AAPG Middle East Region, Shale Gas Evolution Symposium

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Exploration and Development Techniques for Unconventional Resources

Abstract

The productivity of an organic shale is driven by its reservoir quality (RQ) and completion quality (CQ). RQ consists of parameters such as effective porosity, organic content, matrix and system permeability, fluid saturations, net thickness and hydrocarbons in place. We have little control over reservoir quality parameters other than well placement that accounts for their spatial variation. CQ parameters include closure stress magnitudes and profiles, structural setting, mechanical properties, productive fracture geometry dimensions, and their placement relative to each other. Some of these parameters can be addressed via well placement, completion designs and production management strategies. The exploration phase of a project is focused on defining the RQ and CQ and how they vary spatially within a basin. Existing seismic, log and core data is used to high grade acreage. Once the location(s) is selected the data acquisition program should focus on petrophysical and geomechanical assessment from logs and core acquired in a pilot hole. Unlike with conventional reservoirs, without stimulating and producing the well this cannot be truly confirmed. If no horizontal well is planned then strong consideration should be given to completing and producing the vertical well. If a lateral is planned then hydraulic fracture simulations can determine the best lateral landing point and predict frac geometries. Post-frac production management will insure fracture conductivity is not compromised, while assessing the peak production rate and subsequent rate of decline. Ideally six months to one year of production is acquired to more accurately assess ultimate recovery. In the exploration phase completion and economic optimization is not the primary objective. The data acquired at this time will we used to design a field development strategy. Once the potential for commercial production has been indicated the key drivers become well completion optimization and development strategy. This is accomplished by field experimentation supported by design modeling. Different completion designs, well lengths and spacing, and production techniques are evaluated. At the same time the supply chain is developed to feed the rapid increase in well count so that unnecessary costs are eliminated. Many procurement topics with be the same between basins, but each basin will have unique supply chain issues. This presentation will provide workflows to address the key technical and economic challenges for the exploration and field development phases for unconventional reservoirs. A case history from the Fayetteville Shale will show how one US operator achieved these objectives and ultimately developed a reservoir with tens of thousands of wells.