bluuebunny/crossref_metadata_2025 huggingface dataset:
Wellbore Transmissibility from Afterflow-Dominated Pressure Buildup Data
Authors: McKinley R.M.
Published: December 2007

This paper shows how pressure buildup data distorted by afterflow can beanalyzed directly to give a numerical value for effective wellboretransmissibility. Because such data are directly indicative of wellbore-limitedproductivity, the method is helpful in assessing productivity, the method ishelpful in assessing the need for and the effectiveness of a well stimulation. Alternatively, it is a method for interpreting that portion of a pressurebuildup curve not subject to Horner analysis.

The method does not require any estimates of formation or wellboreproperties for the analysis. The procedure consists of first plotting pressurebuildup from flowing plotting pressure buildup from flowing pressure as afunction of shut-in time on a log-log pressure as a function of shut-in time ona log-log scale and, second, matching the data points to one of a set ofparametric type curves. From this match, a numerical value is calculated forwellbore transmissibility. Finally, the shape of the buildup curve indicateseither wellbore damage or stimulation.

The paper describes the generation and use of type curves with computed dataillustrating the effects of wellbore damage or stimulation. A variety of fieldexamples demonstrate the practical utility of the method. practical utility of the method

Introduction

Afterflow, or afterproduction, is the continued influx of fluid from aformation into a wellbore after the well is shut in. The greater the storagecapacity of the wellbore, the longer the duration of afterflow. Such afterflowprecludes a conventional analysis of a pressure buildup curve so long as theafterflow rate is greater than a few percent of the production rate prior toshut in. Consequently, production rate prior to shut in. Consequently, afterflow has generally been regarded as a nuisance. Yet, it is reasonable tosuppose that such data contains valuable information. Certainly most of thepressure change occurs during afterflow provided it is present; hence, pressuremeasurements during afterflow should pressure measurements during afterflowshould be more accurate than at later times. Also, the pressure change in thewellbore during afterflow should reflect a sort of dynamic balance between twolimiting factors:the capacity of the wellbore to store fluid andtheease with which the formation supplies fluid to the wellbore.

This secondfactor, which is indicative of wellbore transmissibility, is the one oftechnical importance since it determines productivity. However, most of thepublications dealing with afterflow are concerned either with estimating itsduration or with correcting pressure buildup data taken during its pressurebuildup data taken during its duration. Gladfelter, et al. gave a method forcorrecting pressure buildup data as early as 1955. Ramey has provided equationsto estimate the duration of afterflow.
Planning and Analysis of Pulse-Tests
Authors: Brigham W.E.
Published: December 2007

Developed here are equations that approximate the pulse-test procedure and that, in turn, are plotted as simple graphs that can be used directly to design and analyze these tests. The necessary calculations require only 10 to 15 minutes.

Introduction

Pulse-testing is a fairly recent procedure that has received some attention in the last 2 years. In this method of testing, a well is pulsed with cycles of injection followed by shut-in, or production followed by shut-in. The pressure response to the cycles is then measured in an offset well.

Articles in the literature1,2 discuss, to some extent, the theory of pulse-testing; but an engineer who wishes to analyze the results of such a test will find that he must make a number of tedious exponential integral calculations.

The paper briefly covers the theoretical rationale behind pulse-testing, and then develops some approximate equations. As a result of these equations, two simple graphs are developed that can be used for design and analysis of pulse-tests. An example calculation is shown later in the text.

General Response Theory

Pulse-testing was first discussed by Johnson et al.l The concepts involved are fairly straightforward. Briefly, the bottom-hole pressure in a shut-in well will respond to production or injection cycles in an offset well. The magnitude and timing of the response depend on the flow rate, the permeability, porosity and thickness of the formation, and the compressibility and viscosity of the fluids that lie between the wells. Inhomogeneities, geometry and boundaries also affect the response, but these factors are not included in the scope of this paper, nor in the literature.

The equations for the response are line-source solutions to the diffusivity equation. For instance, if a well is produced for a time ?t, then shut in, the equation for the pressure response in the shut-in well isEquation 1

Going further, if there are a number of cycles of production followed by shut-in, if each production rate is equal, and if each cycle lasts for an equal period of time (?t), then by superposition the equation for the pressure response becomesEquation 2

where N is the number of equal-length periods of production and shut-in (for instance, for one production and one shut-in period, N=2; Eq. 1).

Eq. 2 is the same as cited by Johnson et al. Notice that each shut-in and production period is assumed equal. This is not necessary, but it is easier to handle theoretically and will be used throughout the rest of this paper. Also notice that Eqs. 1 and 2 are for production and shut-in. For continuity we will continue to speak of production; but the reader should realize that injection and shut-in will work equally well. We would merely reverse the signs.
Simultaneous Determination of Basic Geometrical Characteristics of Porous Media
Authors: Perez-Rosales Candelario
Published: December 2007

A statistical method for determining simultaneously some of the basic geometrical characteristics of porous media such as porosity, specific surface, porous media such as porosity, specific surface, mean pore with, mean grain thickness and absolute permeability is presented. The proposed method is permeability is presented. The proposed method is characterized by its simplicity and the minimum amount of laboratory equipment that it requires. The experimental procedure used to evaluate the various geometrical characteristics is based upon the surface analysis of a sample. in view of this fact the applicability of the method is limited to homogeneous and isotropic materials.

