A Model for Development, Sensitivity Analysis, and Optimization of Gas Reservoirs with or without Aquifer: Part I-The Model and Solution Technique

Abstract

ABSTRACT This work is a study for the development and optimization of gas reservoirs that depend upon the effect of water drive mechanism and production demand schedule. The objectives are to determine the optimum number of wells and time for these wells to be drilled for the gas reservoirs without or with water influx for steady state and unsteady state for linear and radial system, the effect on gas production by water influx, and to perform a sensitivity analysis to study the effect for unsteady state water drive reservoir due to: production rate, permeability, water viscosity, porosity, water compressibility, rock compressibility, and encroachment angle and rock and water compressibility term in material balance equation for volumetric, steady state, and unsteady state water drive reservoir. To solve this problem, an analytical mathematical computer program was designed and implemented. The model is separated into three parts: Volumetric; Steady state water influx, and Unsteady state water influx. The computer program was written by using the volumetric and material balance equation that include Van Everdingen-Hurst unsteady state water influx equation or Schilthuis steady state water influx equation and the latest correlations available in the technical literature, modified and adapted for this work. From the result, it shows that the model can be used to analyze gas reservoir, predict the drilling period for that reservoir and rebuild pressure history of a reservoir from production data. This paper is only concerned with the development of the model computer program and solution techniques. The remaining material will be presented in part II of this series of two papers.