Study on the Characteristics of Fracturing Fracture Propagation and Turning in Carbonate Dry Hot Rock

Thermal reservoir stimulation is a necessary means to achieve effective development of dry hot rocks. Carbonate rock is a typical type of dry hot rock reservoir, it has strong heterogeneity and natural fractures and holes. Fracturing and controlling of hydraulic fracture propagation path is necessary to effective development of Carbonate rockd reservoir. At present, there was relatively little research on the propagation law of directional fracturing fractures in carbonate rocks. In response to the above issues, based on the analysis of the pore characteristics of carbonate rock salt reservoirs in a certain geothermal field, a method for preparing samples with vuggy characteristics was established. The true triaxial hydraulic fracturing physical test was used to study the interference characteristics between the propagation path of hydraulic fracturing fracture and the vuggy under different in-situ stress differences. The propagation path of fracturing fracture was quantitatively studied by using the extended finite element method. The results show that: 1. Under low horizontal in-situ stress difference (K ≤ 0.15), the hydraulic fracturing fracture will expand non-plane when encountering the hole, the smaller the horizontal geo-stress difference is, the larger the turning distance is, and the more complex the fracture morphology is. 2. Under medium horizontal in-situ stress difference (0.15 < K < 0.36), the horizontal geo-stress difference will overcome the stress concentration of the vuggy and carry on the plane expansion, but it will be caught by the hole after encountering the hole, and cannot continue to expand. 3. Under high horizontal in-situ stress difference (K ≥ 0.36), the horizontal in-situ stress difference will overcome the stress concentration of the vuggy and carry on the plane expansion, and will directly pass through the vuggy and continue to expand after encountering the hole. 4. With the increase of horizontal in-situ stress difference, the fracture pressure corresponding to hydraulic fracture decreases gradually. The related research results can be used in optimization design of carbonate dry hot rock thermal storage fracturing process.