Hydrocarbon generation and expulsion features of the Upper Triassic Xujiahe Formation source rocks and their controlling effects on hydrocarbon accumulation in the Sichuan Basin, Central China

2019 ◽  
Vol 55 (7) ◽  
pp. 4977-4996
Author(s):  
Tianyu Zheng ◽  
Xinhua Ma ◽  
Xiongqi Pang ◽  
Dingye Zheng ◽  
Wenyang Wang ◽  
...  
Keyword(s):  
Sichuan Basin ◽  
Upper Triassic ◽  
Source Rocks ◽  
Central China ◽  
Hydrocarbon Generation ◽  
Hydrocarbon Accumulation ◽  
Xujiahe Formation ◽  
The Sichuan Basin

scholarly journals Formation pressure evolution and its causes for the reservoirs of the upper Triassic Xujiahe formation in the northeast portion of the Sichuan basin, China

2021 ◽  
pp. 014459872110124
Author(s):  
Cunjian Zhang ◽  
Jingdong Liu ◽  
Youlu Jiang
Keyword(s):  
Late Cretaceous ◽  
Middle Jurassic ◽  
Sichuan Basin ◽  
Oil And Gas ◽  
Upper Triassic ◽  
Hydrocarbon Generation ◽  
Formation Pressure ◽  
Xujiahe Formation ◽  
The Sichuan Basin ◽  
Early Late

Overpressure is one of the most important factors for oil and gas charging in petroliferous basins. Research on overpressure evolution and its formation mechanisms is of great significance for predicting formation pressures in oil and gas reservoirs before drilling. However, research methods addressing overpressure evolution are not without issues. Based on the measured formation pressures and fluid inclusions, the evolution of the formation pressures in the Xujiahe Formation in the northeast part of the Sichuan Basin was investigated by PVT and basin simulations and the causes of overpressure were also analyzed. The results show that overpressure in the continental strata began to develop at the bottom of the Middle Jurassic Shaximiao Formation. The pressure coefficients of the Upper Triassic Xujiahe Formation range from 1.01 to 1.90, and belong to the normal pressure and overpressure regimes. The present-day overpressure of the Xujiahe Formation is mainly caused by hydrocarbon generation and tectonic compression. The tight reservoirs are conducive to the formation and preservation of overpressure. The pressures in the Xujiahe Formation experienced two evolution processes, namely an “increase-decrease-increase” (eastern area) process and an “increase-decrease” (western area) process. Overpressure began to develop in the Middle Jurassic(J2) period. Due to the hydrocarbon generation taking place, the formation pressures increased rapidly from the Middle Jurassic(J2) period to the early Late Cretaceous (the early part of K2) period. The degree of development of overpressure in the western part of the study area was greater than that in the eastern part of the study during the critical charging period (J3–K1). Since the early Late Cretaceous, the formation pressure has gradually decreased due to tectonic uplift and erosion. From the Oligocene (E3) period to the present, the formation pressures have increased again in local areas due to tectonic compression.

scholarly journals Biomarker distributions and depositional environments of continental source rocks in Sichuan Basin, SW China

2020 ◽  
Vol 38 (6) ◽  
pp. 2296-2324
Author(s):  
Siqin Huang ◽  
Guosheng Xu ◽  
Fanghao Xu ◽  
Wei Wang ◽  
Haifeng Yuan ◽  
...  
Keyword(s):  
Sichuan Basin ◽  
Lower Jurassic ◽  
Upper Triassic ◽  
Depositional Environments ◽  
Source Rocks ◽  
Late Triassic ◽  
Ms Analysis ◽  
Continental Source ◽  
The Sichuan Basin ◽  
Tricyclic Terpanes

In order to study the distributions of the biomarker of the continental source rocks in the Sichuan Basin, 71 source rock samples were collected from the Upper Triassic-Lower Jurassic strata in different regions. The n-alkanes, isoprenoids, terpane, sterane, sesquiterpenes, caranes and aromatics in the extracts were analyzed in detail. GC-MS analysis has been conducted to analyze the biomarker of the continental source rocks. The results of GC-MS analysis indicate that the Upper Triassic source rocks are high in the content of extended tricyclic terpanes, pristane, phytane, gammacerane, C28 regular sterane and carotene. However, they are low in content of rearranged compounds. The ratio of Pr/Ph is less than 1, with the characteristics of tricyclic terpane C21 > C23. The Lower Jurassic source rocks are extremely low in content (even zero) of extended tricyclic terpanes, pristane, phytane, gammacerane, C28 regular sterane and carotene, and high in content of rearranged compounds. The ratio of Pr/Ph is more than 1, with tricyclic terpane C21 > C23. These characteristics are still preserved after maturation. Moreover, during the sedimentation of the source rocks of T3x2–T3x3 members, the supply of continental plants was low (TAR < 1, with regular sterane C27 > C29, 1-MP/9-MP < 1). The source rocks of T3x5 member were low in salinity (slightly low content of gammacerane and carotene), being different significantly from the other Upper Triassic source rocks. In addition, during the sedimentation of the source rocks of J1dn Member, the supply of continental plants was also low (regular sterane C27 > C29, 1-MP/9-MP < 1), being quite different from that of J1l member. Through analysis of the difference in biomarkers, it is indicated that the sedimentary environment had changed from anoxic and brackish water during the Late Triassic to oxygen-rich and freshwater during the Early Jurassic in the Sichuan Basin. During this process, the types of organic matters had changed for several times.

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