Sustaining Fracture Area and Conductivity of Gas shale Reservoirs for Enhancing Long-term Production and Recovery

Natural gas from organic rich shale formations has become an increasingly important energy resource worldwide over the past decade. Extensive hydraulic fracture networks with massive contact surface areas are frequently required to achieve satisfactory economic production in these highly heterogeneous reservoirs, with permeability in the nano-Darcy range. Current operational experience in gas shale plays indicates that the loss of productive fracture area and loss of fracture conductivity, both immediate and over time, are the major factors leading to reduced flow rates, marginal production, and poor gas recovery. This theoretical and experimental project, funded by a RPSEA (Research Partnership to Secure Energy for America) program, is aimed at understanding the multiple causes of loss of fracture surface area and fracture conductivity. The main objectives of the project are: understand the multiple causes of loss of fracture area and fracture conductivity, and define solutions to mitigate the resulting loss of production. Define the types of fracture networks that are more prone to loosing fracture area and define critical parameters, for each reservoir type, (including proppant concentration, fluid interaction, relative shear displacement and others) to preserve fracture conductivity, and define an integrated methodology for evaluating reservoir properties that result in proneness to loss of fracture area and fracture conductivity, and define adequate solutions for the various reservoir types Current results include the evaluation of reservoir geology, mineralogy, reservoir properties, mechanical properties, including surface hardness, and petrologic analysis on cores representative of Barnett, Haynesville and Marcellus reservoir shales. A comparison of these properties provides an initial reference frame for identifying differences in behavior between the various reservoirs, and for anticipating the potential for embedment and loss of fracture conductivity. Actual measurements of fracture conductivity as a function of stress will be measured and presented in the future.