Analysis of Hydraulically Fractured Wells With Pressure Buildup Tests
Authors: Lee W.J. 
Published: December 2007

American Institute of Mining, Metallurgical and Petroleum Engineers, Inc.

This paper was prepared for the 42nd Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Houston, Tex., Oct. 1–4, 1967. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made.

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Methods for analyzing fractured reservoirs by using transient pressure tests have been developed to help characterize these format These techniques permit estimating fracture length and conductivity in formations with either vertical or horizontal fractures, estimating reservoir pressure and permeability in fractured wells. Finite conductivity fractures are considered in this analysis, whereas previous work has been reported only for fractures with infinite conductivity.

Pressure buildup tests may be used for estimating fracture length and fracture conductivity in formations with either horizontal or vertical fractures. These estimates should be useful for evaluating fracture treatments. The estimates are made by comparing observed buildup test behavior to calculated behavior for idealized reservoir models.

Techniques for analyzing pressure buildup tests are suggested to estimate formation permeability and static reservoir pressure. In many fractured wells, conventional procedures for making these estimates are not applicable hence, the suggested methods.

Introduction

Technology for interpreting well tests in fractured reservoirs has been nonexistent until the recent past although large numbers of wells are fractured each year. It has not been possible to estimate formation permeability or static reservoir pressure correctly in many fractured wells, nor has it been possible to estimate fracture length and conductivity, which would aid in evaluating fracturing methods.

The purpose of this study was to help fill this gap in technology by developing methods of analyzing horizontal and vertical fractures of finite conductivity. This work thus extends the work of Russell, who analyzed the transient behavior of vertically fractured wells by assuming the fracture to have infinite conductivity. The attack in both this study and in Russell's investigation was the same: synthetic buildup curves were developed on a computer for ideal reservoir models, and analysis techniques were developed from these curves. In essence, these techniques involve comparing observed transient pressure data with computed data, and finding the model [i.e., the fracture length and conductivity] which best fits the observed data.