作　　者： ; ; ; (衡帅）; (魏元龙）; (侯振坤）; (李丹）;

机构地区： 中国科学院武汉岩土力学研究所岩土力学与工程国家重点实验室

出　　处： 《岩石力学与工程学报》 2015年第S2期3624-3632,共9页

摘　　要： 为研究水平井水中水力裂缝的起裂模式,利用露头介壳灰岩开展室内水平井水力压裂试验,通过压裂液中添加示踪剂、泵压曲线分析、声发射监测定位、压后试样剖切观察等手段对井壁处水力裂缝的起裂和扩展现象进行描述和分析。得到以下结论:(1)水力裂缝的起裂模式可归纳为3类:I型——单一横向裂缝、II型——多条横向裂缝、III型——纵横交叉裂缝。(2)每种起裂模式有特定类型的泵压曲线与之对应:I型起裂模式对应的起裂压力较小,起裂后压力有较大幅度跌落;II型起裂模式对应的起裂压力较大,起裂后压力持续升高,波动剧烈;III型起裂模式对应的起裂压力较大,但起裂后压力波动较小。(3)试样中水力裂缝的起裂模式具有随机性,且起裂压力具有较大的离散性。(4)声发射的活动性能够较好地反映水力裂缝的起裂扩展,水力裂缝起裂的瞬间,声发射活动性最强。(5)声发射事件点子密集分布的区域与实际的水力裂缝位置有较好的一致性,可利用声发射定位结果初步判断水力裂缝的分布。(6)在较高的排量下,水平井更容易形成单一横向裂缝,而在低排量下水力裂缝的起裂形态可能更趋向于复杂,排量是影响水平井起裂模式的一个关键因素。(7)可尝试结合现场压裂泵压曲线推测储层水力裂缝的起裂与扩展。 In order to investigate the initiation modes of hydro-fractures in horizontal wells,Laboratory hydraulic fracturing test was carried out using outcrop shelly limestone to simulate horizontal well hydraulic fracturing. The phenomena of fracture initiation and propagation around the horizontal wellbore were described and analysed by adding tracer to the fracturing fluid,analysing pumping curve,arranging AE monitoring system and splitting sample after test. Conclusions are as follows:(1) The initiation modes of hydro-fractures could be divided into three types:one transverse fracture(mode I),transverse multi-fractures(Mode II),transverse-longitudinal crossed fractures(Mode III).(2) Each hydro-fracture initiation mode has its certain pumping curves. Mode I had a low breakdown pressure followed by a sharp drop. Mode II had a relatively high breakdown pressure,then the pressure went up and fluctuated dramatically. Mode III also had a high breakdown pressure,but the pressure fluctuated slightly.(3) Among the specimens,the three initiation modes occurred randomly and the breakdown pressures were dispersed.(4) The AE activity could reflect the initiation and propagation of hydro-fractures and reached its peak value at the fracture initiation moment.(5) The area in which AE events concentrated was in agreement with the actual location of the hydro-fractures. AE locating results could be used to preliminary judge the distribution of hydro-fractures.(6) One transverse hydro-fracture was more likely to be formed at relatively high pumping rate,while the fracture geometry tended to be complex at relatively low pumping rate. Pumping rate is a key factor to determine the initiation mode.(7) It may be feasible to conjecture the initiation and propagation of the hydro-fractures using site fracturing pumping curves.

关 键 词： 岩石力学 水力压裂 水平井 起裂模式 泵压曲线 声发射

领　　域： [石油与天然气工程]