共查询到20条相似文献，搜索用时 453 毫秒
1.
在页岩油气藏的开发和勘探阶段，需要对储层进行水力压裂改造，形成有利于油气聚集和运移的裂缝.地应力是进行水力压裂改造的重要参数，能够决定裂缝的大小、方向以及分布形态，影响着压裂的增产效果，且最大和最小水平应力差异比（ODHSR，Orthorhombic Differential Horizontal Stress Ratio）是评价储层是否可压裂成网的重要因子.本文探讨了基于地震数据估算地应力的方法，以指导页岩气的水力压裂开发.首先，利用叠前方位地震数据反演得到地层的弹性参数和各向异性参数；其次，基于正交各向异性水平应力差异比近似公式，利用反演得到的弹性参数和各向异性参数估算地层的ODHSR；最后，选取某工区的裂缝型页岩储层的叠前方位地震数据对该方法进行实际应用.实际工区地震数据应用表明，基于叠前方位地震数据反演得到的ODHSR能够有效的识别储层中易于压裂成网的区域. 相似文献
2.
《地球物理学进展》2020,(2)
水力压裂是对低渗透油气田进行储层改造的重要技术,现已在国内外得到广泛应用.但井壁上原有的裂缝会造成水力裂缝在近井筒区域发生转向,诱发提前脱砂、砂堵等现象,甚至导致压裂作业失败.本文以边界元方法、流体力学为理论依据,考虑了近井筒处裂缝的转向行为,建立了含裂缝的井壁起裂及水力裂缝扩展的流固耦合模型.研究发现:当压裂液黏度较小时,裂缝迅速转向至垂直于最小水平主应力的方向;随着黏度的逐渐增大,井底注入压力不断升高,裂缝转向半径亦逐渐增大;压裂液排量对井壁裂缝延伸的影响和黏度对其的影响相似;井壁上原有裂缝的长度对井壁破裂压力有着显著的影响,其长度越长,井壁破裂压力越小;随着水平主应力差值的增大,裂缝的延伸路径会发生明显的转变,所需的延伸压力不断增大;井壁原有裂缝与最大水平主应力方向间的夹角越小,所需的破裂压力及延伸压力也越小. 相似文献
3.
水压致裂法地应力测量若干问题的探讨 总被引：4，自引：0，他引：4
在深层地应力测量中,水压致裂法是最有效的测量方法。本探讨了该方法的几个关键性问题,例如压裂特征参数的取值,三维地应力测量,压裂缝的方向,破裂准则和钻孔轴向秒是主应力的一个方向等问题。 相似文献
4.
引言 当垂直主应力为中间主应力状态时,水压致裂所产生的裂缝方位必然沿着最大主应力方向展布。因此,测定主裂缝的方位,对于确定最大主应力方向、研究区域应力场的形态都是十分重要的。测量压裂裂缝方位通常的方法是用可膨胀橡胶封隔印模器与井下电视,这两种方法的优点是明显的,但它们共同的缺点是只能观察到裂缝在孔壁面上的位置,而其延伸方向 相似文献
5.
《地球物理学进展》2017,(1)
室内水力压裂模拟实验是认识裂缝压裂机理、获取水力压裂信号的有效手段,可为进一步提高水力压裂技术在页岩气等非常规油气资源开发方面的应用提供技术支持.本文根据野外水力压裂施工工艺和微压裂地震信号监测的特点,设计并制造了大模型水力压裂模拟装置,该装置包括真三轴围压系统、水压裂系统和微压裂信号采集系统,可以实现相同或不同围压状态下的水力压裂试验,并对裂缝产生、裂缝扩展的整个物理过程进行水力压力信号和岩石压裂破裂信号的采集,形成了一套完整的微压裂实验技术.通过水力压裂实验,首次在实验室内获得了真三轴围压下大模型的水利压力和水力压裂信号的关系,为水力压裂信号的分析和压裂裂缝的定位提供了基础. 相似文献
6.
