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- Title
临兴地区致密气 “多层系准连续”成藏模式与 大气田勘探实践.
- Authors
杜 佳; 朱光辉; 吴洛菲; 张政和; 高计县; 喻玉洁; 马遵敬; 张 明
- Abstract
Linxing area is located in Jinxi flexure zone of the eastern Ordos Basin, where the first high-yield gas well was explored in the Carboniferous-Permian at the end of 2013 and since then several high-yield gas wells have been discovered. For the purpose of providing support for the evaluation of the Upper Paleozoic natural gas resources in Linxing area, studies and exploration and development practices were conducted on the hydrocarbon accumulation conditions, enrichment laws and hydrocarbon accumulation patterns of tight sandstone gas in this area by means of geological setting investigation, structural evolution dissection, drilling geological analysis and abundant core sampling and experiments. And at the end of 2020, Linxing giant gas field with hundreds of billions of reserves was discovered. The following research results were obtained. First, the Upper Paleozoic source rocks in Linxing area are mainly coal-bearing series deposited in a transitional environment, and they are characterized by high organic abundance, great thickness and a large distribution area. Second, the reservoir is dominated by water or underwater distributary channel deposits that swing frequently and migrate back and forth. Sand bodies are superimposed vertically and connected areally. Secondary dissolution pores are developed. Argillaceous cap rocks are distributed widely in vertical and horizontal directions. Third, the Upper Paleozoic reservoirs were generally densificated in the period of Middle Jurassic. A large number of coal-measure source rocks of Upper Carboniferous Benxi Formation and Lower Permian Taiyuan Formation began to expel hydrocarbon in the Late Jurassic. After hydrocarbon was accumulated and enriched in the reservoirs inside the source rocks, it migrated gradually to the tight sandstone of Middle Permian Lower Shihezi Formation near the source rocks. The top was under the barrier of the regional major cap rocks in the middle of Shihezi Formation. In this way, an intra-source and near-source hydrocarbon accumulation system was formed. Fourth, the Zijinshan Mountain invaded into the Upper Paleozoic in the Early Cretaceous to form a large number of through fault systems. As a result, the regional cap rock in the middle of Shihezi Formation was destroyed, and intra-source and near-source natural gas migrated to Middle Permian Upper Shihezi Formation and Upper Permian Shiqianfeng Formation along faults to form a far-source hydrocarbon accumulation system. Fifth, the effective configuration of source rock-reservoir-cap rock assemblage lays the foundation for the formation of Linxing giant gas field. In conclusion, Linxing gas field has sufficient gas source conditions, "sandwich" lithology combination of quality sandstone-mudstone interbed and good fault and fracture system, which jointly form the "multi-series and quasi-continuous" tight gas accumulation pattern. These research results provide a practical way for CNOOC to realize a breakthrough in onshore oil and gas reserves and production.
- Subjects
CAP rock; GAS wells; DRILL core analysis; PALEOZOIC Era; PETROLEUM reserves; GAS fields; NATURAL gas prospecting; NATURAL gas
- Publication
Natural Gas Industry, 2021, Vol 41, Issue 3, p58
- ISSN
1000-0976
- Publication type
Article
- DOI
10.3787/j.issn.1000-0976.2021.03.007