Characteristics and distribution of "sweet spot" reservoirs in the third and fifth members of Upper Triassic Xujiahe Formation, Western Sichuan Depression, Sichuan Basin

被引：0

作者：

Ye S. ^{[1
]}

Yang Y. ^{[1
]}

Zhang L. ^{[1
]}

机构：

[1] Exploration and Production Research Institute, SINOPEC Southwest Oil & Gas Company, Chengdu

来源：

Oil and Gas Geology | 2021年 / 42卷 / 04期

关键词：

sweet spot" reservoir; Continental source rock; Formation mechanism; Sichuan Basin; Western Sichuan Depression; Xujiahe Formation;

D O I：

10.11743/ogg20210405

中图分类号：

学科分类号：

摘要：

The third and fifth members of Xujiahe Formation in Western Sichuan Depression are characterized by thick source rocks with high TOC and medium- to large-scale delta distributary channel and sheet sandstones of huge in-source accumulation potential. A systematic study was carried out on the characteristics, formation mechanism and distribution of "sweet spot" reservoirs in the two members based on an integration of petrography, pore structure, and petrophysical property analyses with well logging interpretations. The results show that fine-grained thin sandstone interbeds against a delta front to shore-shallow lacustrine environment dominate the two members, with the third member in southern Chengdu Sag containing some single- or multiple-layered thick sandstone against delta distributary channels. The thin sandstone reservoirs are characterized by diverse rock types, fine grain size, and high contents of clay matrix and carbonate minerals, and rather tight due to intensive compaction and carbonate cementation. "Sweet spot" reservoirs in the thin sandstones are mainly the results of hydrocarbon generation, dissolution and fracturing processes. Assemblages of organic-rich shale and fine- to medium-grained sandstone with high content of quartz (feldspar) and small amount of carbonate debris (cement) are considered potential sweet spots. The thick sandstone reservoirs are dominated by secondary pores and fractures. Sweet spots are mostly controlled by granularity, the content of feldspar (quartz) and other soluble (brittle) minerals as well as dissolution intensity, of which the latter is the key factor. The fifth member in the south of Longmenshan front structural belt and Xinchang structural belt is most likely to contain thin sandstone sweet spots because of its high-quality source rocks, high content of quartz (feldspar and clay), and low content of carbonate minerals. While the third member in southern Chengdu Sag is ideal for the thick sandstone sweet spots to develop in quartz (feldspar)-rich medium- to coarse-grained sandstones adjacent to shales vertically and laterally. © 2021, OIL & GAS GEOLOGY Editorial Board. All right reserved.

引用

页码：829 / 840and862

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