为了研究水力压裂中岩石的破裂及裂缝延展规律,开展水力压裂实验模拟.采用大型真三轴压裂设备对花岗岩岩样(300 mm×300 mm×300 mm)进行水力压裂,16道检波器接收,在识别的声发射信号上拾取初至走时,Geiger定位结果表明,压裂中声发射事件位置与压裂示踪剂显示相一致,CT扫描制作的数字岩心准确反映实际的破裂面.从压裂曲线上提取的破裂压力,结合围压分析表明,整个破裂面与初始破裂相一致,岩石破裂后沿该破裂面延展,直至结束.实验分析表明,裂缝发育由裂缝方向和裂缝类型共同决定,遵循裂缝发育能量消耗最小原则,合理解释了本次实验压裂现象;针对实验中单一破裂现象,提出了改进水力压裂设计的建议. 相似文献
7.
相比于常规气藏,页岩气藏有着低孔隙度、低渗透率的特点,大规模开采页岩气需利用水平井压裂技术.研究表明:与最大水平主应力近垂直的方向钻水平井,且地应力差异系数较小时,有利于形成网状裂缝.选择川东南X工区对地应力预测技术在页岩气水平井开发中的应用进行研究,利用地层的构造信息、速度信息和密度信息,求得层位面的地应力参数,预测最大水平主应力方向、最小水平主应力方向以及地应力差异系数;通过区域应力机制分析以及X1、X2、X3三口井的钻井实测诱导缝解释结果和产量情况分析,验证了本文地应力方向和地应力差异系数预测结果的可靠性.在水平井设计时应综合考虑地应力方向和地应力差异系数,以获得良好的压裂效果和产能. 相似文献
8.
为评价页岩油储层可压裂性,以鄂尔多斯盆地长7页岩油储层为例,利用研究区部分已压裂井测井数据,计算得出脆性指数和断裂韧性指数,绘制了可压裂性剖面图,结合脆性指数和断裂韧性指数建立了一种新的页岩油储层可压裂性评价模型,为压裂选层、选井提供前期指导,为页岩油工程甜点的筛选以及压后产能预测提供依据.利用本文模型对研究区L70井、L58井和L295井进行了工程应用,结合可压裂性剖面图和压裂前后正交偶极各向异性成果图对各井裂缝展布情况和压裂效果进行了评价,并与各井实际压裂效果进行了对比分析.评价结果表明:脆性是储层可压裂性重要的影响因素之一,但是脆性较强的储层段可压裂性不一定很好,结合脆性和断裂韧性更能准确、有效的评价页岩油储层可压裂性,长7页岩油储层段与邻层砂岩段相比普遍存在天然裂缝发育程度较低、地应力较高、脆性较差的问题,工程甜点区应选在地应力较低、脆性较强、断裂韧性较小、可压裂性系数较大的页岩油储层段. 相似文献
9.
《地球物理学进展》2016,(4)
泥页岩一般具有低孔、低渗的特性,北美页岩气勘探开发经验表明此类页岩储层需经过大规模的压裂改造才能够获得商业产能,因此页岩可压性是评价页岩是否能作为"甜点"的关键指标之一.本文以焦石坝地区志留系龙马溪组-奥陶系五峰组页岩为例,从岩石脆性、地应力特征以及裂缝发育程度三方面评价焦石坝地区的可压性.其中,利用Rickman公式结合叠前地震反演预测证实焦石坝页岩脆性指数较高,构造主体部位脆性指数大于50%,反映页岩易于破裂;页岩岩心实验室测试数据则表明焦石坝地区页岩水平应力差较小(小于0.14),反映页岩在进行工程压裂时易于形成裂缝网络;同时焦石坝地区页岩岩心可见的大量微裂缝,裂缝预测结果也表明构造主体部位网状裂缝发育,更加有利于页岩储层的压裂改造.综合三方面条件来看,焦石坝地区页岩较好的可压性是本区页岩获得商业开发的关键. 相似文献
10.
