Alternative Method for Pressure Transient Analysis

Abstract

An alternative method is presented for estimation of reservoir properties that are usually estimated in a classic buildup test are obtained using flowing conditions thereby eliminating the need for shut-in periods and measurement of static pressure data. The proposed approach is based on the effect of two consecutive periods of production with different rates in a single well-reservoir model. The well is initially produced at a constant rate until pseudo-steady state conditions are reached, followed by a different rate that will generate a pressure transient response measured at bottom of the wellbore. A mathematical formulation is applied to estimate the reservoir pressure as function of radius of investigation, which is equal to the bottom hole pressure observed during a shut-in buildup test. A single well-reservoir model with known petrophysical parameters, fluid properties, pressure and temperature is used as a reference to evaluate the proposed methodology. The reservoir (i.e. the simulation model) is tested by applying two methods: the first one, is the simulation of a classic buildup test, and the second one, is the simulation of two flow rates periods according to the new theory; the results are compared with the model of reference, calculating percentage of error for permeability, skin, and average reservoir pressure. Additionally, it is demonstrated that a shut-in period is not required to obtain data equivalent to a classic buildup test since it is possible to calculate it from dynamic behavior. The ability to complete a well pressure transient analysis test from flowing conditions and provide valid and reliable results has a direct impact in reduction of cost and deferred production for companies involved in oil and gas operations.