- 责任者：Yang Hua (National Engineering Laboratory for Exploration and Development of Low Permeability Oil and Gas Fields ; Changqing Oilfield Company ; PetroChina ; Xi’an 710018 ; China) ; Zhang Wenzheng
- 刊名：Journal of Earth Sciences and Environment
- 出版年：2013
- 卷期：35(4)
- 页码：p.1-9
- issnNo：ISSN1672-6561
- isbnNo：CN61-1423/P
Mesozoic low-permeability oil reservoirs are extensively distributed in Ordos Basin, mainly in all members of Yanchang Formation, and Chang-6, Chang-8 and Chang-4＋ 5 are the dominating reservoirs. The data from pyrolysis of reservoir rocks show that the oil-rieh features of deep water facies compact sandstone bodies of Chang-7 and Chang-6 in the central part of lake basin are favorable, oil reservoirs are universal in these members, which enable the lake basin to be oil-rich and low-permeability at full basin scale. Rate-controlled mercury, startup pressure gradient and oil infilling tests for reservoir show that gravitational differentiation of oil and water in reservoirs is very difficult, because the sandstone reservoirs of Yanchang Formation are lowpermeability and tight, and consist of tiny migration channels which show high capillary resistance, and the stratum is only relatively slowly inclined. Oil migration and accumulation appear to be passive in terms of dynamic attribute, since oil infilling and large-scale migration, accumulation and reservoir formation require strong dynamics as well as hydrocarbon-bearing fluid. Chang-7 high-quality source rock, which is distributed extensively on large scale in the basin, is capable of large-scale hydrocarbon generation and expulsion, strong hydrocarbon- generating pressurization and efficient hydrocarbon expulsion. Hydrocarbon-generating pressurization provides the power of oil migration and accumulation, and hydrocarbon expulsion provides large-scale hydrocarbon-bearing fluid. So, it can satisfy the dynamics and oil-source conditions as required for formation of large-scale low-permeability and tight sandstone reservoirs, and play a key role in formation of Mesozoic low-permeability and oil-rich reservoirs in Ordos Basin.