Heterogeneity of a Sandy Conglomerate Reservoir in Qie12 Block, Qaidam Basin, Northwest China and Its Influence on Remaining Oil Distribution

Qingshun Gong, Zhanguo Liu, Chao Zhu (), Bo Wang, Yijie Jin, Zhenghao Shi, Lin Xie and Jin Wu
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Qingshun Gong: PetroChina Hangzhou Research Institute of Geology, Hangzhou 310023, China
Zhanguo Liu: PetroChina Hangzhou Research Institute of Geology, Hangzhou 310023, China
Chao Zhu: PetroChina Hangzhou Research Institute of Geology, Hangzhou 310023, China
Bo Wang: Exploration and Development Institute of Qinghai Oilfield Company, CNPC, Dunhuang 736202, China
Yijie Jin: China National Logging Company, Beijing 100101, China
Zhenghao Shi: Exploration and Development Institute of Qinghai Oilfield Company, CNPC, Dunhuang 736202, China
Lin Xie: Exploration and Development Institute of Qinghai Oilfield Company, CNPC, Dunhuang 736202, China
Jin Wu: PetroChina Hangzhou Research Institute of Geology, Hangzhou 310023, China

Energies, 2023, vol. 16, issue 7, 1-19

Abstract: In view of the key geological factors restricting reservoir development, the reservoir heterogeneity of an alluvial fan sandy conglomerate reservoir in the Qie12 block of Qaidam Basin, Northwest China, and its influence on remaining oil distribution, were studied according to geology, wireline logging data, and dynamic production data. This study illustrates that the difference in pore structures, which are controlled by different sedimentary fabrics, is the main cause of reservoir microscopic heterogeneity. Besides, the temporal and spatial distribution of architectural units in the alluvial fan controls reservoir macroheterogeneity. Our results show that the thick sandy conglomerate develops two types of pores, two types of permeability rhythms, two types of interlayers, two types of interlayer distribution, two types of effective sand body architecture, and four types of sand body connecting schemes. The strongest plane heterogeneity is found in the composite channel unit formed by overlapping and separated stable channels of the middle fan, and the unit’s permeability variation coefficient is >0.7. However, the variation coefficient in the range of 0.3–0.5 is found in the extensively connected body unit sandwiched with intermittent channels of the inner fan. The distributions of the remaining oil vary significantly in different architectural units because of the influence of reservoir heterogeneity, including distribution patterns of flow barriers, permeability rhythm, and reservoir pore structures. The composite channel unit formed by overlapping and separated stable channels, or the lateral alternated unit with braided channel and sheet flow sediment of the middle fan, is influenced by the inhomogeneous breakthrough of injection water flowing along the dominant channel in a high-permeability layer. The microscopic surrounding flow and island-shaped remaining oils form and concentrate mainly in the upper part of a compound rhythmic layer. Meanwhile, in the extensively connected body unit sandwiched with intermittent channels of the inner fan, poor injector–producer connectivity and low reservoir permeability lead to a flake-like enrichment of the remaining oil.

Keywords: reservoir heterogeneity; remaining oil; sandy conglomerate reservoir; alluvial fan; Qaidam Basin (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
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