Application of BaSO4 Scale Inhibitors for a CO2 Flood, Rangely Weber Sand Unit, Colorado
Authors: Shuler P. J. , Freitas E. A. , Bowker K. A.
Published: December 2007

The objective of this study was to develop a cost-effective scale-control program for the Rangely field CO2 project. The primary challenge was to identify scale inhibitors to control an existing barium sulfate (BaSO4) problem at the new, low-pH conditions caused by CO2 injection. A secondary concern was the change in produced-water composition and increased calcium carbonate (CaCO3) scaling tendency caused by the dissolution of carbonate minerals in the reservoir rock by the low-pH CO2 injection water.

Laboratory evaluation identified several polymer-based and phosphonate scale inhibitors for the low pH (estimated 4.5) at CO2 production wells and near-neutral pH conditions in the surface facilities. Field tests show a good correlation to laboratory results. Suitable phosphonate products are preferred to polymer inhibitors because their residual concentrations may be determined accurately, they are generally cheaper, and they have a longer squeeze treatment life.
Capillary Pressure Curves From Centrifuge Data by Use of Spline Functions
Authors: Nordtvedt Jan-Erik , Kolltveit Kristofer
Published: December 2007

This paper presents a new parameter-estimation method to obtain a capillary pressure curve from centrifuge data. The wetting-phase saturation is regarded as a function of the capillary pressure curve and is approximated by a spline function. The average wetting-phase saturation can then be calculated analytically if the coefficients in the spline function are known. We formulate an optimization problem and show how to determine these coefficients—i.e., how to determine the capillary pressure curve. Neither numerical integration nor differentiation is performed at any stage in the calculation. The method fits a capillary pressure curve to the data in the interval given by the experiments without the use of the irreducible-wetting-phase-saturation concept. The presented method compares very well to synthetic data and fits a capillary pressure curve to experimental data with a high degree of accuracy. We compare the method to the Hassler-Brunner and Bentsen-Anli procedures for experimental data from a North Sea reservoir rock.
Cake Filtration With Particle Penetration at the Cake Surface
Authors: Corapcioglu M. Yavuz , Abboud Nelly M.
Published: December 2007

Particles in drilling muds build a filter cake on borehole walls and can migrate into the adjacent porous formation and cause formation damage. This study analyzes cake formation, including particle penetration at the cake surface. Mass-balance equations for captured and suspended particles and the fluid phase are averaged along the cake thickness, taking into account conditions on the surface and the septum. Capture mechanisms, such as surface straining, and internal cake erosion and particle capture are included in the analysis. The results are ordinary differential equations in terms of thickness, average particle concentration, average porosity, and such operational parameters as slurry concentration, injection rate, and volumetric solid fraction. Results show that during early stages of cake formation, penetrated-particle concentration peaks and then declines rapidly shortly thereafter. Comparison of predicted cake thickness with experimental data showed an excellent match.
Measuring Interfacial Tensions in a Gas-Condensate System With a Laser-Light-Scattering Technique
Authors: Haniff M. S. , Pearce A. J.
Published: December 2007

A laser-light-scattering technique was used to measure a range of interfacial tensions (IFT's) from 1 to 10-3 mN/m in a methane/propane gas-condensate system. The data were compared with the Weinaug-Katz (WK) and the Hough-Stegemeier (HS) correlations. Results show that the HS correlation performed better when used on the critical isotherm. On other isotherms, the WK correlation gave the better fit.
On-Site Flow Calibration of Turbine Meters for Natural Gas Custody Transfer
Authors: Ting V. C. , Schexnayder L. L. , Conkling D. B.
Published: December 2007

This paper presents the design criteria, performance characteristics, and calibration procedures relating to a turbine-meter flow-calibration facility used in the high-volume custody transfer of natural gas. The facility, located in Venice, LA, is owned and operated by Chevron U.S.A. Inc. and is used to meter sales volumes of up to 500 MMscf/D [14.16 × 106 std m3/d] at a nominal operating pressure of 1, 000 psig [6.9 MPa]. The system includes three 12-in. [30.48-cm] turbine meters used for sales-volume measurement, a bank of sonic nozzles, and a master turbine meter connected in series with the sales meters. The sonic nozzles and master meter serve as flow-proving and -calibration devices. Sonic nozzles are recommended by the turbine-meter standard for meter calibration.