Introduction

The behavior of a fluid flowing through a porous medium depends, among other things, upon the internal geometry of the medium; hence the importance of developing efficient methods to determine the geometrical properties of porous materials. This paper describes a statistical method to determine simultaneously some of the basic geometrical properties of porous materials such as porosity, specific surface, mean pore width, mean grain thickness and absolute permeability. The mathematical formulation has been developed that the data required to calculate the various geometrical characteristics of a sample can be easily measured by analyzing a section of the sample with an evenly spaced grid.
Development of an Expert System To Assist With Complex Fluid Design
Authors: Chiu T. J. , Caudell E. A. , Wu F. L.
Published: December 2007

The design of fluid systems for well completion has always been a perplexing problem for engineers and chemists. Material incompatibilities, chemical interaction, physical restrictions, and cost considerations build a great deal of complexity into the designs. Many engineers do not have the theoretical background needed to evaluate the numerous available additives. Others may not have the practical experience required to optimize a fluid treatment. Expert systems, with their unique structure and knowledge representation, can be used efficiently as tools to advise engineers of the proper base fluids and additives to be selected for a given set of well conditions. Valuable resources and operation costs can be saved by providing good material recommendations. In addition, use of expert systems can help centralize and retain expertise within the organization. The fundamental elements of expert systems—namely, the knowledge base, inference engine, and user interface—are addressed in this paper, along with knowledge acquisition and system implementation. Acid Expert, an expert system designed for matrix-acidizing-treatment recommendation that has been released to locations worldwide, is used as an example for much of the discussion.
Use of New Technologies for Knowledge-Based System Development
Authors: Fenoul R. , Vaussard A.
Published: December 2007

This paper looks at the way that expert systems have been developed and analyzes the problems in this process development. Remedies are proposed and illustrated through a system development under way in which knowledge acquisition design system (KADS) technology for knowledge organization is used.
Multifluid Acid-Fracturing Design Program
Authors: Bartko K. M. , Bender J. P.
Published: December 2007

A multifluid acid-fracturing design program, ACIDFRAC, was developed for IBM PC and Apple Macintosh computers to assist in the design of acid-fracture stimulations. The simulator compares the results of closed-fracture acidization and conventional acid-fracture stimulation. The program was designed for ease of use, incorporating data input windows, on-line help panels, and user-input checks for validity. The user moves through the program with a navigator window. Data validity is checked by a status window. The program has the ability to handle multiple rates, 15 stages, and up to five different fluid systems, correctly handling the fluid properties of each system. The fracture geometry is obtained from a 2D fracture simulator using a Perkins-Kern-Nordgren1, 2 model. The acid-transport model uses an infinite reaction rate and an empirical correlation to partially account for finite reaction rates. Data is output through multiple resizable graphs with zoom and expand capabilities. A complete report can be displayed or printed, including input and digital output data.
CHES: Casing Hydraulic Expert System
Authors: Heinze L. R.
Published: December 2007

An operations-oriented, practical application of expert-systems technology to tubular design and to optimizing bit hydraulics, Casing Hydraulic Expert System (CHES), was developed. Drilling operations are the most costly expenditure in exploiting hydrocarbon fossil fuels. The reduction of drilling cost is more important today than ever before in the oil industry.
A Novel Application of Open Systems at the Wellsite
Authors: Domangue P. M. , Peressini R. J.
Published: December 2007

This paper describes a unique, state-of-the-art oilfield data acquisition and processing system based on open systems. In particular, the paper focuses on the standards used and the experiences of the development team as it followed this sometimes elusive set of concepts.
An Expert System for Miscible Gasflooding
Authors: Khan Sameer. A. , Pope Gary A. , Sepehrnoori Kamy
Published: December 2007

A user-friendly prototype expert system (UTINPUT) was developed for preparing input data sets to design miscible gasfloods with the U. of Texas Compositional Simulator (UTCOMP). The expertise we acquired through literature, simulation experts, and simulation studies was implemented in an expert-system shell with rules, objects, and C.
GEOLITH: An Interactive Geostatistical Modeling Application
Authors: Araktingi U. G. , Hewett T. A. , Tran T. T. B.
Published: December 2007

A menu-driven workstation application program designed to analyze reservoir data and construct reservoir simulation models with a geostatistical approach is presented. The program analyzes reservoir data in the form of well logs and interpreted bed markers and allows interactive fitting of variogram models to data. These models then are used to construct gridded models of reservoir flow properties by kriging and conditional simulations and the use of flow-property transforms of well log values. The interpolation of data to the interwell region is done in a stratigraphic framework that honors the geologic interpretations provided by the bed markers. Small-scale variations are added through a number of methods (matrix, fractal, sequential, simulated annealing) to produce conditional simulations that reproduce the measured variability of properties at unsampled locations. The program also integrates indirect information, such as acoustic impedance derived from seismic data, with well-log data by several different methods.

