bluuebunny/crossref_metadata_2025 huggingface dataset:
Sand Concentration for Maximum Fracture Flow Capacity
Authors: Romero-Juarez Antonio
Published: December 2007

This paper is concerned with the effect of propping-agent concentration on flow capacity of a fracture in the case in which there is embedment of the propping agent. Previous published studies have shown definitely that there is a relationship between fracture flow capacity and propping-agent concentration, and it has been shown that the theoretical results are confirmed by laboratory experiments.

The problem of directly finding sand concentration for maximum flow capacity of a sand-propped fracture is solved, and formulas and charts are given to obtain this concentration under various conditions of effective overburden pressure, medium sand-grain diameter and rock properties. It is shown that, for the same effective overburden pressure and the same rock characteristics, optimum sand concentration in pounds per gallon does not depend on medium sand diameter. For conditions met in hydraulic fracturing operations, it is found that sand concentration in grains per square inch for maximum flow capacity varies within a wide range of values; this indicates the convenience of using data of fracturing pressure and rock characteristics for calculating sand concentration in order to achieve the best results in fracture treatments.

Introduction

It has been pointed out in the published literature that one important factor controls the success of a hydraulic fracturing operation - the propping of the fracture. The main effect of the propping agent is to hold the fracture open by means of the reaction forces that oppose the pressure due to the overburden. It is assumed in this paper that the propping agent is sand, that the grains are spherical and uniform in size, and that this sand is distributed in a monolayer in the fracture.

The existence of a sand concentration value for maximum fracture flow capacity has been recognized since the publication of one of the first studies on the subject. In the reference cited, flow capacity was assumed to be proportional to the cube of the fracture volume per square inch not filled by sand.
A Potentiometric Study of the Effects of Mobility Ratio on Reservoir Flow Patterns
Authors: Bradley H.B. , Heller J.P. , Odeh A.S.
Published: December 2007

A potentiometric model technique is presented for determining the a real sweep efficiency of a five-spot well pattern, at and beyond breakthrough. A sharp interface between displaced and displacing fluids is assumed. Although the prototype system is referred to as a water flood operation, obvious changes in the notation and computations will adapt the results to other displacement processes.

The results of the study include the following.Areal sweep efficiencies for a five-spot well pattern, at and beyond breakthrough, for mobility ratios (displacing to displaced fluid) of 4:1, 2:1, 1:1 and 1:4.Extension of potentiometric analysis to the investigation of the areal sweep-efficiency beyond breakthrough in a five-spot pattern by the application of conformal mapping and conductive-solid models.The use of layers of conductive fabric in representing mobility ratio changes in potentiometric models.The development of a probe mechanism for probing conductive solids.

The results obtained by conductive-cloth models agree with earlier areal sweep efficiencies at breakthrough obtained by Aronofsky and Ramey on the potentiometric analyzer using electrolytic-tank models. Results beyond breakthrough differ from those obtained by the X-Ray Shadowgraph technique. Data from this study show that, for mobility ratios greater than one, water cut rises rapidly as fluid is produced after breakthrough. However, for mobility ratios smaller than one, a large increase in area swept resulted with only a small increase in water cut.

Introduction

In calculating reservoir performance of waterflooding operations and other fluid-injection programs, it is necessary to estimate the areal sweep efficiency before and after injected-fluid breakthrough into production wells. Influence of mobility ratio on oil-production history, before and after breakthrough for a five-spot well pattern, has been studied by X-Ray Shadowgraph techniques and by gelatin models. In none of these investigations was the transition zone controlled experimentally.
Equations for Leak Resistance of API 8-Round Connectors in Tension
Authors: Schwind Brian E.
Published: December 2007

This paper presents stress and leak-resistance equations based on the theory of elasticity for API 8-round connectors in tension and compares results of these equations to those of the finite-element method (FEM) and full-scale physical testing. The new equations identify significant nonconservative aspects inherent in current API methodologies.
Surfactant-Enhanced Low-pH Alkaline Flooding
Authors: Peru Deborah A. , Lorenz Philip B.
Published: December 2007

Sodium bicarbonate was investigated as a potential alkaline agent in surfactant-enhanced alkaline flooding because it has very little tendency to dissolve silicate minerals. In experiments performed with Wilmington, CA, crude oil and three types of surfactants, the bicarbonate/surfactant combination caused a marked lowering of interfacial tension (IFT). Bicarbonate protected the surfactant against divalent cations and reduced adsorption of surfactant and polymer on various minerals. Coreflood tests confirm that sodium bicarbonate plus surfactant can be an effective alternative to the high-pH flooding process.
Near-Critical Condensate Fluid Behavior in Porous Media—A Modeling Approach
Authors: Williams John K. , Dawe Richard A.
Published: December 2007

Retrograde condensate reservoir behavior is complex, particularly the flow behavior of near-critical fluids, with many of the details of the physical processes involved being a matter of speculation. Conventional coreflooding experiments, while providing indispensable macroscopic data (relative permeabilities, capillary pressure, etc.), are very difficult to carry out under representative reservoir conditions and give little insight into the underlying microscopic processes.

