关键词: 分支井构型, 疏松砂岩油藏, 临界生产压差, 塑性破坏深度, 井眼稳定性

Abstract:

The junction stability of multilateral well at different geometry and orientations in loose sand reservoir is very poor. Even though the production drawdown pressure is lower than 1 MPa, junctions collapse and block laterals. Consequently, there is a limited contribution of laterals to productivity. In order to enhance the stability of the multilateral well and increase the critical drawdown pressure, special treatment should be enforced to the junctions. In the normal fault in-situ stress field, regardless of the junctions, the main bore direction should be extended along with the in-situ minimum horizontal 〖JP+3〗principle stress as close as possible. Depth and width of failure area are severely influenced by the build-up rate of laterals.The relationship between the increase of build-up rate and reduction of junction plastic failure depth is found to follow the power function in the same production drawdown pressure. Provided the length and included angle of multilateral well are given, higher build-up rate is,the stability of multilateral well is much better. Another key factor of multilateral well stability is the interval between laterals. Interference could be ignored when interval is larger than 40 m if laterals arranged on different sides, otherwise, the interval should be larger than 45 m. In open hole or screen pipe completion, junction plastic failure depth and sanding swept area increase in function of exponent along with the growth of production drawdown pressure.

Key words: multilateral well configuration, loose sandstone reservoir；critical production drawdown pressure, plastic failure depth, wellbore stability