Fractured Reservoir Prediction--A Case Study in the Sichuan Basin

Ling, Yun; Guo, Xiangyu; Song, Qianggong

This paper discusses the application of fractured reservoir prediction in Southwest China. The depth of the target clastic reservoir is about 4800 meters, with average porosity and permeability 5.7% and 4.3×10-5μm2 respectively. There is a low relief structural trap in the area, six well drilled in the high position, and three of them with gas show, but none of industrial value.

Zero-offset VSP and 8 directional walkaway-VSP was acquired in 2010, a full azimuth 3-D seismic was implemented in 2009. Earth absorption, deconvolution as well as the velocity parameters are evaluated from ZVSP, and are used to drive the processing of the WVSP and 3-D seismic. WVSP was also used to estimate the VTI and HTI anisotropic parameters, which were applied in the 3-D seismic processing. The full azimuth seismic gathers and the imaging result provided good data for the fractured reservoir study.

The main techniques applied in fractured reservoir delineation and prediction including: 1) fracture prediction (intensity and direction) based on the pre-stack azimuth gather; 2) post-stack seismic attributes (frequency, phase, waveform, curvature) based fractured reservoir prediction; 3) stress field prediction based on the structure interpretation.

Application results proved that the pre-stack azimuth gather based prediction can tell us about the fracture developed area; post-stack seismic attribute based approach could reach the indirect prediction result through the seismic attribute variation around the fractured reservoir; while stress inversion could show us the fracture developed area through the spatial variation of the stress. Comprehensive application of these above mentioned techniques provide us more reliable prediction result. Drilling proved that all the suggestion wells are in the fracture developed area, and high production gas was obtained.

Comprehensive interpretation and prediction proved to be effective in fractured reservoir delineation and prediction.

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