Microseismic monitoring of a hydraulic stimulation of a two well pad in the Eagle Ford shale completed as a zipper-frac was used to optimize field development and wellbore spacing, the completion design of the wells, and the treatment schedule. In order to model the discrete fracture network (DFN) resulting from the treatment, event locations and the associated source mechanisms were used to calculate the geometry of the individual fractures (length, height, aperture) as well as their orientation in space resulting in a DFN that is calibrated on microseismic measurements (event magnitude, source mechanisms), the rock properties of the treated reservoir and the injected fluid volume. Distinguishing between the total stimulated rock volume (SRV) where microseismic activity was observed and the part of the SRV that contains proppant filled fractures and will therefore be productive in the long term then allowed for sophisticated wellbore spacing determination. Distance-based material balance proppant filling on a stage-by-stage basis determined an average propped half-length of just under 270 ft showing that the chosen wellbore spacing is likely sufficient. Integration of pump data and the treatment schedule supports that conclusion and showed that stage length and spacing may be slightly decreased in order to enhance complexity and connectivity of the created fracture network resulting in more uniform drainage of the reservoir along the wellbore. Furthermore, a large geohazard was mapped that was continuously activated during 10 stages; treatment efficiency was reduced significantly as almost 10% of the total SRV and created fracture volume could be attributed to the fault. A cumulative surface area plot showing the generation of fracture surface area as a result of the injected fluid volume also showed that the treatment efficiency is reduced towards the end of the injection for the trailing wellbore in the zipper-frac completion.
Completions Evaluation in the Eagle Ford Shale
Neuhaus, Carl W., and Asal Rahimi Zeynal. "Completions Evaluation in the Eagle Ford Shale." Paper presented at the SPE/AAPG/SEG Unconventional Resources Technology Conference, Denver, Colorado, USA, August 2014. doi: https://doi.org/10.15530/URTEC-2014-1921549
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