Xinjiang Petroleum Geology ›› 2025, Vol. 46 ›› Issue (1): 39-47.doi: 10.7657/XJPG20250105

• OIL AND GAS EXPLORATION • Previous Articles     Next Articles

Architecture Characterization of Sandy Braided River Reservoirs: A Case Study of Guantao Formation in Western Block 7 of Gudong Oilfield

DU Juan1(), YIN Yanshu1(), WEN Bin2, REN Li2, WU Wei3   

  1. 1. MOE Key Laboratory of Hydrocarbon Resources & Exploration Technology, Yangtze University, Wuhan, Hubei 430100, China
    2. Lushang Oilfield Operation Area, Jidong Oilfield Company, PetroChina, Tangshan, Hebei 063200, China
    3. Shengli Oil Field Dongsheng Jinggong Petroleum Development (Group) Stock Co., Ltd., Shengli Oilfield, Sinopec, Dongying, Shandong 257001, China
  • Received:2024-09-24 Revised:2024-10-20 Online:2025-02-01 Published:2025-01-24

Abstract:

The sublayers from N1g45 to N1g16 of the Guantao formation in western Block 7 of the Gudong oilfield are typical of braided river deposits, with complex internal sandbody architectures. A detailed analysis of the reservoir architecture is necessary to understand its impact on oil and gas development. By using the Miall’s architectural element analysis method, and constrained by modern braided river scale, the sandbody architecture was characterized. Combining dynamic and static methods, the reservoir architectures were validated, and their influences on waterflood performance and residual oil distribution were identified. The research results show that the study area exhibits sandy braided river deposits, mainly with four sedimentary architecture units: braided river channels, mid-channel bars, overbanks, and floodplains. The braided flow zone is 150-750 m wide, with a width-to-thickness ratio ranging from 47 to 74. Within the braided flow zone, there are four types of architectural patterns: braided river channel-braided river channel, mid-channel bar-mid-channel bar, braided river channel-mid-channel bar-braided river channel, and mid-channel bar-braided river channel-mid-channel bar. The mid-channel bars have average length of 250-350 m and average width of 110-140 m, with a length-to-width ratio of 2.20-2.50. The ratio of mid-channel bar area to channel area ranges from 0.36 to 0.51. The mid-channel bars typically develop 2-4 fall-silt seams with their extension ranging from 70 to 150 m, which are nearly horizontal, with interlayer dip angles between 0.9° and 2.3°. Production performance reveals that due to poor petrophysical properties at the edges of architecture units, oil and gas flows are impeded at the architectural junctions where residual oil will be enriched locally. In contrast, the main parts of the architecture units show good reservoir connectivity and development effects.

Key words: Gudong oilfield, Guantao formation, reservoir architecture, braided river, mid-channel bar, fall-silt seam, residual oil

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