The program has an intuitive and accessible data interface, a structured sequence of user prompts and error checks, and striking graphical presentations of modeling results. With it, the complex task of converting geological data into quantitative reservoir models for flow simulation and reservoir performance prediction is greatly streamlined.
Electronic Publishing of SPE Papers
Authors: Perdue Jeanne M. , Perkins John. L.
Published: December 2007

The SPE is creating an electronic index to more than 24, 000 technical papers and will produce a compact disk-read only memory (CD-ROM) as an initial product. This SPE CD-ROM Masterdisc will be available at the 1992 SPE Annual Technical Conference and Exhibition in Washington, DC, Oct. 4-7. The SPE Board has apppointed an Ad Hoc Committee on Electronic Publishing to coordinate and oversee this project and to recommend standards for submitting SPE papers electronically in the future.
It's Time to Quit Teaching FORTRAN to Engineers
Authors: Murtha J. A.
Published: December 2007

This paper examines the avowed purposes of studying FORTRAN and the types of problems solved by FORTRAN programming. It argues that the goals are not achieved and that the problems can be solved with spreadsheets, with the bonus of simple graphics and attractive output. An alternative proposal is aimed at helping students achieve computer literacy while developing skills and attitudes that would constantly reinforce engineering concepts and would facilitate report writing, both in school and later in their professions. Oil and gas companies will expect their engineers to be computer-literate, to communicate with a broader range of professionals, and to participate in complex decision processes. These engineers should be grounded in engineering fundamentals and communication skills and feel perfectly at home with a PC or workstation. Few will be expected to write source code. Spreadsheets, word processors, electronic mail, and commercial software will be the universal tools of the near future.
Use of Computers To Perform Old Log Analysis
Authors: Barrett D. G.
Published: December 2007

In the past, old gamma ray neutron (GRN) (1940's to 1960's) and old electric (E) logs were not widely used for detailed log analysis because performing this task accurately is manpower intensive. Recent developments in computer hardware and software have made it feasible to digitize and analyze old logs to obtain more accurate reservoir parameters for fields developed from the 1930's to the 1960's before modern logs were available. This paper describes a computer-based method to rescale old GRN and E logs efficiently, then perform shale volume, effective porosity, bulk volume water (BVW), and water saturation calculations. This method leads to more accurate reservoir characterization and reserves determination. Using the computer simplifies this task and reduces the cost enough that old fields may be studied that otherwise might not be economically feasible to study.
Shaly Sand Advisor: Creating a Program To Provide Expert Help
Authors: Walsh J. W. , Brown S. L. , Asquith G. B.
Published: December 2007

Engineering programs often are a collaborative effort between engineers, managers, and software designers. This paper chronicles how a microcomputer program for analyzing well logs from shaly sand formations evolved when an "expert" was used not only to provide technical information but also to aid in developing the overall program structure.
Two-Phase Flow in Horizontal Wells
Authors: Ihara Masaru , Yanai Koji , Takao Shingo
Published: December 2007

Flow in horizontal wells and two-phase flow interaction with the reservoir were investigated experimentally and theoretically. Two-phase flow behavior has been recognized as one of the most important problems in production engineering. We designed and constructed a new test facility suitable for acquiring data on the relationship between pressure drop and liquid holdup along the well and fluid influx from the reservoir. For the theoretical work, an initial model was proposed to describe the flow behavior in a horizontal well configuration. The model uses the inflow-performance-relationship (IPR) approach and empirical correlations or mechanistic models for wellbore hydraulics. Although good agreement was found between the model and experimental data, a new IPR apart from the extension of Darcy's law must be investigated extensively to aid in the proper design of horizontal wells.
Real-Time Monitoring Provides Insight Into Flow Dynamics During Foam Cementing
Authors: Purvis D. L. , Smith D. D.
Published: December 2007

Use of computer systems for on-site and postjob analysis of cementing operations has proved effective for improving quality control and increasing the probability of successful primary cementing. This paper outlines the steps needed to measure surface parameters accurately and model changing downhole conditions during foam cementing. The equations used to calculate downhole flow dynamics and the algorithms used are presented.
Horizontal Systems Technology for Shallow Site Remediation
Authors: Karlsson Haraldur
Published: December 2007

Innovations in drilling and completion technology for horizontal well bores maximize the hydrologic benefits of horizontal wells for aquifer remediation. In many hydrologic scenarios, horizontal wells exhibit groundwater flow characteristics, drawdown distribution, and contaminant capture capabilities superior to those of vertical wells. In addition, comparison of installation, operation, and maintenance costs for vertical and horizontal groundwater-recovery systems reveals substantial savings engendered by horizontal wells, despite higher drilling costs. Development of a casing drilling and completion system, described in detail in this paper, has allowed the environmental industry to begin reaping the benefits of horizontal wells, which include safer, more efficient remediation operations.