This paper examines the performance of on-site calibration of gas turbine meters. The Venice facility successfully demonstrated that on-site calibration of gas-metering devices can ensure accurate gas-flow measurement under field conditions.
Field Verification of Drilling Models and Computerized Selection off Drill Bit, WOB, and Drillstring Rotation
Authors: Maidla E. E. , Ohara Shiniti
Published: December 2007

A computer program was developed for the simultaneous selection of a roller-cutter bit, bit bearing, weight on bit (WOB), and drillstring rotation that minimizes drilling cost per foot for a single bit run. Two drilling models were tested with data from five wells located offshore Alagoas, Brazil. Results show that the rate of penetration (ROP) of the fifth well can be predicted with coefficients calculated from the four previous wells, resulting in cost savings.
Corrosion-Resistant Alloys for Hot, Deep, Sour Wells: Properties and Experience
Authors: Asphahanl A. I. , Prouhèze J. C. , Petersen G. J.
Published: December 2007

Nickel-based, corrosion-resistant alloys (CRA's) were subjected to extensive corrosion testing and evaluation for potential use in hot, deep, sour wells. The Ni-Cr-Mo-W system was used in sour-gas wells in south Mississippi, Wyoming, and Mobile Bay. Corrosion data, mechanical properties, and resistance to environmental stress cracking are described for several oil country tubular goods (OCTG). Better understanding of metallurgical factors and of the role of alloying for enhanced resistance to corrosion, along with advances in materials processing, are reviewed in terms of their impact on OCTG product reliability, improved safety, and cost-effectiveness.
Stabilization of Montmorillonite Clay in Porous Media by High-Molecular-Weight Polymers
Authors: Zaitoun Alain , Berton Nicole
Published: December 2007

A dynamic method is proposed for checking the stability of clay in porous media for different brine conditions and the stabilizing effect provided by several anionic and nonionic high-molecular-weight polymers. The method consists of injecting brine at decreasing salinity levels into clayey sandpacks until unstabilized permeability reduction is reached from the dislodging of clay particles that become trapped in pore restrictions. The last stable state before clay destabilization is characterized by a critical salinity concentration (CSC). As expected, montmorillonite clay 5% dispersed in a sandpack is more stable in the presence of KC1 than NaCl brines, giving CSC values of 5, 000 and 27, 500 ppm, respectively. Polyacrylamides are much better clay stabilizers than carboxymethyl cellulose (CMC) or xanthan gum (XG), lowering the CSC of KC1 to 1, 000 to 2, 000 ppm and the CSC of NaCl to 6, 000 to 7, 000 ppm. A low-molecular-weight shear-degraded polyacrylamide is shown to keep good stabilizing power without inducing the high permeability reduction values obtained after adsorption of high-molecular-weight products. In addition to preventing clay migration, polyacrylamides are also shown to inhibit clay swelling.
Analysis of Cementing Turbulators
Authors: Wells M. R. , Smith R. C.
Published: December 2007

This paper presents the results of a study to determine the ability of commercially available mechanical aids called "turbulators" to alter the flow profile and thus enhance the displacement efficiency of typical cementing operations. Results are presented for both the predictions and the measurements showing the effects of pump rate, viscosity, density, and turbulator blade geometry on the induced flow angle along the pipe axis (thus effective swirl length). The results indicate that mud-displacement efficiency can be improved dramatically with mechanical aids that alter the flow profile in the annulus between the casing and the hole. Simple guidelines are provided for spacing turbulators, and two case histories are presented that substantiate the laboratory findings.
Pore-Scale Heterogeneity From Mercury Porosimetry Data
Authors: Yuan H. H.
Published: December 2007

This paper describes a quantitative method of determining pore-scale heterogeneity with constant-rate mercury porosimetry data from the apparatus for pore examination (APEX). Besides being used as a measure of heterogeneity, APEX pore-scale information can be used to assess quantitatively the effect of rock texture or pore geometry on the efficiency of any process, such as EOR, aimed at recovering waterflood residual oil. The paper shows a method for calculating EOR displacement efficiency from APEX poroshmetry data. Berea sandstones and San Andres dolomites are used as examples.
Permeability Modification by In-Situ Gelation With a Newly Discovered Biopolymer
Authors: Vossoughi Shapour , Buller C. S.
Published: December 2007

In a typical gelled polymer process, a polymer reacts with a metal ion to yield a 3D crosslinked system. The success of the process depends on monitoring a large number of variables, including the concentrations of the metal ions, polymer, and reducing agent. Controlling these variables in field-scale tests is extremely difficult, if not impossible. Devising a process with fewer variables is therefore desirable. The in-situ gelation process in this paper uses a newly discovered biopolymer produced by Cellulomonas flavigena Strain KU. The bacteria produce the biopolymer when cultured in a simple salts medium containing any one of a variety of hexoses, pentoses, disaccharides, or such inexpensive substrates as starch or molasses as the carbon and energy sources for growth. The polymer produced remains associated with the producer bacteria, causing them to aggregate and to settle out from the growth medium. The polymer is extracted from the bacteria easily by suspension in dilute alkali. Upon neutralization of such extracts, the polymer precipitates as a hydrogel. The gelation process is reversible, and the hydrogels are stable at high temperatures. A linear coreflood was performed to reveal the feasibility of using the microbial polymer for the in-situ gelation process. The core initially was waterflooded and then flushed with acid. The subsequent injection of an alkaline solution of the polymer resulted in in-situ formation of hydrogels.
Permeability Reduction by a Xanthan/Chromium (III) System in Porous Media
Authors: Hejri Shahab , Francois Jousset , Green D. W. , McCool C. S. , Willhite G. P.
Published: December 2007

