bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of Limestone Formation Characteristics From Well Logs
Authors: Cregeen D.J. , Moir H. 
Published: December 2007

Introduction
The evaluation of limestone formations by well logs has brought many interesting problems to light, some of which are as yet unresolved. While a major purpose of well logging is to ensure that zones containing producible hydrocarbons are not bypassed, this paper is more concerned with the further information that can be derived from the logs to assist in more clearly defining reservoir characteristics, fluid content and performance. In the hard limestones of Southeast Arabia sufficient evidence has not yet been gathered to allow any large-scale tailoring of the logging program; a number of logs are still run which ostensibly can be used to compute the same parameter. The validity of some of these measurements is discussed, and some tentative interpretations are made concerning their significance. In this paper, the five selected topics are discussed in light of their application to the hard limestone reservoirs under review.

Water Saturation, Sw
Well-log analysis lends itself readily to the determination of water saturation and, hence, to computation of hydrocarbon reserves. However, it is advisable to obtain confirmation of the values so obtained by alternative methods because several factors influence the basic data from which these values are derived. As has been pointed out elsewhere, water saturations of 2 to 50 per cent of the available pore space have been observed in oil-producing formations. This wide range invalidates the possibility of choosing a reasonable value by inspecting the available choices and, thus, makes corroboration from other sources essential.
The methods used to determine connate-water saturation in the formations under review were core analysis of formations cut under oil-base mud, measurement of capillary pressures of cores and log analysis. Each of these methods suffers from limitations, and only where mutual agreement exists may a value be accepted with confidence. Since the log-analysis method offers distinct advantages over the other two, affording as it does a measurement under reservoir conditions, it was of interest to attempt to resolve the uncertainties inherent in the method by comparing results obtained on cores in the laboratory.
Measured and Calculated Horizontal Stresses in the Travis Peak Formation
Authors: Walls J. D. , Dvorkin Jack 
Published: December 2007

Summary
This paper presents the results of an experimental program to determine in-situ horizontal stress magnitudes from the dynamic mechanical properties of tight-gas sand cores. These measurements were made on 47 vertical plug samples from the Gas Research Inst. (GRI) test wells, Staged Field Experiment (SFE) Wells 1 through 3. The wells were cored in the Travis Peak formation of east Texas from ≈ 6,500 to ≈ 9,500 ft deep. Vertical overburden stress gradient was measured in one well using a downhole gravimeter.
The core mechanical properties were used with the Anderson and Newberry equations to calculate in-situ horizontal stress. Actual in-situ minimum horizontal stress was determined from instantaneous shut-in pressures measured during minifracture and microfracture tests. The Newberry equation was found to give results that agreed best with measured horizontal stress. A closer match was obtained between measured and calculated horizontal stress values when we used dynamic Poisson's ratio from partially gas-saturated samples. The assumptions and limitations of the procedure are presented.
Incorporation of 2D Fluid Flow into a Pseudo-3D Hydraulic Fracturing Simulator
Authors: Weng Xiaowei 
Published: December 2007

SummaryPseudo 3D (P3D) hydraulic fracturing models often overpredict fracture height for a poorly contained fracture. This is caused partly by either the neglect of the fluid flow component in the vertical direction or a crude treatment of the 2D fluid flow in the fracture as 1D flow in the vertical direction in the fracture-height calculation. This paper presents a height-growth model that adopts a flow field more representative of the actual 2D flow in a fracture. In this model, the fracture is divided into two regions: an inner region where the flow direction is nearly horizontal, and an outer region where the flow field is approximated by a radial flow from an imaginary source. The governing equations for determining height growth rate and the numerical method for solving these equations are described. A commercial P3D simulator was modified by replacing its original height-growth model with this 2D flow-height model. The modified simulator was tested against the original simulator and the Terra Tek and U. of Texas fully 3D simulators. The modified P3D simulator incorporating the new height model showed significant improvement over the original model in height calculations and good agreement with the fully 3D models.
How Hydrolyzable Metal Ions React with Clays to Control Formation Water Sensitivity
Authors: Veley Carl D. 
Published: December 2007

Hydrolyzed metal ions prevent clay dispersion by displacing the exchangeable cations and becoming firmly attached to clay surfaces. Formations treated with soluble compounds of hydrolyzable metals are highly resistant to permeability damage from clay movement.

