bluuebunny/crossref_metadata_2025_split huggingface dataset:
Properties of Homogeneous Reservoirs, Naturally Fractured Reservoirs, and Hydraulically Fractured Reservoirs From Decline Curve Analysis
Authors: Blasingame T. A. , Lee W. J. 
Published: December 2007

ABSTRACT
This paper proposes analysis techniques for post-transient, flow at constant bottomhole pressure. Rate-time decline curves approximate this flow regime. Reservoir characteristics for homogeneous reservoirs, vertically-fractured reservoirs, and naturally-fractured reservoirs can be obtained using these techniques. These analysis techniques are based on the exponential, post-transient, constant-pressure radial flow solutions for each case. We show that theory predicts a linear relation between log (rate) and time for these curves. Thus, a straight line on a semi-log rate vs. time plot may be the line predicted by the analytical solution for that reservoir. If so, important formation characteristics can be estimated analytically. Reservoir pore volume is determined directly while other reservoir characteristics are calculated indirectly. These new techniques are a very powerful extension of transient well testing.
Perforation Geometry and Skin Effects on Well Productivity
Authors: Todd B. J. , Bradley D. J. 
Published: December 2007

ABSTRACT
A computer model based on the Darcy solution to the Radial Diffusivity Equation was written to evaluate perforated oil well completions. The model was verified using standard well testing techniques and compares favorably with similar models written previously. The results of this study clearly point to these conclusions: Normal amounts of well and perforation damage reduce four shot per foot (0.305 m) productivity to an unacceptable level. Twelve shots per foot (0.305 m) is recommended for future completions.Gun phasing affects productivity. Sixty degree phasing gives the best results, with productivity reductions for larger angles.Perforation length should be maximized at the expense of hole diameter, down to a diameter of 0.25 inches (0.64 cm).Gun standoff decreases penetration of small diameter, through-tubing guns. These guns should be avoided where possible.
Curve Fitting of Real-Gas Pseudopressure and Its Practical Application
Authors: Schafer-Perini A. L. , Miska S. Z. 
Published: December 2007

ABSTRACT
The real gas pseudo pressure concept is a very useful technique for calculating gas well deliverability and in the analysis of pressure transient tests. Current use of the real gas pseudo pressure requires application of numerical integration and interpolation methods. Here, an approximation of the m(P) function is proposed which eliminates the need for numerical intergration. A simple power type equation is found to fit the m(P) function over a broad range of gas properties and reservoir conditions. Practical examples are provided to illustrate the usefulness of the proposed approximation.
The Effect of Injected Fluid Volume on Heavy Oil Displacement in a Porous Medium
Authors: Reitman V. , Rajan V. S. V. , Heidrick T. R. 
Published: December 2007

ABSTRACT
In situ recovery of heavy oil generally involves the use of steam or hot water to displace the oil. The recovery is controlled by the extent to which the displacing fluid can mobilize the oil and saturate the pores of the reservoir. Modelling of any such recovery process requires a knowledge of the permeabilities of the oil-water-rock system.
Relative permeabilities are often measured in cores using displacement experiments. These permeabilities are measured as a function of saturation and are sometimes correlated as power law functions of the initial water saturation, Swc, and residual oil saturation, Sor. The "end" of the displacement process is assumed to be after four to five pore volumes of fluid injection with the exact value somewhat arbitrarily chosen by each particular researcher, often on the basis of capillary number considerations.
In this paper, the method of characteristics solution of the one-dimensional flow equations is used to investigate the effects of various parameters, such as mobility ratio, on the number of pore volumes of injected fluid that are required to reach the residual oil saturation. For some heavy oils, it is shown that of the order of one hundred or more pore volumes of injected water may be required before reaching the residual oil saturation. The apparent steady saturation profile observed by some researchers may have resulted in premature termination of some experiments. Also, the apparent " end-effect" observed by many researchers can be attributed in part to the extreme variations in the permeability-saturation profile.
The main advantage of this analysis is an iterative approach which enables a researcher to design suitable experiments for relative permeability determinations. Also, with an assumed mathematical form of the permeability versus saturation relationship, the total curve can be generated from a limited number of displacement experiments.
Financial and Technical Decision Making for Surfactant Flooding
Authors: Barua J. , Prescott T. , Haldorsen H. H. 
Published: December 2007

ABSTRACT
This paper presents a method for making prudent business and technical decisions for surfactant flooding projects in spite of the uncertainty associated with reservoir properties, surfactant flood performance, and oil price forecasts. A hypothetical surfactant flooding project is used to demonstrate this method and each algorithm is explained in detail.
This method optimizes the operational decisions of a surfactant flood and presents the economic assessment of the project. The accuracy of this assessment depends on the uncertainty in the project but this method quantifies both the effect of this uncertainty and the financial risk.
Surfactant flooding is used as the example in this study but the algorithms can be applied to all oil & gas development projects.
The Effect of Dissolved Gas on Geothermal Brine Viscosity
Authors: Ostermann R. D. , Paranjpe S. G. , Godbole S. P. , Kamath V. A. 
Published: December 2007

