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页岩水平井重复压裂现地应力场计算方法
A method for calculating current in-situ stress field before refracturing horizontal shale wells
李奎东1 纪国法2,3 刘 炜1 肖佳林1 李少明1 熊力坤1
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DOI:
作者单位:1. 中国石化江汉油田分公司石油工程技术研究院 2. 长江大学·非常规油气湖北省协同创新中心 3. 长江大学·湖北省页岩气开发工程技术研究中心
中文关键字: 页岩 水平井 重复压裂 现地应力场 应力转向
英文关键字:Shale; Horizontal well; Refracturing; current in-situ stress field; Stress diversion
中文摘要:    页岩水平井分段压裂改造后产能递减快、稳产期短,需要进行重复压裂以提高页岩气井的产量和最终可采资源量,而重复压裂的成功与否决定于选井选层工作和压裂优化设计,尤其是弄清重复压裂前现地应力场的分布情况以确保满足老缝张开与新缝起裂条件。为此,充分考虑构造运动、储层天然裂缝分布情况及层理关系,基于测井数据和施工压力数据,构建了原地应场计算模型;并依据等效主裂缝理论,采用加权平均法计算缝内净压力,在生产衰竭诱导基础上,通过线性叠加原理建立了页岩多段簇水平井重复压裂现地应力场计算方法。结果表明:①页岩水平井原地应力计算方法中,原地应力场水平应力构造系数由压裂施工数据反演得到,可真实反演原地应力场大小;②根据不同裂缝段簇和孔隙压力降低产生的诱导应力变化特征建立的诱导应力场计算方法,对实例井的计算结果和压后产量变化都显示长水平段多段簇压后裂缝诱导应力已使地应力场发生转向。结论认为:页岩水平井重复压裂现地应力场计算方法能够为现场重复压裂优化设计提供理论支持。
英文摘要:    After staged fracturing is implemented for horizontal shale wells, the productivity declines rapidly and the stable production period is short. So, refracturing shale-gas wells is needed to improve both production and ultimate recoverable resources. The success of refracturing is dependent on well and layer selection, and optimal fracturing design, and it is particularly necessary to determine the distribution of current in-situ stress field before this refracturing to ensure certain conditions for opening old fractures and splitting new fractures. Based on well-logging and construction pressure data, a model to calculate the in-situ stress field was established with full consideration of tectonic movement, distribution of natural fractures in reservoirs, and bedding correlation. Then, according to the theory of equivalent principal fracture, the net pressure within fractures was calculated by means of the weighted average method.Fin ally, on the basis of induced production depletion, one method for calculating the present in-situ stress field before multi-staged and cluster refracturing was established according to the linear superposition principle. Results show that (1) speaking of the meth ds for calculating the in-situ stress of horizontal shale wells, the horizontal stress construction coefficient of in-situ stress field is inverted from fracturing data, and it can reflect the true value of in-situ stress field; and (2) some results are obtained for typical well by the induced stress field calculation method which is established according to the change characteristics of induced stress generated by different fracture stages/clusters and pore pressure drop, and both these results and the change of postfrac production rate show that the in-situ stress field is diverted by fracture-induced stress after the multi-staged/cluster fracturing in long horizontal section. In conclusion, this method for calculating the present in-situ stress field before refracturing horizontal shale wells can provide theoretical support for optimal design.
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国内统一连续出版物号:CN51-1159/TE |国内发行代码: |国际标准出版物号:ISSN1673-3177 |国际发行代码:
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