Evaluation of Volume Refracturing Effect in Vertical Wells in Existing Blocks

doi:10.7657/XJPG20200319

Abstract

Abstract:

Based on the concepts of volume fracturing in horizontal wells, field tests of volume refracturing in vertical wells have been carried out in each oilfields of PetroChina. Because the geostress fields in vertical wells in existing blocks are complex and it is impossible to evaluate fracturing effect by using microseismic monitoring technique on a scale, this paper establishes a fracturing effect evaluation method based on well test data, flowback data and production data. The evaluation model proposed in this paper considers the true nonlinear flow in formations, and uses the product of nonlinear factor and absolute permeability to represent apparent formation permeability. The stimulated area can be classified into several secondary fracture areas according to fracture network complexity. The differences among different secondary areas on the double logarithmic curves are analyzed. Sensitivity analysis shows that the length of major fracture has a few impacts on later production, so that the major fracture length can be used as a basic parameter to do production match. Taking a vertical well in an existing block in Changqing oilfiled as a case, it is considered that premature shut-in pressure survey will result in deviations, there will be some risks of water breakthrough during volume refracturing in vertical wells. In the flowback and production stages, the effect of volume refracturing becomes poorer and poorer, which is more obvious in the core area. During the production stage, the permeability in the core area is only 13.3% of that in the flowback stage and the stimulated area in this stage is 30.0% of that in the flowback stage.

Key words: existing block, vertical well, reservoir, volume refracturing, nonlinear flow, numerical well test

CLC Number:

TE357.14

ZHANG Anshun, YANG Zhengming, LI Xiaoshan, XIA Debin, ZHANG Yapu, ZHAO Xinli. Evaluation of Volume Refracturing Effect in Vertical Wells in Existing Blocks[J]. Xinjiang Petroleum Geology, 2020, 41(3): 372-378.

Figures/Tables 8

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