ABSTRACT
Reservoir brines typically contain dissolved salts and gases. While correlations have been published for prediction of viscosity as a function of temperature, pressure and salinity, little data is available regarding the effect of dissovled gases on brine viscosity. In the current work, the viscosity of methane and ethane saturated water and brine has been measured at 100, 150, and 250°F over a pressure range of 0-7,500 psig.
For methane in pure water, viscosity increases by up to 6%. At pressures above 2,000 psig, the viscosity is independent of saturation pressure. Dissolved ethane showed no measurable effect on water viscosity. Brine viscosity also increases with methane saturation pressure. A correlation is presented for the correction of brine viscosity to account for gas saturation.
Experimental and Simulation Studies of Laboratory In-Situ Combustion Recovery
Authors: Onyekonwu M. O. , Pande K. , Ramey H. J. , Brigham W. E. 
Published: December 2007

ABSTRACT
This paper discusses the effects of some parameters on the in-situ combustion process. The paper is in two parts. The first part discusses a laboratory in-situ combustion tube run. Important design parameters such as fuel concentration, air requirement, oxygen utilization efficiency and combustion front velocity may be determined from the analysis of laboratory tube run data. The second part of the paper discusses numerical simulation of the laboratory tube run and results from in-situ combustion simulation studies. A thermal simulator was used to investigate the effects of relative permeability, rock thermal conductivity, heat losses, API gravity of oil, initial conditions, oxygen concentration, and other parameters on fuel availability and combustion front velocity.
Results from simulation studies show that oil viscosity, residual oil saturation (gas/oil system) and oxygen mole fraction in the injected gas should have the greatest effect on fuel availability. Relative permeability data and rock thermal conductivity also affect the amount of fuel available for combustion. Factors which may cause an increase in combustion front velocity may also cause an increase in the amount of fuel burned if the heat front moves slower than the combustion front. The use of a thermal simulator for this study made it possible to study a wide range of parameters which would involve a substantial effort to investigate experimentally.
Application of the Parallel Resistance Concept to Well Test Analysis of Multilayered Reservoirs
Authors: Mavor M. J. , Walkup G. W. 
Published: December 2007

ABSTRACT
A new development of a multi-layered reservoir model is presented which considers the layers to be in communication only at the well. The importance of the presentation is the simplicity of the mathematical model and the use of the model to derive improved well test analysis techniques for both single and double porosity reservoirs. Analysis techniques based upon both pressure and flow rate data required to determine individual layer properties are presented.
Through the use of the Laplace Transformation, the behavior of a multi-layered reservoir system can be treated as an equivalent resistance network in which the total resistance to fluid flow can be obtained by adding the resistances to fluid flow in each layer using the elementary concept of resistances in parallel. The resistance functions for both single and double porosity layers with infinite, closed, or constant pressure outer boundaries are presented. The effects of wellbore storage are included.
Development of layered reservoir models where the layers are of different type (single or double porosity), with differing rock and fluid properties, and with differing outer boundaries is easily accomplished with the parallel resistance approach. Solutions for the wellbore pressure and the pressure in the reservoir for constant rate tests as well as solutions for the rate response during a constant pressure test are discussed.
A method to include wellbore storage into any reservoir model is presented as is a method for directly extending single porosity solutions to double porosity systems.
Slug Test and Drillstem Test Flow Phenomena Including Wellbore Inertial and Frictional Effects
Authors: Saldana-C. M. A. , Ramey H. J. 
Published: December 2007

ABSTRACT
During the flow period of a drillstem test from deep and highly-productive wells, the liquid column inside the wellbore can experience rapid acceleration changes. Also, flow velocities in the pipe can become extremely large. Therefore, inertial and frictional forces can be expected to be important in a dynamical relationship between flow rate and bottomhole pressure.
A mathematical formulation including the effects of inertia and friction on the wellbore liquid column during a drillstem test is presented in this paper. Solutions for this formulation are obtained by assuming a large initial cushion and laminar flow during the test. This leads to a linear mathematical problem that is solved in the transformed Laplace-space. Solutions, in terms of the dimensionless groups of physical parameters that govern the response of practical wellbore-reservoir systems, are calculated by applying the Stehfest algorithm for numerical inversion of Laplace transformations.
The results presented in this paper provide criteria useful to evaluate the magnitude of inertial and frictional effects from rough estimates of the properties of a wellbore-reservoir system. These criteria can be utilized to minimize undesired inertial and frictional effects through design of a drillstem test. Results also indicate practical conditions under which inertial and frictional effects are significant. The solution method presented in this paper can be used to estimate reservoir properties by matching bottomhole pressure data measured during the flow period of a drillstem test. Also, the flow rate solutions provided by this method can be considered in pressure buildup data analysis of a subsequent shut-in period during a drillstem test.
Geological and Geochemical Techniques for Mapping Fractures and Fluid Flow Patterns in Geothermal Reservoirs
Authors: Moore J. N. , Nielson D. L. 
Published: December 2007

