Reservoir characteristics and diagenesis of Devonian Donghetang Formation in Bachu-Maigaiti area

According to the analyses of rock slice, cast slice, SEM and well logging data, the sedimentary, petrologic characteristics and diagenesis of the upper and the lower sandstone segments of the Donghetang Formation in the Bachu-Maigaiti area were studied. Deposited in littoral environment, the Donghetang Formation was featured by higher compositional maturity and textural maturity, and both of the 2 maturities were higher in the upper sandstone segment than in the lower one. Dissolution pores served as the main reservoir space, and their distribution was determined by grain size and intergranular material. For example, the dissolution pores were well developed in the sandstone segment with bigger grain size and calcareous cementation. The most important diagenesis effects included compaction, cementation, cement dissolution, quartz alkali dissolution, metasomasis, recrystallization and structure cataclasis. According to the division standard of diagenetic phase, the Donghetang Formation was in the B stage of middle phase.