An Analytical Model to Predict the Deliverability of a Multiple Fractured Horizontal Well (MFHW)

Abstract

Abstract The tight gas resource potential in the Western Canadian Sedimentary Basin is enormous. To date, however, it remains relatively unexploited and underdeveloped. The use of multiply fractured horizontal wells (MFHW) appears to be the "breakthrough" technology needed to economically exploit reasonably thick tight gas zones with effective in-situ permeabilities between 0.1 mD and 0.005 mD. This exploitation technology is already being applied in Europe and, in a more limited extent, in the U.S. Its application in Canada is currently being tested and/or evaluated by several of the larger majors. (This technology also has the potential for enhancing the deliverability of conventional gas.) An analytical model has been developed to predict the deliverability and production forecast of a multi-fractured horizontal well in a tight gas pool that includes the initial, transient production period. Using the DTC (discounted technical cost) approach to evaluate the economic feasibility of tight gas resources, the majority of the deep, high pressure tight gas evaluated in this study appears to be commercially viable, even at today's gas prices. Advances In Tight Gas Production Technology Historically, the development of tight gas reservoirs has involved drilling vertical wells and hydraulically fracturing them, often with the use of large amounts of proppant. These large fracs are known as massive hydraulic fracs (MHF) and typically involved hundreds of thousands or even millions of pounds of proppant. Quasi government bodies in the United States, such as the Gas Research Institute (GRI) and the Department of Energy (DOE), have been heavily involved in promoting research into the production of tight gas sands (Ref. 1). The GRI and Advanced Resources International (Ref. 2) have highlighted four key new technologies which they believe have the greatest application for the efficient development of tight gas sands: - 3D Seismic - Integrated Approaches to Natural Fracture Detection - Improved Well Completions/Stimulations - Selected Use of Horizontal Wells We believe that multiply fractured horizontal wells (MFHW) is one such technology. Spencer (Ref. 5) surmised that natural fractures played a key role in the production of most tight gas reservoirs so that if the extent and direction of the natural fractures can be predicted and is sufficiently intense and laterally extensive, horizontal and/or multi-lateral wells can be used to promote otherwise uneconomic pay zones. The logical corollary to this is to question whether a network of induced fractures from a horizontal well could be used where the natural fissuring has limited development; and, particularly, where the stress regimes allow the resulting induced fractures to intersect the natural fissuring.