关键词: 超临界CO2压裂, 井间干扰, 缝间干扰, 诱导应力, 井距优化

Abstract: The staged multi-cluster fracturing of horizontal wells is a key technology for the development of unconventional oil and gas reservoirs. While rationally using fracturing-induced stress to increase the volume of reservoir reconstruction, avoiding sand plugging and fracturing interference caused by inter-well interference is a key scientific issue in fracturing process optimization. In this paper, aiming at the problem of fracture interference and interwell interference of staged multi-cluster fracturing using supercritical CO₂, a fluid-solid coupling extended finite element method is used to establish a fracture-induced stress calculation model for studying single wells and multi-wells. We consider the flow and fluid loss of supercritical CO₂ in fractures, and systematically study the disturbance stress of fracturing operation from the lithological characteristics of unconventional oil and gas reservoirs, the distribution of in-situ stress field and construction technology, etc. The propagation mechanism and stress disturbance characteristics of multi-cluster hydraulic fractures in a single well are revealed, and on this basis, the inter-well fracture interference law of multi-wells is studied. The results show that the fracturing interference limit in reservoirs with high level of stress difference and high elastic modulus is relatively large, and the formation of low level of stress difference and low elastic modulus needs to appropriately increase the cluster spacing to reduce inter-cluster interference. After well 1# is fractured, the asymmetry coefficient of hydraulic fractures in adjacent well 2# first increases and then decreases with the well spacing; when the well spacing is equal to the fracturing interference limit, the asymmetry coefficient λ reaches the maximum, and the well circumference is reformed The range is the largest, but the asymmetry of the two wings of the fracture may lead to insufficient reservoir production. This research provides a theoretical basis for horizontal well subdivision cutting and fracturing and threedimensional well pattern design optimization, which is of great significance for the efficient development of unconventional oil and gas resources in the context of the“carbon peaking and carbon neutrality”strategy.

Key words: multi-cluster fracturing, inter-well interference, inter-fracture interference, induced stress, well spacing optimization