ABSTRACT
Permeability in high-temperature geothermal systems is dominantly fracture controlled. However, fracture characteristics and cross cutting relationships among fracture sets are generally difficult to define from cuttings samples alone. In addition, the sparse number of wells in most systems limits the data that can be obtained on the areal fracture distribution. Despite these inherent difficulties, petrologic techniques and mathematical simulations can be used to develop the models of fracture geometry, permeability, and alteration that must be addressed by reservoir engineers. Our fracture studies have taken two approaches; first, establishing predictive structural models, and, second, documenting fluid-rock interaction using alteration mineralogy and geochemistry. Examples of the use of these techniques from active geothermal fields in the U. S. and Canada are described.
Laboratory Determination of Effective Liquid Permeability in Low-Quality Reservoir Rocks by the Pulse Decay Technique
Authors: Amaefule J. O. , Wolfe K. , Walls J. D. , Ajufo A. O. , Peterson E. 
Published: December 2007

ABSTRACT
This paper discusses the application of transient pulse decay technique for determination of effective liquid permeabilities in low-quality reservoir rocks. Effective oil and water permeabilities ranging in values from 0.5 md to 290 nd (2.9 × 10−4 md) were determined by this technique with excellent reproducibility.
Low quality reservoir rocks commonly characterized by high porosity but very low permeability, are generally friable, sensitive to stress, fluid velocities, and volumes of fluid throughput. Effective liquid permeabilities are usually determined by the dynamic displacement technique. This method, which involves the flow of large volumes of fluid throughput before flow rate and differential pressure stability is achieved, is time consuming and not particularly suited to low quality rocks. In contrast, the pulse decay technique, previously developed for measurement of tight gas permeability, easily permits rapid determination of effective oil and water permeabilities with minimal pore volumes throughput at low velocities.
This paper reviews mathematical computational techniques and outlines proper experimental protocols for accurate determination of liquid permeabilities in low quality rocks. The experimental techniques allow for simultaneous determination of liquid compressibility needed as input data in most reservoir engineering calculations. Effective oil and water permeability data generated by the transient pulse decay are needed to predict fluid recoveries in low quality reservoirs.
Type-Curve Techniques for Hydraulically Fractured Lenticular Formations
Authors: Yousef O. M. , Evans R. D. 
Published: December 2007

ABSTRACT
The development, analysis, and evaluation of type curve matching techniques for lenticular gas bearing formations are presented. The type curves are generated using a three dimensional, single phase, transient reservoir simulator modified to take into account lenticular sand lenses and hydraulically created fractures. The gas bearing sand lenses are assumed to be randomly distributed in orientation and space throughout the formation. Type curves are generated for an unfractured formation and vertically fractured formation with finite conductivity. Assuming different sand lense fractions, type curves are generated and compared with type curves developed for continuous (so called blanket) sand formations. The results of this comparative analysis indicates that the type curves for lenticular formations are significantly different from those of the blanket sand case that it may be possible to assess the degree of lenticularity of a given formation. Conclusions are drawn from the research presented and recommendations given concerning future research efforts.
Beauty or Beast: Tyler Formation Waterflooding in Central Montana—Field Results
Authors: D’Hooge J. A. 
Published: December 2007

ABSTRACT
Currently, twenty-four projects have been, or are being, waterflooded in the Pennsylvanian age Tyler Formation of Central Montana. The heterogeneous nature of the Tyler sandstone reservoir lends itself to quick injected water breakthrough, reservoir discontinuities, poor areal sweep efficiency, and considerable difficulity in geologic interpretation. Despite all the negative factors, the Tyler secondary projects have exhibited favorable results. This case study shows that reservoir quality plays an important role in realizing higher recovery efficiencies. An understanding of the nature of the beast is required in order to maximize the recoveries from the Tyler Formation. In addition, polymer augmented waterflooding provides a possible means of enhancing these projects.
Reservoir Characteristics and Stimulation Techniques in the Bakken Formation and Adjacent Beds, Billings Nose Area, Williston Basin
Authors: Cramer D. D. 
Published: December 2007

