Fluid evolution in the Dabei Gas Field of the Kuqa Depression, Tarim Basin, NW China: Implications for fault-related fluid flow
Fluid evolution in the Dabei Gas Field of the Kuqa Depression, Tarim Basin, NW China: Implications for fault-related fluid flow
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DOI：
10.1016/j.marpetgeo.2016.08.024
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发表时间：
2016-12
影响因子：
4.2
通讯作者：
Xiaowen Guo;Keyu Liu;C. Jia;Yan Song;Mengjun Zhao;Q. Zhuo;Xuesong Lu
中科院分区：
文献类型：
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作者：
Xiaowen Guo;Keyu Liu;C. Jia;Yan Song;Mengjun Zhao;Q. Zhuo;Xuesong Lu
中国西部库车坳陷大北气田发育一系列断裂相关褶皱，形成主要油气聚集圈闭。大北气田不同断层相关褶皱中的巴什基奇克（K1bs）砂岩储层表现出相似的过剩流体压力、地层水类型和矿化度以及轻质油气性质。圈闭K1bs砂岩储集层中的轻质油气同源，热成熟度分别为1.4%~1.6%Ro和1.7%~2.3%Ro。为了研究与断层相关的褶皱圈闭中的流体演化，进行了综合流体包裹体分析，包括岩相学、荧光光谱、显微测温、激光拉曼光谱和热力学建模。不同断层相关褶皱中的流体包裹体记录的流体演化表明，地层流体的特征是在正常静水压力下约>9-5Ma的低盐度。从5Ma到3Ma，地层水矿化度和流体压力迅速增加。地层水在大约 3 Ma 时达到最高盐度，而储层中孔隙流体超压随着时间的推移而降低。 K1bs 砂岩储层中发现了两期石油充注和一次天然气充注，其中第二期石油充注发生在 5~4 Ma 左右，而天然气充注发生在 3~2 Ma 左右。与油气充注相关的新流体的注入引起了气田内不同断层相关褶皱圈闭中地层水盐度的变化。大北气田的流体演化可以用来指示与断层相关的流体流动，因为逆冲断层被认为是流体运移的主要通道，并且流体流动受这些逆冲断层重新活动的控制。大北气田不同断层相关圈闭中K1bs砂岩储层油气充注历史、地层水盐度和流体压力演化的相似性表明，断层相关流体流动过程和逆冲断层的活动自约9 Ma以来是同时发生的。
A series of fault-related folds developed in the Dabei Gas Field of the Kuqa Depression, western China form major traps for hydrocarbon accumulation. The Bashijiqike (K1bs) sandstone reservoirs in the different fault-related folds of the Dabei Gas Field display similar excess fluid pressure, formation water type and salinity, and as well as light oil and gas properties. The light oil and gas in the K1bs sandstone reservoir of the traps share the same source and were generated at a thermal maturity level of 1.4–1.6% Roand 1.7–2.3% Ro, respectively. To investigate the fluid evolution in the fault-related fold traps, an integrated fluid inclusion analysis was performed including petrography, fluorescence spectroscopy, microthermometry, Laser Raman spectroscopy and thermodynamic modeling. The fluid evolution recorded by the fluid inclusions in the different fault-related folds indicates that the formation fluid was characterized by low salinity at normal hydrostatic pressure from approximately >9–5 Ma. From 5 to 3 Ma the formation water salinity and fluid pressure increased rapidly. The formation water attained the highest salinity at approximately 3 Ma to present while the pore fluid overpressure decreased with time in the reservoir. Two episodes of oil and one episode of gas charge were identified in the K1bs sandstone reservoir with the second episode of oil charge occurring around 5–4 Ma, while the gas charge occurred around 3–2 Ma. The injection of new fluids associated with oil and gas charge caused changes of the formation water salinity in the different fault-related fold traps within the gas field. The fluid evolution in the Dabei Gas Field can be used to indicate fault-related fluid flow as the thrust faults are suggested to be the primly pathways for fluid migration and the fluid flow was controlled by the reactivation of these thrust faults. The similarity of the oil and gas charge histories, formation water salinity and fluid pressure evolution in the K1bs sandstone reservoirs among the different fault-related traps in the Dabei Gas Field implies that the fault-related fluid flow process and activation of the thrust faults were concomitant since approximately 9 Ma.