超短半径径向水平井抽采煤层气渗流规律的数值模拟 总被引：3，自引：0，他引：3
为得到超短半径径向水平井开采煤层气过程中的气体渗流规律以及进行产量预测,在基本假设条件下,建立了径向水平井开采煤层气的固流耦合渗流数学模型;在一定的边界条件及初始条件下,利用Matlab软件进行编程计算后,得到直井和不同数目分支径向水平井开采煤层气1000天后的压力场、速度场和气产量变化规律。数值模拟结果表明,在一定的生产区域和开采时间,随着径向水平井分支数目的增加,煤储层压力下降范围更广,气体流速场干扰加强,压力漏斗降大面积扩展,煤层气有效供气区及解吸面积大幅增长,煤层气解吸能力及稳产能力加强,煤层气产量大幅度增加;同时,气产量增幅随着井筒分支数目的增加而下降,分支井数目理论上应存在一个最优值。模拟结果显示了超短半径径向水平井技术开采煤层气的有效卸压作用,对煤层气工业增产技术的选择和钻孔方案的布置具有重要的理论指导意义。 相似文献
11.
采用煤矿井下专用的小孔径水压致裂地应力测量装置,在山西省的晋城、潞安、汾西、华晋、阳泉、平朔、大同等矿区,完成了160个测点的地应力测量,测点地质条件涵盖了山西省煤矿大部分条件.基于实测数据,分析了地应力与测点埋深的关系,不同深度条件下煤矿矿区井下地应力状态;绘制出山西省煤矿矿区井下地应力分布图,并与震源机制解的分析结果进行了比较,得出山西省煤矿矿区井下地应力场分布特征与变化规律.煤矿井下水平应力总体上随着埋深增加而增大,但由于各矿区地质条件差异较大,导致地应力测试数据离散性也较大;埋深小于250 m的岩层应力状态主要为σH>σh>σV型,埋深处于250~500 m的岩层应力状态以σH>σV>σh型为主,埋深较大的矿区主要为σV>σH>σh型;最大水平主应力与垂直主应力的比值绝大部分集中在0.5~2.0之间,而且随着埋深增加,侧压比呈现减小的趋势,并向1附近集中;最大水平主应力与最小水平主应力的比值主要集中在1.5～2.0之间;平均水平主应力与垂直主应力的比值大多处于0.5～1.5,尤以0.5～1.0之间最多;山西省煤矿矿区从北到南,最大水平主应力方向发生了较大变化.北部最大水平主应力方向为NE,往南发生偏转到NNW;靠东部与西部偏向NW;靠东南部出现了多变的方向.井下实测数据与震源机制解相比在部分区域一致性较好,而在另一些区域存在明显的差异.特别是在受较大地质构造影响的区域,水平主应力方向往往发生明显的扭转和变化. 相似文献
12.
WANG Xiaoqiong XU Jianguo ZHAO Chenxu LIU Tongyuan GE Hongkui SHEN Yinghao WU Shan YU Jiayao HUANG Rongyan 《中国地震研究》2020,34(2):167-186
The premise of hydraulic fracturing is to have an accurate and detailed understanding of the rock mechanical properties and fracture propagation law of shale reservoirs. In this paper, a comprehensive evaluation of the mechanical properties of the shale oil reservoir in the south of Songliao Basin is carried out. Based on the experiments and the in-situ stress analysis, the fracture propagation law of three types of shale reservoirs is obtained, and the suggestions for fracturing are put forward. The results have shown that the fracture propagation of pure shale and low mature reservoir is easy to open along the bedding plane under compression loading, which is greatly influenced by the bedding. Sand-bearing shale is slightly better, the fractures of which are not easy to open along the bedding plane. The mechanical experimental results show that all the samples have the characteristics of low compressive strength, low Young''s modulus and strong anisotropy, indicating that the shale oil reservoir is certain plastic, which is related to its high clay mineral content and controlled by the bedding development. Compared with pure shale and low mature shale, the sand-bearing shale has less clay content and less developed bedding, which maybe the main reason for its slightly better brittleness. Overall, the expansion of hydraulic fracture is controlled by in-situ stress and bedding. Because of the development of bedding, it is easy to form horizontal fractures. Thus it is not suitable for horizontal well fracturing. Because of the high content of clay minerals, the applicability of conventional slick hydraulic fracturing fluid is poor. It is suggested to use vertical well or directional well to carry out volume fracturing. In this way, the effect of bedding can be effectively used to open and connect the bedding and form a larger fracture network. 相似文献
13.