Introduction
Water-sensitive formations present severe problems in drilling, testing, completion, production and waterflooding operations. Sensitive formations are characterized by a sharp loss of permeability on contact with water, but sometimes this permeability loss is accompanied by formation disintegration and sand production.
A formation's sensitivity to fresh water is usually increased by exposure to monovalent cations (e.g., Na+, NH+, Li+, K+) and decreased by exposure to divalent cations (e.g., Ca++, Mg++, Ba++). Therefore, fresh water is more likely to cause permeability damage when it follows sodium chloride brine than when it follows calcium chloride brine.
This phenomenon has been reported several times, but no information was found concerning the effects of trivalent or tetravalent cations on sensitive formations. Since formations treated with divalent cations are more stable (less easily damaged) than those treated with monovalent cations, it seems reasonable that treatment with more highly charged cations should produce even greater stability.
The purpose of this study was to investigate the effects of highly charged cations on formation water sensitivity. The primary interest was the effect of such cations on water permeability. Consequently, most of the laboratory work consisted of direct permeability studies. permeability studies. Damage Theory
The permeability of any argillaceous (clay bearing) sediment depends on how tightly the individual clay particles are bound together. Permeability will be particles are bound together. Permeability will be maximum if all the particles are bound together in compact, oriented aggregations too large to be transposed by moving fluids. Permeability will be minimum if these particles completely disperse and become entrained in the moving fluids. Such entrained particles form microscopic filter cakes on narrow pore particles form microscopic filter cakes on narrow pore openings and very effectively restrict fluid flow. Intermediate permeability losses will be noted when the compact aggregations only partially disperse, i.e., separate into smaller aggregations. In this case, the entrained solids are larger and form filter cakes that are considerably less effective in blocking fluid flow. It follows that sensitivity is related to how extensively the clay particles can separate or disperse.
In all clay-water systems, there are certain factors tending to disperse the clay particles and certain other factors tending to hold or drive them together. The relative combined strengths of these opposing factors determine whether the particles will disperse or stick together. Any fluid flowing through a formation will cause permeability damage if the clay-dispersing factors exceed the binding factors.
JPT
P. 1111
Eggbeater PDC Drillbit Design Eliminates Balling in Water-Based Drilling Fluids
Authors: Zijsllng D. H. , Illerhaus Roland 
Published: December 2007

SummaryThis paper describes a novel polycrystalline-diamond-compact (PDC) -bit concept based on insights into PDC-bit cutting mechanism and rock behavior during drilling. The design comprises a hydraulic layout that optimizes bit cleaning and cuttings removal in soft and sticky formations. Significant improvements in performance have been achieved in Cretaceous and Triassic formations drilled with water-based muds.
A Unified Approach to Drillstem-Failure Prevention
Authors: Hill T. H. , Seshadri P. V. , Durham K. S. 
Published: December 2007

Summary
Practical drillstem-failure prevention seems to be based more on individual knowledge of specific failures than on any standard model. To present a broader approach to drillstem-failure prevention, this paper draws on failure-prediction models, failure-investigation results, drillpipe finite-element analysis, and the API/IADC Drillstring Database to construct a unified approach to failure prevention.
Economic and Reserve Evaluation of Coalbed Methane Reservoirs
Authors: Dhir R. , Dern R.R. , Mavor M.J. 
Published: December 2007

Summary
This paper presents examples of a reservoir-simulation-based technique for evaluating coalbed methane reserves. Simulation results and an economic analysis model that incorporates the effects of nonconventional fuel tax credits are used to compute economics. A statistical model quantifies economic risk on the basis of uncertainty in relevant geologic properties.

Introduction
The purpose of this paper is to discuss a methodology for the estimation and classification of reserves from coalbed methane reservoirs and to present a technique for determining the 'economic feasibility of proposed coalbed methane investments.
Coalbed methane reservoirs are characterized by the nonconventional nature of gas storage and fluid production, which limits the use of traditional decline curve or volumetric methods for reserve estimations. To account accurately for the physical phenomena affecting production, an approach based on the use of reservoir simulators is recommended. Applications of this approach for different reserve categories are presented.
Production from coalbed methane reservoirs is affected by several reservoir and geologic factors. Some of these factors can be determined with standard formation evaluation methods; others must be inferred by production analysis. The use of production history matching as a reservoir analysis tool is illustrated.
Natural gas production from coalbed methane reservoirs in the U.S. qualifies for a nonconventional fuel tax credit under Sec. 29 of the Internal Revenue Code (lRC). If these credits can be utilized, the positive effects on project economics are quite significant. These effects are demonstrated by various examples.
Reservoir-property estimates and production forecasts are subject to a certain level of uncertainty. It is important to recognize the effects of these uncertainties on the predicted economic returns from a project. A unique approach to quantifying the geologic risks associated with coalbed methane projects is presented.
Closing the Loop: Production Data Management by PC's in the Field
Authors: Taylor S. 
Published: December 2007

