Oil & Gas Geology ›› 2017, Vol. 38 ›› Issue (3): 448-456,466.doi: 10.11743/ogg20170304

Previous Articles     Next Articles

Oil content and occurrence in low-medium mature organic-rich lacustrine shales: A case from the 1st member of the Eocene-Oligocene Shahejie Formation in Well Luo-63 and Yi-21,Bonan Subsag, Bohai Bay Basin

Li Zhiming1,2,3,4, Qian Menhui1,2,3,4, Li Maowen1,2,3,4, Jiang Qigui1,2,3,4, Liu Peng1,2,3,4, Rui Xiaoqing1,2,3,4, Cao Tingting1,2,3,4, Pan Yinhua1,2,3,4   

  1. 1. Wuxi Research Institute of Petroleum Geology, RIPEP, SINOPEC, Wuxi, Jiangsu 214126, China;
    2. State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development, Wuxi, Jiangsu 214126, China;
    3. State Energy Center for Shale Oil Research and Development, Wuxi, Jiangsu 214126, China;
    4. SINOPEC Key Laboratory of Petroleum Accumulation Mechanisms, Wuxi, Jiangsu 214126, China
  • Received:2016-08-31 Revised:2017-04-20 Online:2017-06-28 Published:2017-07-10

Abstract: This paper studied oil content and occurrence in low to medium mature organic-rich lacustrine shales by taking the cored section of the 1st Member of the Eocene-Oligocene Shahejie Formation in Well Luo63 and Yi21 in Bonan subsag,Zhanhua sag,Bohai Bay Basin,as an example.Oil content was evaluated qualitatively by using chloroform bitumen "A" and oil saturation indices (OSI) after light hydrocarbon correction,and oil occurrence was studied both qualitatively and quantitatively through thin section observation,SEM observation,and thermal desorption.The results show that organic-rich shales in the 1st Member of Shahejie Formation (Es1) contain over 1% chloroform bitumen "A",whereas the oil saturation indices (OSI) indicate modest oil content to oil show,with a few samples display high potential for shale oil production,after light hydrocarbon correction.Oils retained in the organic-rich shales occur both in association with organic macerals (adsorption or dissolution in bitumenite and laminate alginate),and in bedding fractures,stress induced microfractures,intergranular and intercrystalline pores,grain boundary fractures and mineral dissolution pores.High molecular weight hydrocarbons occur mainly in association with insoluble organic matter,by adsorption or in dissolution,accounting for 68%~84% of total oil content (with an average of 75%).The free low to medium molecular weight hydrocarbons occur mainly in various fractures and pores,accounting for 16%~32% of total retained oil (with an average of 25%).The contents of practicable movable oil (sum contents of light hydrocarbon correction and thermal desorption at 200℃) are in the range from 0.62 mg/g to 1.76mg/g (with an average of 1.12 mg/g) and the movable oil ratio (the percentage of practicable movable oil content in total oil content) from 5.39% to 9.10%,with an average of 7.06%.The sum of light oil thermal desorption at 200℃ and light hydrocarbon correction can be used reasonably to evaluate shale oil resource potential in organic-rich shales.

Key words: oil content, low-medium mature, organic-rich shale, Shahejie Formation, Bonan Subsag, Bohai Bay Basin

CLC Number: