Reservior Characteristics and Main Controlling Factors of Tight Gas in Shaximiao Formation in Yanting Area of Tianfu Gas Field

Abstract As a key layer for continental tight gas exploration and development in the Sichuan Basin, the Shaximiao Formation of the Middle Jurassic (J 2 S) has submitted proven reserves in the Yanting Area of the Tianfu Gas Field for two consecutive years, with huge exploration and development potential. Since the old well was tested in Member 1 of Shaximiao Formation (J 2 S 1 ) in Yanting area, many wells have obtained high-yield industrial gas flow, confirming that the fluvial sandstone reservoir contains gas. Compared with the more mature area in Jianyang Area in Tianfu Gas Field, the gas reservoir of J 2 S 1 in Yanting area is a lithologic reservoir under the same sedimentary background, with a relatively lower pressure gas reservoir and higher gas saturation. Based on core observation, scanning electron microscopy, analysis and testing, this paper studies the reservoir characteristics and main controlling factors of the sandstone of J 2 S 1 in Yanting area. The results show that: (1) It is a shallow deltaic sedimentary system controlled by southern provenance, and the underwater diversion channel sandstone is a favorable microfacies of J 2 S 1 in Yanting area; (2) The reservoir lithology is mainly fine-medium grained clastic feldspar sandstone and feldspar clastic sandstone with low content of miscellaneous base and cement; The reservoir space is residual intergranular pores, followed by intergranular dissolved pores and a small amount of intragranular dissolved pores; (3) It is dominated by Class II and III reservoirs, and the median porosity is 8.9% and the median permeability is 0.216mD, which has the characteristics of low porosity and ultra-low permeability; (4) Advantageous sand bodies, superior reservoirs and favorable source-fault-sandstone configuration relationships together control the gas filling and enrichment of J 2 S 1 in Yanting area. The research results can provide a scientific basis for the prediction of favorable reservoir distribution areas and the deployment of natural gas exploration and development schemes of J 2 S 1 in Yanting area.