ABSTRACT
In the Billings Nose area, the Bakken formation is a shale and silty carbonate sequence, capable of producing oil in association with adjacent beds when naturally fractured, Oil/surfactant breakdown and gelled oil fracture treatments have been commonly utilized to stimulate these zones. The best fracturing results have been attained with use of small quantities of fluid loss additives and high concentrations of proppant. However, pre-frac acidization, in association with a selective perforating method, may improve completion efficiency.
A Study of the Economic Impact of Enhanced Oil Recovery in Wyoming
Authors: Terry R. E. , Varma J. K. 
Published: December 2007

Abstract
Various enhanced oil recovery (EOR) methods were considered in an economic analysis of the twenty-six largest fields in Wyoming. This analysis indicates that a majority of the fields are currently best suited to polymer augmented waterflooding or CO2 flooding, based on an average price of $1.25/Mscf for CO2 and $2.50/lb for polymers. With these prices, all floods were economically viable in reservoirs less than 6000 feet deep at a base price of about $26.00/bbl for oil. In deeper reservoirs, most CO2 floods were uneconomic when using a twelve percent minimum acceptable rate of return as the basis of decision. A lower CO2 price, in the range of $0.50 – $0.75 per Mscf, would make most of the CO2 floods economic in reservoirs up to 12000 feet deep.
As a result of the anticipated increase in enhanced oil recover revenues to the state through royalties and taxes were also estimated. The total amount of EOR oil recoverable by the use of currently available EOR techniques is estimated to be about 1.5 billion barrels. Assuming that one-third of the potential target--500 million barrels--is recovered in the next thirty years, the present value of the state revenues (at an, eight percent discount rate) would be about 1.1 billion dollars. This is based on an inflation rate of five percent. Five other situations with varying crude oil prices and inflation rates were also investigated.
Oil recovery should be aided by CO2 development in southwestern Wyoming, scheduled to begin in 1987. As a result, CO2 floods may replace polymer floods as the process of choice in some fields.
Detailed Core Description of a Dolomite Sample From the Upper Madison Limestone Group
Authors: Honarpour M. M. , McGee K. R. , Crocker M. E. , Maerefat N. L. , Sharma B. 
Published: December 2007

ABSTRACT
Improvements in reservoir characterization can greatly enhance reservoir performance predictions. Heterogeneity within most reservoirs, such as the Madison Group, can be better understood from integration of results from detailed core analyses. A fractured dolomite core sample from the Upper Madison Group, near Carter Creek gas field in southwest Wyoming was studied in detail to supplement the current methodology for delineating heterogeneities in core samples. Directional permeability, fracture system orientation, and other heterogeneities related to the core sample fabric were determined and quantified by studies of: impregnated thin-sections and use of computed tomography x-ray intensity, x-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. Computed tomography (CT) is a fast, nondestructive, qualitative and quantitative tool for the evaluation of fracture systems and associated mineralogy. The scanning procedure employed involved assigning a density range that would highlight minerals having characteristic CT densities. This procedure helped to identify variations of fracture infilling materials. The core analyses data were integrated with the regional geology, downhole logs, and production data for final evaluation.
Carbon Dioxide Corrosion in Oilwell Cements
Authors: Bruckdorfer R. A. 
Published: December 2007

ABSTRACT
Carbon dioxide corrosion studies of oil-well Portland cements were initiated using a new micro-sample technique to determine the effect of carbonic acid on portland cement slurry formulations and to develop a high carbonic acid corrosion-resistant cement for carbon dioxide Enhanced Oil Recovery applications.
Earlier results from studies using two-inch API cement cubes showed carbonic acid had essentially no effect on cement after relative short test periods at elevated temperatures. Similar results with two-inch API cement cubes also were reported in recent literature. Because carbonic acid corrosion in cements was difficult to observe and measure using two-inch API cement cubes, a new microsample technique was developed. Use of this new technique, which represents an accelerated testing method, showed oil-well cements undergo a rapid deterioration in a wet carbon dioxide environment. Similar tests with two-inch cubes showed essentially no cement deterioration under the same conditions.
Experimental details of this new microsample technique are discussed. Data relating cement strength loss and carbon dioxide penetration depths to cement type and slurry formulation are reviewed. Included in the discussion is a new cementing formulation which shows significant promise as a high carbondioxide-resistant, oil-well cement.
Erosion Damage in Oil and Gas Wells
Authors: Venkatesh E. S. 
Published: December 2007

ABSTRACT
Erosion damage in oil and gas wells are inevitable at high velocities. This is especially true when solid particles are produced.Current method of reduced production velocity as recommended by API is not satisfactory. Research in the direction of obtaining insight into erosion damage in oil field equipment indicates much work is required. This paper is an attempt in that direction.