A unified model for the formation and distribution of both conventional and unconventional hydrocarbon reservoirs

• Published in: Di xue qian yuan. Vol. 12; no. 2; pp. 695 - 711
• Main Authors: Pang, Xiongqi, Jia, Chengzao, Chen, Junqing, Li, Maowen, Wang, Wenyang, Hu, Qinhong, Guo, Yingchun, Chen, Zhangxin, Peng, Junwen, Liu, Keyu, Wu, Keliu
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 01.03.2021; Elsevier Science Ltd; State Key Laboratory of Petroleum Resources and Prospecting,Beijing 102249,China; College of Geosciences,China University of Petroleum-Beijing,Beijing 102249,China; Chemical and Petroleum Engineering,Schulich School of Engineering,University of Calgary,Calgary T2N 1N4,Canada%The University of Texas at Arlington,Arlington,TX 76019,USA%Institue of Geomechanics,China Academy of Geological Science,Beijing 100081,China%Chemical and Petroleum Engineering,Schulich School of Engineering,University of Calgary,Calgary T2N 1N4,Canada%Bureau of Economic Geology,University of Texas at Austin,Austin TX 78713,USA%CSIRO Energy,26 Dick Perry Ave,Kensington,WA 6151,Australia%State Key Laboratory of Petroleum Resources and Prospecting,Beijing 102249,China; College of Geosciences,China University of Petroleum-Beijing,Beijing 102249,China%Exploration&Development Research Institute,China National Petroleum Corporation,Beijing 100724,China%State Key Laboratory of Petroleum Resources and Prospecting,Beijing 102249,China; Chemical and Petroleum Engineering,Schulich School of Engineering,University of Calgary,Calgary T2N 1N4,Canada; College of Science,China University of Petroleum-Beijing,Beijing 102249,China%State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development,Beijing 100083,China%State Key Laboratory of Petroleum Resources and Prospecting,Beijing 102249,China
• Subjects: Accumulation; Anomalies; Basins; Buoyancy; Exploratory drilling; Fossil fuels; Heat transmission; Hydrocarbon accumulation; Hydrocarbon dynamic field; Hydrocarbon reservoirs; Hydrocarbon resources; Hydrocarbons; Lithology; Oil exploration; Permeability; Porosity; Reservoirs; Shale gas; Shale oil; Tectonics; Unified model of reservoirs formation; Fossil fuels; Hydrocarbon resources; Unified model of reservoirs formation; Hydrocarbon dynamic field; Hydrocarbon reservoirs; Hydrocarbon accumulation
• ISSN: 1674-9871; 2588-9192
• DOI: 10.1016/j.gsf.2020.06.009

The discovery and large-scale exploration of unconventional oil/gas resources since 1980s have been considered as the most important advancement in the history of petroleum geology; that has not only changed the balance of supply and demand in the global energy market, but also improved our understanding of the formation mechanisms and distribution characteristics of oil/gas reservoirs. However, what is the difference of conventional and unconventional resources and why they always related to each other in petroliferous basins is not clear. As the differences and correlations between unconventional and conventional resources are complex challenging issues and very critical for resources assessment and hydrocarbon exploration, this paper focused on studying the relationship of formations and distributions among different oil/gas reservoirs. Drilling results of 12,237 exploratory wells in 6 representative petroliferous basins of China and distribution characteristics for 52,926 oil/gas accumulations over the world were applied to clarify the formation conditions and genetic relations of different oil/gas reservoirs in a petroliferous basin, and then to establish a unified model to address the differences and correlations of conventional and unconventional reservoirs. In this model, conventional reservoirs formed in free hydrocarbon dynamic field with high porosity and permeability located above the boundary of hydrocarbon buoyancy-driven accumulation depth limit. Unconventional tight reservoirs formed in confined hydrocarbon dynamic field with low porosity and permeability located between hydrocarbon buoyancy-driven accumulation depth limit and hydrocarbon accumulation depth limit. Shale oil/gas reservoirs formed in the bound hydrocarbon dynamic field with low porosity and ultra-low permeability within the source rock layers. More than 75% of proved reserves around the world are discovered in the free hydrocarbon dynamic field, which is estimated to contain only 10% of originally generated hydrocarbons. Most of undiscovered resources distributed in the confined hydrocarbon dynamic field and the bound hydrocarbon dynamic field, which contains 90% of original generated hydrocarbons, implying a reasonable and promising area for future hydrocarbon explorations. The buried depths of hydrocarbon dynamic fields become shallow with the increase of heat flow, and the remaining oil/gas resources mainly exist in the deep area of “cold basin” with low geothermal gradient. Lithology changing in the hydrocarbon dynamic field causes local anomalies in the oil/gas dynamic mechanism, leading to the local formation of unconventional hydrocarbon reservoirs in the free hydrocarbon dynamic field or the occurrence of oil/gas enrichment sweet points with high porosity and permeability in the confined hydrocarbon dynamic field. The tectonic movements destroy the medium conditions and oil/gas components, which leads to the transformation of conventional oil/gas reservoirs formed in free hydrocarbon dynamic field to unconventional ones or unconventional ones formed in confined and bound hydrocarbon dynamic fields to conventional ones. [Display omitted] •A unified model for the formation and distribution of both conventional and unconventional reservoirs.•Conventional reservoirs in free hydrocarbon dynamic field with high porosity and permeability.•Unconventional tight reservoirs in confined hydrocarbon dynamic field with low porosity and permeability.•Shale oil/gas reservoirs in the bound hydrocarbon dynamic field with low porosity and ultra-low permeability.