摘要
在储层压裂改造过程中,注入流体会改变储层孔隙流体压力以及岩石有效应力,从而影响压裂裂缝的扩展行为。为此,以鄂尔多斯盆地三叠系延长组长6段致密砂岩储层为研究对象,采用高温高压拟三轴压裂实验系统,结合岩心CT扫描及裂缝三维重构技术,研究了储层孔隙中注入不同类别流体(ScCO_(2)、N_(2)和水等)以及在不同压力情况下对致密砂岩储层压裂裂缝形态的影响。研究结果表明:①在相同孔隙压力流体并清水压裂条件下,注入ScCO_(2)和N_(2)均能降低岩石的起裂压力,其中ScCO_(2)影响最大,与无孔隙流体试样相比起裂压力降低了24.04%;②与无孔隙流体试样相比,孔隙中充满水的压裂试样起裂压力有所升高(上升约1.1%);③与3种相同孔隙压力流体下的清水压裂相比,ScCO_(2)压裂起裂压力最低,裂缝扩展形态也最复杂,裂缝平均分形维数增大了1.85%;④注入岩石孔隙中CO_(2)压力越高,ScCO_(2)压裂后裂缝的形态越复杂,ScCO_(2)的黏度最低,易在孔隙中流动,压裂时更容易沟通天然裂隙和寻找岩石弱面,激发裂缝扩展,加之高孔隙压力降低了岩石的有效应力,从而降低了起裂压力,并诱导产生了复杂裂缝网络。结论认为,在非常规储层压裂改造时,建议向致密储层内注入一定量的CO_(2),使孔隙压力达到储层有效应力的60%~80%后,再进行ScCO_(2)压裂,以达到提升压裂改造效果的作用,该方法为非常规油气储层CO_(2)高效压裂改造提供了理论和方法支撑。
In the process of reservoir fracturing,the injected fluid can alter the pore fluid pressure and effective rock stress,thereby influencing the propagation behaviors of hydraulic fractures.Taking the Triassic Yangchang Chang 6 tight sandstone reservoir in the Ordos Basin as the research object,this paper studies the effects of different fluids(ScCO_(2),N_(2),water,etc.)injected into reservoir pores and different pressure conditions on the morphology of hydraulic fractures in tight sandstone reservoirs by using a high-temperature and high-pressure pseudo triaxial fracturing experimental system,combined with core CT scanning and three-dimensional fracture reconstruction technology.And the following research results are obtained.First,under the same condition as slickwater fracturing with the same pore fluid,injecting ScCO_(2) and N_(2) can both reduce the fracture initiation pressure of rocks,with ScCO_(2) having the greatest impact,which reduces the initiation pressure by 24.04%compared with the samples without pore fluid.Second,compared with the sample without pore fluid,the fracturing sample with pores filled with water has a higher fracture initiation pressure(about 1.1%higher).Third,compared with slickwater fracturing with three kinds of pore fluid respectively,ScCO_(2) fracturing achieves the lowest fracture initiation pressure and the most complex fracture propagation morphology,with an average fractal dimension increase of 1.85%.Fourth,the higher the pressure of the CO_(2) injected into the rock pores,the more complex the fracture propagation morphology after ScCO_(2) fracturing.ScCO_(2) has the lowest viscosity,so it is easy to flow in pores to communicate natural fractures and search for weak rock planes,thus stimulating fracture propagation.In addition,high pore pressure leads to a decrease in the effective rock stress,thereby reducing the fracture initiation pressure and inducing the formation of a complex fracture network.In conclusion,to perform fracturing stimulation of unconventional reservoirs,it is recommended to inject a certain amount of CO_(2) into the tight reservoir to increase the pore pressure to 60%-80%of the effective reservoir stress,and then conduct ScCO_(2) fracturing to enhance the fracturing effect.This method provides theoretical and methodological support for the efficient CO_(2) fracturing of unconventional oil and gas reservoirs.
作者
王海柱
余星
石明亮
王斌
薛小佳
陈文斌
陶亮
张国新
Cheremisin Alexey
Stanchits Sergey
WANG Haizhu;YU Xing;SHI Mingliang;WANG Bin;XUE Xiaojia;CHEN Wenbin;TAO Liang;ZHANG Guoxin;Cheremisin Alexey;Stanchits Sergey(State Key Laboratory of Oil and Gas Resource and Engineering//China University of Petroleum-Beijing,Beijing 102249,China;No.2 Gas Production Plant,PetroChina Changqing Oilfield Company,Yulin,Shaanxi 719000,China;Oil and Gas Technology Institute,PetroChina Changqing Oilfield Company,Xi'an,Shaanxi 710018,China;Skolkovo Institute of Science and Technology,Bolshoi Boulevard 30/1,Moscow,Russia)
出处
《天然气工业》
北大核心
2025年第9期114-124,共11页
Natural Gas Industry
基金
国家自然科学基金杰出青年科学基金项目“油气井流体力学与工程”(编号:52425402)
国家自然科学基金国际(地区)合作与交流项目“非纯CO_(2)压裂干热岩裂缝扩展机理及造储方法研究”(编号:W2412078)
国家自然科学基金青年科学基金项目“粗糙迂曲缝内超临界CO_(2)微细支撑剂携带机理研究”(编号:52204021)
中国石油大学(北京)科研启动基金项目“页岩复杂缝网内微细支撑剂铺置与压嵌规律研究”(编号:2462022BJRC002)。
关键词
超临界CO_(2)
致密砂岩储层
孔隙流体
起裂压力
水力压裂
裂缝形态
三维裂缝重构
分形维数
Supercritical CO_(2)
Tight sandstone reservoir
Pore fluid
Fracture initiation pressure
Hydraulic fracturing
Fracture morphology
3D fracture reconstruction
Fractal dimension
