Analysis of microscopic pore structure and seepage mechanism of the Fuyang Oil Reservoir in Chaoyanggou Terrace

Abstract

Based on the core samples of the typical channel sandstone from Fuyu and Yangdachengzi Reservoir, CT scanning physical experiments and digital core reconstruction technology were used to characterize the microscopic pore structure and analyze the seepage mechanism of low-permeability sandstone. By means of quantitative analysis of mineral composition and scanning electron microscopy, the types and contents of core minerals were identified, and three pore types were classified: intergranular pores, intragranular pores and interstitial pores. The equivalent radius distribution curve of the total pore space was calculated, showing an obvious bimodal structure, and the peak values were mainly approximately 50 μm and 1 μm. The reconstructed digital core model was used to simulate oil-water two-phase seepage. The simulation results showed that the oil-water coseepage zone of Fuyu Reservoir was wide and the residual oil saturation was approximately 30%-45% in the process of oilfield development. The residual oil saturation of Yangdachengzi Reservoir was approximately 40%-55%. Under the action of capillary force and hydrophilicity, the water phase preferably entered the small pore channel, and the small pore channel formed the water lock before the large pore channel. Compared with the Fuyu Reservoir, the throat radius of Yangdachengzi Reservoir was smaller, and the number was greater, which made it easier to form a water lock, and the residual oil saturation was higher.

Keywords

• fuyu reservoir
• yangdachengzi reservoir
• digital core technology
• pore structure
• percolation mechanism
• chaoyanggou terrace