Abstract

In recent years, type curves analysis have been used in conjunction with conventional methods to obtain better interpretation of pressure test data. The derivative type curve is the most definitive because it can identify subtle changes in slopes (dp/dt) which are difficult to recognize with conventional methods. The pressure-derivative type curve is not readily applicable because it is based on pressure drawdown solution. Unfortunately, this limitation of drawdown type curves to analyze pressure buildup data collected after short producing times, are not well understood by the practicing engineers.

An additional problem that occurs in derivative type curve analysis is differentiation of pressure/time data. Several algorithms for differentiating data were tried to select the best algorithm which removes as much noise as possible without effecting the signal.

An improved pressure transient test analysis for gas wells is achieved by adapting the solutions of the liquid flow problem by normalizing pseudopressure and pseudo-time. This normalization also allows constants of the working equations to remain unchanged.

The purpose of this paper is to (1) select the best differential algorithm to smooth out the pressure data for derivative type curve analysis, and (2) to illustrate how the pressure-derivative method has been applied to gas wells in Badak and Nilam fields.