Summary
Accounting and engineering groups have long commanded a high level of expertise in the ability to manipulate well production data for the calculation of well performance trends, reserve estimations, and lease-hold accounting. Unfortunately, the data crucial to the accuracy of this work are often affected negatively by human error (or mathematical ability) in the calculation of production volumes, the time available (or interest) in performing "paperwork"-oriented tasks, and the timeliness with which computed data are made available to these groups. To correct this situation, we have developed a PC-based Production Acquisition Allocation and Reporting System (PAARS) for field and office personnel. With this system, all data entry and allocations are still assembled in the field, but all calculations are done by the PC. Additional tracked data include personnel costs and activities, regulatory compliance information, and marketing data.
Whenever desired, data are transmitted to a central PC or mainframe data base, where they become immediately available for use by accounting, engineering, marketing, and management personnel. At the Offshore Div., for example, the office staff has current production and well test data available off the PC network, for every operated well, when they arrive at work in the morning.
Numerous customized reports are available for use by field and office personnel. The system also automatically generates the government reports required by the regulatory staff. The system has been used throughout the Offshore Div. for 4 years with considerable success and was recently adapted for land operations. In addition, OGCI Software has now joined with Samedan to include PAARS (now PA_PAARS) for distribution with its family of Production Analyst programs.
A Task Management System for Compliance With Health, Safety, and Environmental Regulations
Authors: Crump J. J. , O'Gorman T. P. 
Published: December 2007

Summary
Shell Western E&P Inc. (SWEPI) has developed a new computer system to help it comply with health, safety, and environmental (HS&E) regulations. It is a task management system that functions at the detailed inventory level. It schedules work, instructs operations, and records compliance status. This article discusses design and development of the system.
Interactive Reservoir Simulation
Authors: McVay D. A. , Bastian P. A. , Epperson B. D. 
Published: December 2007

Summary
This paper describes a system that allows engineers to monitor and control a reservoir simulation run during its execution. The system consists of a 3D, three-phase black-oil reservoir simulator running simultaneously with an interactive graphics pre- and postprocessor. Previous authors have described systems that allow monitoring of job execution with simultaneous graphics displays; the system described here is unique in that the engineer can modify simulator and well-control parameters during the execution. While the system will be helpful in detection and correction of timedependent data problems, it will be very useful in optimizing reservoir management decisions in future performance projections.
The system is implemented on an IBM-compatible 486 microcomputer with commercially available multitasking software, although it can be implemented easily on any microcomputer or workstation capable of multitasking. We show that implementation of the system required only a moderate amount of modification of the pre- and postprocessor and even less modification of the reservoir simulator.
Risk Profile Modification of Energy Projects: The Impact of Controlling Financial Risk Utilizing Swaps
Authors: Larson B.O. 
Published: December 2007

Summary
The commodity futures and swaps markets are thought to be the invention of speculators, the bane of the oil business, or possibly something confined to finance departments of major corporations. In actuality, they should be considered more as an insurance vehicle and can be used at the project level to modify the risk profile of a property. In this context, an increased familiarity with them can be useful for an engineer. Either futures or swaps can be used to guarantee or modify product prices. While this does not necessarily maximize cash flow or present worth, it can protect a project or company for several years from downside price risk, thereby reducing the risk of the venture. This can be particularly important if lower product prices would cause unacceptable cash flows or net incomes. Reducing risk by limiting downside price exposure could alter budgeting decisions, allow continued or expanded operations of a particular property, or increase debt capacity.

Introduction
As commodity markets have increasingly assumed the role of discovering near-term prices for oil and are beginning to affect natural gas prices similarly, several financial products have been developed that can reduce product pricing risk. Risk can be reduced directly in the futures market or in the over-the-counter market with financial institutions and trading companies using hedging products like swaps. The role that these products play and the importance of understanding it are increasing as price volatility becomes more pronounced. Their impact is highest and their cost is lowest over the immediate future (1 to 5 years). This may also be the period of maximum producing rate, highest present worth, and maximum uncertainty concerning price; thus, they can provide substantial risk protection.
Futures and swaps markets exist for crude oil, natural gas, and several refined hydrocarbon products. While gas futures and swaps can be executed, that market is less well-developed than the oil market, and the relative prices in the two markets do not necessarily correlate. This paper is limited to crude oil transactions to avoid those complications and to concentrate on the risk-modification aspects of hedging. Most comments and all concepts are equally valid for natural gas production.
This paper briefly outlines how oil futures and swaps function and then concentrates on demonstrating the effect of swaps on risk management at the project level through specific examples. An attempt is made to focus on the basic fundamentals of altering project risk rather than dealing with the infinite variability of swaps or the mechanical complexities of executing futures contracts.
Drilling the First Horizontal Well in the Gulf of Mexico: A Case History of East Cameron Block 278 Well B-12
Authors: Fisher E. K. , French M. R. 
Published: December 2007

