富台潜山凤山组现今地应力场数值模拟及 有效裂缝分布预测

为明确富台潜山凤山组现今地应力特征,根据钻井诱导缝走向及井壁崩落方向对其现今地应力方向进行判断,并通过测井资料及经验公式计算得出关键井现今地应力。通过确定岩石力学参数并建立有限元模型,以关键井地应力为约束条件,对研究区凤山组现今地应力场进行数值模拟,分析现今地应力场对裂缝有效性的影响,进而预测有效裂缝分布。研究结果表明,富台潜山凤山组水平最大主应力为90.6~181 MPa,为北东东—南西西方向;水平最小主应力为61.9~110 MPa,为北北西—南南东方向。断裂带为应力低值区,东、西两侧低洼地带为应力高值区,背斜核部为应力分布稳定区,背斜两翼存在应力变化梯度带。北东东—南西西方向为研究区凤山组有效裂缝优势走向,有效裂缝发育最有利地区为背斜核部,其次为背斜两翼,东、西两侧低洼地带则不利于有效裂缝的保存。

Numerical simulation of current in-situ stress field of Fengshan formation and distribution prediction of effective fracture in Futai buried hill

In order to analyze the characteristic of current in-situ stress field of the Fengshan formation, using the strike of drilling inducing fracture and direction of hole-wall collapsing, the direction of current in-situ stress of the Fengshan formation was judged, and the value of current stress is calculated by logging data and empirical formula. Based on above, taking ground stress results of key wells as constraint condition, horizontal distribution of current in-situ stress field was analyzed by numerical simulation with confirming rock mechanical parameters and building finite element model. Meanwhile, the impact on fracture efficacy of current in-situ stress field was analyzed. The result demonstrates that, the maximal horizontal principal stress is 90.6-181 MPa, and the direction is close to NEESWW;the minimal horizontal principal stress is 61.9-110 MPa, and the direction is close to NNW-SSE. Low value of current stress appears in faults. The value of current stress in arch core distributes stably. There are two stress gradient zones in anticlinal flanks. High value of current stress appears in the low-lying areas near the east and west sides. According to the simulation results, the impact of stress on the fracture efficacy was analyzed. Effective fracture strike of the Fengshan formation is close to NEE-SWW. The arch core is the best area for effective fracture development, followed by the anticlinal flanks and the low-lying areas.