History Matching Production Data Using Analytical Solutions for Linearly Varying Bottomhole Pressure

Abstract

ABSTRACT Performance of gas wells is often modeled using analytical solutions which are based on the assumption of constant pressure production at the wellbore. A variable pressure history can be modeled by using superposition of these constant pressure solutions. Unfortunately, each pressure change results in a spike in the resulting production rate. In practice, wells are often operated such that pressure declines slowly and smoothly until line pressure is reached. Thus, superposition of constant pressure solutions does not accurately model production in real wells. In this paper we present a procedure for calculating production rate and cumulative production using superposition of solutions for bottomhole pressure which varies linearly with time. These solutions for linearly varying bottomhole pressure may be easily obtained from the constant pressure solution for the same reservoir geometry. Rates calculated using superposition of linear pressure solutions model actual production data more faithfully than do those calculated using superposition of constant pressure solutions.