The Oil-bearing Property Characteristics and Evaluation of Lucaogou Formation Shale Reservoirs in Malang Sag

Key words: 
• shale oil /
• reservoirs /
• oil-bearing property /
• oil enrichment mechanism /
• Malang sag

Abstract: Through geochemical analysis, physical analysis and mercury intrusion analysis of conventional shale core and sealing drilling shale core, combining with the production oil test, this paper discussed the oil-bearing property of Lucaogou Formation shale oil reservoirs in Malang sag. It also studied the accumulation mechanism of shale oil, and the characteristics favorable reservoir development and distribution. The results show that the oil-bearing property of Lucaogou Formation shale is under the control of the richness of organic matter and porosity of the shale reservoirs. The TOC (%) of the shale reservoirs enriched oil should be more than 4%, and the porosity should be more than 3%. Volume-oil-bearing rate (Po, %) can  reflect  the oil-bearing property of the shale reservoirs more accurate than the oil saturation.  For shale reservoir  enrichment in oil, the volume-oil-bearing rate should be more than 1%. Mercury injection data indicate that oil enrichment mechanism of shale reservoir is different from conventional sandstone reservoirs. Oil entering the shale reservoirs includes two processes, one is that hydrocarbon was stranded in source rock without migration, the other is that oil moved into poorsource rock system near high quality source rock by short distance primary migration. Beneficial lithologic association is the main influence factor for shale oil enrichment. The configuration relation of mudstone interbedded by argillaceous limestone, argillaceous dolomite or in calcareous mudstone and dolomitic mudstone is primarily  the optimal lithologic association, and has the best oil-bearing property, which is deposited in sedimentary environment of deep lake and semi-deep lake.