Consistency of stress state,locations and source mechanisms of events induced by hydraulic fracturing: downhole monitoring 
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下载免费PDF全文 Zuzana Jechumtálová Fangdong Chu Gang Yu Jan Procházka 《Geophysical Prospecting》2018,66(7):1315-1326
We present results of processed microseismic events induced by hydraulic fracturing and detected using dual downhole monitoring arrays. The results provide valuable insight into hydraulic fracturing. For our study, we detected and located microseismic events and determined their magnitudes, source mechanisms and inverted stress field orientation. Event locations formed a distinct linear trend above the stimulated intervals. Source mechanisms were only computed for high‐quality events detected on a sufficient number of receivers. All the detected source mechanisms were dip‐slip mechanisms with steep and nearly horizontal nodal planes. The source mechanisms represented shear events and the non‐double‐couple components were very small. Such small, non‐double‐couple components are consistent with a noise level in the data and velocity model uncertainties. Strikes of inverted mechanisms corresponding to the nearly vertical fault plane are (within the error of measurements) identical with the strike of the location trend. Ambient principal stress directions were inverted from the source mechanisms. The least principal stress, σ3, was determined perpendicular to the strike of the trend of the locations, indicating that the hydraulic fracture propagated in the direction of maximum horizontal stress. Our analysis indicated that the source mechanisms observed using downhole instruments are consistent with the source mechanisms observed in microseismic monitoring arrays in other locations. Furthermore, the orientation of the inverted principal components of the ambient stress field is in agreement with the orientation of the known regional stress, implying that microseismic events induced by hydraulic fracturing are controlled by the regional stress field. 相似文献
14.
Laboratory hydrofracture experiments were performed on triaxially stressed specimens of oil shale and low-permeability granite. The results show that either shear or tension fractures could develop depending on the level of differentials stress, even in specimens containing preexisting fractures. With 1 kb of confining pressure and differential stress greater than 2kb, hydraulic fluid diffusion into the specimens reduced the effective confining pressure until failure occurred by shear fracture. Below 2kb of differential stress, tension fractures occurred. These results suggest that hydraulic fracturing in regions of significant tectonic stress may produce shear rather than tension fractures. In this casein situ stress determinations based on presumed tension fractures would lead to erroneous results. 相似文献
15.
Numerical evaluation of the shear stimulation effect in naturally fractured formations 总被引：1，自引：0，他引：1
In shale gas fracking, the stimulated natural fracture system is often critical to the gas production. In this paper, we present the results of state-of-the-art modeling of a detailed parametric evolution of the shear stimulation effect in discrete fracture network (DFN) formations. Two-dimensional computational modeling studies have been used in an attempt towards understanding how naturally fractured reservoirs response in hydraulic fracturing. Simulations were conducted as a function of: (1) the in-situ stress ratio; (2) internal friction angle of DFN; (3) DFN orientation with the stress field; and (4) operational variables such as injection rate. A sensitivity study reveals a number of interesting observations resulting from these parameters on the shear stimulation in natural fracture system. This work strongly links the production technology, geomechanical evaluation and aids in the understanding and optimization of hydraulic fracturing simulations in naturally fractured reservoirs. 相似文献
16.
