Abstract
In this article, the characteristics of Chang 8 reservoir of Triassic Yanchang Formation in northern Shaanxi are studied by using polarizing microscope, field emission scanning electron microscope, image particle size, X-ray diffraction analysis of clay, and constant pressure mercury intrusion. The study shows that the target layer is in a relatively stable and uniform sinking burial period after deposition, and the lithology composition in the area is relatively complex, mainly composed of debris–feldspar sandstone and feldspar sandstone, with the characteristics of fine grain and high content of interstitial material. The porosity of the reservoir is generally between 4% and 12%, with an average of 8.05%. The permeability is generally between 0.03 × 10−3 and 0.5 × 10−3 μm2, with an average of 0.16 × 10−3 μm2. Strong compaction and well-developed cementation of calcareous, siliceous, and authigenic illite are important reasons for the formation of extra-low porosity and extra-low permeability reservoirs. But at the same time, because of the protective effect of chlorite film, some residual intergranular pores are preserved, which makes the some reservoirs with relatively good physical property, forming a local relatively high-porosity and high-permeability section of the “highway.”
Highlights
Triassic Yanchang Formation is rich in oil resources in northern Shaanxi
We present study of petrology, pore structure, and diagenesis of Chang 8 reservoir in this area
Rock thin sections were identified by polarizing microscope (LEICA 4500P) with a resolution of 0.27 μm and a grain size detection range of 3 to 5,000 μm; Image particle size analysis was conducted with an image analyzer (CIAS-V3.4), and the minimum measurement length was 0.0312 mm; X-ray diffractometer (D8 Focus) was used for clay mineral analysis with the power of 2.2 kW; the rotation range of 2θ was 2° to 168, and the minimum readable step size was 0.0001°
Summary
Triassic Yanchang Formation is rich in oil resources in northern Shaanxi. After more than 30 years of continuous exploration and development, the main oil reservoir Chang 6 has a high degree of exploration and development, and the sustainable development is very difficult. With the deepening of oil and gas exploration in Yanchang Formation of Ordos Basin, new breakthroughs have been made in the exploration of Chang 8 in Wuqi, Zhijing, Ansai, and other areas in northern Shaanxi region of the basin, proving that there are rich oil resources. Low Permeability and Tight Reservoir the whole basin, and relatively few related to the northern Shaanxi area [7]. There are few research results on reservoir characteristics, pore structure characteristics, diagenetic evolution, and tight factors of Chang 8 in Wuqi, Zhijing, and Ansai Yanchang Formation in northern Shaanxi area. It is necessary to further study the reservoir in this area
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have