Pressure Buildup Test Analysis Procedure of a Vertical Well Completed Within a Pair of Inclined Sealing Faults

Abstract

Pressure buildup test analysis has been used to investigate near wellbore environment, estimate reservoir pressure and reveal external reservoir boundary types. However, despite of these benefits no consideration has been given for the angle of inclination of the faults or boundaries within which the well is completed. The angle of inclination of the boundaries of a reservoir has a significant impact on the pressure behavior and performance of a well. Knowledge of the inclination angle of the faults assist in well placement for optimum production. The objective of this paper, therefore, is to develop a procedure for calculating the angle of a well completed within a pair of inclined sealing faults using pressure buildup test analysis. A well completed in an infinite-acting reservoir produces number of images inversely proportional to the angle of inclination and dependent on nature of the faults. This number of images, n, can also be related to the angle at which the faults are inclined. The principle of superposition is used to aggregate pressure drop history of a vertical shutin after a constant rate of production. Pressure buildup test procedure was developed from the total pressure expression following the rate history. The procedure considered fault angle and distances from an object well of every image formed because of the inclination of the sealing faults. The buildup test procedure developed shows linear partial variation of Horner ratio at early shutin time and late shutin time, assuming constant rate of production before shut in. The coefficient of the early time Horner's ratio is the early flow time slope. The late time Horner's ratio has coefficient which is the product of the early time slope and the number of images formed due to sealing faults angle. The result shows that that the model is only valid for long shutin time, and the second slope must be gotten at the late time region for higher accuracy. Finally, the procedure does not depend on well design or distances of the images from the object well. The analysis procedure developed here can be used to estimate the angle of inclination of two faults within which a well is completed. Near wellbore characterization is also possible. Decision on well location for optimum well production or injection can be made from the angle of inclination of the faults.