Equation of State Modelling of Field Development Plan and Economic Analysis of Gas Condensate Reservoir of Ahdi Field in Pakistan

Abstract

Gas condensate systems have been widely produced for the production of valuable liquid condensate along with gas, generating a greater revenue than conventional gas reservoirs. This project focuses on the development of an accurate equation of state model to monitor the behavior of a gas condensate system and utilizing the said fluid model for history matching and field development. The field development plan is the first step to model an efficient gas condensate system and is generally different from conventional methods of field development due to the liquid dropouts involved during production. Therefore, it requires the equation of state model which is used for compositional reservoir simulation. This type of fluid model is necessary to create a simulation model of a reservoir, which at times, is inaccurate due to unavailability of data and low-grade lab equipment. Most of the uncertainties arise due to wrong sampling of the fluid. The fluid model is generated using the IPM Suite’s PVTP software. The major problem in modelling the equation of state is associated with the use of pseudo components. These components constitute a sensitive parameter of the equation and their improper estimation results in an inaccurate fluid model. The next phase of the project involves history matching which finally allows the formulation of a field development plan for the gas condensate system. The simulation is performed using Schlumberger’s Eclipse reservoir simulator. It is aimed to produce the reservoir in such a manner that the rate of pressure drop is kept low for maximum gas recovery above dew point pressure, and to minimize the liquid dropouts in the reservoir when the pressure falls below the dew point. Various case scenarios such as varying the number of wells and application of fractures were modelled and the best case was selected for development of the field based on factors including maximum production, recovery factor and economics involved in the project.