Importance of Preexisting Fractures to Completion and Production Efficiencies in the Marcellus Shale Energy and Environmental Lab MSEEL

The Marcellus Shale Energy and Environmental Lab (MSEEL) provides a publicly available dataset and a hypothesis-driven field test of the significance of preexisting natural fractures at multiple scales on the effectiveness of the stimulation of an unconventional reservoir. Sonic and microresistivity imaging show the presence of numerous preexisting cemented fracture swarms, which are evaluated in terms of their influence on the fracture stimulation. Natural fracture intensity in the Boggess 5H and MIP-3H were interpreted based on wireline and logging while drilling (LWD) image logs showing that 1000's of calcite and bitumen cemented, but relatively weak, fractures are present along the laterals as swarms that are at an angle to the present-day stress regime. Fractures with complex bitumen and calcite filling were recognized in cores from pilot wells at the micro and macroscales (micron to millimeter). The importance of pre-existing fractures on geometric stimulations was evaluated and compared to cluster locations that avoided intense preexisting fractures using fiber-optic distributed acoustic and distributed temperature sensing (DAS/DTS) data and supported by production and simulation. Fiber-optic DTS and DAS measurements were coupled with wireline and LWD image logs from the lateral to recognize preexisting and cemented fractures. This data is supplemented with core analysis including (CT and thin sections) from vertical pilot wells shows that clusters in parts of a stage dominated by preexisting fractures have significantly more hydraulic fracture activity to the point that other clusters appear largely inactive. In addition, processed fiber-optic data indicates that preexisting fractures can form near-well bore leak-off pathways to previous stimulated stages. Both can lead to stimulation and subsequent production inefficiencies. Two wells (Boggess 1H and 3H) that attempted to avoid preexisting fractures showed a significant increase in fracture stimulated volume based on decline curve analysis and microseismic. Production history and simulated future production support the conclusion that avoiding preexisting fractures in the Marcellus Shale can increase estimate ultimate production. We present conclusions about stage and cluster spacing and the significance of preexisting natural fractures on stage isolation and fracture efficiency. The publically available data and workflow allow others to use, verify, and evaluate our findings using the same initial data.