Affiliation:
1. 1 Shandong Provincial Key Laboratory of Deep Oil & Gas China University of Petroleum (East China) Qingdao 266580 China cup.edu.cn
2. 2 Shandong Provincial Key Laboratory of Reservoir Geology China University of Petroleum (East China) Qingdao 266580 China cup.edu.cn
3. 3 School of Geosciences China University of Petroleum (East China) Qingdao 266580 China cup.edu.cn
4. 4 Research Institute of Petroleum Exploration and Development Shengli Oilfield SINOPEC Dongying 257022 China cnpc.com.cn
5. 5 Wuxi Research Institute of Petroleum Geology Petroleum Exploration and Production Research Institute SINOPEC Wuxi 214126 China sinopecgroup.com
6. 6 Oil and Gas Survey China Geological Survey Beijing China cgs.gov.cn
7. 7 Southwest Geophysical Prospecting Research Institute BGP Inc. China National Petroleum Corporation Chengdu 610213 China cnpc.com.cn
8. 8 Changqing Oil Field Company PetroChina Xi’an 710021 China petrochina.com.cn
Abstract
Abstract
Lacustrine shale is characterized by rapid lithofacies transformation and compositional heterogeneity, which present challenges in shale oil sweet spot evaluation and distribution prediction and should be systematically studied. Field emission-scanning electron microscopy (FE-SEM), low-pressure adsorption isotherm analysis, mercury intrusion porosimetry (MIP), and triaxial compression testing were employed to comprehensively analyze the oil-bearing capacity, reservoir properties, fluidity, and frackability of different lithofacies. Via analyses of mineral composition, total organic carbon (TOC) content, and sedimentary structure, seven lithofacies were identified: organic-rich calcareous shale (L1), organic-rich laminated calcareous mudstone (L2), organic-rich laminated carbonate-bearing mudstone (L3), intermediate-organic laminated calcareous mudstone (L4), organic-poor laminated calcareous mudstone (L5), organic-poor thin-bedded calcareous mudstone (L6), and organic-rich laminated silty mudstone (L7). Considered together, the oil-bearing capacity, reservoir properties, fluidity, and frackability suggested that the L1 and L7 lithofacies were high-quality sweet spots, with satisfactory oil-bearing capacity (TOC>3.5%; S1>10 mgHC/grock), well-developed pores and microfractures, notable fluidity (as indicated by a high oil saturation index value), and suitable brittleness. The sweet spot distribution was predicted according to multiresolution graph-based clustering analysis of well logs. The results indicate that comprehensive research of the key factors for shale oil and lithofacies prediction can promote sweet spot prediction and enhance shale oil exploration.
Funder
Fundamental Research Funds for the Central Universities
Specialized Fund for Shandong Postdoctoral Innovation Project
China Postdoctoral Science Foundation
National Natural Science Foundation of China