Simple physical models can yield many insights into the fundamental pore-scale physics of condensates that may lead to eventual clarification and understanding of the macroscopic processes occurring in the reservoir. The salient features are the use of partially miscible liquid/liquid systems, critical-point universality, and micromodels, giving controlled realizations of porous media. Experimental observations are presented that illustrate pore-scale behavior of near-critical fluids; wettability phenomena and gravity effects are seen to be especially important. Finally, the implications of these observations for macroscopic processes are discussed.
Applications of Real-Time Matrix-Acidizing Evaluation Method
Authors: Prouvost L. P. , Economides M. J.
Published: December 2007

A new technique for real-time matrix-acidizing job evaluation has recently been presented that uses reservoir transients during acid injection to simulate pressure response of the unperturbed reservoir and compares simulated pressures with measured values. The difference between these values is attributed to the changing skin effect. An associated pretreatment injection/falloff test is presented as an essential element of that method. It involves injection of an inert fluid (water or reservoir oil) and analysis of the ensuing falloff for a period during which pumping has stopped, just before acid enters the perforations. Injection resumes immediately thereafter.

Two field case studies, a water-injection well in a fissured carbonate reservoir and an oil well completed in a sandstone reservoir, demonstrate the technique. For both treatments, conclusions are drawn regarding the effectiveness of the acid injection. The job evolution is demonstrated, and forecasts of expected well performance for unstimulated and stimulated cases are presented. The skin evolution is shown as a function of injection time. The simulated and measured pressure values for both treatments are shown, indicating the real-time job progression.
Influence of Compound Grease on the Performance of Premium Connections
Authors: Tsuru Eiji , Maruyama Kazushi , Yazakl Youichi , Peters Ekwere J.
Published: December 2007

We investigated the harmful effect of compound grease on premium connections. The pressure buildup of compound grease trapped between threads was measured during and after makeup of the connection. The resulting hoop stress in the coupling and the reduction in the seal interference were also measured. Mathematical models were developed to calculate coupling stress and grease pressure. Results indicate that for the conventional API buttress-thread profile, the pressure of trapped compound grease remains permanently high after the connection is made up because of the small thread-clearance area. This high pressure results in a high coupling stress and a large reduction in seal interference diameter, thereby degrading the integrity of the connection. To solve this problem, the thread profile was redesigned with a thread-clearance area larger than that of conventional buttress thread. The connection with the new thread design showed a significantly lower pressure buildup, coupling stress, and seal interference reduction than that with the conventional thread design. Therefore, premium connections with the new thread design are recommended over those with conventional buttress thread design for wells in hostile environments.
Temperature Distribution in Synthetic Diamond Cutters During Orthogonal Rock Cutting
Authors: Prakash V. , Appl F. C.
Published: December 2007

A heat-transfer model based on the finite-element method is developed for synthetic polycrystalline-diamond-compact (PDC) cutters used in oil well drill bits. The model is verified by comparison with single-cutter experiments. Effects of process variables, such as film coefficient and diamond thickness, on the temperature distribution in the cutter are studied.
Use of Pattern-Recognition Techniques in Analyzing Downhole Dynamometer Cards
Authors: Dickinson Roderick R. , Jennings James W.
Published: December 2007

Four pattern-matching methods are presented to evaluate the downhole condition of sucker-rod-pumped wells. Comparing the generated pump dynagraph of a well being tested to various downhole dynagraphs characteristic of particular rod-pump problems allows the pattern-matching methods to diagnose a variety of different pump conditions. In the future, one of the pattern-matching methods could be incorporated into an automated system designed to monitor the performance of an oilfield's rod-pumped wells.
Permeability Reduction Mechanisms Involved in In-Situ Gelation of a Polyacrylamide/Chromium(VI)/Thiourea System
Authors: McCool C. S. , Green D. W. , Willhite G. Paul
Published: December 2007

An investigation of the in-situ gelation of a polyacrylamide/chromium(VI)/thiourea system under flow conditions in unconsolidated sandpacks is presented. High flow resistance was observed in a localized section of the sandpacks that was consistent with deep-bed filtration mechanisms. A method to measure the size of aggregates in a gel solution is also presented. Results from this method showed that the gel aggregates grow with reaction time and distance traveled through the sandpack, supporting the conclusion that filtration is a dominant factor in the in-situ gelation process under flow conditions.
Simulation of the Effects of Mixing in Gasdrive Core Tests of Reservoir Fluids
Authors: Negahban Shahin , Shiralkar Gautam S. , Gupta Surendra P.
Published: December 2007

This paper shows that inclusion of a physical dispersion formulation in a fully compositional simulator improves the ability to model and interpret the displacement characteristics of horizontal gasdrive corefloods conducted in 2-in.-diameter, 2- to 32-ft-long, horizontal Berea cores at secondary and tertiary conditions. Foremost among these improvements are (1) quantifying the effects of mixing, characterized by the Peclet number (L/αe), on breakthrough time and displacement efficiency; (2) simulating the effect of core length on miscibility development observed experimentally for multiple-contact-miscible (MCM) displacements with vaporizing/extraction mass transfer, including immiscible behavior in short cores (large mixing) and miscible behavior in long cores (small mixing); and (3) eliminating the need to adjust the number of gridblocks to match coreflood performance.
Development of Correlations To Predict Biopolymer Mobility in Porous Media
Authors: Hejri Shahab , Willhite G. P. , Green D. W.
Published: December 2007