Introduction

Much of the pollution in the U.S. is buried in the subsurface, where such cleanup methods as excavation or vertical wells have been applied to extract contaminated soil and groundwater. These methods have disadvantages with regard to effectiveness and cost; however, horizontal drilling, a proven oilfield technology, allows well constructions that capture large areas of contamination, which shortens the remediation period and reduces operation and maintenance costs. In addition, the system described here offers particular safety advantages.

Recent public demand for cleaner air, soil, and water has led to increased federal and private-sector spending on remediation. Horizontal wellbore technology may reduce long-term remediation budgets, as numerical modeling studies indicate.

Background

Extraction of contaminated groundwater from aquifers or vapor-phase contaminants from vadose soil zones is based on the same engineering principles as production of oil and gas from reservoirs. Horizontal wells have increased recovery efficiency in hydrocarbon reservoirs. Similarly, horizontal wells have significant advantages over vertical wells in contaminated soils and aquifers. In addition, horizontal wellbore technology will open avenues of innovative remediation technologies in R&D.
Drilling Long Salt Sections Along the U.S. Gulf Coast
Authors: Barker J. W. , Feland K. W. , Tsao Y-H.
Published: December 2007

As the petroleum industry has matured along the U.S. gulf coast, the need to drill long salt sections to reach hydrocarbons has increased. This paper summarizes the special techniques that have been developed to drill long salt sections and reviews case histories where long salt sections have been successfully drilled. A new analytical equation to predict the rate of salt creep into a wellbore is also presented.
API Tubular Ovality and Stresses in Horizontal Wells With a Finite-Element Method
Authors: Akgun Ferda , Mitchell Bill J. , Huttelmaier H-Peter
Published: December 2007

A finite-element program, ANS YS, was used to determine the change in physical dimensions of oilfield tubulars and the growth of stresses in their walls as these tubulars were run and landed into a drillhole. Ovalities and axial and tangential stresses modeled with a finite-element method (FEM) are presented in easy-to-use charts for 7- and 95/8-in.-OD API casing. Axial bending stresses with the FEM are are compared with those under Lubinski's bending equation and the classic beam-bending equation.
South Belridge Tulare Simulation Study: Steamflood in a Heterogeneous Stratified Reservoir
Authors: Chiou R. C. S. , Weinstein H. G. , Smith R. C. , Barrett R. A. , DuBois D. P.
Published: December 2007

Thermal reservoir simulation is used to develop an operational strategy for the Tulare sand of the South Belridge field. History matching of an ongoing steamflood that has been in operation since 1981 is used to test the validity of the model. The primary purpose of the simulation study is to evaluate and design the optimum steamflood for an expansion project in the undeveloped, southern portion of the field. The simulation model also is used to study operating policy options for current operations as well as for new development. This study results in the recommendation that a 5-acre, nine-spot pattern be developed for the Southern Expansion Project. Study of operating policy shows that steamflood performance can be improved by shutting in marginal producing layers and optionally cutting back the steam-injection rate.
A Mechanistic Investigation of Waterflood Diversion Using Foamed Gels
Authors: Miller Matthew J. , Fogler H. Scott
Published: December 2007

Although gel treatments have gained acceptance for injection well profile modification, high treatment cost and potential loss of low permeability zone injectivity curbs implementation. This study investigates an in-situ generated foamed gel barrier that is well suited for long-term waterflood diversion because it provides an intermediate degree of plugging, yet requires substantially less polymer than bulk gels. Microvisual observations indicate foamed gel barriers are initially impermeable but break down when the pressure exceeds a critical value. This critical pressure that initiates breakdown varies with foam quality, permeability, and gel properties.
Pressure-Transient Behavior in a Reservoir With a Finite-Conductivity Fault
Authors: Abbaszadeh Maghsood , Cinco-Ley Heber
Published: December 2007

An analytical solution for transient-pressure behavior of an active well near a nonintersecting finite-conductivity fault of infinite length is presented. Flow along and across the fault plane is considered. Type curves in terms of fault skin factor and conductivity are presented for various reservoir mobility and diffusivity ratios on two sides of the fault. Pressure derivatives exhibit a negative unit slope line followed by quarter-slope bilinear flow characteristics for high-fault conductivities. A special method is presented to calculate distance to conductive faults based on a Cartesian plot of pressure derivative vs. reciprocal of shut-in time. Finally, a field pressure-buildup test from a faulted reservoir is analyzed by the model.
Generalization of Wellbore Effects in Pressure-Transient Analysis
Authors: Fair Walter
Published: December 2007

Wellbore effects have been recognized as being important in the analysis of pressure-transient tests for many years. Other works have evaluated the effects of wellbore storage and phase redistribution on pressure-transient response, and analysis methods that account for these effects are well known. It is also known, however, that other wellbore phenomena may affect pressure-transient response, but little has been presented that evaluates or generalizes wellbore phenomena in common pressure-transient tests.

