Characteristics of Jurassic Fault and Its Control Effect on Hydrocarbon Accumulation in the Block 4 in the Center of the Junggar Basin
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    Abstract:

    Objectives: Block 4 is located in the middle of the Junggar basin. It contains vast quantities of recoverable oil and gas, and has huge potential for exploration and production, but in the low degree of exploration. Combing fault geometry with kinematics features, effects of Jurassic faults control hydrocarbon reservoirs are studied in this research. Methods: On the basis of the study of regional tectonic stress field, dividing the type of fracture; analyzing the tectonic environment formed by fracture, and summarize the structural style of fault through intricate layer and fault interpretation, combining coherence attribute and time slice to carry out fault combination. Statistical the type of the fault (fault properties, strikes, tendencies and whether it is source fault for classification of fracture and comparison of subregional differences, by means of the balanced profile technique, calculating the fracture activity rate and the fracture kinematics characteristics. Discussing how the oil reservoir controlled by fault according to the correlation between drilling oil and gas display level and the distance from oil source fracture, compilation of reservoir profile and calculation of SGR of the upper level of drilling reservoir Results: Through statistics, the number of normal faults on the plane is more than that of the reverse fault, and there is almost no relative dominance or tendency in the normal fault while the strike of the reverse fault is NW tending to be SW. Most of the faults in the work area are cut to the J1b, which can be defined as the source fault. The fault activity rate shows that the rate of D1—D1 west is 0.80~6.99 m/Ma, D2 north is 1.36~9.50 m/Ma,D6 is 0.80~6.99 m/Ma. As a whole, the fracture activity rate is the highest during the period of the middle Jurassic(J2x, J2t); the fracture activity rate is the medium level during the early Jurassic(J1b, J1s), the fault activity rate is the lowest during the late Jurassic(J3q). In the study area, four types of concealed traps are identified; the lithological traps include fault communication and fault isolation, and structural lithological traps include fault occlusion and fault clamping. The results of SGR calculation of the fault shows that the lateral sealing ability of the faults in the upper dip direction of the J2x of D8 well is better, and the lateral sealing property of the upper dip direction of the J2t reservoir in D11 well is poor. Conclusions: The Jurassic faults in the study area are mainly strikeslip faults, with four patterns: positive flower structure, negative flower structure, upright strike slip fault with a lack of branch faults, and Isolated or echelon middle angle reverse fault. Dong 1— Dong 1 western area is characterized by middle angle isolated or echelon fracture abnormal faults. Some of the faults have positive flower structure which represent extension in the early stage of Jurassic and compresso- shear in the and late stage of Jurassic. Dong 2 northern area has the characteristics of negative flower structure with the mechanism of transtension. Dong 6 area has the feature of negative flower and strike- slip faults with lack of brunch. Those features show extension happened in the early stage of Jurassic and transtension happened in the middle and late stage of Jurassic. Temporality, the highest average fault activity rate happened in the middle stage of Jurassic. The early stage of Jurassic average fault activity rate is lower than the rate in the middle stage of Jurassic and better than the rate in the late stage of Jurassic is the lowest Spatially, Dong 2 northern area has the highest average fault activity rate in the early to middle stage of Jurassic, the rate is lower than Dong 1— Dong 1 western area in the late stage of Jurassic. Dong 6 area has the lowest average fault activity rate during Jurassic. The effects of how faults control hydrocarbon migration show in the following aspects: the faults in reservoir rocks is the primary control of hydrocarbon enrichment; faults traps is the main storage space for hydrocarbon; lateral sealing of trap influence hydrocarbon accumulation.

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LIU Hui, HU Xiuquan, LIANG Jiaju, XU Guosheng, DAN Yong, XIANG Kui, ZHAO Yongfu, ZHANG Jianwu.2018. Characteristics of Jurassic Fault and Its Control Effect on Hydrocarbon Accumulation in the Block 4 in the Center of the Junggar Basin[J]. Geological Review,64(6):1489-1504.

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History
  • Received:March 27,2018
  • Revised:
  • Adopted:
  • Online: November 15,2018
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