Abstract:
The tight sandstone reservoirs from the Taiyuan, Shanxi and Xiashihezi Formations of the Daniudi Gas Field were studied. In view of the punctate type, zonary structure and multistage morphology of quartz overgrowth, and combined with the homogenization temperature fluid inclusions, the quartz overgrowth were divided into three stages, among which the stage Ⅱ was most developed and contained some organic inclusions. Quartz solution was found in the stages Ⅰ and Ⅲ. The corresponding reservoir physical property gradually became poor with the increasing stage of quartz overgrowth and the increasing width of enlargement margin; however, the porosity of the stage Ⅲ was obviously higher than that of the previous two stages. Pore filling was dominant when the content of siliceous cement was over 3% at the Daniudi Gas Field. After the quartz overgrowth in the stage Ⅲ, sandstone reservoirs were densified completely. Under the whole compact background, alkalinity dissolution resulted in pores of quartz solution type, which offered reservoir space for the Daniudi Gas Field, and was the main cause for secondary pores in the second member of the Taiyuan Formation.