This paper describes the flow and rheological behavior of biopolymer solutions in sandpacks over a wide range of permeability and frontal advance rates. Empirical correlations were developed to estimate polymer mobility in porous media. The correlations are based on porous medium properties, polymer concentration, and rheological parameters for the polymer derived from steady-shear measurements.
Review of an Immiscible CO2 Project, Tar Zone, Fault Block V, Wilmington Field, California
Authors: Spivak Allan , Garrison William H. , Nguyen John P.
Published: December 2007

The Long Beach Oil Development Co. (LBOD) tertiary immiscible CO2 project began in March 1982 with the injection of a mixture of about 85% CO2/15% N2 into the Tar zone of Fault Block V in the Wilmington field, Los Angeles County, CA. The 330-acre [134-ha] project had been waterflooded since 1961, and the water cut was more than 95%. Gas was injected alternately with water for a period of about 5 years. This paper reviews project performance from inception to the end of 1987.
Pressure-Transient Behavior of Horizontal Wells With and Without Gas Cap or Aquifer
Authors: Kuchuk F. J. , Goode P. A. , Wilkinson D. J. , Thambynayagam R. K. M.
Published: December 2007

New analytic solutions are presented in real time and as Laplace transforms for horizontal wells in reservoirs bounded at the top and bottom by horizontal planes. Two types of boundary conditions are considered at these planes, and the Laplace-transform pressure solutions are used to include wellbore-storage and skin effects. Solutions are based on the uniform-flux, line-source solution, but differ from most existing solutions owing to the use of pressure averaging to approximate the infinite-conductivity wellbore condition and use of the correct equivalent wellbore radius for an anisotropic reservoir. New flow periods (regimes) are identified, and simple equations and existence criteria are presented for the various flow periods that can occur during a transient test.
Novel Breaker/Filtration Process Reduces the Cost of Recycling Viscosified Brine Completion Fluids
Authors: McIntyre James A. , Kalnins John M. , Varjlan Richard D. , Powell John
Published: December 2007

A novel process for recycling polysaccharide-viscosified brine completion fluids was developed. The process uses oxidants generated directly in the used brine by electrolysis to "break" the viscosity. The treated brines can be filtered with conventional equipment, reviscosified, and reused. The process has been applied on a laboratory scale to Br-/Cl- brines containing Na+, K+, Ca+2, and Zn+2 cations. Calculations with information from pilot-scale tests on NaBr/NaCl brines indicate that the process should be attractive economically.
Interpretation of Dielectric Permittivity Measurements in the 20- to 50-MHz Frequency Range
Authors: Sherman Michael M.
Published: December 2007

Laboratory measurements of the dielectric permittivity in the 20- to 50-MHz (2×107- to 5×107-cycle/sec) frequency range of brine-saturated rocks are difficult to obtain. An interpretation model is introduced in which laboratory measurements in the 100-to 1300-MHz (2×108- to 1.3×109-cycle/sec) range are used to calibrate an interpretation method in the 20- to 50-MHz (2×107- to 5 × 107-cycle/sec) range. The method is illustrated with an example from the Weber formation in Colorado. In the example, movable oil is calculated using one porosity and two dielectric logs.
Comparison of Implicit and Explicit Methods for Interpreting Displacement Data
Authors: Richmond Peyton C. , Watson A. Ted
Published: December 2007

The Johnson-Bossler-Naumann (JBN) and related methods for interpreting displacement experiments provide explicit, or pointwise, estimates of relative permeability that must be interpolated or smoothed when entire relative permeability functions are desired. In this paper, we compare relative permeability functions obtained with an implicit (regression-based) method with those estimated with explicit values. We show that the functions obtained with the regression-based method are most consistent with the measured data.
Acoustic Flowmeter Field Test Results
Authors: McBane Richard A. , Campbell Raymond L. , DiBello Edward G.
Published: December 2007

The newly developed borehole acoustic flowmeter provides data to locate depth precisely and to quantify gas production from individual gas entries, even when they are spaced closely together, for low-flow-rate gas-producing zones in a typical Devonian shale well in the Appalachian basin. Data from a field test conducted in Aug. 1987 are presented, along with the measurement theory involved. A comparison to a conventional spinner flowmeter on the same well is also presented.
Concrete Hulls for Tension-Leg Platforms
Authors: De Oliveira João G. , Fjeld Svein
Published: December 2007

This paper describes the main features of a concrete-hull tension-leg-platform (TLP) concept developed for the Heidrun field in the Haltenbanken area of the Norwegian sector of the North Sea. The hydrodynamic response and the methods adopted to optimize the hull dimensions, as well as the mooring system and hull mechanical outfitting, are discussed first. Then construction methods are briefly described. Inspection, maintenance, and repair are also addressed. Finally, the advantages of the concrete-hull TLP concept are summarized, including the concrete hull's adaptability to a large range of design requirements, low cost, and short construction time. This paper shows that the concrete-hull TLP is a very cost-efficient solution for the development of deepwater fields.
New Gypsum/Polymer Mud System Eliminates Gumbo Problems on Tommeliten Field Production Wells
Authors: Sunde Egil
Published: December 2007

