Xinjiang Petroleum Geology ›› 2025, Vol. 46 ›› Issue (5): 582-590.doi: 10.7657/XJPG20250508

• RESERVOIR ENGINEERING • Previous Articles     Next Articles

Main Controlling Factors of Tilted Oil-Water Contact of Shallow Heavy Oil Reservoirs of Qigu Formation in Block HQ1,Karamay Oilfield

YAN Yonghe1(), LI Haibo1, ZHU Aiguo1, ZHANG Wuji1, ZHANG Jing1, LIU Gang2, CHEN Yanhui1, WANG Biao1   

  1. 1. Research Institute of Exploration and Development, Xinjiang Oilfield Company, PetroChina, Karamay, Xinjiang 834000, China
    2. Research Institute, Shaanxi Yanchang Petroleum (Group) Co. Ltd., Xi'an, Shaanxi 710065, China
  • Received:2024-12-02 Revised:2025-01-03 Online:2025-10-01 Published:2025-09-30

Abstract:

In order to determine the oil-water relationship and its controlling factors in the shallow heavy oil reservoirs of the Qigu formation in Block HQ1, Karamay oilfield, the study focuses on the h-4 well area, which exhibits significant oil-water distribution complexities at the reservoir margins. Using the data of dense well pattern and test analysis, the influences of sand body distribution, hydrodynamic conditions, reservoir properties, hydrocarbon charging pressure, and tectonic activities on the oil-water contact (OWC) are identified. The h-4 well area demonstrates distinctive OWC characteristics, where the water boundary is parallel with the structural line in the east, and the water boundary obliquely intersects the structural line in the west, resulting in a tilted OWC. This tilted OWC is believed to have been resulted from the periodical fracture opening due to tectonic activities and the OWC adjustment hysteresis is caused by oil viscosity variation, indicating a coupled mechanism of tectonism and unsteady reservoir formation. The fracture opening in the western part of the study area provided oil migration pathways, facilitating oil accumulation in the Qigu formation. Subsequent fracture sealing and reactivation events led to reservoir compartmentalization, creating a OWC that is high in west and low in east. Oil biodegradation shaped a similar viscosity feature. The combined effects of tectonic activities and viscosity variations significantly retard horizontal adjustments of OWC, characterizing the reservoir as a unsteady hydrocarbon accumulation system.

Key words: Karamay oilfield, Block HQ1, Qigu formation, heavy oil reservoir, oil-water contact, oil viscosity, unsteady reservoir

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