K. Aminian

The Application of ANN for Zone Identification in a Complex Reservoir

Reservoir characterization plays a critical role in appraising the economic success of reservoir management and development methods. Nearly all reservoirs show some degree of heterogeneity, which invariably impacts production. As a result, the production performance of a complex reservoir cannot be realisticall y predicted without accurate reservoir description. Characterization of a heterogeneous reservoir is a complex problem. The difficulty stems from the fact that sufficient data to accurately predict the distribution of the formation attributes are not usually available. Generally the geophysical logs are available from a considerable number of wells in the reservoir. Therefore, a methodology for reservoir description and characterization utilizing only well logs data represents a significant technical as well as economic advantage. One of the key issues in the description and characterization of heterogeneous formations is the distribution of various zones and their properties. In this study, several artificial neural networks (ANN) were successfully designed and developed for zone identification in a heterogeneous formation from geophysical well logs. Granny Creek Field in West Virginia has been selected as the study area in this paper. This field has produced oil from Big Injun Formation since the early 1900s. The water flooding operations were initiated in the 1970s and are currently still in progress. Well log data on a substantial number of wells in this reservoir were available and were collected. Core analysis results were also available from a few wells. The log data from 3 wells along with the various zone definitions were utilized to train the networks for zone recognition. The data from 2 other wells with previously determined zones, based on the core and log data, were then utilized to verify the developed networks predictions. The results indicated that ANN can be a useful tool for accurately identifying the zones in complex reservoirs.

A New Approach for Reservoir Characterization

Predicting reservoir performance reliably requires an accurate model of the reservoir. For reservoir simulation, identifying and predicting flow units depend strongly on the permeability distribution. For reservoirs having few permeability measurements, such as most reservoirs in the Appalachian basin, statistical and artificial-intelligence techniques could identify flow units on the basis of limited core-analysis data supplemented by minipermeameter measurements, geological interpretations, and well-log data.

Gas-Well Production Decline in Multiwell Reservoirs

This paper introduces a pseudosteady-state constant-pressure solution for gas wells. The solution was used to develop a type-curve-based method to history match and predict multiwell gas reservoir production. Good agreements between the predicted and actual gas well production rates were obtained.

Pressure analysis of an unstimulated horizontal well with type curves

This paper reports that horizontal wells are effective alternatives to fractured vertical wells in several reservoir types, including low-permeability sandstones and shales. An understanding of fluid flow relationships is a prerequisite for efficient use of horizontal technology. The pressure-buildup data analyzed her were recorded in a horizontal completion in a low-permeability gas-bearing shale. The well was drilled and tested to verify laboratory and computer modeling research. After the general solutions were developed, the data were analyzed to describe reservoir properties and the effectiveness of the completion. Results of the type-curve analysis indicate that the contributing well length was shorter than the actual drilled length and that the contributing reservoir thickness was less than the typical net pay. Numerical modeling was used to verify the calculated parameters. Results fully support the well length and reservoir thickness determined through type-curve analysis, indicating that an unstimulated horizontal well completed in a heterogeneous formation may be insufficient to link the full vertical extent of the reservoir to the wellbore.

Performance Evaluation of Waterflood Project in Southern West Virginia

Granny Creek oil field is located in Southern West Virginia in the Appalachian Basin. R has been producing from the Big Injun formation. Primary production was initiated in the 1920’s and continued until early 1970’s. Around the mid 70’s, new wet:: were drilled and a waterflood project was started which is still in progress. During the course of the waterflood project, some problems were encountered. These problems included, inconsistency in sweep efficiency in adjacent patterns, and high injection pressure. In this field often two adjacent five spot patterns with similar injection to por~ volume ratios exhibit totally different oil ai~d water production rates, While water does not breakthrough in some patterns for months, other patterns experience instantaneous water breakthrough. Unusually high injection pressure is obsewed almost throughout the field, and yet some injection wells exhibit normal injection pressures, references and Illustrations at Ihe end of paper, Presented in this paper is a summary of approaches, methodologies, results and conclusions that have been reached during the performance evaluation of this waterflood project. With the aid of resei :oir simulation studies, some major heterogeneities were ct~aracterized and modeled for this field. Interpretations of seismic studies were used to confirm the orientation of such heterogeneities in the field.

A Simple Method for Evaluating Pore Surface Mineralogy

Majority of mineralogical studies directed at hydrocarbon producing formations are conventional studies that treat the formation as a bulk entity. Focusing on pore surface mineralogy, which is the identification of the elemental composition of the pore surface, seems to be a more realistic approach, since fluids in the formation come into direct contact with these elements on the surface. Rock-fluid properties such as relative permeability, nettability, capilla~ pressure and certain rock properties, are influenced by pore surface mineralogy. Hence, characterization of pore surface mineralogy will enhance understanding of the interaction between fluid and the porous medium. This paper discusses Multiple Voltage Scanning Electron Microscopy as a novel method for characterization of pore surface mineralogy. Multiple Voltage Scanning Electron Microscopy, a new method that has references and illustrations at the end o/ 395 successfully been used to study the surface of particles, has been implemented to identify the elemental composition of pore surface. Results of the investigations of pore sufface mineralogy for a resewoir in West Virginia is presented. This reservoir has experienced high injection pressures during a watetiooding project. The concentration of clays on the pore surface can be a possible explanation for high injection pressure. This paper will t~ to direct the attention of scientists and researchers to this issue and emphasize ?he importance of pore surface mineralogy and its effects on rock-fluid properties.

Permeable rock model using an array of pores

Abstract A simple model approximating a porous medium has been developed to study fluid flow path behavior in acomplex porous media. The model consists of a network of interconnected pores. The pores are connected by pore connections, or more precisely ostioles. The pores are assumed to be much larger than ostioles and therefore all flow resistance lies in the ostioles. Two different sizes have been assigned to ostioles: large and small. The results obtained from this uncomplicated model indicates that the fluid flow path in a porous medium is complex and almost always goes through a small ostiole. The flow path is generally down the network with some lateral flow. The rate of lateral flow is a function of the percent of small ostioles and peaks near 37 percent. The clogging of small ostioles is inevitable if the fluid carries any type of particle or emulsions.

A Systematic Evaluation for Future Developments of Gas-Bearing Formations in West Virginia

This paper evaluates and identifies areas/counties with the highest potential for future development of gas bearing formations in West Virginia. The gas bearing formations under study consist of, but are not limited to, Big Injun, Berea, and Benson horizons. The qualitative and quantitative interpretations of data and assessment of various areas/counties for future development are enhanced by computer generated 2-dimensional maps. The maps are the quantitative representation of various reservoir parameters such as porosity, gas saturation, open flow potential, pay zone thickness, etc. The results of the study provide sources of regional comparison as well as a guide for future leasing.