This paper presents an analysis of generalized wellbore phenomena, including both mass-related and momentum effects, shows how these are incorporated into general solutions of the diffusivity equation, and provides general guidelines for recognizing these effects in pressure-transient data. In addition, it is shown that the phase redistribution formulation for pressure-transient analysis is actually a special case of wellbore mass-related phenomena, which has much wider applicability than previously realized. Besides general methods for accounting for wellbore phenomena, analytical pressure solutions are also presented for several situations, including heating or cooling of wellbore fluids, phase changes in the wellbore, and inertial effects owing to rapid acceleration or deceleration of wellbore fluids.
Conditional Simulation Method for Reservoir Description Using Spatial and Well-Performance Constraints
Authors: Hird Kirk B. , Kalkar Mohan G.
Published: December 2007

This paper describes a conditional simulation technique that constrains areal permeability fields to typical statistical information and indirectly to waterflood well performance. Near-well effective permeability and reservoir connectivity characteristics are used as indirect well-performance constraints. Results are validated by examining simulated waterflood performance of a five-spot pattern. This technique can be used to reduce the uncertainty of future well performance significantly. Additionally, the effect of alternative operating scenarios, such as infill drilling, can be evaluated more realistically.
Dynamic Filtration of Invert-Emulsion Muds
Authors: Jiao Di , Sharma M. M.
Published: December 2007

Dynamic-filtration experiments conducted on oil-based muds show that the dynamic-filtration rate is much higher than API filtration rates. The use of water-wet solids results in very poor-quality external mudcakes and high fluid-loss rates. Better external mudcakes are formed by mixing equal parts organophilic clay and mud. Filtration-loss-control additives (asphalt mineral pitches) do not reduce the equilibrium filtration rate, but do reduce spurt loss and limit solids invasion. In brine-saturated rocks, the invasion rate for oil-based muds is significantly smaller than for water-based muds because capillary pressure prevents the oil phase from entering the core in oil-based muds. Oil-based mudcakes are softer and more shear-sensitive than water-based mudcakes. Scanning electron microscope (SEM) photomicrographs indicate that oil-based mudcakes consist of individual water droplets coated with clay particles. This cake structure gives rise to the low permeability and shear sensitivity of oil-based muds.
Safety Initiatives Enhance Integrity of Offshore Platform Operations
Authors: Gilbert D.L. , Mayhew R.E.
Published: December 2007

Following an in-house survey team's review of Exxon Co. U.S.A.'s offshore operations in the Gulf of Mexico, the Offshore Div. Risk Evaluation and Control (RECON) team initiated a number of upgrade programs directed at preventing an accident potentially resulting in injury, damage, or pollution; providing effective response if an accident should occur; and providing for safe and timely platform abandonment if the accident escalates beyond control. This paper describes the gulfwide procedural and equipment enhancements undertaken to address these three areas of personnel safety.

Enhancement Program Objectives

The RECON team, formed in Oct. 1989, addressed issues involved in the enhancement of personnel safety at offshore platforms. The team divided its efforts into three basic categories: accident prevention, response/control, and platform abandonment.

To reduce the probability of an incident (fire or hydrocarbon release), a number of procedural issues were addressed and modified. Simultaneous-operations procedures were rewritten and expanded, and training was provided to enhance employee understanding. Safety-systems operating guidelines were revised to communicate management expectations more effectively, to introduce control procedures, and to minimize the bypassing of safety devices. Equipment lockout/tag-out guidelines also were expanded to underscore the importance of this maintenance requirement. The frequency and level of investigation regarding emergency shutdown testing were increased to levels appropriate to ensure operation in a real emergency. Pipeline riser inspection and protection were enhanced. Additionally, a releasable fusible device was developed to allow closure of wellhead surface safety valves (SSV's) in a situation without fire when they are locked open during wireline operations.

Several emergency response issues were addressed. Emergency response training involving scenario drills was developed, conducted, and implemented. Platform firewater systems were upgraded, and fire response training was enhanced. Alarm, communications, and emergency lighting systems were upgraded and expanded. Orientation of personnel regarding emergency procedures and equipment was improved through the development of site-specific orientation brochures and tours, as well as the production of a new orientation video for first-time visitors.
KGEOFLOW: A New Reactive Transport Simulator for Sandstone Matrix Acidizing
Authors: Sevougian S. David , Lake Larry W. , Schechter Robert S.
Published: December 2007

This paper reports on the first modeling of sandstone matrix acidization using a comprehensive geochemical simulator based on the partial local equilibrium assumption. This new model allows any combination of kinetic and equilibrium reactions involving any number of chemical species, which greatly increases the simulator's predictive abilities compared to existing sandstone acidizing models. The new simulator, KGEOFLOW, which is applicable to a variety of reactive transport processes in petroleum reservoirs, is used to predict optimal acid injection rates based on the amount of mineral dissolution and precipitation.
Stimulation Results in the Giddings (Austin Chalk) Field
Authors: Meehan D. N.
Published: December 2007