This paper presents an experimental study on gelation of a xanthan/chromium(III) system in unconsolidated sandpacks at frontal velocities between 3 and 120 ft/D. High flow resistance developed at specific locations in the sandpacks in experiments conducted at velocities up to 35 ft/D; the locations correlated with velocity. No significant flow resistance developed in the sandpacks at frontal velocities of 83 and 118 ft/D. The effects of flow and shear rates and permeability on development of high flow resistance in the sandpacks are discussed. A conceptual model of the gelation process that incorporates filtration of gel aggregates is presented.
Performance Review off a Miscible CO2 Tertiary Project: Rangely Weber Sand Unit, Colorado
Authors: Hervey J. R. , Iakovakis A. C.
Published: December 2007

A miscible CO2 flood was initiated in the Rangely Weber Sand Unit (RWSU) in Colorado in Oct. 1986. The project calls for injection of a 30% slug of CO2 at a 1:1 water-alternating-gas (WAG) ratio. Ultimate incremental recovery is estimated to be 114 million STB. Current incremental recovery accounts for 34.5% of production.
Design of a Major CO2 Flood, North Ward Estes Field, Ward County, Texas
Authors: Winzinger Rudi , Brink J. L. , Patel K. S. , Davenport C. B. , Patel Y. R. , Thakur G. C.
Published: December 2007

The reservoir engineering aspects of the design of a major west Texas CO2 flood are presented. The design included a detailed fieldwide geologic study, a CO2 injectivity test, laboratory work, and reservoir simulation. CO2 flooding is predicted to recover an additional 8% of the original oil in place (OOIP).
Liberation of Solution Gas During Pressure Depletion of Virgin and Watered-Out Oil Reservoirs
Authors: Kortekaas Theo F. M. , van Poelgeest Frits
Published: December 2007

Multipurpose experimental equipment was constructed to investigate the buildup of gas saturation during depressurization of virgin and watered-out oil reservoirs at representative conditions. The measured dependencies of critical gas saturations on gas/oil interfacial tension (IFT), amount of dissolved gas, pressure-decline rate, and structure of the porous medium are discussed. In addition, experimental results indicating significant reductions of waterflood residual oil saturation (ROS) owing to the presence of a gas saturation are presented.
Predicting Temperature Profiles in a Flowing Well
Authors: Sagar Rajiv , Doty D. R. , Schmldt Zellmir
Published: December 2007

A simple model suitable for hand calculations is presented to predict temperature profiles in two-phase flowing wells. The model, developed with measured temperature data from 392 wells, assumes that the heat transfer within the wellbore is steady-state. Comparisons between the model's predictions and field data indicate that the model is highly accurate within its range of application.
Modeling and Design of Jet Pumps
Authors: Hatzlavramidis D. T.
Published: December 2007

Models for jet pumps currently are derived under the assumption that the power and well fluids are incompressible liquids that, in many cases, are assumed to have equal densities. When either the well or the power fluid contains gas, current design practices still use the equations for incompressible liquids and account for the presence of gas by modifying the mass-flow-rate ratio and the friction-loss coefficients. This paper proposes a new approach to modeling pumps operating under multiphase-flow conditions.
Use of Low-Shear Pumps and Hydrocyclones for Improved Performance in the Cleanup of Low-Pressure Water
Authors: Flanigan David A. , Stolhand James E. , Shimoda Elwyn , Skilbeck Frank
Published: December 2007

Although the advantages of using hydrocyclones for oily water cleanup are well proven, their use has been limited to applications where adequate system feed pressure for satisfactory operation was present. To use hydrocyclones in low-pressure operations, research testing was undertaken to determine the most suitable pumping system. Successful field trials with a low-shear progressive cavity pump and a single-liner hydrocyclone were conducted in the U.S. These trials provided the basis for full-scale tests on the Hutton platform in the U.K. sector of the North Sea. These tests demonstrated the feasibility of using large, low-shear, progressive cavity pumps in conjunction with multitube hydrocyclone units. A long-term evaluation of the pumped system was completed on the Hutton platform following these reported results. This work not only demonstrated the feasibility of pumped hydrocyclone oily water cleanup systems, but also resulted in analytical techniques that greatly assist in optimizing hydrocyclone operation.
A New Caustic Process for Softening Produced Water for Steam Generation
Authors: Jan R. J. , Reed T. G.
Published: December 2007

Oilfield produced water containing a high concentration of total dissolved solids (TDS) and hardness can successfully be softened for use as oilfield steam-generator feedwater. At the Belridge field in Kern County, CA, the combination of caustic softening and weak-acid cation exchange has been used to soften produced water containing 11, 000 TDS and 550-ppm hardness to < 1-ppm hardness. The resultant sludge containing calcium carbonate and magnesium hydroxide is concentrated by centrifuging and is disposed of in a landfill. Compared to the use of conventional strong-acid ion exchange followed by weak acid or weak acid followed by weak-acid ion exchange systems, the process offers the benefits of lower capital and chemical costs, partial silica removal, and elimination of liquid waste discharge. This paper gives design parameters and operating conditions and discusses future applications in thermal recovery projects.
Modeling Pressure-Transient Behavior of Sectionally Homogeneous Reservoirs by the Boundary-Element Method
Authors: Kikani Jitendra , Horne Roland N.
Published: December 2007