A new gypsum/polymer mud system eliminated gumbo problems on Tommeliten field production wells. The success of the system was achieved by use of simple, widely known products, with great emphasis placed on understanding chemical interactions. The selection of rheology and mud weight also contributed to the success. The concept resulted in a 30% reduction in time spent on tripping, circulating, and reaming, and no time was lost because of hole instability when casings were run.
An Efficient and Accurate Model for the Structural Analysis of Threaded Tubular Connections
Authors: Kwon Young W. , Klementich Erich F. , Ko Kwang I.
Published: December 2007

A structural analysis model for threaded tubular connections was developed by use of advanced mechanics. This computationally efficient model yields acceptably accurate solutions for stresses compared with other available methods, such as experimental (strain gauge) or finite-element analysis (FEA) procedures. Beam-on-elastic-foundation equations are used to compute stresses caused by the assembly of the connection while the bolt/nut and Lamé equations are used for axial loads and pressures.
A Pore-Level Investigation of Foam/Oil Interactions in Porous Media
Authors: Manlowe David J. , Radke Clayton J.
Published: December 2007

Direct visual studies of foam flow in etched-glass micromodels containing residual oil demonstrate that foam decays as a result of breakage of pseudoemulsion films. Foam films collapse whenever nearby thin aqueous films separating gas bubbles and oil rupture. Consequently, surfactant formulation for foam insensitivity to oil in porous media should be based on stabilizing pseudo-emulsion films.
An Approximate Analysis Method for Multiphase Flow Data
Authors: Vo Dyung T. , Raghavan Rajagopal
Published: December 2007

We analyze responses in wells producing at constant pressure under multiphase flow conditions and present methods to obtain estimates of effective permeability and the mechanical skin factor. All required information can be obtained from constant-composition expansion (CCE; flash) data, and the influence of relative permeability can be incorporated with Jones and Raghavan's theory. We demonstrate data-analysis procedures for semilog and type-curve techniques. We theoretically justify using liquid flow solutions to analyze multiphase flow responses by type-curve matching, and we discuss the design and application of multistep pressure tests.
Transient Pressure Behavior off Commingled Reservoirs
Authors: Kuchuk Flkri J. , Wilkinson David J.
Published: December 2007

This paper presents a new general analytic formulation for pressure-transient behavior of commingled systems (layered reservoirs without crossflow). The formulation includes the effects of surface and downhole flow-rate variations and of wellbore storage resulting from the wellbore volume's location below the flow-rate measuring point (at any location in the wellbore, including the surface and sandface). The method can be applied to a variety of layered reservoirs. Each individual subzone (reservoir) in the system can be different, with different initial and outer-boundary conditions, and each zone can start to produce at a different time. The well completion for each layer can also be different.

New Laplace-domain solutions are presented for partially penetrating slanted wells and partially penetrated wells with and without a gas cap. The solution for slanted wells is based on that of Cinco-Ley et al. but includes the correct effective wellbore radius for the case of an anisotropic formation. Solutions to a few selected commingled systems are also presented to explore the application of the formulation.
Applications of Pulsed-Neutron-Capture Logs in Ekofisk Area Fields
Authors: Corwith Jeffrey R. , Mengel Frank
Published: December 2007

Phillips Petroleum Co. Norway is engaged in an extensive reservoir-monitoring program in the seven greater Ekofisk area fields. This program includes pressure-transient testing, production log surveys, compaction monitoring, and pulsed-neutron-capture (PNC) log surveys. This paper describes the applications of PNC logging in the six Ekofisk area chalk reservoirs and the analysis techniques associated with those applications.

Gas has been injected into the upper portion of the Ekofisk reservoir since 1975, and waterflooding was initiated in 1987. These projects complicate PNC log analysis. Water breakthrough reduces or eliminates the "acid effect, " which can mask any increase in water saturation unless the acid-effect change can be quantified. Gas-saturation changes can introduce systematic error in water-saturation calculations unless taken into account. Phillips Petroleum Co. Norway recognized these complications and developed solutions that can be applied as part of the "standard" analysis techniques. Examples of each application are presented.
Evaluation of Accuracy of Estimating Air Permeability From Mercury- Injection Data
Authors: Kamath Jairam
Published: December 2007

Published theoretical and correlative models and extensions developed during this study were examined to evaluate the accuracy of predicting air permeability from mercury-injection data. A recently developed statistical technique, bootstrapping, was used to compare different variables for correlation with permeability and to demonstrate that correlations by lithology or by field often are not statistically different.
A Method for Designing Fiberglass Sucker-Rod Strings With API RP 11L
Authors: Jennings J. W. , Laine R. E.
Published: December 2007

