Pore Characterization and Gas Storage Capacity of Marine and Non-Marine Shales in China

Shaobo Liu, Hua Tian, Xingzhi Ma, Maozhen Wang, Mengjun Zhao, Shihu Fang, and Lin Jiang
Research Institute of Petroleum Exploration and Development, PetroChina, Beijing, China

Based on the study of pore and gas storage capacity of marine and lacustrine shale with different maturity, it is found that: (1) The mineral component of marine shale in Sichuan basin of China is similar to that of Barnett shale with high brittle minerals of quartz and calcite, high TOC. Lacustrine shales from Bohai Bay basin and Fuxin basin are characterized by low maturity and high clay content. (2) The adsorption capacity of different shale in China is generally lower than 5m3/t, which is positively related to TOC, specific pore volume with diameter less than <50nm and maturity. (3) Pore diameter in clay minerals is generally larger than >50nm. These pores are mainly distributed in illite in high maturity marine shale and in I/S in low maturity lacustrine shale. Gas in this kind of pores exists as free gas. (4) Meso and micro pores (<50nm ) are mainly distributed in organic matter and controlled by TOC. Most of the gas in this kind of pores exists as adsorption gas. (5) Theoretically adsorption gas is equal to, more than and less than free gas when shale pore diameter is, smaller than and larger than 4.28nm respectively, and the ratio of pore specific surface to pore volume is, higher than and lower than 1.4nm-1 respectively. Tested pore diameter of shale through N2 adsorption method shows that free gas exists dominantly in shale. (6) Based on the data of porosity and sorption isothermals, a gas prediction model is setup and is used for the prediction of gas content changing with depth in Sichuan basin.

AAPG Datapages/Search and Discovery Article #90180©AAPG/SEPM/China University of Petroleum/PetroChina-RIPED Joint Research Conference, Beijing, China, September 23-28, 2013