Optimization Study of Unequal Fracturing Length for Rhombus Inverse Nine-spot Well Pattern in Low Permeability Reservoir

Abstract

Abstract:

The inverse rhombus nine-spot well pattern is widely used in the development of low permeability reservoirs, but there are few extensive and intensive studies for the fracture length ratio of production wells and water-injection wells at different locations. Based on the parameters in a low permeability reservoir of Changqing Oilfield, a numerical simulation model was established. In this paper, to study the different configuration modes effect of fracture water-flooding, different fracture lengths were disposed in the side parts of the production wells, the corners of the production wells and injection wells at the inverse rhombus nine-spot well pattern. Streamline simulation and numerical simulation results show that the fracture length of injection wells is key to reservoir fluid production and water flooding effect. The fracture of side portion of the production wells is easier to flow into the water compared with the fracture at the corner section of the production wells, and has a great influence on the water-cut of the reservoir. In the inverse rhombus nine-spot well pattern, it is required to optimally design unequal lengths of fractures in low permeability reservoir. Fractures effects of the length of the side parts of the production wells on water-flooding development can be divided into three distinct phases. With the length of the injection wells fracture increasing, the early (Ⅰ-stage) curve becomes long, the medium term (Ⅱ-stage) curve is shortened, and the later period (Ⅲ-stage) curve almost has no change at all. With the increase of the fracture length at corner section of a production well, oil recovery of the reservoir increases, and there exists a “reversal” phenomenon when the fracture length is too long at corner section of a production well. With the fracture length of injection wells increasing, the optimum fracture length at the corner section of the production well is reduced, while the fracture length of the side parts of the production well increases. The research results have important guiding significance for optimizing the crack design, improving the sweep coefficient and development effect of diamond-shaped anti-nine-point well pattern in low permeability reservoir.

Key words: low permeability reservoir, rhombus inverse nine-spot well pattern, water-flooding, unequal fracture length, fracturing

CLC Number:

TE319

XU Zhenhua, LIU Pengcheng, WANG Wenhuan, XIA Jing, HAO Mingqiang, PENG Huanhuan. Optimization Study of Unequal Fracturing Length for Rhombus Inverse Nine-spot Well Pattern in Low Permeability Reservoir[J]. Geoscience, 2017, 31(03): 606-613.

Figures/Tables 9

Fig.1 Geological model plane grid pattern diagram

Fig.2 Grid simulation well pattern

Fig.3 Simulation of flow patterns in well patterns with different fractures

Table 1 Streamline simulation well crack parameters setting

图3 编号	注水井裂缝穿透比	角井裂缝穿透比	边井裂缝穿透比	生产2年综合含水率/%	采出程度/%
(a)	0.23	0.23	0.23	39.96	38.71
(b)	0.23	0.23	0.63	64.71	36.63
(c)	0.23	0.63	0.23	35.16	40.44
(d)	0.63	0.23	0.23	69.11	43.55

Fig.4 The FOE curve with the fracture penetration ratio of 0.17 in water injection wells

Fig.5 The FOE curve with the fracture penetration ratio of 0.37 in water injection wells

Fig.6 The FOE curve with the fracture penetration ratio of 0.57 in water injection wells

Fig.7 The FOE curve with the fracture penetration ratio of 0.77 in water injection wells

Table 2 Optimization of cracks in side wells and angle wells in different water injection wells crack penetration ratio of the case

分组编号	注水井穿透比	角井优化穿透比	边井优化穿透比	生产2年综合含水率/%	原油采出程度/%
1	0.17	0.77	0.43	40.3	57.00
2	0.37	0.70	0.50	60.7	58.32
3	0.57	0.63	0.63	75.2	59.51
4	0.77	0.57	0.70	82.1	60.57

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