This paper presents a method for using the API recommended practice for the design of sucker-rod pumping systems with fiberglass composite rod strings. The API method is useful for obtaining quick, approximate, preliminary design calculations. Equations for calculating all the composite material factors needed in the API calculations are given.
Investigation of Retarded Acids Provides Better Understanding of Their Effectiveness and Potential Benefits
Authors: Crowe Curtis W. , McGowan Gerald R. , Baranet Sandy E.
Published: December 2007

An automated acid-reaction kinetics tester (ARKT) was developed and used to evaluate various retarded-acid systems. Studies of several commercially available acid retarders revealed that some functioned by depositing hydrophobic films on carbonate surfaces while others were foaming agents that stabilized a CO2 foam barrier on the rock surface. In the absence of filter-cake development, viscosity imparted by the addition of gelling agents had little effect on reaction rate. Emulsification of acid was shown to reduce reaction rate, with the greatest retardation provided by oil-external acid emulsions.
Lisburne Reservoir Limited-Drainage Test: A Pilot Test Case History
Authors: Currier Barbara H.
Published: December 2007

Pilot tests were run in the Lisburne reservoir before field startup. The second pilot, the limited-drainage test (LDT), obtained production history for a confined producing well, as well as reservoir description and producing-mechanism information. This paper discusses the data gathered and the data interpretation that led to a better understanding of the Lisburne reservoir.
Factors Influencing Unsteady Relative Permeability of a Mixed-Wet Reservoir Rock
Authors: Mohanty K. K. , Miller A. E.
Published: December 2007

Capillarity, viscous fingering, and heterogeneity influence the flow in a core plug and hence affect the relative permeability determined from an unsteady test. Several unsteady water/oil relative permeability tests were carried out in a mixed-wet core while in-situ 3D saturation distribution was monitored by a computerized-tomography (CT) scanner. Results illustrate that, in the early part of the Johnson-Bossler-Naumann (JBN) method, relative permeability is dominated by fingering and heterogeneity effects. The later part of this method (> 1 PV), however, represents the relative permeability of the end-face saturation and is influenced by the capillary number and throughput. Thus, laboratory results must be scaled to the field on the basis of the flow parameters: end-effect, capillary, instability, and heterogeneity numbers.
Centrifuge Measurements of Capillary Pressure: Part 1-Outflow Boundary Condition
Authors: O'Meara D. J. , Hirasaki G. J. , Rohan J. A.
Published: December 2007

The capillary pressure curve is estimated from centrifuge measurements with the assumption that Pc =0 at the outflow end of the core. With the proper end piece to support the core sample, this boundary condition is valid in practically all circumstances. If the end piece is wetted by the produced liquid, however, experiments show that the capillary pressure curve is altered significantly. Theoretical analysis demonstrates that film drainage can displace the zero-capillary-pressure boundary condition to the bottom of the end piece or farther. Accordingly, we recommend that the displaced phase not wet the end piece; in the case of water, a teflon end piece is recommended over the commonly used rubber one. When the end piece is not a problem, the condition for 100% liquid saturation at the outflow face can be expressed as a critical Bond number, which is rarely exceeded. Saturation profiles for an experiment just below the critical Bond number were in excellent agreement with predictions. Pendant drops at the outflow face can result in a nonzero capillary pressure at the outflow face, but this effect is insignificant. Good agreement was obtained between mercury injection and centrifuge-measured capillary pressure curves. Attention is drawn to the importance of core jacketing, core cleaning, and equilibration times in providing reliable centrifuge-measured capillary pressure curves.
Conditional Simulation of Reservoir Heterogeneity With Fractals
Authors: Hewett Thomas A. , Behrens Ronald A.
Published: December 2007

The displacement efficiency of fluids injected into heterogeneous formations depends on the nature of reservoir-property variations and their spatial correlations. Conditional simulation is a geostatistical technique for creating property distributions, with any desired resolution, that have a prescribed spatial correlation structure and that match measured data at their sampling locations. Conditional simulations of reservoir heterogeneity can be used to address the two major issues in characterizing reservoirs for performance modeling: scaling of flow processes and properties and dealing with the uncertainty resulting from missing information in reservoir descriptions. The correlation structure emphasized in this study is a fractal model. Examples of conditional simulations of areal distributions and vertical cross sections of properties are presented. Simulations of fluid flow through different realizations of the simulated geology are compared with each other and with simulations of fluid flow through more homogeneous distributions derived by lumping parameters into discrete flow units or by smoothly interpolating well-log data. Results show that flow predictions in conditional simulations of the geology have greater fluid channeling, with earlier breakthrough of the injected fluids and less complete sweep of the formation. Flow simulations in multiple realizations of the heterogeneous geology provide a probability distribution of reservoir performance that may be used to evaluate the risk associated with a project caused by incomplete sampling of the reservoir-property distribution.
Experimental Aspects of Partitioning Tracer Tests for Residual Oil Saturation Determination With FIA-Based Laboratory Equipment
Authors: Knaepen W. A. I. , Tijssen Robert , van den Bergen E. A.
Published: December 2007

