Study On Fracturing Optimization Design Of Carboniferous Volcanic Rocks In Che 21 Area

Based on the carboniferous volcanic reservoirs geological characteristics of Che 21 block in Xinjiang Oil field, this project researched the mechanism of hydraulic fractures propagation and fracturing fluid filtration in naturally fractured reservoirs; analyzed the relationship of fracturing material and fracturing performance; studied on the influence of fracturing parameters and perforation design on hydraulic fractures geometry. According to results of these researches, the following five main conclusions were achieved.(1) Because of the naturally fractures in the reservoir of Che 21 block, the hydraulic fractures tend to propagate into complex fractures network, and the fluid loss increase dramatically during fracturing. Therefore, it is necessary to prevent branching fractures propagation, decrease natural fractures fluid loss, and place more proppants in hydraulic fractures to improve the petroleum recovery of deep reservoir.(2) Quantitative analysis method of fracturing fluid loss along the natural fracture was established to study particle filling mechanism, using multiple particles is more benefit for reducing fluid loss in natural fracture as well as promoting the effective filling and support after fracture closing.(3) The fracturing materials optimization study indicates that:gelling fracturing fluid can satisfy the stimulation requirement in Che 21 block; the optimal fracturing strategy includes alternately injecting the 30/50 mesh proppants with 5% sand ratio and 70/120 mesh proppants with 15% sand ratio for filtration reduction, and injecting the 20/40 Xinjiang between quartz sand to prop hydraulic fracture.(4) The fracturing geometry optimization simulation implies that:the designed half-length of hydraulic fracture for volcanic breccia reservoir and tuffaceous sandstone reservoir is 120m with conductivity of 20D·cm; the designed half-length of hydraulic fracture for this tufa reservoir is 90m with conductivity of 25D·cm.(5) The fracturing parameters optimization research demonstrates that:the optimal fracturing parameters include 42% pre-pad fluid,22?24% sand ratio,1.7m~3/m sand-carried capacity for naturally fractured reservoir; the optimal fracturing parameters include 34% pre-pad fluid,18% sand ratio,1.9m~3/m sand-carried capacity for fractureless reservoir; and the optimal pump rate is 3.0-3.5 m~3/min for both reservoir.(6) The improved fracturing optimizing method has obvious stimulating effect while applicated with two dead oil wells, the production of the two wells rise to 4.77t/d and 6.36t/d respectively after fraturing.This research provides important guidelines for future fracturing design in the target reservoir and has a theoretical value for clarifying the hydraulic fracture propagation mechanism and fracturing fluid dynamic filtration mechanism in Che 21 block of Xinjiang Oil field. Furthermore, it can offer a technological support for the scientifically and efficient development as well as improve the comprehensive economic efficiency of Xinjiang Oil Field.