新疆油田七东1区克下组地应力特征及人工裂缝延伸方向*

新疆油田七东1区克下组在压裂施工过程中,通过微地震监测存在水平裂缝的可能。利用凯瑟尔实验测定该区块水平地应力大小及构造应力系数,建立了该区块组合弹簧模型的地应力计算模型,利用测井资料分析了七东1区地应力分布规律。分析结果表明:七东1区地应力状态存在明显的分界线,分界线大致为东北-西南走向;区块西北部最小水平主应力大于垂直主应力,处于逆断层应力状态;区块东南部最小水平主应力小于垂直主应力,处于正断层应力状态,中间存在走滑断层应力状态过渡带;因此压裂裂缝形态具有明显的区域性分布,即东南部为垂直裂缝,西北部压裂形成水平裂缝。分析结果与水力裂缝形态的分布规律一致。该地区存在水平裂缝的新认识,将对压裂工艺的改进及提高小层动用程度具有重大意义。

The in-situ stress characteristics and fracture extension direction on lower Karamay formation of Qidong-1 Area in Xinjiang Oilfield

The fracture form on lower Karamay formation of Qidong-1 area in Xinjiang Oilfield has obvious regional distribution, namely for the vertical fracture in southeast, and the horizontal in northwest. Basing on the Kaiser experiment to determine the horizontal in-situ stress and tectonic stress coefficient of this block, the in-situ stress calculative model of composite spring model in this block is established. Then the in-situ stress distributive rule can be analyzed by logging data. The results show: there is an obvious dividing line in the in-situ stress distribution of Qidong-1 area, which is rough from northeast to southwest. The minimum horizontal stress in northwest is greater than the vertical effective stress, meaning this region is a reverse stress fault. The minimum horizontal stress in southeast is less than the vertical effective stress, meaning this region is the normal stress fault. The middle of the block is transition zone of the strike-slip fault. The results consistent with the distributive rule of fracture form, which can guide the later drilling and fracturing operation.