摘要
地应力求取及可压性评价是进行页岩压裂设计的基础,由于页岩构造和组分的特殊性,目前尚未建立统一的页岩可压性评价方法。为此,以川东南某页岩气区块为研究对象,基于该页岩气区块十余口压裂井196段施工数据,在建立井口压力与井底压力实时转换模型的基础上,反演了该区块储层的破裂压力和水平主应力,反演结果与岩心测试结果相对误差低于10%;综合考虑储层岩石特性和施工参数,选取脆性指数、最小水平主应力梯度、储层破裂压力梯度、两向水平主应力差异系数、综合砂液比、滑溜水占比、40/70目和30/50目支撑剂占比等7个参数作为评价参数,通过变异系数法获得各评价参数的权重,建立了基于应力反演的页岩可压性评价方法。利用该方法计算了目标区块4口放喷测试井的综合可压性指数,发现综合可压性指数与测试产量具有较好的正相关性。其中1口井一些层段在利用该方法计算地质特征相似已压裂层段综合可压性指数的基础上,通过调整施工参数,使综合可压性指数提高。研究表明,基于应力反演的页岩可压性评价方法可充分利用施工数据,指导页岩气井压裂施工,对于实现页岩气井"一段一策、精细压裂",提高单井产能及区块整体开发效果具有重要意义。
The evaluation of in-situ stresses and fracability is the basis of shale fracturing design. However, it is still challenging to establish a unified fracability evaluation method due to the unique structure and composition of shale. A new evaluation method of shale fracability based on stresses inversion was developed in this paper with a southeastern Sichuanshale block as the research object. The inversions of break down pressure and horizontal principal stresses were performed for reservoirs in the block with the fracturing data of 196 intervals of more than 10 wells after establishing a real-time conversion model for wellhead and bottom hole pressure. The relative error between inversion results and core test results was less than 10%. Depending on the comprehensive consideration of rock characteristics and fracturing parameters of the reservoirs, seven evaluation parameters were selected: the brittleness index, minimum horizontal principal stress gradient, fracture pressure gradient, difference coefficient of minimum and maximum horizontal stresses, comprehensive sand to liquid ratio, proportion of slick water, and proportion of 40/70-mesh and30/50-mesh proppant. The weight of each evaluation parameter was determined by the coefficient-of-variation method.The resulting evaluation method for shale fracability was implemented to calculate the comprehensive fracability indexes of four wells subjected to blowout test wells in the target block, and comprehensive fracability index was found to be positively correlated well with test production. Specifically, comprehensive evaluation parameters were improved with respect to intervals of one well after the adjustment of fracturing parameters based on the evaluation and calculation of the comprehensive fracability index of fractured intervals with similar geological characteristics. The research shows that the new approach, which is an evaluation method of shale fracability based on stress inversion, can make full use of fracturing data to guide the fracturing of shale gas wells. It is of great significance for carrying out "one interval one scheme, fine fracturing" to increase the productivity of single well, and to enhance the overall development effect of the block.
作者
刘尧文
卞晓冰
李双明
蒋廷学
张驰
LIU Yaowen;BIAN Xiaobing;LI Shuangming;JIANG Tingxue;ZHANG Chi(Sinopec Chongqing Fuling Shale Gas Exploration and Development Co.Ltd.,Chongqing 408014,China;State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development,Beijing,102206,China;Sinopec Research Institute of Petroleum Engineering,Beijing,102206,China)
出处
《石油钻探技术》
CAS
CSCD
北大核心
2022年第1期82-88,共7页
Petroleum Drilling Techniques
基金
国家自然科学基金项目“海相深层油气富集机理与关键工程技术基础研究”(编号:U19B6003)资助。
关键词
页岩
地应力
脆性指数
可压性
变异系数
shale gas
in-situ stress
brittleness index
fracability
coefficient of variation
