Pressure-transient analysis for fractured wells producing at constant pressure

Past solutions to many well-test problems considered the wells to be produced at a constant rate. It has become apparent that there are many cases in which constant-pressure production is more common. Gas wells, geothermal wells, and even oil wells are operated at constant pressure during most of their producing life. Constant-pressure well-test data for fractured wells are commonly analyzed using type-curve-matching techniques that may result in nonunique solutions. By the use of a semianalytic model, a set of correlations has been developed that reduces the nonuniqueness problem, as well as accounts for well-test data in which the well is produced at high rates. When applied to high-flow-rate wells, this technique uses the bilinear flow period to determine an apparent fracture conductivity for constant-pressure drawdown or buildup tests. These apparent values can be corrected to true conductivities by the use of correlations presented in this study. These relationships were derived through computer simulation of a wide range of possible situations. In summary, this paper presents for the first time a technique that analyzes buildup and drawdown data from wells produced at constant pressure with turbulent flow in the fracture. Two example applications, one for buildup and one for drawdown, aremore » included to demonstrate the use of these techniques.« less