煤矿冲击地压的微地震监测研究

为了研究煤矿冲击地压与岩层在三维空间破裂之间的关系,进而探索依据岩层破裂规律预测和预报冲击地压的可能性,文中采用自行研制的防爆型微地震定位监测（MS）系统,基于定位原理,监测了山东华丰煤矿冲击地压煤层（四层煤）及其解放层（六层煤）开采过程中的岩层破裂过程和二次应力场分布变化的过程,得到了如下结论：冲击地压的发生与岩层破裂密切相关,四层煤下顺槽处于六层煤顶板破裂区的外边缘时,正处于高应力区内,在此处掘进容易引发冲击地压,必须将六层煤下顺槽位置向实体煤侧移动20 m以上,或将四层煤下顺槽位置内移20 m以上,才能消除四层煤的冲击地压;六层煤和四层煤开采时,工作面前方断层活化的距离分别为250 m和350 m左右,根据这一距离,及时对断层带进行卸压处理,可以消除由断层带引发的冲击地压;监测显示了工作面周围岩层的三维破裂形态和范围,为矿井确定防水煤柱的高度提供了可靠的依据;监测证明了厚层砾岩的破裂、断层活化、采场附近关键层的破裂是引起冲击地压的主要原因,证明了所研制的硬件和定位软件具有较高的精度和实用性,可以在煤矿和边坡、隧道等领域应用.     

Impact of water and nitrogen fracturing fluids on fracturing initiation pressure and flow pattern in anisotropic shale reservoirs

A numerical model is proposed to investigate the impact of water and nitrogen fracturing fluids on the fracturing initiation pressure and the flow pattern in anisotropic shale reservoirs. This model considers the anisotropy of shale deformation and permeability, the compressibility of fracturing fluid, and the fluid moving front. A crack initiation criterion is established with the stress intensity factor of mode I crack. Both crack initiation pressure and seepage area are verified and analyzed. These results show that shale deformation and permeability anisotropy, fracturing fluid compressibility, viscosity, and pressurization rate have significant impacts on fracturing initiation pressure and seepage area.     

Dislocation generation, slip systems, and dynamic recrystallization in experimentally deformed plagioclase single crystals

Three samples of gem quality plagioclase crystals of An60 were experimentally deformed at 900 °C, 1 GPa confining pressure and strain rates of 7.5–8.7×10⁻⁷ s⁻¹. The starting material is effectively dislocation-free so that all observed defects were introduced during the experiments. Two samples were shortened normal to one of the principal slip planes (010), corresponding to a “hard” orientation, and one sample was deformed with a Schmid factor of 0.45 for the principal slip system [001](010), corresponding to a “soft” orientation. Several slip systems were activated in the “soft” sample: dislocations of the [001](010) and 110(001) system are about equally abundant, whereas 110{111} and [101] in ( 31) to ( 42) are less common. In the “soft” sample plastic deformation is pervasive and deformation bands are abundant. In the “hard” samples the plastic deformation is concentrated in rims along the sample boundaries. Deformation bands and shear fractures are common. Twinning occurs in close association with fracturing, and the processes are clearly interrelated. Glissile dislocations of all observed slip systems are associated with fractures and deformation bands indicating that deformation bands and fractures are important sites of dislocation generation. Grain boundaries of tiny, defect-free grains in healed fracture zones have migrated subsequent to fracturing. These grains represent former fragments of the fracture process and may act as nuclei for new grains during dynamic recrystallization. Nucleation via small fragments can explain a non-host-controlled orientation of recrystallized grains in plagioclase and possibly in other silicate materials which have been plastically deformed near the semi-brittle to plastic transition.     

