超临界CO2分段多簇压裂井间干扰规律研究

水平井分段多簇压裂是非常规油气藏开发的关键技术，在合理利用压裂诱导应力增大储层改造体积的同时，避免井间干扰所导致的裂缝砂堵和压裂窜扰，是压裂工艺优化中的关键科学问题。文章针对超临界CO₂分段多簇压裂的缝间干扰和井间干扰问题，采用流固耦合的扩展有限元方法研究单井及多井裂缝诱导应力演化特征，充分考虑裂缝内超临界CO₂流动和滤失，从非常规油气储层岩性特征、地应力场分布及施工工艺等多方面对压裂扰动应力进行系统研究，揭示单井分段多簇压裂缝扩展机制及应力扰动特征，在此基础上研究多井井间压裂缝干扰规律。结果表明：高水平应力差、高弹性模量的储层中压裂干扰界限较大，低水平应力差、低弹性模量地层需适度增大簇间距，减小簇间干扰；老井压裂后，其邻井压裂缝非对称系数随井间距呈先增大、后减小的趋势；当井间距等于压裂干扰界限时，非对称系数λ达到最大，且井周改造范围最大，但裂缝两翼的非对称性可能导致储层动用不充分。本研究为水平井细分切割压裂和立体式井网设计优化提供理论基础，在“双碳”战略背景下对非常规油气资源高效开发具有重要意义。

Research on Inter-well Interference Law of Supercritical CO2 StagedMulti-cluster Fracturing

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.