Diagenetic facies of carbonate rocks in Yijianfang Formation, Shunbei area, Tarim Basin

Abstract

The diagenetic facies of the Ordovician Yijianfang Formation in the Shunbei area of the Tarim Basin was analyzed using drilling core description, thin section observation, as well as logging trace and seismic data analysis. There are five diagenetic facies types: dissolution, dolomitization, fracture, cementation and hydrothermal facies, which were further divided into eight subfacies: atmospheric freshwater dissolution, burial dissolution, fracture dissolution, penecontemporaneous dolomitization, burial dolomitization, subsea cementation, freshwater cementation, and burial cementation. Five composite diagenetic facies were identified: cementation-hydrothermal, fracture-dissolution, fracture-cementation, fracture-hydrothermal, and dolomitization-cementation-hydrothermal facies. The subsea cementation subfacies was developed in the low system tract, while the tectonic-hydrothermal and cementation subfacies were developed in the high system tract. In intraplatform beach sediments, atmospheric freshwater dissolution and atmospheric freshwater cementation subfacies, and a small amount of tectonic-hydrothermal subfacies developed. In interstitial marine sediments, there developed burial dolomitization, dissolution and cementation subfacies. In intraplatform reef sediments, atmospheric freshwater dissolution and atmospheric freshwater cementation subfacies occur. The diagenetic facies evolution was controlled by tectonics, sedimentary facies and sequence and constrained by point, single well profiles, diagenetic facies connected wells and root mean square amplitude attributes. The distribution of favorable diagenetic facies in the Shunbei area is gradually transitions from the southwest to the northeast.

Keywords

• diagenetic facies
• carbonate
• yijianfang formation
• ordovician
• shunbei area
• tarim basin