A Methodology To Determine Initial Field Development Strategy For A Naturally Fractured Shale Gas Resource

by
Raymond Leslie Johnson, Jr., MSE

University of Texas at Austin, 2000
Supervisors: Kamy Sepehrnoori
Mark A. Miller

Shale reservoirs represent a large portion of the world’s clastic reservoirs and a large unconventional gas resource. Naturally fractured shale reservoirs that are organic-rich, highly porous, highly gas-desorptive, and possess extremely low values of permeability are often targeted for shale-gas potential. While these reservoirs generally possess low matrix permeability values, a well-connected set of natural fractures can access the highly porous matrix, containing a high degree of total organics with good gas storage potential. Furthermore, a well-placed hydraulically created fracture can provide the necessary conduit to access the required portion of the shale-gas reservoir to achieve well economics.

In a naturally fractured reservoir understanding the distribution and storativity of the natural fracture network is a key element to predicting productivity. This reservoir storativity must be fed from a greater matrix of relatively high total organic content and capable of desorbing gas; thus an understanding of matrix and gas desorption properties is essential. Next, the ability to place a hydraulic fracture in this complex environment is based on the understanding the stress framework and accounting for any influences or complexities that affect treatment placement.

To achieve integration and optimization of these components requires simulation. A hydraulic fracture simulator is used to evaluate the optimal solution of fracture half-length. The resultant created fracture half-lengths are used in a reservoir simulator to forecast production rates with differing well spacing. The results of these simulations are evaluated in an economic framework to produce a developmental strategy for a given set of conditions.

This report will utilize several hydraulic fracturing tools (e.g., bottomhole treating pressure analysis, three-dimensional (3D) hydraulic fracture modeling) along with shale-gas reservoir characterization tools (e.g., log and core evaluations, 3D reservoir simulation) to develop an initial field development strategy for an example naturally fractured shale gas resource- the Wolfcamp Shale.

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