The Seismic Identification of Small Strike-Slip Faults in the Deep Sichuan Basin (SW China)

Abstract

Recently, the “sweet spot” of a fractured reservoir, controlled by a strike-slip fault, has been found and become the favorable target for economic exploitation of deep (>4500 m) tight gas reservoirs in the Sichuan Basin, Southwestern China. However, hidden faults of small vertical displacements (<20 m) are generally difficult to identify using low signal–noise rate seismic data for deep subsurfaces. In this study, we propose a seismic processing method to improve imaging of the hidden strike-slip fault in the central Sichuan Basin. On the basis of the multidirectional and multiscale decomposition and reconstruction processes, seismic information on the strike-slip fault can be automatically enhanced to improve images of it. Through seismic processing, the seismic resolution increased to a large extent enhancing the fault information and presenting a distinct fault plane rather than an ambiguous deflection of the seismic wave, as well as a clearer image of the sectional seismic attributes. Subsequently, many more small strike-slip faults, III–IV order faults with a vertical displacement, in the range of 5–20 m, were identified with the reprocessing data for the central Sichuan Basin. The pre-Mesozoic intracratonic strike-slip fault system was also characterized using segmentation and paralleled dispersive distribution in the Sichuan Basin, suggesting that this seismic process method is applicable for the identification of deep, small strike-slip faults, and there is great potential for the fractured reservoirs along small strike-slip fault zones in deep tight matrix reservoirs.