裂缝诱导应力场影响因素敏感性评价

The sensitivity evaluation on influence factors of fractures induced stress field

为了更好地利用诱导应力场干扰使裂缝发生转向,提高裂缝复杂程度,以裂缝产生的水平诱导应力差为评价指标研究了不同因素对诱导应力差的影响程度。基于应力叠加原理,简化传统诱导应力模型物理量关系,推导出了多条裂缝叠加的水平诱导应力差数学模型,并分析了影响裂缝诱导应力差的单因素变化规律。结合正交试验法和灰色关联理论,评价了各个参数影响的敏感性排序,并提供了多因素共同作用下最佳参数组合的确定方法。结果表明该评价方案中各影响因素对水平诱导应力差的敏感性排序由强到弱依次为裂缝净压力、地层泊松比、裂缝条数、裂缝长度、裂缝间距以及水平距离。现场应用效果证明该评价方法能够确定各因素对储层应力场改造的重要性,为优化水平井分段压裂裂缝参数提供了有效依据。

In order to make better use of induced stress field disturbance to cause fractures steering, and increase the complexity of fractures, this paper selects horizontal induce stress difference as the evaluation standard, and studies the impacts of different fac- tors on induced stress difference. Based on the stress superposition principle and simplifying the physical quantities relationship of the traditional stress model, the mathematical model of horizontal induce stress difference of multiple fractures superimposing is de- duced, and the change law of influence factors of fractures induced stress difference is analyzed. Then combined with the orthogo- nal experiment and gray relational theory, the sensitivity degree of each influence factor is evaluated and the method to determine the optimal parameter combination under the action of multiple factors is provided. The results show that, in this evaluation pro- gram, the sensitivity descending order of the factors is fracture net pressure, Poisson＇s ratio, fracture number, fracture length, frac- ture spacing and horizontal distance. According to the application in the gas field, the evaluation method can determine the impor- tance of each factor on the transformation of the reservoir stress field, which provides an effective basis to optimize horizontal well staged fracturing fracture parameters.