Pressure-transient solution in a piecewise homogeneous reservoir with arbitrary geometry of each region is proposed by the Laplace domain boundary-element method (BEM). Any number of such regions with different rock and fluid properties can be included in the solution procedure. This formulation can solve for impermeable barriers of any shape, size, and orientation, including large pressure-support sources (aquifers) and fluid-injection problems that show composite behavior. Any number of line-source wells can be included. Example solutions are verified against known analytical solutions. Injection-fluid-front velocity is calculated as part of the solution; thus, the fluid fronts can be tracked in a quasistationary sense. The analytical aspects of this procedure are discussed. BEM solutions are accurate because the method retains the free-space Green's function of the governing differential operator as a global weighting function in the integral equation.
A New Front-Tracking Method for Reservoir Simulation
Authors: Bratvedt Frode , Bratvedt Kyrre , Buchholz C. F. , Holden Lars , Holden Helge , Risebro N. H.
Published: December 2007

This paper presents a new numerical method for solving saturation equations without stability problems and without smearing saturation fronts. A reservoir simulator based on this numerical method is under development. A set of test problems is used to compare the simulation results of the new simulator with those of an existing finite-difference simulator (FDS).
The Averaging Process in Permeability Estimation From Well-Test Data
Authors: Oliver Dean S.
Published: December 2007

Permeability estimates from the pressure derivative or the slope of the semilog plot usually are considered to be averages of some large ill-defined reservoir volume. This paper presents results of a study of the averaging process, including identification of the region of the reservoir that influences permeability estimates, and a specification of the relative contribution of the permeability of various regions to the estimate of average permeability. The diffusion equation for the pressure response of a well situated in an infinite reservoir where permeability is an arbitrary function of position was solved for the case of small variations from a mean value. Permeability estimates from the slope of the plot of pressure vs. the logarithm of drawdown time are shown to be weighted averages of the permeabilities within an inner and outer radius of investigation. The estimate is shown to be influenced most strongly by permeabilities at a distance r=0.015(k¯t/ϕμct)½[5.6×10−5]. Fully 50% of the contribution to the permeability estimate is from the reservoir volume in the range from r=0.011(k¯t/ϕμct)½[4.1×10−5] to r=0.022(k¯t/ϕμct)½[8.1×10−5]. An analytic expression for the weighting function is derived in this paper.
Temperature Data for Optimizing Cementing Operations
Authors: Tllghman S. E. , Benge O. G. , George C. R.
Published: December 2007

Cement slurries must be designed for the downhole conditions at the time of the cement job. Of all the factors that influence cement slurry design, bottomhole circulating temperature (BHCT) is potentially the most important element. Measurement of BHCT, the temperature within the wellbore that accounts for the cooling effects of fluid circulation, is not a standard field procedure for several reasons. A recently developed tool, however, simplifies temperature measurement under true circulating conditions. The new temperature recorder allows BHCT to be measured under normal operating conditions. The electronic memory recorder is dropped down the drillstring or lowered by wireline/slickline. When the tool is retrieved, the recorded data are transferred to a personal-computer disk. With this temperature information, the cement slurry can be designed with a high degree of confidence. This paper describes the temperature-recording memory gauge, its features, and its operation. Examples of data collected under field conditions illustrate its application.
Method To Quantify Viscosity Effects on Dispersion Test Improves Testing of Drilling-Fluid Polymers
Authors: Hale A. H.
Published: December 2007

Many of the available polymers are claimed to inhibit cuttings dispersion effectively. The experiments done to support these claims show the effectiveness of the polymers in inhibiting dispersion of sized shale through the hot rolling dispersion test. One of the most significant factors in this test is the viscosity of the test fluid. The fluid viscosity can create the illusion that a particular product effectively inhibits cuttings dispersion. A method is presented in which the dispersion-inhibiting effect of viscosity can be subtracted from the amount of shale retained to obtain a more accurate determination of the effectiveness of a drilling-fluid additive to inhibit cuttings dispersion. A comparison is presented that clearly demonstrates that the partially hydrolyzed polyacrylamide (PHPA) polymer is the best available polymer to inhibit cuttings dispersion cost-effectively.
Gas-Influx Detection With MWD Technology
Authors: Bryant T. M. , Grosso D. S. , Wallace S. N.
Published: December 2007

This paper describes a new gas-influx detection technique that monitors the acoustic responses of annular measurement-while-drilling (MWD) pulses to provide a rapid, early warning of the development of potential gas-kick situations. The technique has been evaluated in both water- and oil-based muds during about 40 gas-kick simulations at two full-scale testing facilities. Free gas is identified by amplitude attenuation and phase delay of MWD fundamentals and their harmonic frequencies. Detection is independent of influx location because the entire length of the annulus between the bit nozzles and a surface-pressure transducer is sampled. Detec tion of potential gas-kick situations generally occurred within minutes of influx initiation, before any significant gas expansion.

