Sinopec Uncovers High-Yielding Shale Gas Reserve in Sichuan Basin

The Qijiang shale gas field is the first shale gas field discovered in medium-deep and deep strata in a complex tectonic zone on the margin of the basin. Shale gas buried at the depth of over 3,500 meters is defined as deep shale, and the burial depth of Qijiang's shale formations ranges from 1,900 to 4,500 meters, with the majority being deep shale. With complex overlying strata, the project faced great challenges such as a significantly greater depth and variable ground stress.

To tackle the question of how a shale gas reservoir was formed in the basin margin with such complex surface and underground conditions, Sinopec's team conducted more than 10,000 lab analysis tests on the core at the depth of 1,320 meters.

This revealed the development and maintenance mechanism of deep shelf shale pores and identified the deep shale can develop vast reservoirs with high porosity, and also revealed the sweet spots of projecting the deep shale targets.

The team collected high-precision 3D seismic data of deep shale gas covering an area of 3,662 square kilometers in the complex zone of the southeastern margin of the Sichuan Basin as well as drilling data of existing wells in southern Sichuan.

After repeated discussion and screening, Sinopec has innovated a deep shale gas seismic prediction technology with pressure coefficient and gas content, fracture prediction and horizontal ground stress difference as the core – the equivalent of performing a CT scan of the strata to achieve the breakthrough in predicting the 'sweet spots' of deep shale gas.