塔河油田盐下地区原油地球化学特征及不同期次油气成藏贡献

Geochemical characteristics of crude oil and contributions to hydrocarbon accumulation in multiple stages in Tahe subsalt area

徐勤琪 储呈林 郭小文 刘永立 张黎 罗明霞

XU Qinqi CHU Chenglin GUO Xiaowen LIU Yongli ZHANG Li LUO Mingxia

1. 中国石化 西北油田分公司 勘探开发研究院, 乌鲁木齐 830011; 2. 中国石化 石油勘探开发研究院 无锡石油地质研究所, 江苏 无锡 214126; 3. 中国地质大学(武汉) 资源学院, 武汉 430074

1. Research Institute of Exploration and Production, SINOPEC Northwest Oilfield Branch Company, Urumqi, Xinjiang 830011, China; 2. Wuxi Research Institute of Petroleum Geology, SINOPEC, Wuxi, Jiangsu 214126, China; 3. Faculty of Earth Resources, China University of Geosciences (Wuhan), Wuhan, Hubei 430074, China

对于多旋回叠合盆地，油气藏形成的过程往往伴随着多期次的原油充注，但并非每一期原油充注都对现今油藏形成起到关键作用。流体包裹体方法只能对原油充注期次和时间进行限定，而无法确定各期充注原油对油藏的贡献。针对上述问题，以塔河油田盐下地区奥陶系碳酸盐岩油藏为例，采用原油地球化学、流体包裹体法、荧光光谱和单井模拟分析方法，系统揭示了研究区原油的荧光特征、油气成藏期次和成藏时间。原油生物标志化合物参数分析结果表明，其母质相同且沉积于海相弱还原环境，再通过与研究区烃源岩进行油源对比，确定了原油均来自下寒武统玉尔吐斯组烃源岩。原油芳烃中甲基菲指数和二苯并噻吩参数是定量评价原油成熟度的有效指标，计算得到塔河油田盐下地区原油成熟度(Ro)在0.90%～1.47%之间，可能对应了多期油气充注。此外，在对盐下地区奥陶系储层油包裹体荧光光谱分析、共生盐水包裹体测温和测盐的基础上，结合单井埋藏史和热史模拟，确定盐下地区存在加里东中期(420 Ma)、海西中期(318 Ma)和喜马拉雅晚期(10 Ma)3期原油充注。对比原油和3期油包裹体荧光光谱参数，认为喜马拉雅晚期是盐下地区的主成藏期，为盐下地区的奥陶系油藏贡献了最多的原油。

The process of hydrocarbon accumulation in polycyclic superimposed basins often involves multistage crude oil charging, but not every stage of crude oil charging plays a significant role in the current hydrocarbon accumulation. Fluid inclusion methods can only provide constraints on the stages and time of crude oil charging, but cannot determine the contribution of each stage of crude oil charging for hydrocarbon accumulation. To study the contributions of different stages of crude oil charging for the reservoirs, the Ordovician carbonate reservoirs in the subsalt area, Tahe oilfield (Tahe subsalt area) were taken as an example. This study employed crude oil geochemistry, fluid inclusion analysis, fluorescence spectrum, and single well simulation analysis methods to systematically reveal the fluorescence characteristics of crude oil and hydrocarbon accumulation stages and time of the study area. The analysis of crude oil biomarker parameters indicates that the crude oil has the same parent material and was deposited in a marine weak reducing environment. By comparing the crude oil with the study area’s source rocks, it was determined that all the crude oil was derived from the source rocks of the Lower Cambrian Yuertusi Formation. The aromatic methylphenanthrene index and methyldibenzothiophene parameters of crude oil serve as effective indicators for the quantitative evaluation of crude oil maturity. The calculated crude oil maturity (Ro) in the Tahe subsalt area ranges from 0.90% to 1.47%, and this may correspond to multiple stages of oil and gas charging. Based on fluorescence spectrum analysis of oil inclusions and homogeneity temperature and salinity measurements of associated saline inclusions in the Ordovician reservoirs in the Tahe subsalt area and the study area’s burial history of single well burial history and thermal history simulation, it was determined that the oil reservoirs in the Tahe subsalt area experienced three stages of crude oil charging during the stages of middle Caledonian (420 Ma), middle Hercynian (318 Ma) and late Himalayan (10 Ma). By comparing the fluorescence spectrum parameters of crude oil and oil inclusions in these three stages, it is concluded that the late Himalayan is the primary stage of hydrocarbon accumulation in the Tahe subsalt area, making the largest contribution for the Ordovician reservoirs in the Tahe subsalt area.

中国石化科技部项目“塔北奥陶系油气富集规律与增储目标评价”(P21048-3)资助。

https://doi.org/10.11781/sysydz202401111