砂砾岩水力裂缝扩展规律初探

A Primary Investigation on Propagation Mechanism for Hydraulic Fractures in Glutenite Formation

胜利油田砂砾岩油藏主要分布在东营凹陷北部陡坡带,储层物性差,以低渗透、特低渗透为主,储层埋藏深,压裂改造难度大。在盐22、永920、车66、丰深等区块压裂/酸压施工60多井次,从施工曲线上反映出不同地区、不同埋藏深度的储层在裂缝扩展过程中具有不同的特点,存在砂堵及加砂困难的现象。由于砾石的存在,导致压裂液在裂缝中的流动状态发生变化,从而影响缝内压力场和流场分布。利用大尺寸真三轴模拟压裂试验系统,对人造岩样进行水力压裂裂缝扩展机理模拟试验,模拟了无砾石、有砾石在不同压差、不同砾石粒径条件下的裂缝扩展规律,通过对试验施工曲线的分析,定性地分析了砾石存在对裂缝扩展的影响,为下一步进行数值模拟研究提供了依据。

The glutenite reservoirs in Shengli Oilfield were mostly distributed in the northern steep slope area of Dongying Depression,where physical property was poor and permeability was low,reservoir was deeply buried,it was difficult for reservoir fracturing and reconstruction .Over sixty fracturing or fracture acidizing operations were carried out in Block Yan22,Yong920,Che66 and Block Fengshen . It could be seem from the curves that different fractures at different depths had different characteristics during the fracture expansion .It was difficult for sand blocking and sand usage.The flow state of fracturing fluid in fracture could be varied because of the existance of gravel,by which the distribution of pressure and flow field in it were affected .Several simulation experiments on the expansion mechanism of hydraulic fracturing are carried out by employing a large-sized and true triaxial simulation test system to study the rules of fracture expansion under different pressures and particle diameters with or without gravel.The influence of the existed gravel on fracture propagation is qualitatively analyzed and several conclusions are finally obtained by contrastively studying experiment curves,it provides references for the further numerical simulation research on it.