摘要
为确定支撑剂铺置模式对水力裂缝导流能力的影响规律,通过对加砂和返排过程中支撑剂颗粒的定性受力分析,研究了支撑剂在水力裂缝内的铺置模式,在此基础上建立了支撑剂颗粒数目以及裂缝导流能力的理论计算模型,定量地把支撑剂铺置模式和裂缝导流能力关联起来。结果表明:支撑剂在裂缝内的铺置过程为通过受迫流动形成的两阶段非自然堆积过程,包括支撑剂颗粒被高黏度携砂液高速携带进裂缝内部的无序随机渐次堆积以及在工作液反向携带和裂缝有效闭合压力共同作用下的有序紧密压实堆积。根据最大填充率能量原理和颗粒堆积稳定性原理,经过两阶段的非自然堆积过程后,支撑剂颗粒的配位数会越来越大,颗粒体系的填充率会越来越大,颗粒之间的孔隙体积会越来越小,直至达到最稳定的六方密堆积或立方密堆积或二者的混合模式。六方密堆积模式和立方密堆积模式所对应的裂缝导流能力基本相当,但远低于正方体堆积模式。在实际压裂施工过程中,即便支撑剂颗粒体系可能达不到也会趋近这两种紧密堆积模式,最终的裂缝导流能力仍然会远小于立方体堆积模式。本文的理论模型以及研究结论可为水力压裂设计提供分析工具和理论依据。
In order to obtain knowledge about the effect of packing modes of proppants on hydraulic fracture conductivity,qualitative force analysis was conducted to investigate the packing modes of proppants in a hydraulic fracture,and based on this,theoretical models were established to quantitatively calculate the quantity of proppant particles and the conductivity of a hydraulic fracture.The results show that the packing process of proppants in a hydraulic fracture is a two-stage particle packing process through forced flow,including a gradual packing one and a compact packing one.The former belongs to a stochastic disordered packing,while the latter an orderly close packing.According to the maximum-filling-rate energy principle and the particle-packing stability principle,after the two-stage packing process,the proppant system should have the increasing coordination number and the increasing filling rate until it reaches the hexagonal close packing mode or the cubic close packing mode or the most stable hybrid mode.The two close packing modes share almost the identical fracture conductivity,however far below that of the cubic loose packing mode.It is conclude that in a real fracturing treatment,even the proppant particle system may not reach but will approach toward these close packing modes,and the final fracture conductivity will still be far below that of the cubic loose packing mode.This work can serve as a theory base for hydraulic fracturing design.
作者
赵传峰
曹博文
肖月
许泽宇
ZHAO Chuan-feng;CAO Bo-wen;XIAO Yue;XU Ze-yu(Research Institute of Unconventional Resources, China University of Petroleum, Beijing 102249, China;Petro China Zhejiang Oilfield Company, Hangzhou 310023, China;CNPC Engineering Technology R&D Company Limited, Beijing 102206, China)
出处
《科学技术与工程》
北大核心
2021年第19期7997-8004,共8页
Science Technology and Engineering
基金
中国石油天然气集团有限公司-中国石油大学(北京)战略合作科技专项(ZLZX2020-01-03-04)。
关键词
水力裂缝
支撑剂铺置模式
导流能力
颗粒堆积
六方密堆积
立方密堆积
hydraulic fracture
proppant placement pattern
conductivity
particle packing
hexagonal close packing
cubic close packing
