Abstract
Vaca Muerta shale is among the most promising unconventional plays outside of North America. Like other shale plays, it is developed using multistage hydraulic fracturing technology. In this experiment, dual microseismic arrays were deployed during stimulation to monitor fracture geometry. Beyond location of events, moment tensor inversions were performed on three horizontal wells. Fault plane solutions were derived based on the double-couple model from moment tensor results. Then the fault plane solutions were used as inputs for calculating stress field by minimizing the misfit between regional stress field and a cluster of fault plane solutions. The stress inversion results show that the stress direction derived from each stage is consistent with regional tectonic stress direction. The post-stimulation stress regimes vary between strike-slip and reverse faulting, which indicates stress shadowing effects among neighbor stages. The uncertainties are estimated using the statistical bootstrapping method. In addition, the stress inversion results were compared with ISIP (Instantaneous Shut-In Pressure) data and b-values and show some level of consistency.
Introduction
Vaca Muerta Shale in the Neuquen Basin of central west Argentina is a massive unconventional resource play outside of North America. The same technology of horizontal drilling combined with multi-stage hydraulic fracturing are being implemented to extract hydrocarbon from the tight organic rich shale formation. The quality of rock is comparable to the major plays in North America such as Marcellus, Eagle Ford and Bakken (Cataldo et al. 2016). Argentina is estimated to have the world's second largest shale gas reserve according to US Energy Information Administration. Production from Vaca Muerta is rapidly increasing, with a prediction up to 1 million BOE/D in 15 years (Donnelly 2018).
Microseismic has evolved into a mainstream monitoring technique for hydraulic fracturing. The advantage from microseismic is the 4D coverage in space and time. However, the majority of microseismic monitoring projects only uses the location information to define stimulated rock volume. Going beyond “dots in the box” becomes an urgent need for the microseismic community to provide better information to influence the operational design (Tan et al. 2014; Zhang et al. 2018).
