High-frequency sequence stratigraphy of carbonate and the corresponding shoal reservoir characteristics

Deep carbonate of Tarim Basin has become an important study target of shoal reservoirs at present, and the reservoir capacity and its control factors of high-frequent meter scale cyclic carbonate strata have been the purposes of this study. This research has selected the upper layer of strata of Yingshan formation in Keping area of Tarim Basin as the target stata, and analyzed by anatomying its outcrop, sampling and studying microscopic flakes. The result shows that the strata of Yingshan formation has deposited as high-frequent meter-scale cyclic sequence, and been an aggradational pattern between parasequence sets. Each parasequence set contains four parasequences which limestone was thickening during depositing period, the external style and internal composition between parasequence sets and parasequences are apparent self similarity. Calcarenite and bioclastic debris are the main particle types of shoal reservoirs, and the size gradually has increased up. Cement and means of contact between particles are consistent with the aggradational high-frequency sequences. All of the above fully have proved that the depositional energy increases from the parasequence sets A to C, and the high-energy deposition environment provides the basic condition for forming excellent shoal reservoir. Cracks and fissures are the main reservoir spaces of Yingshan formation shoal reservoir, but deep diagenesis shortly has not conducted to form effective dissolution intergranular pore, and reduced the capacity of quality shoal reservoir as the prerequisite for high-energy environment. As a result, the tectonic uplift has been the leading factor to control Yingshan formation to be II category reservoir.