Oil & Gas Geology ›› 2024, Vol. 45 ›› Issue (3): 816-826.doi: 10.11743/ogg20240317

• Methods and Technologies • Previous Articles     Next Articles

Well-log-based assessment of movable oil content in lacustrine shale oil reservoirs: A case study of the 2nd member of the Paleogene Funing Formation, Subei Basin

Jun LI(), Youlong ZOU(), Jing LU   

  1. Petroleum Exploration and Production Research Institute,SINOPEC,Beijing 100026,China
  • Received:2024-01-30 Revised:2024-05-30 Online:2024-06-30 Published:2024-07-01
  • Contact: Youlong ZOU E-mail:lijun67.syky@sinopec.com;zouyl.syky@sinopec.com

Abstract:

Recent years have witnessed significant progress in the exploration and exploitation of shale oil in continental basins in East China. However, the assessment of shale oil productivity is largely hindered by the evaluation of oil mobility. By investigating the shale oil in the Subei Basin, we propose two well-log-based methods for assessing the movable oil content in shales: the two-dimensional nuclear magnetic resonance (2D NMR) method and the conventional logging. An identification plot for movable oil is thereby established using the 2D NMR-derived longitudinal and transverse relaxation time (T1 and T2, respectively), acting to assess fluid types like adsorbed oil and irreducible water. By exploring the relationships of free hydrocarbon content (S1) with sedimentary environments and structures, along with the correlation between S1 and logging responses, we analyze the response sensitivities of conventional well-log-derived resistivity and sonic interval transit time to S1 and organic matter content, and establish a well-log-based quantitative assessment model for S1. Furthermore, a method for assessing S1 using log data is developed to calculate both movable oil saturation and oil content. The results reveal that saline environments and lamellar structures promote hydrocarbon generation and migration from organic matter, resulting in high S1.

Key words: oil-bearing property, mobility, movable oil content, well-log-based assessment, shale oil, Subei Basin

CLC Number: