Deng Rui, Wang Yunpeng, Chen Chengsheng
State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.
CAS Center for Excellence in Deep Earth Science, Guangzhou, 510640, China.
ACS Omega. 2022 Apr 20;7(17):14933-14943. doi: 10.1021/acsomega.2c00584. eCollection 2022 May 3.
The diversity of fluid phases in the oil-gas system and complexity of petroleum genesis bring difficulties to the exploration and development of oil and gas. The phase state and evolution of the complex reservoirs in the Halahatang Depression, Tabei Uplift of the Tarim Basin remains unresolved. In this paper, we simulated the phase characteristic of reservoirs in different blocks and layers including Xinken (O), Ha6 (C), Repu (K), and Yueman (O) distributed from north to south of this area using PVTsim software; rebuilt the burial, temperature, and pressure histories of different blocks and layers by using the PetroMod (1D) software; and recovered the fluid phase evolution process by combined basin modeling, PVT simulation, and fluid inclusion thermal metrics results. The phase modeling results show that the Xinken (O), Ha6 (C), and Yueman (O) reservoirs are confirmed to be oil reservoirs, and the Repu (K) reservoir is in the condensate gas phase currently. The vital time points and temperature and pressure conditions for the three oil reservoirs of Xinken (O), Ha6 (C), and Yueman (O) that transited from the gas-liquid phase to the liquid phase are 356 Ma (57.45 °C, 12.93 MPa), 331 Ma (35.67 °C, 4.03 MPa), and 454 Ma (63.63 °C, 13.27 MPa), respectively. The Ordovician reservoir in the Xinken block underwent three stages of accumulation, which occurred at 400-379 Ma (Devonian), 282-256 Ma (Permian), and 18-16 Ma (Neogene), respectively, and after final accumulation, it remained in a single oil phase state. The Ordovician reservoir in the Yueman block underwent two stages of accumulation in the 294-290 Ma (Permian) and 25-12 Ma (Paleogene-Neogene) and remained in a single oil phase state until now. The Carboniferous reservoir in the Ha6 block was deduced to be charged in the 94-86 Ma (Cretaceous) according to the published authigenic illite K-Ar isotope dating results and then stayed in a single oil phase state unalterably. As for the Cretaceous reservoir in the Repu block, the time point of 11 Ma (98.86 °C, 35.56 MPa) is vital for changing from the gas-liquid coexistence phase state to the condensate gas phase one. In contrast with the Ordovician (ZG7-5) and Cambrian reservoirs (ZS1, ZS5) in the Tazhong Uplift, the oil and condensate gas reservoirs in the Tabei Uplift enjoy a lower pressure range, lower GOR, and a heavier oil density and viscosity. This study provides a quantitative way to rebuild the geologic evolutionary process, phase characteristics, and phase evolution process in complex reservoirs.
油气系统中流体相态的多样性以及石油成因的复杂性给油气勘探开发带来了困难。塔里木盆地塔北隆起哈拉哈塘凹陷复杂油藏的相态及演化问题仍未解决。本文利用PVTsim软件模拟了该地区自北向南分布的不同区块和层位（新垦（奥陶系）、哈6（石炭系）、热普（白垩系）和玉满（奥陶系））油藏的相态特征；利用PetroMod（1D）软件重建了不同区块和层位的埋藏史、温度史和压力史；并结合盆地模拟、PVT模拟和流体包裹体热计量结果恢复了流体相态演化过程。相态模拟结果表明，新垦（奥陶系）、哈6（石炭系）和玉满（奥陶系）油藏为油藏，热普（白垩系）油藏目前处于凝析气阶段。新垦（奥陶系）、哈6（石炭系）和玉满（奥陶系）三个油藏从气液相转变为液相的关键时间点及温度、压力条件分别为356 Ma（57.45℃，12.93 MPa）、331 Ma（35.67℃，4.03 MPa）和454 Ma（63.63℃，13.27 MPa）。新垦区块奥陶系油藏经历了三期成藏，分别发生在400 - 379 Ma（泥盆系）、282 - 256 Ma（二叠系）和18 - 16 Ma（新近系），最终成藏后一直处于单一油相状态。玉满区块奥陶系油藏在294 - 290 Ma（二叠系）和25 - 12 Ma（古近系 - 新近系）经历了两期成藏，至今一直处于单一油相状态。根据已发表的自生伊利石K - Ar同位素测年结果，哈6区块石炭系油藏推断在94 - 86 Ma（白垩系）充注，之后一直处于单一油相状态未发生改变。对于热普区块白垩系油藏，11 Ma（98.86℃，35.56 MPa）这个时间点对于从气液共存相态转变为凝析气阶段至关重要。与塔中隆起奥陶系（ZG7 - 5）和寒武系油藏（ZS1、ZS5）相比，塔北隆起的油藏和凝析气藏具有更低的压力范围、更低的气油比以及更高的原油密度和粘度。本研究为重建复杂油藏的地质演化过程、相态特征及相态演化过程提供了一种定量方法。