So called "water-fracs" have obtained excellent results in the Austin Chalk formation of Giddings field. This inexpensive treatment uses high volumes of water but no proppant. The reasons the treatment is successful include imbibition, gravity drainage, skin damage removal, and repressurization of the reservoir to enhance recovery. Union Pacific Resources Co. (UPRC) has treated about 250 vertical and 150 horizontal wells with very high economic success rates. Incremental recoveries from horizontal well water fracs alone exceed 5 million bbl of oil equivalent (6 Mcf = 1 bbl).
Determination of Steam Quality and Flow Rate Using Pressure Data From an Orifice Meter and a Critical Flowmeter
Authors: Chien Sze-Foo , Schrodt James L. G.
Published: December 2007

A method for measurement of steam quality and flow rate has been developed, laboratory tested, and packaged for thermal EOR applications. The method consists of an orifice flow meter in series with a critical flow meter. The flow through the orifice is subcritical. The critical-flow meter can be a static choke, a venturi, a nozzle, or a thick orifice, etc. Steam flow rate equations for orifice flow and for critical flow were established with empirically derived constants. These two equations were combined and solved to determine the steam quality and flow rate.

The basic mechanical parts of the measurement system are rugged and inexpensive. The pressure transmitters and flow computer are portable and can be used for spot checks or for continuous monitoring. The steam quality and flow rate information obtained make it possible to evaluate the performance of steam distribution systems and thus to identify where modifications to the distribution system piping are needed.
High-Velocity Flow in Porous Media
Authors: Firoozabadi Abbas , Thomas L. K. , Todd Bert
Published: December 2007

High-velocity gas flow causes a pressure drop greater than that predicted by Darcy's law. This subject has been addressed from a theoretical and an experimental standpoint. The purpose of this paper is to summarize previous literature on this phenomenon and to clarify recent misconceptions that have arisen. Additional flow experiments have been made and analyzed to support the conclusions of this work.
Effect of Wettability and Spreading on Recovery of Waterflood Residual Oil by Immiscible Gasflooding
Authors: Oren Paul E. , Val Pinczewski W.
Published: December 2007

This paper investigates the mobilization and recovery of waterflood residual oil by immiscible gasflooding in 2D glass micro-models under strongly oil- and water-wet conditions. Two oil/water/gas systems, one displaying a positive and the other a negative spreading coefficient (oil over water), were used. The results clearly show the importance of fluid/solid and fluid/fluid interactions on tertiary oil recovery. Oil recovery was highest for the oil-wet displacements where the oil formed thick wetting films. Recovery was considerably lower for the positive spreading system under strongly water-wet conditions where the oil was observed to form thin but continuous spreading films. Recovery was lowest for the negative spreading system under strongly water-wet conditions where no oil films were formed.
Openhole Cavity Completions in Coalbed Methane Wells in the San Juan Basin
Authors: Palmer I.D. , Mavor M.J. , Seidle J.P. , Spitler J.L. , Voiz R.F.
Published: December 2007

Coalbed methane wells in the San Juan basin can be highly profitable, with gas production up to about 10 MMcf/D at depths of about 3,000 ft, if the wells are successfully completed with the openhole cavity technique. We report the first measurement of cavity size (radius of about 5 ft) and shape. A cavity can resemble a cylindrical bookcase with shale ledges like shelves. We also report correlations between successful cavity completions and such reservoir/rock parameters as compressive strength, coal rank, permeability, and reservoir pressure (for example, there is no correlation with the minimum coal compressive strength). In this area, wells completed with the openhole cavity technique often produce roughly 10 times more gas than wells completed with hydraulic fracture stimulations. Wellbore mechanics associated with the cavity - e.g., the enlarged wellbore plus enhanced permeability beyond the cavity - does not seem to explain the cavity/fracture production discrepancy. A number of other possibilities are explored, including permeability anisotropy and completion damage to the reservoir or fracture. Severe damage apparently is associated with hydraulic fracture stimulations in the fairway zone, which would explain their poor performance compared with cavity wells.

Introduction

In 1987, Meridian Inc. began developing properties in Unit 30-6 (Fig. 1) using openhole cavity completions. Sixty-one wells produced gas at an average rate of almost 4 MMcf/D (with some at 10 to 12 MMcf/D) in 1990. In an adjoining unit (NEBU, Fig. 1) Devon Energy Corp. completed almost 100 coalbed methane wells similarly. Again, rates averaged about 4 MMcf/D. A summary of recent cavity completions is given elsewhere.

The openhole cavity completion has become the technique of choice in a sweet spot or high-potential fairway region (Fig. 2). Within the boundary of the fairway, wells with openhole cavity completions produce at 1 MMcf/D or more. The fairway is characterized as an overpressured area with generally thicker coal seams and enhanced natural fracturing.
Storage of Natural Gas as Frozen Hydrate
Authors: Gudmundsson J-S. , Parlaktuna Mahmut , Khokhar A. A.
Published: December 2007

The stability of a natural gas hydrate during storage at atmospheric pressure and below-freezing temperatures was studied in the laboratory. The gas hydrate was produced in a stirred vessel at 2- to 6-MPa pressure and temperatures from 0 to 20°C. The hydrate was refrigerated and stored in deep freezers at −5, −10, and −18°C for up to 10 days. The natural gas hydrate remained stable when kept frozen at atmospheric pressure.
Pressure Drops in Horizontal Wells: When Can They Be Ignored?
Authors: Novy R. A.
Published: December 2007

