DOI: 10.3724/SP.J.1249.2018.04345

Journal of Shenzhen University Science and Engineering (深圳大学学报理工版) 2018/35:4 PP.345-352

Production capacity prediction model for multi-stage fractured horizontal well coupled with imbibition in tight oil reservoir

In the procedure of large-scale hydraulic fracturing in tight and shale oil formation, the flow-back efficiency is only up to 10%. Parts of oil could be replaced out by the fracturing fluid retained in formation through the imbibition process, leading to the increase of single well productivity. In order to characterize the effects of fracturing fluid retention and imbibition on the performance of fractured horizontal well in tight reservoir, a mathematical model considering fluid imbibition for well production prediction is developed by using Darcy's law, in which the imbibition is represented in terms of capillary pressure between matrix and fracture, and the fluid flow in low-permeability reservoir is modeled by incorporating the threshold pressure gradient. A semi-analytical solution is achieved by applying Laplace transform and Stehfest numerical inversion. The analytical solution is also verified by numerical solution using Eclipse software. The effects of fracturing fluid retention, formation wettability and threshold pressure gradient on the performance of fractured horizontal well in tight oil are then analyzed by using the novel model. The results show that the higher amounts of fracturing fluid retention and the lower value of threshold pressure gradient could be helpful to enhance well production. In order to increase well production, the capillary pressure should be weaken in oil-wet reservoir, while the imbibition effect should be enhanced in water-wet formation. The novel model for fractured horizontal well in tight oil provides a theoretical foundation for analysis of oil recovery using imbibition and the further development of tight oil formation.

Key words:tight oil,imbibition,fractured horizontal well,productivity calculation,cross flow,composite model

ReleaseDate:2018-07-26 10:51:02

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