摘要
超临界CO_(2)复合压裂采用超临界CO_(2)作为前置液,胍胶压裂液作为携砂液,现场试验已初步验证了该技术的有效性。然而,超临界CO_(2)复合压裂过程中,两阶段流体如何协同作用影响着最终的裂缝形态及导流能力,对此仍缺乏系统深入的实验研究和认识。为了深入认识超临界CO_(2)复合压裂机理,采用室内三轴压裂实验方法,系统对比了胍胶压裂、超临界CO_(2)压裂、超临界CO_(2)复合压裂3种方式的裂缝扩展形态特征,定量表征了裂缝宽度、复杂度和渗透率等关键参数,从实验室角度揭示了复合压裂的缝网复杂度增强和增渗机理。研究结果表明:①超临界CO_(2)压裂比胍胶压裂更容易连通层理等不连续面,形成更多分支裂缝,产生更为复杂的裂缝形貌;②随着层理倾角的增加,超临界CO_(2)复合压裂更容易形成复杂的裂缝网络,在层理倾角为90°时,复合压裂可广泛连通岩石中层理和天然裂缝,增加改造体积;③超临界CO_(2)复合压裂中,胍胶压裂可以显著增加超临界CO_(2)压裂阶段裂缝的复杂度(增加33.6%)和宽度(增加7.08倍),并使渗透率提升一个数量级。结论认为,该研究结果揭示了超临界CO_(2)复合压裂两阶段流体的前置造缝、缝网扩展及协同增渗机制,可为页岩气、煤层气、致密气等非常规储层的高效压裂改造提供理论依据和技术支撑。
Supercritical CO_(2) compound fracturing,which takes supercritical CO_(2) as the pad fluid and guar gum fracturing fluid as the sand-carrying fluid,has been verified to be effective in field tests.However,the synergetic effect of the two-stage fluids on the final fracture morphology and conductivity in the process of supercritical CO_(2) compound fracturing has not been experimentally studied and understood systematically.To understand the mechanisms of supercritical CO_(2) compound fracturing,this paper adopts the indoor triaxial fracturing experiment method to compare the morphological characteristics of fracture propagation in three modes,i.e.,guar gum fracturing,supercritical CO_(2) fracturing,and supercritical CO_(2) compound fracturing,and quantitatively characterize the key parameters like fracture width,complexity and permeability.In addition,the fracture network enhancement and permeability enhancement mechanisms under compound fracturing are revealed from the perspective of experimental study.The following results are obtained.First,compared with guar gum fracturing,supercritical CO_(2) fracturing is more likely to connect discontinuities such as bedding,to form more branch fractures,producing a more complex fracture morphology.Second,as the bedding inclination increases,supercritical CO_(2) compound fracturing will form a complex fracture network more easily.And when the bedding inclination reaches 90°,compound fracturing can extensively connect the bedding and natural fractures within the rocks,so as to increase the stimulated volume.Third,in supercritical CO_(2) compound fracturing,guar gum fracturing can significantly increase the complexity and width of the fractures formed during the supercritical CO_(2) fracturing stage,with the fracture complexity increased by 33.6%,the width increased by 7.08 times,and the permeability increased by an order of magnitude.In conclusion,the research results reveal the pad fluid fracturing,fracture network propagation and synergetic permeability enhancement mechanisms of two-stage fluids in supercritical CO_(2) compound fracturing,which can provide theoretical basis and technical support for efficient fracturing stimulation of unconventional reservoirs of shale gas,CBM and tight gas.
作者
蔡灿
冯彪
陈浩
张烈辉
杨显鹏
CAI Can;FENG Biao;CHEN Hao;ZHANG Liehui;YANG Xianpeng(High-pressure Jet Theory and Application Technology Laboratory,School of Mechanical Engineering,Southwest Petroleum University,Chengdu,Sichuan 610500,China;MOE Key Laboratory of Oil and Gas Equipment//Southwest Petroleum University,Chengdu,Sichuan 610500,China;State Key Laboratory of Oil&Gas Reservoir Geology and Exploitation//Southwest Petroleum University,Chengdu,Sichuan 610500,China)
出处
《天然气工业》
北大核心
2025年第9期104-113,共10页
Natural Gas Industry
基金
国家自然科学基金重点项目“海相页岩水平井超临界二氧化碳压裂机理与一体化模拟研究”(编号:52234003)
国家自然科学基金面上项目“深井高压气体射流辅助钻井破岩机理及携岩特性研究”(编号:42472383)
四川省自然科学基金青年基金项目“复杂裂缝内水驱CO_(2)多相流动机理及支撑剂运移规律”(编号:25QNJJ2040)。
关键词
超临界二氧化碳
压裂
页岩
裂缝扩展
裂缝宽度
渗透率
增渗机理
Supercritical CO_(2)
Fracturing
Shale
Fracture propagation
Fracture width
Permeability
Permeability enhancement mechanism
