Study on parameters influencing fracture propagation and the influence of sensitive parameters on CO2 enhanced oil reservoirs in Gulong shale oil

Abstract

The CO₂ fracturing of shale oil reservoirs is influenced by engineering and geological parameters. In this paper, the CO₂ fracturing in Gulong shale oil is taken as the research object. First, the production dynamic characteristics and the advantages and disadvantages of CO₂ fracturing effect in Gulong shale oil reservoirs are summarized. Second, the influencing factors such as crude oil viscosity, initial oil to gas ratio, and permeability on CO₂ enhanced oil production are analyzed, and the law of sensitive factors affecting CO₂ enhanced oil reservoirs is summarized. Third, by comparing different blocks, the relationship between CO₂ intensity and cumulative oil production is elucidated. Results show that: (a) under the same injection volume, the viscosity of the fracturing fluid increases from 40 mPa·s to 120 mPa·s, the maximum length of a single fracture decreases by 32 m, and the maximum fracture width increases by 0.84 mm. (b) When the cluster spacing is 7 m, there is severe interference between the seams. After increasing the spacing between clusters to 15 m, there is a certain loss in the length of fracture propagation. (c) The viscosity of crude oil is directly proportional to the CO₂ oil change rate. When the oil to gas ratio is low, it has an auxiliary effect on CO₂ assisted fracturing in oil production increasing.