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3-D Seismic Attribute-Assisted Analysis of Microseismic Events Within the Marcellus Shale


Microseismic monitoring is often used during the process of oil and gas exploitation to monitor seismicity induced by hydraulic fracturing, a common practice in the Appalachian Basin. Anthropogenically-induced minor upward fracture growth is not uncommon in the Marcellus shale; however, in the area of study, more extensive upward fracture growth was observed. In order to ascertain which areas are more likely to experience brittle failure first, 3D seismic data are analyzed to uncover variations in acoustic properties associated with upward growth zones overlying the Marcellus. The reservoir's response to hydraulic fracture treatments from six horizontal wells provides considerable insight into local stress anisotropy and optimal well spacing needed to maximize drainage area during the field development phase. 3D seismic attributes such as 3D curvature, chaos, dip deviation, variance, and ant tracking will be used to identify more intensely deformed areas. Areas of higher curvature and local seismic discontinuity, for example, generally define more intensely deformed areas. In turn, more intensely deformed strata are generally associated with zones of increased fracture intensity, and these zones may represent areas of increased risk for out-of-zone stress release in response to hydraulic fracturing. In addition to the 3D seismic and microseismic surveys, completions data such as stage and perforation locations, pumping pressure, and proppant concentration are incorporated into the analysis of upward growth phenomena. Hydraulic fracture treatments were alternated between wells in a “zipper frac” fashion so that well-to-well interactions associated with alternating treatments can also be examined to identify the possible extent of cross-stage fracturing or re-fracturing and their possible role in the development of out-of-zone growth. The outgrowths of this study will provide insights that may help improve real time fracture control, well placement and spacing, and increase effective drainage area. The results of the study may lead to the development of 3D seismic interpretation workflows that can be used to vary treatment design, increase cost-effectiveness and improve recovery efficiency of field-scale shale gas development efforts.