Partitioning tracer tests are used to determine residual oil saturation (ROS). At Koninklijke/Shell Laboratorium, Amsterdam, laboratory equipment based on the flow injection analysis (FIA) method has been constructed for rapid (within 2 hours) and accurate (better than 8%) determination of the equilibrium partition coefficient of tracers between crude oil and brine under simulated reservoir conditions. The apparatus makes possible investigation of the influence of all relevant parameters on the partition coefficient: tracer type and concentration, crude oil type, pressure (up to 34 MPa [4, 930 psi]), GOR's, temperature (up to 150°C [302°F]), and brine salinity. The FIA equipment has been critically evaluated with model compounds. Its versatility has been verified with experimental results obtained on dead and live crudes.
Stochastic Modeling in Reservoir Simulation
Authors: Ding L. Y. , Mehra R. K. , Donnelly J. K.
Published: December 2007

This paper outlines details of a method that includes uncertainty in deterministic simulations. The method uses the probability distributions of reservoir and geological properties to obtain a likelihood distribution of the output variables. The Monte Carlo sampling (mcs) method is often applied, but it is impractical for simulation studies because the number of computations becomes excessive. This paper uses an analytical thermal screening model to compare various variance-reduction methods with MCS simulations. The Latin hypercube sampling (LHS) method is then selected to conduct numerical simulations. The methods allow computation of the partial correlation coefficients, which, as demonstrated, can be used to determine the sensitivity of process variables.
Reservoir Studies With Geostatistics To Forecast Performance
Authors: Tang R. W. , Behrens R. A. , Emanuel A. S.
Published: December 2007

Example geostatistics and streamtube applications are presented for waterflood and CO2 flood in two low-permeability sandstone reservoirs. The hybrid approach of combining fine vertical resolution in cross-sectional models with streamtubes resulted in models that showed water channeling and provided realistic performance estimates. Results indicate that the combination of detailed geostatistical cross sections and fine-grid streamtube models offers a systematic approach for realistic performance forecasts.
Reservoir Simulation of Generally Anisotropic Systems
Authors: Shiralkar Gautam S.
Published: December 2007

This paper presents numerical techniques for the simulation of reservoir systems characterized by a nondiagonal tensor representation of areal permeability. A nine-point method of discretization for calculating reservoir flow and a well-inflow model based on the concept of equivalent wellblock radius are presented.
Asphaltene Deposition in Production Facilities
Authors: Thawer Ruksana , Nicoll David C. A. , Dick Graeme
Published: December 2007

Asphaltene deposition in the tubing and production facilities caused operational problems in the Ula reservoir. Laboratory and field studies were carried out to determine the point of asphaltene precipitation. Laboratory observations were made on the regimes of deposition as a function of decreasing pressure down to and below the bubblepoint of "live" crude oil samples. The tubing areas affected by deposition in the field corresponded to those identified in the laboratory and by subsequent pressure and temperature modeling of the wells. Large asphaltene deposits were also found in the production separators.
Studies of Water-Continuous Emulsions of Heavy Crude Oils Prepared by Alkali Treatment
Authors: Plegue T. H. , Frank S. G. , Fruman D. H. , Zakln J. L.
Published: December 2007

Pumping of heavy crudes as concentrated oil-in-water (O/W) emulsions may be a feasible pipeline transport scheme for viscous crudes. Many crude oils can be emulsified by treatment with alkali without the addition of expensive surfactants. In experimental studies of seven crudes, stable emulsions could be formed with four by alkali treatment; two could not be emulsified; and one formed unstable emulsions. High shear viscosity, particle size, and stability measurements on 60% emulsions formed with various amounts of alkali are reported. High shear viscosities below 100 mPa·s [100 cp] at 25°C [77°F] indicate that concentrated emulsions of some crudes can be transported in pipelines at concentrations of 60% and higher.
Rheological Evaluation of Dense Suspensions: Simulation of a Fresh Cement Paste
Authors: Clark P. E. , Shaughnessy R. J.
Published: December 2007

The rheology of fresh cement pastes is a function of not only particle size, shape, and concentration, but also the cement setting reactions. This greatly complicates the analysis of data obtained in any rheological experiment. To separate the slurry contribution to the system rheology from the chemical reaction component, a slurry of marble-dust particles is used to represent a cement slurry.

In this study, both tube-flow and concentric-cylinder [Rheometrics Pressure Rheometer™ (RPR)] rheometers are used to evaluate the rheological behavior of the dense suspensions. The apparent "slip" of the suspension makes correlation of the flow curves generated from the two viscometers difficult. The degree of slip in both viscometers becomes increasingly significant as the marble-dust concentration increases. The use of a grooved bob in the concentric-cylinder viscometer considerably reduces the amount of slip. Large annular gaps can also contribute to inconsistent results. An analysis of the data from both types of viscometers is presented.