Some tests also evaluated a downhole MWD mud-resistivity sensor. Results indicated that both these techniques, and particularly the pulse acoustics, can provide unequivocal confirmation of gas and an earlier warning of gas-kick situations than conventional kick-detection techniques.
Simulation of Block-to-Block Processes in Naturally Fractured Reservoirs
Authors: Fung Larry S.-K.
Published: December 2007

Simulation of fractured reservoirs with the dual-porosity/dual-permeability approach involves discretization of the solution domain into two collocated continua called the matrix and the fracture. The original idealized model assumes that the matrix acts essentially as a source or sink to the fracture, which is the primary conduit for fluid flow. In multiphase flow situations, this idealization was found to be inadequate. Enhancements are needed to represent the local matrix/fracture and matrix/matrix drainage and imbibition processes. Attempts to represent these processes include the gravity-segregated model, the subdomain model, the pseudofunction method, and the dual-permeability model.

This work examines the mechanisms involved in gas/oil gravity drainage in terms of the block-to-block process. Current methods for treating this problem are reviewed to identify deficiencies. A new approach is proposed in which these mechanisms can be represented properly in the field-scale simulation of these reservoirs. The method involves the calculation of pseudo capillary potentials, which in an average sense (on a computational block basis) give the correct flow behaviors. These pseudos can be calculated a priori if a vertical equilibrium (VE) assumption can be made about the fluid distribution in the matrix blocks. When the VE assumption is not valid, the pseudos can be determined from fine-grid simulations.
Small-Particle-Size Cement
Authors: Ewert D. P. , Almond S. W. , Bierhaus W. M.
Published: December 2007

Successful remedial cementing has historically been difficult in wells with large-interval, multizone, gravel-packed completions. The reason is the inability of conventional oilfield cements to penetrate gravel packs adequately. Small-particle-size cement (SPSC) was developed to penetrate gravel packs and to provide the zonal isolation required. This paper details the laboratory work, job design, and field implementation of this new cement.
Subsidence-Induced Well Failure
Authors: Bruno M. S.
Published: December 2007

This paper describes the influence of reservoir compaction and surface subsidence on well casing damage, including compression, buckling, shear, and bending failure mechanisms. Casing damage from shear stresses within the overburden is identified as a primary failure mode for many reservoir conditions. This is consistent with several field observations.
Field Testing of Variable-Speed Beam-Pump Computer Control
Authors: Guffey C. G. , Rogers J. D. , Hester L. R.
Published: December 2007

A variable-frequency drive (VFD) used to change the speed of beam-pump motors was tested on seven wells to control the rate of oil pumping. Increased power consumption was observed, but on certain wells, increased production rates can result in overall benefits.
A Model Describing Steam Circulation in Horizontal Wellbores
Authors: Arthur J. E. , Best D. A. , Lesage R. P.
Published: December 2007

A model to evaluate heat losses, steam quality, and pressure profiles during steam circulation in a horizontal wellbore was developed. The model simulates countercurrent flow stream and accounts for the interactions of heat transfer, fluid flow, phase changes, slippage between steam and water, and flow regime changes. Development of this model arose from a need to determine the wellbore heat-loss distribution during the warm-up phase in Mobil Oil Canada's (Mocan's) horizontal well at Cold Lake. Results from the model were verified with actual field data.
Feasibility of Cyclic CO2 Injection for Light-Oil Recovery
Authors: Thomas G. A. , Monger-McClure T. G.
Published: December 2007

Field performance trends are presented for cyclic CO2 injection in light-oil sandstone reservoirs. Results indicate that the mass of CO2 injected is the best predictor of stimulated oil production rate and ultimate incremental recovery. The correlations enhance understanding of the single-well process, improve reservoir selection criteria, and suggest operational guidelines.
Permeability Modification Simulator Studies of Polymer-Gel-Treatment Initiation Time and Crossflow Effects on Waterflood Oil Recovery
Authors: Gao Hong W. , Chang Ming-Ming , Burchfield Thomas E. , Tham Min K.
Published: December 2007

A 3D, three-phase (oil/water/gas) permeability modification simulator was developed by incorporating an in-situ gelation model into a black-oil simulator (BOAST). Several important features that describe gel-system transport in a porous medium were considered. Simulation results showed that the effectiveness of a gel treatment in either an injection or production well or in an injection and a production well together decreased as kV/kH increased. The best gel treatment initiation time in the injection well only or the injection and production wells together was approximately when water breakthrough occurred. The new simulator is useful to simulate and to optimize any combination of primary production, waterflooding, polymer flooding, and permeability modification treatments.
Oil Recovery by Imbibition in Low-Permeability Chalk
Authors: Cuiec Louis , Bourbiaux Bernard , Kalaydjian François
Published: December 2007

