China Petroleum & Chemical Corp. (Sinopec) has announced a major shale gas discovery with a proven reserve of 145.968 billion cubic metres (bcm) in the Sichuan Basin, southwestern China.
The newly discovered Qijiang shale gas field was delivered by Sinopec Exploration Company and Sinopec Southwest Oil & Gas company.
The field reserves are located in medium-deep and deep strata in a complex tectonic zone on the margin of the basin, the first for a shale gas field.
The shale formations are buried at a depth ranging from 1,900m to 4,500m with the majority being deep shale.
The shale gas at the depth of more than 3,500m is defined as deep shale.
Due to the complex overlying strata, the project faced challenges including a significantly greater depth and variable ground stress, said Sinopec.
In its statement, Sinopec said: “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 1,320m.
“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.”
Sinopec team collected high-precision 3D seismic data of deep shale gas covering an area of 3,662km2 in the complex zone of the south-eastern margin of the Sichuan Basin.
The company has also collected drilling data of existing wells in southern Sichuan.
Sinopec created a deep shale gas seismic prediction technology using pressure coefficient and gas content, fracture prediction, and horizontal ground stress difference, to predict the sweet spots of deep shale gas.
The company has also developed a three-dimensional fracturing technology for deep shale that leverages precision cutting, pressurisation and expansion, balanced expansion, and guaranteed filling.
It has improved the daily shale gas production of a single well to achieve the 300,000, 400,000 and 500,000 cubic metres marks in a sequence, said Sinopec.
Last month, Sinopec made a new shale gas discovery in the Sichuan basin in China, which is expected to contain 387.8bcm of gas.