The Reiner-Riwlin equation, derived for a Bingham fluid, was used to approximate the flow curves generated with the concentric-cylinder viscometer. Marble-dust suspensions displayed antithixotropic behavior regardless of the water/solids ratio tested. These data are representative of an antithixotropic system that builds structure as the shear rate is increased. The duration of the tests affects the observed data only when sedimentation occurs during the test. When the denser marble-dust suspensions are tested, sedimentation occurs in the viscometer, producing an irregular shear thinning. Marble-dust suspensions generally provide a good model system for gaining an understanding of the rheological properties of fresh cement pastes.
Quartz Technology Allows for Wider Downhole Pressure Testing Range
Authors: Dennis J. R. , Zeller V. P.
Published: December 2007

This paper presents a quartz-thickness shear-mode transducer for use in a borehole environment. The pressure sensor is a direct-conversion device that uses a noncylindrical shell to convert and to transmit forces to the quartz-crystal resonator. A brief conceptual description of the transducer is given. Laboratory and field examples illustrate the exceptional performance of the quartz-thickness shear-mode transducer.
Equilibrium Acid Fracturing: A New Fracture Acidizing Technique for Carbonate Formations
Authors: Tinker S. J.
Published: December 2007

The equilibrium-acid-fracturing technique was developed to stimulate wells in the Wasson San Andres Denver Production Unit. This new treatment technique maximizes acid contact time with the fracture faces while allowing control of the created fracture dimensions. Maximum acid contact time is essential to create highly conductive etched pathways on the fracture faces of cool dolomite formations that react slowly with acid. Control of fracture dimensions is important in the San Andres Denver Unit because fractures tend to grow uncontained in at least one vertical direction and the oil column is bounded by permeable gas-bearing intervals above and permeable water-bearing intervals below.

With this technique, a fracture of desired dimensions is created by injection of acid at fracturing rates. The volume of acid required to create the desired fracture dimensions is determined by a 2D fracture-geometry program with design parameters determined from fracture field testing and laboratory testing. Injection is then continued at reduced rates that maintain equilibrium with the fluid leakoff rate from the created fracture faces. Maintaining equilibrium between injection and leakoff allows the created fracture to be held open without significant further fracture extension. Equilibrium is achieved in the field by maintaining the injection pressure below the fracture extension pressure but above the fracture closure pressure determined by fracture field testing.

This paper presents the background and theory of this technique along with design procedures, field examples, results, and conclusions. Results of the equilibrium-acid-fracture treatments and other acid stimulations performed in the Denver Unit are also compared.
State-of-the-Art Modeling for Unconventional Gas Recovery
Authors: King Gregory R. , Ertekin Turgay
Published: December 2007

A series of mathematical and numerical developments that simulate the unsteady-state behavior of unconventional gas reservoirs is reviewed. Five major modules, considered to be unique to the simulation of gas reservoirs, are identified. The inclusion of these models into gas reservoir simulators is discussed in mathematical detail with accompanying assumptions.
Improved Prediction of Wet-Gas-Well Performance
Authors: Oudeman Pieter
Published: December 2007

A series of field tests on liquid loading of gas wells demonstrated that various types of behavior could be encountered in such wells. On the basis of the test results, an improved model for predicting the performance of gas wells producing liquids was formulated. This model takes into account multiphase reservoir performance and the vertical flow performance of the tubings for wet gas. It provides improved estimates for gas deliverability and the remaining life of watering-out gas wells, compared with common methods that calculate "critical" conditions at a single point (usually the wellhead) in the tubing string.
North Sea Experience With Aluminum Drillpipe
Authors: Tarr Brian A. , Graham Iain A.
Published: December 2007

Aluminum drillpipe was used to drill the first five directional wells from a North Sea platform. A comparison with steel drillpipe showed that the operational problems of using the aluminum drillpipe outweighed the benefits in the directional wells drilled. Therefore, steel drillpipe was specified for subsequent, similar platform wells.
Sour-Gas Sweetening During Offshore Drillstem Tests—A Case History
Authors: Casselman Robert L.
Published: December 2007

This case history details the use of Sulfa-Check®, a sour-gas sweetener, on two exploratory well drillstem tests (DST's) offshore California. Also included is a brief description of the Sulfa-Check process and comments on future plans. This case history is intended to show that Sulfa-Check can be applied effectively in a sour-gas offshore DST. It will show Sulfa-Check's performance on each of the exploratory wells and explain the solutions initiated to mitigate problems incurred in subsequent DST's. This information is presented for future operators' use in preparing an economical and safe sour-gas DST.
Optimizing Sandstone Acidization
Authors: Ponce da Motta Eduardo , Plavnik Benjamin , Schechter R. S.
Published: December 2007

The treatment of sandstone formations with mixtures of HF and HCI to remove formation damage is a widely practiced stimulation method; however, little attention normally is given to process optimization. This paper presents a procedure design that minimizes the total acid volume required to remove damage from a fixed-zone, near-wellbore region. To account for differences in formation mineralogy, a single laboratory coreflood experiment with field cores is necessary but more are recommended. The optimization method relies on scaling this experiment to a radial-flow geometry, where acid flux rates may differ substantially from those used in the single core test. Changing the injection rate is shown to result in a minimum acid volume at an optimum injection rate, and this optimum is found for a specific example.
Scale Formation in Reservoir and Production Equipment During Oil Recovery: An Equilibrium Model
Authors: Haarberg Torstein , Selm Ingrid , Granbakken Dag B. , Østvold Terje , Read Peter , Schmidt Terje
Published: December 2007