This paper describes experimental studies of spontaneous imbibition of oil by water in a low-permeability outcrop chalk. At constant and high interfacial tension (IFT), the importance of capillary forces and the existence of a predominantly countercurrent mechanism were established. Additional experiments were performed to investigate the influence of length and of various boundary conditions. In another investigation, we modified the IFT at the sample boundary by using pairs of conjugate phases of the w-hexane/ethanol/brine ternary system. Final recovery increased when IFT was lowered. We give a numerical interpretation for this last result.
Proper Nozzle Location, Bit Profile, and Cutter Arrangement Affect PDC-Bit Performance Significantly
Authors: Garcia-Gavito Daniel , Azar J. J.
Published: December 2007

An experimental study comparing the effects of polycrystalline-dia-mond-compact (PDC) -bit design features on the dynamic pressure distribution at the bit/rock interface was conducted on a full-scale drilling rig. Results showed that nozzle location, bit profile, and cutter arrangement are significant factors in PDC-bit performance.
New Technologies Address the Problem Areas of Coiled-Tubing Cementing
Authors: Carpenter R. B.
Published: December 2007

Coiled-tubing cementing has been practiced successfully on the Alaskan North Slope for several years. This paper discusses the special problems faced when this technology was applied to offshore U.S. gulf coast operations. The innovative solutions and procedures developed to improve the economic and technical success of coiled-tubing cementing are also discussed. Comparative laboratory and computer studies, as well as field case histories, will be presented to show the economic merit of this technology.
A Practical Approach to Drilling-Fluid Surveillance and Management
Authors: McLane M. A. , Medley G. H.
Published: December 2007

Since the mid-1980's, Exxon Co. U.S.A. has used low-solids, polymer-extended (LSPE) drilling fluids extensively in its Rocky Mountain operations. These muds, combined with good surveillance and management, have improved drilling performance and reduced costs significantly. This paper summarizes our experience with LSPE muds and describes surveillance techniques developed to optimize drilling performance. It also reviews guidelines for maintaining these muds and discusses limitations on their use. Case histories from three Wyoming field areas are included for background data. These field data are used to describe the evolution of LSPE mud surveillance tools and to illustrate the benefits of using an LSPE mud system. Potential problems that may occur when these muds are used also are discussed.
Application of Freshwater and Brine Polymer Flooding in the North Burbank Unit, Osage County, Oklahoma
Authors: Moffitt P. D. , Zornes D. R. , Moradi-Araghi Ahmad , McGovern J. M.
Published: December 2007

A freshwater polymer-flood project was implemented in a 1, 440-acre area of the North Burbank Unit (NBU) in 1980 with sequential injection of 4.2 million lbm of polyacrylamide and 4.0 million lbm of a 2.9% aluminum citrate crosslinking solution. Response to polymer flooding has been very pronounced, with ultimate incremental oil recovery projected to exceed 2.5 MMSTB of oil and total project oil expected to be 4.5 MMSTB. A crosslinked polymer-flood process for use in brine was developed that displays equally favorable performance characteristics as the freshwater polymer-flooding system.
Measurement and Computation of Near-Critical Phase Behavior of a C1/nC24 Binary Mixture
Authors: Bjorlykke Ole P. , Firoozabadi Abbas
Published: December 2007

Equations of state (EOS) satisfactorily predict phase behavior and density of reservoir fluids outside the retrograde and near-critical regions. Predictions in these regions, however, are an unresolved problem. A first step to improve the understanding of retrograde and near-critical regions would be to measure the phase behavior of well-defined binary hydrocarbon mixtures of very different molecular sizes. This paper reports measurements on a C1/nC24 binary mixture with a wide retrograde and critical region. Measured dewpoints are in the range of 12, 000 to 15, 500 psia [82.74 to 106.8 MPa]. Retrograde liquid volumes and gas densities at three different temperatures were measured. Liquid phase compositions and densities also were measured on a selective basis. Conventional use of the EOS failed to predict the phase behavior of the model binary system. The data will be useful in modifying the EOS in the retrograde and near-critical regions.
Brassey Oil Field, British Columbia: Development of an Aeolian Sand—A Team Approach
Authors: Woofter D. M. , MacGillivray John
Published: December 2007

This paper presents a case study of how an aggressive engineering/geoscienceteam approach provided the development plan for the Brassey oil field. Miscibleflooding of the field began only 2 years after discovery. The geological andgeophysical technical contribution to field development are emphasized.
Estimation of Radial Permeability Distribution From Well-Test Data
Authors: Oliver Dean S.
Published: December 2007

This paper presents a method of estimating a radial permeability distribution that would reproduce the pressure data obtained in a well test. The method is applied to three examples: permeability variation in a composite reservoir, porosity variation in a composite reservoir, and permeability variation with inaccurate data. The permeability estimates obtained are shown to be smoothed versions of the actual permeability distribution, and an estimate for the resolution width of the smoothing is provided. One significant advantage of the solution method applied in this paper is the ability to estimate permeability variation without dividing the reservoir into zones of constant permeability.
State-of-the-Art Simultaneous Downhole Flow-Rate and Pressure Measurement Equipment
Authors: Haws G. W. , Knight B. L.
Published: December 2007

