Abstract

With more and more of gas production emerging from tight reservoirs, that are costly to develop and maintain, the challenge increases dramatically to accurately simulate the behavior (history and prediction) of such reservoirs in order to come with cost-effective development plan.

Some of the challenges that rise during the development of tight heterogonous gas reservoirs are: initial drop in the productivity of some wells, liquid dropout, the need to mechanically fracture wells in some areas to sustain high production rates, and the need for non-conventional wells (multilateral/maximum reservoir contacts) to efficiently deplete such type of tight reservoirs.

Each one of the above challenges requires special technical treatment in order to simulate fluid movements with high confidence levels of accuracy. For example, comprehensive reservoir and fluid characterization studies, that captures important fluid behavior/drives inside the complex rock textures, are vital for realistic and reliable simulation. Implementation of local grid refinement near well bore, using conventional and unconventional girding, is essential to correctly simulate production mechanism across and around the induced fracture systems.

Careful design of simulation grid systems, efficient lumping of gas components (Fluid Characterization) and business-driven up-scaling were main keys to speed up the delivery of accurate solutions with practical approximations.

In this paper, a case history for a tight gas reservoir that has been explored, developed and operated by Saudi Aramco, will be used to highlight the day-to-day challenges that are facing simulation engineering, utilizing state-of-art soft/hardware technologies, to come up with feasible and cost-effective development scenarios that can be confidently considered in the decision-making process.

Introduction

The subject reservoir is spread over an area of more than 150 km X 35m and consists of four overlaying reservoirs each separated with thick barrier. The field was in production since approximately seven years. Some of the wells drilled across the subject reservoir were completed after being hydraulically acid-fractured.

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