| Longmaxi Formation is a major target for shale gas exploration in Laifeng-Xianfeng block outside the Sichuan
Basin. In order to study the reservoir characteristics and its influence on gas content in this kind of complex tectonic area,
Longmaxi Formation of Lower Silurian in Well Laidi 1 has been taken as the research object. By the sampling and
analysis of 5 field outcrops, the pore type and structure of the reservoir have been observed and analyzed by means of thin
section identification, scanning electron microscope, low-temperature liquid nitrogen adsorption-desorption experiment,
field desorption and other conventional means, and the parameters of the reservoir are fitted with DFT pore volume and
gas content of the reservoir. The results show that: (1) The pore types of Longmaxi Formation in the study area are mainly
intergranular pore, intragranular pore, organic matter pore and small-scale fracture. (2) The proportion of mesopore to
pore volume is the largest, micropore is the second, macropore is the smallest, and their developmental degree is
controlled by total organic carbon (TOC) and clay mineral content. (3) The gas content has a positive correlation with
TOC, clay minerals content and total pore volume, while the secondary pyrite content has a good positive correlation with
the ratio of free gas to adsorbed gas. (4) The Longmaxi Member 3 of Well Laidi 1 has high clay mineral content, strong
reservoir plasticity and certain resistance to destroy. Therefore, the reservoir has good sealing property and abnormal high
pressure. The gas content of the section with certain material basis in the Longmaxi Member 3 is equivalent to that of the
Longmaxi Member 1 with high TOC. It is pointed out that it is an important breakthrough for exploration in the future to
look for a reservoir section with good local sealing, abnormal high pressure, high clay mineral content and a certain TOC
content far away from the deep fault in the complex tectonic areas with general material basis and poor overall
preservation conditions. |