Frictional losses create a pressure drop within a horizontal wellbore. Should this pressure drop be significant relative to drawdown (the difference in pressure between reservoir and wellbore), the pressure far downhole could nearly equal the pressure in the reservoir. Friction can thus reduce productivity. This paper reports guidelines that indicate whether friction matters in a particular well.
Experimental Verification of Dimensional Analysis for Hydraulic Fracturing
Authors: de Pater C. J. , Cleary M. P. , Quinn T. S. , Barr D. T. , Johnson D. E. , Weijers Leen
Published: December 2007

We have derived model laws that relate experimental parameters of a physical model of hydraulic fracture propagation to the prototype parameters. Correct representation of elastic deformation, fluid friction, crack propagation, and fluid leakoff forms the basis of the scaling laws. For tests at in-situ stress, high fluid viscosity and low fracture toughness are required. Tests on cement blocks agreed with the scale laws based on elastic behavior.
Generalized Equations Relating Pressure of Individual Wells and Grids in Reservoir Modeling
Authors: Odeh A.S. , Al Hussainy R.
Published: December 2007

In a recent paper, van Poollen et al. presented equations relating observed field pressures to those calculated by a numerical simulator. The equations are applicable to steady- and semi steady-state flow for wells draining circular areas and using an equivalent block radius. They implicitly assume that wells are located at the center of the drainage area. In this note we present equations that generalize the previous method and relate field to model pressures for various shapes of drainage area, well pressures for various shapes of drainage area, well location and grid configuration. Using the generalized equations of flow of Brons and Miller, and following a method of derivation similar to that reported by van Poollen et al., we obtain:For steady-state flow:

.................(1)

For semisteady-state flow:

...................(2)

For unsteady-state flow:

.....................(3)

where subscripts m and f refer to the model and field, respectively, and P D theta of Eq. 3 is the dimensionless initial pressure. For a circular system A pi r, and CA = 31.6 from Ref. 3. If we substitute these values in Eqs. 1 and 2, we obtain the results of van Poollen et al. as represented by their Eqs. 14a and 14b. In a manner analogous to that of van Poollen et al. the average reservoir pressure can be related to the dynamic pressure by using a dimensionless time based on the drainage area A rather than radius. Also, the relation between the average reservoir pressure and the simulator pressure in Eqs. 1 and 2 can be based on producing time as well as shut-in time, since it is possible to generate one method from the other as was shown by Ramey.

NOMENCLATURE

A = area in sq ftB = formation volume factor, res. bbl/STBCA = shape factorDD =c = compressibility, 1/psih = thickness, ftk = permeability, md PD, m, t = dimensionless model pressure, [141.2kb/ PD, m, t = dimensionless model pressure, [141.2kb/(q B)]P PD = dimensionless average reservoir pressure PD = dimensionless average reservoir pressure P = pressure, psiq = production rate, STB/Drw = well radius, ftt = flow time, days= porosity fraction= viscosity, cp

P. 277
Statfjord Field: Field and Reservoir Management Perspectives
Authors: Aadland Atle , Dyrnes Olav , Olsen S. R. , Drønen O. M.
Published: December 2007

The Statfjord field, the largest North Sea oil field, has been on production since 1979. We think that production decline is imminent; however, oil production was close to a record for the field in 1991. This paper discusses the reservoir drainage strategy; the situation after 13 years of production; and short- and long-range perspectives for further field development, which includes a high well activity level to maintain the well production potential. Most of the wells drilled and scheduled are either horizontal wells or extended-reach wells, extending toward the flanks of the field. A large effort has been put into mapping remaining reserves by developing detailed reservoir simulation models. The production and well activities have been optimized on the basis of the results from the new models. Exploitation of business opportunities, such as processing of third-party crude from tie-in and subsea satellite fields and external gas storage, gives a new perspective for an oil field on production decline. In addition to these long-range plans, studies of such recovery methods as water-alternating-gas (WAG), surfactant, and polymer injection are continuing.
Natural Gas at Any Price
Authors: Grinnell Bates M.
Published: December 2007

Comprehensive studies of past and future demand, interfuel competition, and potential supplies of energy are essential to conclusions on the demand for and the supply of natural gas in the U. S. Refined petroleum products, gas liquids, gas, electricity, coal, and products, gas liquids, gas, electricity, coal, and nuclear fuel each was examined in the light of its past and probable future interaction with other fuels competing for the same markets. Although there are hundreds of end uses, consumption may be classified readily under three headings: Residential-Commercial, which includes space heating and cooling, cooking, and lighting; Industrial, including a myriad of boiler fuel, heating, lighting, and power uses; and Transportation, fuel for motor vehicles, aircraft, railroads, and vessels. Where electricity competes in these markets, a further analysis was made to determine the particular fuel to be used in generating it. Use of energy from nuclear fusion or fission undoubtedly will expand rapidly, but it is considered that its share of the total energy market will not be appreciable before 1980, the end of the period covered in these forecasts.