随着水力压裂技术在页岩气开发中的广泛应用,加拿大西部盆地的诱发地震活动显著增加.目前对于诱发地震的综合表征方法还不成熟.本文采用一种综合地质、岩石力学及流体力学的研究方法,对Fox Creek地区2015年2月8日发生的M 3.0诱发地震事件进行了综合表征.首先,利用高分辨率三维反射地震资料,采用蚂蚁体追踪技术识别潜在断层.其次,利用测井曲线和压裂施工数据等资料定量求取岩石力学及地应力参数,建立三维地质力学模型,明确水力压裂缝的空间扩展规律.最后,建立流体-地质力学耦合模型,计算水力压裂过程中断层附近的孔隙压力及局部应力变化,利用摩尔-库仑破裂准则判定断层激活的时间与空间位置,揭示本次诱发地震事件的触发机制并提出风险控制对策.结果表明,三条由Precambrian基底向上延伸至Duvernay地层的近垂直断层在水平井压裂过程中被激活.由于水平井的部分压裂缝与断层沟通,注入流体沿断层的高渗透破裂带向下迅速扩散,在基底位置激活断层并诱发M 3.0地震事件.其中孔隙压力增加是本例中断层活化的主要因素.现场措施表明,增大压裂水平井与已知断层之间的距离被可以有效地降低地震风险.因此在进行水平井钻井及压裂作业之前,明确地下断层的分布位置至关重要. 相似文献
17.
— We addressed effects of in situ stress on the formation of flow pathways in fractured rocks in geothermal reservoirs, especially for HDR projects. Here we focused on fractures which are critically-stressed, causing shear slip in a current stress field. The sliding is likely to break sealing in the fractures and, as a result, to increase their permeability. Such a mechanism is possibly significant under high-temperature conditions at geothermal fields because of temperature enhancement on chemical reactions for the sealing. We present a procedure to estimate the orientation of the critically-stressed fractures relative to axes of in situ principal stress with the aid of the Mohr diagram. The procedure allows us to evaluate intuitively how the orientation changes with factors such as magnitude of in situ principal stresses and pore pressure. We applied the procedure to estimate possible orientations of the critically-stressed fractures in major HDR test sites. Results show that overall alignments of microseismicity during hydraulic stimulation are within predicted ranges for possible orientations of the critically-stressed fractures. Furthermore, it was found that if the state of in situ stress is not favorable to cause sliding of natural fractures, it tends to lead a high wellhead pressure at hydraulic stimulation and a high recovery rate at circulation. On the other hand, if the state of in situ stress is favorable for sliding, it tends vice versa to lead a low wellhead pressure at hydraulic stimulation and a low recovery rate at circulation. 相似文献
18.
2008年和2009年, 通过和新加坡宜康地质技术有限责任公司合作, 在新加坡18个浅钻孔中进行了水压致裂地应力测量. 通过测量获得了新加坡地壳浅部的现今应力状态, 为新加坡拟建地下管缆隧道设计施工提供了地应力依据, 也为世界应力环境数据库提供了参考. 测试结果表明, 在38.00~56.95 m深度域内最大水平主应力σh值为3.45~9.64 MPa, 最小水平主应力σh为2.49~6.28 MPa. 水平主应力和用上覆岩层重量计算的垂直应力σv之间的关系为σh>σh>σv,最大、最小水平主应力平均值分别是垂直应力平均值的5.13倍和3.23倍, 表明新加坡应力场以水平应力为主导. 初步分析认为, 新加坡陆域浅部构造应力场的量值大致呈南、北两端偏低, 中间高的态势, 在北端最大与最小水平主应力值都小于它们各自的平均值, 而南端则与平均值相当. 最大水平主应力优势方向为NE—NEE向, 该方向与前人在其邻区获得的构造应力场方向和由震源机制解反映的主压应力方向较为一致. 新加坡现今构造应力场状态与印度板块、澳大利亚板块、菲律宾板块与欧亚板块的汇聚作用有着密切的联系. 根据库仑摩擦滑动准则, 断层面摩擦系数取0.6~1.0, 分析了研究区内断层产生摩擦滑动的可能性. 相似文献
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