LI Y Z，LIANG B，XIA L J，ZHANG H，ZHANG J，FAN L X，YE L. Physical property characteristics and controlling factors of the first member of the Dainan Formation in the steep slope zone of the Gaoyou Sag [J]. Journal of Henan Polytechnic University( Natural Science), doi: 10.16186/j.cnki.1673-9787.2024090021.

Received：2024-9-11

Revised：2024-11-27

Online：2025-07-19

Physical property characteristics and controlling factors of the first member of the Dainan Formation in the steep slope zone of the Gaoyou Sag (Online)

Li Yuezhe ^1，2，Liang Bing ¹，Xia Lianjun ¹，Zhang Hao ¹，Zhang Juan ¹，

Fan Lixin ¹，Ye Lin ²

（1. Jiangsu Oilfield Company, SINOPEC, Yangzhou 225009,Jiangsu, China；2. School of Geosciences, Yangtze University, Wuhan 430100, Hubei,China）

Abstract: Objectives In order to explore the evolution and development laws of the clastic rock reservoir of the first member of the Dainan Formation during the period of lake basin conversion from the faulted-depression to faulted type in the early stage of the faulted basin. Methods The core and logging data of 43 wells in Zhenwu-Caozhuang, Xuzhuang and Shaobo areas in the southern steep slope of the first member of Eocene Dainan Formation in Gaoyou Sag of Subei Basin were selected. Through core and microscope observation and description, powder particle size, scanning electron microscope SEM, mercury injection and other experimental techniques, reservoir compaction to reduce porosity COPL, cementation to reduce porosity CEPL and other parameters analysis, combined with the tectonic characteristics and sedimentary evolution characteristics of fault-type basin, the differences in petrology, physical properties and structural characteristics of E₂d₁ reservoir are analyzed. The sedimentary genesis of high-quality reservoirs and the main controlling factors affecting the quality difference and heterogeneity of reservoirs are also expounded. Results The lithology of different sub-members is similar, mainly feldspathic lithic quartz sandstone, the average quartz content is not significantly different, and its rock debris types are mainly igneous and metamorphic rocks, with slight differences in lithology in different periods and zones. The reservoir properties of each sub-member are obviously different, showing that the reservoir properties of the middle E₂d₁² sub-member are slightly better than those of the overlying and underlying strata. The average values of porosity and permeability are 14.16 % and 33.8×10^-3 μm², respectively. The reservoir pores are mainly composed of primary intergranular pores, intragranular dissolved pores, and intergranular dissolved pores. The pore reduction mechanism is mainly due to compaction, and cementation is a relatively minor mechanism. Conclusions The sedimentation affected by the tectonic evolution of the transition period and diagenesis are one of the better factors for the E₂d₁² reservoir. During this period, the sedimentary distribution of the fan delta front is the most extensive. The sandstone structure maturity and composition maturity are relatively high, and the anti-compaction ability is strong. The dissolution of carbonate cements is strong, forming a large number of secondary pores and improving their reservoir properties.

Key words：Gaoyou depression; E₂d₁; reservoir characteristics; heterogeneity; reservoir genesis

CLC: TE122.1