Requirements for Gas

Forecasts of demand for gas, summarized in Table 1, include consumption in specific end-use markets, plus relatively small annual amounts to fill pipelines, for underground storage, for losses, and amounts unaccounted for. The total, then, is more accurately termed requirements. Fig: 1 shows consumption by type of customer. The amount of gas required annually in the U. S. is expected to increase from 20.4 Tcf in 1968 to 28.1 Tcf by 1975, and to 32.8 Tcf by 1980. The forecast rates total more than 325 Tcf during this 12-year period, or an average of 27 Tcf/year. Unfortunately, period, or an average of 27 Tcf/year. Unfortunately, additions to reserves reported by the American Gas Association (AGA) never have been this great, coming close only in 1956 when discoveries of new fields and pools, and extensions and revisions of prevailing reserves amounted to 24.7 Tcf. Current estimates by this group show that in 1968 only 13.7 Tcf was added to proved reserves, making that year one of the poorest on record. poorest on record.

JPT

P. 937
Reservoir Simulation Grids: Opportunities and Problems
Authors: Aziz Khalid
Published: December 2007

Grid selection is one of the most difficult and time-consuming tasks in the simulation of geologically complex reservoirs.

A grid is imposed on a reservoir so that we can solve the nonlinear flow equations that predict the reservoir's response to changes at wells or other boundaries.

Therefore, I first discuss the role of grid geometry in the evaluation of each term in the flow equations. Then I describe several conventional and some new gridding techniques, as well as their advantages and disadvantages. Next I make recommendations based on my own experience and discussions with colleagues. My assessment is that grids should be as close to orthogonal as possible. Also, local grid refinement should be used with care; its inappropriate use can be counterproductive. Considerable progress has been made recently on the use of flexible grids, but efficient use of unstructured, locally orthogonal grids requires further research. Techniques that automatically align the grid with major reservoir features (e.g., faults) are being developed and are expected to simplify grid generation.

Introduction

A reservoir simulator predicts reservoir performance by solving flow equations on a discrete grid chosen by the simulation engineer to represent the reservoir. The grid normally is selected with one or more of the following considerations in mind.Reservoir geology and size and the data available for reservoir description.Type of fluid displacement or depletion process to be modeled.Past and anticipated field development (location and type of wells).Numerical accuracy desired.Available software options.Objectives of the simulation study.Competence of the simulation engineer or team.Available computer resources, time constraints, or project budget.

In the early days of reservoir simulation, the last consideration often determined the number of gridblocks, and the available software limited the choice of grid type, usually to block-centered Cartesian or cylindrical grid. Research in reservoir simulation and hardware developments, especially over the past 10 years, has greatly extended the gridding options available.
A New Representation of Wells in Numerical Reservoir Simulation
Authors: Ding Yu , Renard Gérard
Published: December 2007

Numerical PI's are used to relate wellblock and wellbore pressures and the flow rate of a well in reservoir simulations by finite differences. This approach is based on an "equivalent wellblock radius," req,o. When nonuniform grids are used, req,o may create an error in wellbore pressure or oil rate. This paper presents a new well representation. The analytical solution for near-well pressure is included by modifying the transmissibilities between gridblocks so that flow around a well is described fully. The new method is applicable to nonuniform grids and nonisolated wells.
Determining a Proper Flood Pattern from a Three-Well Pilot in a Channel Sand
Authors: Lane A.B.
Published: December 2007

Introduction

This is a review of the performance and development of a waterflood project of a channel sand reservoir; it describes how, by carefully observing the performance of a skeleton three-well injection pilot, the flood pattern can be changed to flood a narrow channel sand pattern can be changed to flood a narrow channel sand successfully. The area involved is the 717-acre Lewis Booch delta, which were deposited in the northwest-miles northwest of Allen in Ponototoc County, Okla. (see Figs. 1 and 2).

Geology

"Most channel sands are elongated, lenticular, and commonly erratic. They may be completely isolated lenses of sand, enclosed in shale, or they may be spread out sheetwise in the uppermost part and in this manner merge laterally with other neighboring channel sands. The latter is exemplified by the sands of the Booch delta, which were deposited in the northwestern shelf of the McAlster basin of Oklahoma in early Pennsylvanian time. This delta covers an area of more than 2,000 square miles."*

The Booch Sand unit reservoir is a part of the generalized delta-type distributary system of channel sands that diverge south-southeast into the McAlester basin. Structure is of little importance in channel sands of this type. The maximum dip in any direction for this sand bar is less than 2 degrees. Lateral shale-out is very abrupt. a 10-acre offset to a producing well with 15 to 20 ft of pay can be void of any sand.

Development

The discovery well shown as Unit Well 22 was completed in April, 1944. Of the 50 Booch sand wells completed, 37 were drilled between 1952 and 1958. Approximately 15 Booch dry holes were drilled to define the sand bar (see Fig. 3).

JPT

p. 195