Abstract
When cold fluid is injected into low-temperature, low-pressure, low-permeability reservoirs containing wax-bearing heavy oil, cryogenic paraffin deposition and heavy oil condensation will occur, thus damaging the formation. Moreover, the formation pressure coefficient is low and the working fluid flowback efficiency is low, which affects the fracturing stimulation effect. Therefore, an in situ heat/gas clean foam fracturing fluid system is proposed. This system can ensure that conventional fracturing fluid can create fractures and carry proppant in the reservoir, generate heat in situ to avoid cold damage, reduce the viscosity, and improve the fluidity of crude oil. The in situ heat fracturing fluid generates a large amount of inert gas while generating heat, thus forming foam-like fracturing fluid, reducing fluid loss, improving proppant-carrying performance, improving gel-breaking performance, effectively improving crack conductivity, and is clean and environmentally friendly. Based on the improved existing fracturing fluid system, in this paper, a new type of in situ heat fracturing fluid system is proposed, and a system optimization evaluation is conducted through laboratory experiments according to the performance evaluation standard of water-based fracturing fluid. Compared with the traditional in situ heat fracturing fluid system, the fracturing fluid system proposed in this study generates a large amount of inert gas and form foam-like fracturing fluid, reduces fluid loss, enhances the proppant-carrying capacity and gel-breaking performance, improves crack conductivity, the gel without residue and that the gel-breaking liquid is clean and harmless.
Highlights
Fracturing stimulation can effectively transform low-pressure, low-permeability reservoirs, and increase productivity
A new type of in situ heat/gas clean foam fracturing fluid system is proposed based on low-pressure, low-temperature reservoirs containing wax-bearing heavy oil
The fracturing fluid system consists of heat-generating agent A + heat-generating agent B + 1 # catalyst + 506 thickener + 506 crosslinking agent3 + gel breaker + low-temperature breaker + clay stabilizer + fracturing assistant + pH regulator; the system is suitable for low-temperature, low-pressure, low-permeability reservoirs containing waxbearing heavy oil
Summary
Fracturing stimulation can effectively transform low-pressure, low-permeability reservoirs, and increase productivity. A new type of in situ heat/gas clean foam fracturing fluid system is proposed based on low-pressure, low-temperature reservoirs containing wax-bearing heavy oil. According to the reservoir characteristics of XX oilfield, the temperature-increasing interval of the in situ heat system was 50–60 °C, so 1–2 mol/L heat-generating agents A and B were the optimal range. The fracturing fluid system consists of heat-generating agent A + heat-generating agent B + 1 # catalyst + 506 thickener + 506 crosslinking agent3 + gel breaker + low-temperature breaker + clay stabilizer + fracturing assistant + pH regulator; the system is suitable for low-temperature, low-pressure, low-permeability reservoirs containing waxbearing heavy oil. Using the determined optimal concentration of the heat-generating agent and catalyst, the sand-carrying performance evaluation of the fracturing fluid system and the system concentration were optimized. Photographic observations were obtained at 30-min intervals, and the measurement duration was 2 h
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