Determination of Gas Well Deliverability of Vertically Fractured Wells

Abstract

American Institute of Mining, Metallurgical, and Petroleum Engineers Inc. Abstract The applicability of commonly accepted radial flow solutions to estimate deliverability of vertically fractured gas wells was examined. Synthetic deliverability data (isochronal and flow after flow) were generated using a two-dimensional single-phase gas simulator. The effect of fracture length and pressure level and PVT data was investigated. Flow-after-flow data PVT data was investigated. Flow-after-flow data also were used to investigate the application of the Odeh-Jones method for analyzing variable rate drawdown data to determine formation permeability and skin factor (fracture length) permeability and skin factor (fracture length) for a vertically fractured gas well. It is shown in this study that conventional methods of predicting deliverability from short-time isochronal and flow-after-flow tests will lead to calculation of erroneous values of absolute open flow (AOF) than that which would be obtained from long-time flow tests. Depending on specific conditions, these errors can be either lower or higher than actual values. It is also shown that flow exponents different from unity can be obtained from short time flow tests even though laminar flow prevails. This result is a consequence of prevails. This result is a consequence of changing flow regimes that result due to the vertical fracture. This study also indicates that if the Odeh-Jones method of analysis is used, then data obtained for analysis should correspond to the pseudo radial flow period. If early data where linear flow controls pressure behavior are used, then erroneous results will be obtained. Introduction Gas well deliverability tests are multipoint tests consisting of three or more flows with pressures, rates, and other data being recorded as a function of time. These tests are usually required by state regulatory agencies for proration purposes and to obtain an allowable. In addition, these tests can provide information for reservoir and provide information for reservoir and production engineering studies. production engineering studies. Basically there are two different types of deliverability tests:flow-after-flow tests andisochronal tests. Both of these are very well documented in the literature. Gas deliverability is often determined by use of the empirical equation: ......................(1)