This paper presents a reliable model for the solubility products of scale-forming minerals. Our model solubilities are in relatively good agreement (±5% to 10%) with the most reliable solubilities in aqueous solutions of up to twice the seawater concentration at temperatures of 20 to 150°C and pressures up to 40 MPa. An equilibrium model for the reactions responsible for scale formation is developed. The CO2 equilibria between the gas, oil, and water phases and in the water phase itself are considered. By combining a hydrodynamic model for the transport of water through an oil reservoir during waterflooding with the proposed equilibrium model, we can estimate the amount of precipitate formed in the reservoir.
Field Applications of PHPA Muds
Authors: Kadaster A. G. , Guild G. J. , Hanni G. L. , Schmidt D. D.
Published: December 2007

Mud systems with partially hydrolyzed polyacrylamide polymer (PHPA) are used worldwide and have proved effective and versatile for inhibiting troublesome shale formations. We made significant changes in the generally recommended compositions for these systems and developed a systematic approach to applying them. The most significant changes are (1) the constant maintenance of 1.0 lbm/bbl [2.9 kg/m3] PHPA (active) on the basis of materials balance and the supplemental addition of PHPA to account for its loss and degradation, (2) tightly controlled fluid loss, and (3) selective use of seawater and NaCl for inhibition.
Determining the Productivity of a Barrier Island Sandstone Deposit From Integrated Facies Analysis
Authors: Sharma Bijon , Honarpour M. M. , Jackson S. R. , Schatzinger R. A. , Tomutsa Llvlu
Published: December 2007

Two crossplot techniques, based on core-calibrated resistivity, porosity, and gamma ray (GR) logs, are described that distinguish barrier island sandstones from genetically different nonbarrier sandstones in the Muddy sandstone reservoir in Unit A of Bell Creek field, Montana. The barrier island sandstones are separated further and grouped into two log facies, one consisting of highly productive facies (foreshore, shoreface, etc.) and the other, a less-productive facies (lower shoreface). The distinct crossplot pattern for each facies group is due to similar petrophysical properties of each facies group resulting from deposition within a unique depositional setting.

Fluid production results from primary, secondary, and two EOR pilot projects indicate that in the barrier island reservoir at Bell Creek, the distribution of facies, with their characteristic reservoir properties and heterogeneities, dominates primary production, waterflood-sweep efficiency, distribution of residual oil saturation, and the performance of the chemical EOR pilot projects.
Hydrocarbon Type Identification With MWD Neutron Porosity Logging: A Case Study
Authors: Slmms G. J. , Koopersmlth C. A.
Published: December 2007

Measurement-while-drilling (MWD) information accurately defined gas, oil, and water in an offshore field. Basic MWD and wireline formation evaluation data compare favorably. A cost saving of $130, 000 was realized when MWD information was used instead of wireline data on one well. In the future, MWD logs may serve as the primary evaluation data on routine development wells in similar fields.
Development and Validation of Equation-of-State Fluid Descriptions for CO2/Reservoir-Oil Systems
Authors: Negahban Shahin , Kremesec V. J.
Published: December 2007

This paper discusses the required data, methodology, and validation for developing equation-of-state (EOS) fluid descriptions for the vaporizing-CO2/reservoir-oil systems. Validation of the EOS description is shown by an ability to predict additional first-contact data and slim-tube performance over a wide range of pressures covering both immiscible and multiple-contact-miscible (MCM) conditions. Slim-tube performance is predicted with a fully compositional simulator that uses a physical dispersion formulation. The relative permeability curves and dispersivity of the slim tube were measured and honored during all simulations.
Observations and Correlations for Immiscible Viscous-Fingering Experiments
Authors: Pavone Didier
Published: December 2007

We studied immiscible two-phase flow instabilities in porous media under drainage conditions. The objective of our experiments was to improve our understanding of viscous fingering so that we could avoid it or at least account for it in flow simulations. This paper first presents the molding technique used to observe and measure viscous fingering in large, 3D, natural consolidated porous samples. Moldings of 16 flows showed instabilities that looked like fingers and stable displacements behind the unstable front. We correlated breakthrough recovery, mean local saturation, finger volume and width, pressure drop, and saturation profiles with dimensionless numbers. Three kinds of displacements occurred: stable displacements, with macroscopic viscous fingering, and displacements with both macroscopic and microscopic viscous fingering. Finally, we determined linear ID relative permeabilities.
Influence of Texture on Steady Foam Flow in Berea Sandstone
Authors: Ettinger R. A. , Radke C. J.
Published: December 2007

An understanding of texture, or bubble-size, evolution is paramount for modeling foam flow in porous media in that fine textures may impart large flow resistances. Bubble size, in turn, is determined by complicated lamella creation and decay processes. We study, for the first time, the quantitative role of bubble size in the steady flow of strong foam through a 0.8-μm2 Berea sandstone. Inlet and outlet textures are determined from photomicrographs taken of bubbles flowing through specially designed visual cells. Concurrent measurements of pressure and liquid-saturation profiles by microwave attenuation are acquired for gas velocities from 1 to 3 m/d and foam qualities from 70% to 90%, A simple, 1D foam population-balance model is outlined to quantify the observed flow and texture behavior. Agreement between the proposed model and the new bubble-size and flow data is adequate. The population-balance method proves to be a useful tool.