oa On the Development and Stimulation of Tight Gas Reservoirs

Development of tight gas reservoirs is an integrated effort between many disciplines, including geoscience and subsurface engineering. In all tight gas reservoirs, effective stimulation is one of the key factors for economic gain. Globally, ExxonMobil has developed many tight gas reservoirs with matrix compositions ranging from sandstones, shales and carbonates. Various well geometries, combined with diverse artificial stimulation techniques are used to increase well productivity resulting in improved economics. This paper will present a road map of reservoir-based selection criteria which will result in a suitable stimulated wellbore configured to optimize gas recovery from tight reservoirs. ExxonMobil tight gas field examples are also presented including new technology used for stimulating multiple zones over long gross intervals. Estimates of the effective area of reservoir exposed by various stimulations are obtained by fracture modeling and mapped using a productivity model to determine the number and kind of stimulations required. The optimization process combines the type of well required (vertical, deviated, or horizontal) and an economic target (recovery rate and volume). This process is repeatable and effective in the development of new tight gas reservoirs. Some of the important findings that control the wellbore selection and completion method are: - Gross height of the reservoir to be developed - Effective stimulated area, or the conductive area communicating with the well bore - The effective permeability for gas - The areal extent of reservoir beds