Li Jiaqi, Kang Zhihong, Kang Zhijiang, Liu Xing, Zhang Xuemei
School of Energy Resources, China University of Geosciences, Beijing 100083, China.
School of Energy Resources, China University of Geosciences, Beijing 100083, China.
Sci Total Environ. 2024 Feb 20;912:169363. doi: 10.1016/j.scitotenv.2023.169363. Epub 2023 Dec 18.
In recent years, the Ordovician carbonate reservoirs in the Tarim Basin have received attention due to continuous advancements in of deep strata exploration for oil and gas. The Ordovician carbonates in the Tahe Oilfield have experienced multiple phases of tectonic movement and ancient karst action to form reservoirs consisting of multi-scale spaces such as large caves, fractures, and dissolution pores. This study identifies indicators of atmospheric freshwater karst and hydrothermal karst in the Ordovician carbonate rocks of the Tahe Oilfield by comparing and analyzing lithological observation, geochemical data, fluid inclusions, logging interpretation, and seismic data. The spatial and temporal distribution of karst reservoirs are summarized, and the results show that the stage of tectonic movement and pulsating uplift of strata occurred in the early Caledonian and Hercynian orogenies, and the carbonate rocks were uplifted to the surface and large-scale atmospheric freshwater karstification. In the deeper strata, the thermal convection of fluids caused by volcanic activity accelerated the thermochemical sulfate reduction (TSR), and the generated HS gas accompanied the upward transport of hydrothermal fluids, which further dissolved and modified the original karst system, increasing the storage space. However, away from the heat source, calcite (positive Eu anomaly, higher Sr/Sr ratio, lower δO value,) reprecipitated due to the temperature reduction, so the role of hydrothermal activity in reservoir reconstruction is limited. The two karst action patterns indicated that epigenetic karstification is an important process for forming carbonate reservoirs in the Tahe Oilfield and the basis of hydrothermal karst reservoir formation. This study demonstrates the research and exploration value of karstification for the geo-energy field, which could benefit sustainable development in the Tarim Basin.
近年来，随着塔里木盆地深层油气勘探的不断推进，奥陶系碳酸盐岩储层受到关注。塔河油田的奥陶系碳酸盐岩经历了多期构造运动和古岩溶作用，形成了由大型洞穴、裂缝和溶蚀孔隙等多尺度空间组成的储层。本研究通过对岩性观察、地球化学数据、流体包裹体、测井解释和地震数据的对比分析，识别了塔河油田奥陶系碳酸盐岩中大气淡水岩溶和热液岩溶的标志。总结了岩溶储层的时空分布，结果表明，加里东早期和海西期造山运动发生了构造运动和地层脉动隆升阶段，碳酸盐岩隆升至地表并发生大规模大气淡水岩溶作用。在更深的地层中，火山活动引起的流体热对流加速了热化学硫酸盐还原（TSR），生成的HS气体伴随热液流体向上运移，进一步溶解和改造了原始岩溶系统，增加了储集空间。然而，远离热源的地方，由于温度降低，方解石（正铕异常、较高的Sr/Sr比值、较低的δO值）重新沉淀，因此热液活动在储层改造中的作用有限。这两种岩溶作用模式表明，后生岩溶作用是塔河油田碳酸盐岩储层形成的重要过程，也是热液岩溶储层形成的基础。本研究展示了岩溶作用在地热能源领域的研究和勘探价值，可为塔里木盆地的可持续发展提供帮助。
