Study of hydrocarbon charging history of tight sandstone reservoirs using an integrated fluid inclusion approach exemplified by Chang 8 sandstone reservoir in Zhenjing area， Ordos Basin
Yang Peng1,2, Zhang Likuan1, Cao Binfeng1,2, Hu Caizhi3, Qiu Guiqiang3, Ma Liyuan3, Yin Wei3, Li Chao1,2, Lei Yuhong1
1. Key Laboratory of Petroleum Resource Research， Institute of Geology and Geophysics， Chinese Academy of Sciences， Beijing 100029；
2. University of Chinese Academy of Sciences， Beijing 100049；
3. SINOPEC Exploration & Production Research Institute， Beijing 100083
With an integrated approach based on multi—technique analysis of fluid inclusions， including petrography， micro—beam fluorescence spectroscopy and microthermometry， the paper determined oil charge timing， and revealed coupled diagenetic evolution and hydrocarbon accumulation in Yanchang Formation Chang 8 Member of Zhenjing area， Ordos Basin. There exist two distinct intergranular oils with yellow and blue—white fluorescence， with the latter more frequently observed. Unlike intergranular free oils， three types of oil inclusions are identified. They also show fluorescence， varying from yellow， yellow—green to blue—white， and the dominant fluorescence color is yellow—green to blue—white. Aqueous fluid inclusions， associated with oil inclusions fluorescing yellow color， exhibit the peak homogenization temperatures of 80℃～90℃， whereas those coeval with oil inclusion fluorescing yellow—green to blue—white fall in the range of 105℃～115℃ and 110℃～120℃ respectively. It was revealed that three phases of hydrocarbon charging occurred， respectively， during early part（138～130Ma）and late part（124～105Ma）of the Early Cretaceous， and in Late Cretaceous. The first phase was related to small amounts of low—maturity oil， while the second phase， the most critical stage for hydrocarbon accumulation， was dominated by mature oil. The last phase was secondary accumulation accompanied by destruction of ancient oil pools. The early diagenesis of the studied reservoir， highlighted by physical compaction， grain—coating chlorite and kaolinite and micritic calcites， was followed by early hydrocarbon injecting in intermediate—high permeability conditions. With continued burial and compaction， quartz overgrowth， kaolinite and sparry calcites was precipitated， markedly making the reservoir tightened. In low—permeability reservoirs， late hydrocarbon migration and accumulation was determined by early charging.
Yang Peng,Zhang Likuan,Cao Binfeng et al. Study of hydrocarbon charging history of tight sandstone reservoirs using an integrated fluid inclusion approach exemplified by Chang 8 sandstone reservoir in Zhenjing area， Ordos Basin[J]. Chinese Journal of Geology, 2016, 51(3): 946-960.