Summary
East Cameron Block 278 Well B-12 was the first horizontal well drilled in the Gulf of Mexico. This well, located in the Texaco Inc. operated East Cameron 265 field, was drilled and completed in May 1990. The objective formation was a high-permeability, shallow, unconsolidated gas sand located about 1, 450 ft below the mudline (BML). The success of this well proved that horizontal wells are viable alternatives to extended-reach development wells from offshore platforms in the Gulf of Mexico. The cost to drill and complete this horizontal well was less than comparable extended-reach development wells drilled in the same field. A minimal increase in drilling costs accompanied by considerable savings in completion costs resulted in favorable economics for the project. Drilling a shallow horizontal well in the Gulf of Mexico presented several challenges. This paper discusses prewell planning, formulation of contingency plans, and implementation of a drilling/completion program designed to meet these challenges.
Oilfield Environmental Control Technology: A Synopsis
Authors: Wojtanowicz A.K. 
Published: December 2007

Summary
This paper shows, in a systematic way, that the long-term solution to the environmental issue in petroleum engineering is the development of a new area: environmental control technology (ECT). ECT is defined as intrinsic in and integrated with an oilfield process. Its preventive function is contrasted to the remediating nature of conventional waste-management technology (WMT). This paper has two objectives: to identify and qualify ECT for petroleum engineering and to overview recent ECT developments, particularly in oilfield production operations.

Introduction
In the 1980's, low oil prices forced oilfield technology to focus on economic efficiency and productivity. Simultaneously, environmental regulatory pressure added a new factor to petroleum engineering economics: the cost of working within the constraints of an environmental issue. The industry is absorbing this cost while revising oilfield technology to reduce the environmental impact. The new area, ECT, has the potential to become a widely accepted way for the oil industry to address the environmental issue.
The API is currently working on a supporting agenda for reauthorization of the U.S. Clean Water Act. One important issue of the new act introduces the concept of pollution prevention to the permit procedure. In regulatory language, pollution should be prevented through source reduction, which necessitates improvements to oilfield processes to reduce waste generation. API supports the concept but favors the inclusion of other preventive measures in this act, such as recycling, reuse (beneficial use), and treatment (to comply with discharge criteria).These and similar past regulatory actions have altered the industry's approach to the oilfield environmental issue. As a result, the remediation approach represented by WMT is being replaced with a preventive approach (ECT). The heart of ECT is prevention of environmental impact. The other features need further clarification.

Identification of ECT
A general definition of ECT is presented in the appendix, along with a description of its basic methods. Ref. 1 discusses the position of ECT among other techniques used by the oil industry to tackle the environmental issue. (The nontechnical means are social, legal, commercial, scientific, and logistic.)
The technical approach to the environmental issue usually is undertaken after the nontechnical means become redundant or uneconomical.
Modeling a Repressured Waterdrive Gas Reservoir
Authors: Moltz A.K. 
Published: December 2007

Summary
Reservoir modeling confirmed reserve losses occurring in a waterdrive gas reservoir to justify blowdown project initiation. The material-balance models initially used could not match the water influx and repressuring observed in the reservoir. This paper shows that material-balance calculations need to be modified to account for trapped-gas compression that occurs with repressuring, and demonstrates the use of a "simple" numerical simulation model to predict performance. Numerical simulation enabled us to match reservoir behavior successfully, quantifying the effects of trapped-gas compression, and to identify the importance of critical blowdown rates and timing for optimizing reserve recovery from this repressuring waterdrive gas reservoir.

Introduction
The Tom O'Connor 5,100 Ft Sand is a gas reservoir located in Refugio County, TX. This fairly homogeneous Frio sandstone contains dry gas with a moderate directional waterdrive from the southwest. Fig. 1 gives a composite log and a structure map of the reservoir. At the start of this study, the reservoir was already in the later stages of depletion, having recovered 85% of the original gas in place.
During a period of low gas market demand, the reservoir experienced significant water advancement and gas-zone repressuring from a lengthy production curtailment by the purchaser. Gas-zone pressures increased from 800 to 1,100 psig during this period (see Fig. 2). The operator successfully demonstrated that substantial reserve losses were occurring and obtained a special gas allowable to blow down the reservoir .
Reservoir modeling was performed to confirm and quantify the gas reserve losses resulting from production curtailment and to predict the additional recovery that would result from blowdown initiation. Numerical simulation was used effectively to model the historical performance of the reservoir and to determine the optimum blowdown rate to maximize recovery.

Model Development
A simple tank-type model was developed with constant reservoir rock and fluid properties. The model incorporated radial flow from one central producer and contained a limited, directional aquifer as indicated by performance. Fig. 3 gives the reservoir input properties and model layout. Fig. 4 shows historical water encroachment and remaining free-gas volumes determined from known gas/water contact locations based on drill wells and gamma ray/neutron log surveys. Model accuracy was enhanced by the lengthy performance data available, which allowed excellent model calibration through history matching.