摘要
薄互层致密砂岩储层由于其砂泥叠置沉积,纵向非均质性强的特点,在水力压裂施工中,裂缝难以垂向扩展,有效沟通储层,明确薄互层水力裂缝垂向扩展规律对薄互层致密砂岩的开发具有重要意义。针对鄂尔多斯盆地临兴区块下石盒子组薄互层致密砂岩储层,通过建立薄互层致密砂岩地层裂缝扩展模型,研究了储隔层间应力差、储隔层厚度、岩石力学性质等地质因素和压裂液黏度、施工排量等工程因素对水力压裂裂缝扩展的影响,并通过现场井压裂效果和微震检测数据验证了模型的可靠性与准确性。研究结果表明:储隔层间应力差和储隔层厚度是影响水力裂缝穿层扩展最主要的地质因素,当应力差大于4 MPa时,裂缝垂向扩展受到抑制;弹性模量大的隔层有利于裂缝垂向扩展;泊松比对裂缝垂向扩展几乎没有影响;压裂液黏度对裂缝垂向扩展影响较小;泵注排量对裂缝垂向扩展有促进作用,但当排量增加到一定程度后,裂缝扩展放缓,对于不同的应力差,存在不同的最优排量。因此,对于薄互层致密砂岩水力压裂,低储隔层厚度、低储隔层应力差、高弹性模量和高注入排量能有效促进裂缝垂向扩展。研究成果可为该类储层水力压裂施工设计提供一定理论依据。
Thin interbedded tight sandstone reservoirs are characterized by strong vertical heterogeneity due to the superimposed pattern of the deposited sandstones and mudstones.As a result,hydraulic fractures are difficult to propagate vertically to effectively connect the reservoirs.Given this,ascertaining the vertical propagation patterns of hydraulic fractures in thin interbeds is of great significance for the development of thin interbedded tight sandstones.With the thin interbedded tight sandstone reservoirs of the lower Shihezi Formation in the Linxing block,Ordos Basin as a case study,this study built the fracture propagation model of these sandstones.Accordingly,it analyzed the effects of geological factors(i.e.,the stress difference between reservoirs and interlayers,the thicknesses of reservoirs and interlayers,and rock mechanical properties)and engineering factors(i.e.,the viscosity and injection rate of fracturing fluids)on the propagation of hydraulic fractures.Moreover,this study verified the reliability and accuracy of the model based on field hydraulic fracturing performance and microseismic monitoring data.The results of this study are as follows:(1)The stress difference between reservoirs and interlayers and the thicknesses of reservoirs and interlayers were the major geological factors affecting the vertical propagation of hydraulic fractures,which was restrained when the stress difference was greater than 4 MPa.(2)The interlayers with high elastic moduli were conducive to the vertical fracture propagation.(3)Poisson’s ratio almost had no effect on vertical fracture propagation.(4)The viscosity of fracturing fluids had little effect on the propagation.(5)The injection rate of fracturing fluids promoted vertical fracture propagation,which,however,slowed down when the injection rate increased to a certain extent.Different stress differences corresponded to different optimal displacements.Therefore,factors that can effectively promote vertical fracture propagation during the hydraulic fracturing of thin interbedded tight sandstones include small thicknesses of reservoirs and interlayers,small stress differences between reservoirs and interlayers,high elastic modulus,and high injection rate.The results of this study will provide a theoretical basis for the hydraulic fracturing design of similar sandstone reservoirs.
作者
杨帆
梅文博
李亮
孙泽宁
安琦
杨琦
陆美全
杨睿月
YANG Fan;MEI Wenbo;LI Liang;SUN Zening;AN Qi;YANG Qi;LU Meiquan;YANG Ruiyue(China United Coalbed Methane Corp.Ltd.,Beijing 100016,China;National Key Laboratory of Petroleum Resources and Engineering,China University of Petroleum(Beijing),Beijing 102249,China)
出处
《煤田地质与勘探》
EI
CAS
CSCD
北大核心
2023年第7期61-71,共11页
Coal Geology & Exploration
基金
中海油集团公司重大科技专项项目(CNOOC-KJ 135 ZDXM 40)
中国科协青年人才托举工程资助项目(2021QNRC001)。
关键词
薄互层
致密砂岩
水力压裂
裂缝扩展
数值模拟
thin interbed
tight sandstone
hydraulic fracturing
fracture propagation
numerical simulation