Geological Controls on Reservoir Properties and Production Potential of Lower Paleozoic Shale Gas Plays in Sichuan Basin

Li, Xinjing; Qiu, Zhongjian

Silurian "hot shale" with high thermal maturity is known as source rock of Paleozoic petroleum systems and now the unique self-contained reservoir in situ with advances in horizontal drilling and multi-stage hydraulic fracturing. It has evolved through several tectonic events which form different sets of existing natural fractures in response to regional stress models. The comparison of geological characteristics about marine shale reservoirs between the individual regions inside and outside China, especially located on siliciclastic shelves, provides a useful method to delineate the evolution and distribution of the organic rich shale formation.

Upper Ordovician to Lower Silurian shale analysis such as logs, Pyrolysis, XRD, XFD, thin sections, CL, SEM and QEMSCAN indicate that mineralogical composition variations and fabric anisotropy at scales are notable in Sichuan Basin and surrounding regions. These variables are integrated to recognize several lithofacies rather than a whole homogeneous unit. The stacking patterns and trends of Lower Palaeozoic hydrocarbon-bearing shale successions of the area, associated with complex present regional in-situ stress data, confirm the impact of depositional environments and tectonic events on rock geochemical and geomechanical characteristics correlate with these lithofacies which at least partially control the response to hydraulic fracturing stimulation and then production potential of shale gas in multi zones. Furthermore, the comprehensive geologic approach shows some insights into understanding key geological factors and processes in different areas to identify prospective shale gas fairway over Sichuan Basin.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013