Development of simultaneous downhole flow-rate/pressure measurement equipment has permitted better determination of reservoir properties. Application of such equipment to layered reservoirs allows determination of individual layer properties. This paper reviews state-of-the-art pressure and flow-rate devices, discusses the advantages and limitations of specific equipment, and addresses the need to evaluate current tools and areas for future research.
Proton Magnetic Resonance and Pore Size Variations in Reservoir Sandstones
Authors: Howard James J. , Kenyon William E. , Straley Chris
Published: December 2007

Proton nuclear-magnetic-resonance (NMR) longitudinal relaxation time, T1, in water-saturated sandstones is related closely to pore size distributions. Most of the sandstones shown in this paper exhibit a relatively narrow T1 distribution curve, corresponding to a rather narrow distribution of the large pores visible by optical microscopy of thin sections. The surface relaxivity, ρ, which scales NMR T1 into pore size, is evaluated by comparing mean T1 for each sample with average pore diameter and volume/surface area data obtained from digitized thin sections. Permeability estimated from NMR parameters closely approximates measured permeability for these samples. These permeability estimates are closer than the variations in surface relaxivity would predict. This apparent contradiction results from parallel effects on the permeability and proton relaxation by clays in the pores.
Field Application of a Method for Interpretation of Horizontal-Well Transient Tests
Authors: Shah Piyush C. , Gupta Deepak K. , Singh Lehmbar , Deruyck Bruno G.
Published: December 2007

In a multitransient test in the Bombay High field offshore India, simultaneous measurement of downhole pressure and flow rate enables identification of early- and late-time pseudoradial-flow regimes and intermediate linear flow. Analysis of these successive flow regimes yields estimates of the anisotropic formation permeabilities and the mechanical skin factor. In a second interpretation step, these estimates are refined through a weighted, nonlinear least-squares history match of either the measured transient-wellbore-pressure or the flow-rate data. An algorithm is presented to compute the well rate from transient pressure, given the characteristic response model of the single-well system.
A Unified Model for Predicting Flowing Temperature Distribution in Wellbores and Pipelines
Authors: Alves I. N. , Alhanati F. J. S. , Shoham Ovadia
Published: December 2007

This paper presents a general and unified equation for flowing temperature prediction that is applicable for the entire range of inclination angles. The equation degenerates into Ramey's equations for ideal gas or incompressible liquid and into the Coulter and Bardon equation, with the appropriate assumptions. This work also proposes an approximate method for calculating the Joule-Thomson coefficient for black-oil models.
Application of Curable Resin-Coated Proppants
Authors: Norman L. R. , Terracina J. M. , McCabe M. A. , Nguyen P. D.
Published: December 2007

Laboratory investigation of the interactions between fracturing fluids and resin-coated proppants (RCP's) revealed (among other conclusions) that RCP's are incompatible with oxidizing breakers. Areas covered included RCP effect on fluid rheology, fluid relationship to RCP strength, theoretical study of required RCP strengths to prevent flowback, and experimental measurement to establish minimum strength.
Interpretation and Theoretical Modeling of Scale-Inhibitor/Tracer Corefloods
Authors: Sorbie K. S. , Wat R. M. S. , Todd A. C.
Published: December 2007

This paper describes a theoretical approach to determine the inhibitor dynamic adsorption isotherm from coreflood experiments. The main feature of the isotherm that contributes principally to the long squeeze life is highlighted. The problems of modeling near-well squeeze treatments and an improved simulator are discussed.
Optimal Fracture Stimulation of a Moderate-Permeability Reservoir — Kuparuk River Unit, Alaska
Authors: Pearson C. M. , Bond A. J. , Eck M. E. , Lynch K. W.
Published: December 2007

Sixty-five percent of the reserves of the Kuparuk River field, the second-largest producing oil field in the U.S., is contained in a 20- to 80-md-permeability sandstone. This paper provides details of stimulation design advances made over the past 3 years in this formation. The design steps for optimizing fracture treatments in a moderate-permeability formation require primary emphasis on fracture conductivity rather than on treatment size or fracture length. This philosophy was used for the 140 new wells documented in this paper. Treatment size was gradually increased once a commensurate increase in fracture conductivity was obtained. Applying the new design to the refracturing of 88 producing wells in the field resulted in an incremental 40, 000 BOPD, a significant portion of the field's 300, 000 BOPD.
Estimation of Capillary Pressure and Relative Permeability Functions From Centrifuge Experiments
Authors: Nordtvedt J. E. , Mejia Gerardo , Yang Pin-Huel , Watson A. T.
Published: December 2007

A method to estimate capillary pressure and relative permeability curves simultaneously from transient, multirate centrifuge experiments performed on homogeneous rock is presented. The unknown functions are represented with B-splines, and the number of knots and coefficient values are selected through a regression-based procedure. The method is demonstrated by use of experimental data for dolomite and sandstone samples with air/water and oil/water fluid systems. An analysis of the accuracy of the estimates is presented. The capillary pressure curve and regions of both relative permeability curves can be estimated accurately.
Recent Advances in the API Quality Program
Authors: Gollhofer F. R.
Published: December 2007

