Prospect analysis of the deep marine shale gas exploration and development in the Sichuan Basin, China

Abstract

The shale gas exploration and development in Sichuan Basin had achieved a major breakthrough remarkably. However, the business development focused on the marine shale gas in shallow layers (vertical depth 3500 m) business development in Wufeng Formation-Longmaxi Formation is the key to the rapid growth of shale gas production in the Sichuan Basin. In the literature, authors analyzed the geological characteristics of the deep shale gas of the Wufeng Formation - Longmaxi Formation in southern Sichuan Basin through particular dissection and analysis of deep wells in comparison to the shallow layers. The thickness of organic-rich shale in the deep region of southern Sichuan Basin measures to be more than 120 m, which is larger than that of the shallow layers in Fuling area. The vertical TOC change remains constant whereas the thickness of high-quality shale is approximately forty meters in both regions. Nevertheless, the RO is higher in the deep region of southern Sichuan Basin. The calcareous content of the organic shale increases while the silicon content decreases from the Fuling area down as it gets deeper into the region in southern Sichuan Basin. It is quite evident in research that the shales in the Wufeng Formation – Longmaxi Formation of the deep to shallow layers of southern Sichuan that there are not many differences in depositional environment, lithology, TOC, etc. However, there are four major differences: (1) The porosity of shale in the deep region of southern Sichuan Basin is higher than that in Fulin gas field due to the corrosion pore. (2) The gas-bearing properties are better in the deep regions of southern Sichuan Basin because they have better preservation condition compared to that of the shallow region of Fuling. (3) However, gas-bearing properties are worse in the local region of stronger structure deformation and the basin boundary fault zone. (4) The shale gas resources in the deep regions of southern Sichuan Basin are great and have wide prospects for exploration and development. In order for a breakthrough to be generated in deep shale gas commercial development in the soonest possible time, authors propose the following: utilize strengthening evaluation of small layer contrasting so as to explain fine structure and predict fracture; strengthen the research on drilling and fracturing technology for deep shale gas; strengthen research on wells column; and support technology for efficient production of shale gas. Keywords: Sichuan basin, Lower Silurian, Longmaxi formation, Deep shale gas, Marine facies