Abstract

As the low permeability and porosity, some severe problems including rapid production decline and low recovery ratio usually occur in Jimsar Shale Oil Field. Re-fracturing of horizontal wells is a good treatment to improve oil production and recovery ratio by enlarging the contact area between the wellbore and reservoir. Therefore, the field tests of horizontal well re-fracturing were carried out in Jimsar shale oil reservoir. However, it varied in effect. In this paper, based on the engineering parameters of primary fracturing, a fuzzy evaluation model was established firstly to quantify the potentiality of candidate horizontal wells for re-fracturing. For the test wells, a production history match was completed using reservoir numerical simulation method and the oil saturation before re-fracturing was obtained. By comparing the location of high-saturation area and new perforation, rationality of re-fracturing stages selection is determined. Finally, comprehensively using fracturing pressure and microseismic data, the initiation and propagation areas re-fractured was obtained, which showed the location of new fractures. Above all, the reason for poor re-fracturing effect is analyzed. The results show that quantitative index of each test well ranks low among the candidate wells, which means the test wells have the low potentiality to be re-fractured. For the test wells, numerical simulation results show that new perforations of re-fracturing are not located in high-oil-saturation area. The fracturing pressure of re-fracturing stages is generally smaller than primary fracturing, and the microseismic event locates in highly depleted area, which means large quantities of fluid flow into primary fractures and few new fractures are created during re-fracturing.

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