The API now has more than 3 years’ operating experience in licensing manufacturers under the API Quality Program. The API evaluation procedures, described in this paper, provide consistency in evaluation and should allow full participation of petroleum equipment suppliers in the worldwide market during the 1990's and into the 21st century. The program's flexibility will allow it to cope with significant changes resulting from the planned European Common Market's "Global Approach to Certification and Testing" scheduled to occur in 1992.
Scale Prediction and Laboratory Evaluation of BaSO4 Scale Inhibitors for Seawater Flood in a High-Barium Environment
Authors: Mazzolini E. I. , Bertero Luigi , Truefitt C. S.
Published: December 2007

The potential for scale formation after seawater injection must be carefully studied when a new oil field is being developed in order to provide proper input data for the basic engineering design. This paper presents the results of a study of several facets of scale occurrence and control for a developing North Sea field characterized by a high-salinity, high-barium (up to 1, 000 ppm) formation brine. The results justify consideration of new technologies, such as treatment of the seawater to reduce the sulfate content.
Multilayer Flowmeter Testing Combined With 3D Field Modeling To Enhance the Ameland Field Development
Authors: Vogelij Harry N. J. , Leach Michael J. , Kapteyn Pieter K. A.
Published: December 2007

To assess the level of differential layer depletion in the Ameland gas field, production logging surveys were conducted and interpreted with a multilayer testing (MLT) technique to derive layer pressures. Results were used in a 3D simulation study showing that layer pressure differentials were controlled by offtake redistribution and could be sustained only if vertical permeabilities in siltstone/shale layers were extremely low. Units in undrained flank blocks could be underdepleted by as much as 10 MPa and drilling these blocks would increase developed reserves.
High-Pressure Well Design
Authors: Krus Harrle , Prieur Jean-Marie
Published: December 2007

Shell U.K. E&P (Shell Expro), operator in the U.K. North Sea on behalf of Shell and Esso, plans to drill 20 high-pressure wells during the next 2 years. The well design is based on new standards developed after the U.K. Dept. of Energy restriction on high-pressure drilling in the autumn of 1988. Studies were carried out to optimize casing design and drilling performance on these wells. Several casing schemes, including a slim-hole option, were analyzed. The material specifications for casing and drillpipe were reviewed to ensure that they met the loads imposed during drilling, well-control, and well-testing operations. The requirement for sour-service material was weighted against possible H2S adsorption by the mud film. As a result, a new drillstring and two high-pressure casing schemes have been specified. The high-pressure casing scheme used depends on the maximum expected surface pressure.
Blowout Risk Analysis of Gas-Lift Completions
Authors: Grassick D. D. , Kallos P. S. , Dean Simon , King S. D. J.
Published: December 2007

A dynamic risk analysis was performed on four different gas-lift completions using a computer simulator. Results are presented to allow comparison of the designs in terms of blowout risk and minor leakage during production and to provide insight into the effect of critical components and operations on the overall well safety.
Specific Surface and Fluid Transport in Sandstones Through NMR Studies
Authors: Borgia Glullo C. , Brighenti Giovanni , Fantazzini Paola , Fanti Gian D. , Mesini Ezio
Published: December 2007

Recent nuclear magnetic resonance (NMR) studies in water-saturated porous media showed that magnetic resonance relaxation of 1H nuclei is a powerful tool for studying the interplay between geometry and fluid transport. Proper combinations of spin-lattice relaxation lifetime, T1, and porosity allow permeability to be predicted. T1, as defined here, provides a bridge between structural and transport properties because it can be viewed as a dynamically weighted (by diffusion) version of the specific surface. In this paper, we probe this role of T1 for a suite of clean sandstone samples in which, besides permeability and porosity, specific surface by mercury porosimetry and the formation resistivity factor (FRF) also have been measured. We studied the correlations among these properties and found that the ability of T1 to estimate permeability is a result of its linear dependence on the PV-to-surface ratio, Vp/S. For clean sandstone rocks, one may view the reciprocal electrical resistivity formation factor, 1/F, as representing the transport properties and the factor T12 as representing the distance scale, giving k∝T12/F. A suitable analysis of the spin-lattice relaxation curve can yield an estimate of an appropriate specific surface pertinent to permeability because it indirectly accounts for the connectivity of the pore space. This NMR approach constitutes a useful technique for a better reservoir characterization and for studying some elusive properties of natural porous media in a nondestructive manner. Theoretical and phenomenological correlations among permeability, porosity, FRF, and PV-to-surface ratio can be established.
Use of Dip and Azimuth Horizon Attributes in 3D Seismic Interpretation
Authors: Mondt Jaap C.
Published: December 2007

Through a combination of interactive interpretation and powerful automated tracking, horizons can be interpreted efficiently on every available trace in a 3D seismic survey. Horizon-related seismic attributes then are extracted and processed to enhance interpretation. Dip and azimuth attributes play an important role in this respect. They enable an interpreter to map subtle trace-to-trace variations in event time or reflection character. Areal pattern analysis leads to detailed interpretations of structure (faults and flexures) and stratigraphy (channels and fans) and to the recognition of geophysical artifacts (statics, acquisition effects, and noise).