实验变形岩石低温破裂作用的微观机制

通过对湿度和压力分别达300℃和3GPa干条件下实验变形的一系列花岗岩样品的系统光学和扫描电镜显微构造分析,识别出了几种具有不同特点及不同变形机制的显微破裂型式:a.微破碎带;b.微透镜带;c.短程破裂;d.扭折带破裂;e.粒内破裂;f.颗粒边界破裂。评价了它们与高压型和低压型破裂的显微构造对应性,认为a和f是低压破裂的特征性构造型式;b、c和d在高压破裂中最为典型;而e则可以出现在两种破裂型式中。本文阐述了破裂作用的微观机制,包括破裂的成核、扩展、生长和连接。破裂作用、由破裂诱发的脆性破裂和碎裂流动在目前实验变形条件下占主导地位,而在相对较高温条件下晶质塑性也起着一定的作用。破裂作用的成核可以始于颗粒边界,而引起摩擦颗粒边界滑移,也可以始于相邻颗粒或晶内包体颗粒的一些端点,或始于晶内双晶和解理面。破裂的生长和扩展一般是由于一些破裂的侧向延伸、相近破裂系统的联合和不同破裂系统的转变。低压样品的最终破裂一般归咎于一些贯穿性微断层的出现及主断层附近微破裂群的产生,微破碎角砾岩是其主要构造岩类型,类似于天然张性断层带构造;而沿主高压破裂附近却从未见到这种微破裂群的出现,主要表现为主破裂面及一些均匀分布的短程破裂构造, 典型构造岩为构造透镜体, 类似于天然压性与压扭性断层构造。两种破裂在成核、扩展与位移发育诸方面表现出的差别有助理解它们在声发射方面的差异。     

应用相干技术和孔隙度反演技术进行储层预测--以四川盆地DFC构造为例

运用相干分析和孔隙度反演对四川盆地DFC构造的下三叠统嘉二1至嘉一段储层进行了裂缝和孔隙度预测,并给出了有利储层分布。DFC构造发育两条主要断层,其相干异常分为四类:条带状、线状、团块状、点状。带状或线状异常沿断层分布,比较发育,是断层或裂缝的反映;团块状异常较发育,但方向性不强,可能是地下溶洞、溶孔、微细裂缝密集地带或多组小规模断裂交织而成的破碎带的综合响应,还可能是储层物性变化所致。DFC构造的储层,平均孔隙度相对较低,大部分为2%左右,属Ⅳ类储层,少部分为Ⅲ类,只有与裂缝、溶洞相结合才能形成有效储层。     

高能气体压裂技术在油气资源开发中的应用研究

在不同的围压及加载速率下 ,高能气体压裂可产生 3～ 5条径向裂缝 ,形成的多缝体系具有明显的增产效果。三轴试验结果认为高能气体压裂在井中造成的压力高于水力压裂所产生的压力 ,并有可能超过岩石弹性极限 ,使得卸载时产生永久变形 ,在地层中产生一定缝宽的残余裂缝 ,虽无支撑裂缝也不闭合。现场试验对工艺可行性及成功率进行了验证 ,表明工艺成功 ,具均有不同程度的增产效果     

Comparison of Numerical and Physical Models for Understanding Shear Fracture Processes

An understanding of the formation of shear fractures is important in many rock engineering design problems. Laboratory experiments have been performed to determine the Mode II fracture toughness of Mizunami granite rock samples using a cylindrical `punch-through' testing device. In this paper we attempt to understand and interpret the experimental results by numerical simulation of the fundamental shear fracture initiation and coalescence processes, using a random array of displacement discontinuity crack elements. It is found that qualitative agreement between the experimental and numerical results can be established, provided that shear-like micro-scale failure processes can be accommodated by the failure initiation rules that are used in the numerical simulations. In particular, it is found that the use of an exclusively tension-driven failure initiation rule does not allow the formation of macro-shear structures. It is apparent, also, that further investigation is required to determine how consistent rules can be established to link micro-failure criteria to equivalent macro-strength and toughness properties for a macro-shear slip surface.     

The role of the Pernicana Fault System in the spreading of Mt. Etna (Italy) during the 2002–2003 eruption

Flank instability and collapse are observed at many volcanoes. Among these, Mt. Etna is characterized by the spreading of its eastern and southern flanks. The eastern spreading area is bordered to the north by the E–W-trending Pernicana Fault System (PFS). During the 2002–2003 Etna eruption, ground fracturing along the PFS migrated eastward from the NE Rift, to as far as the 18 km distant coastline. The deformation consisted of dextral en-echelon segments, with sinistral and normal kinematics. Both of these components of displacement were one order of magnitude larger (~1 m) in the western, previously known, portion of the PFS with respect to the newly surveyed (~9 km long) eastern section (~0.1 m). This eastern section is located along a pre-existing, but previously unknown, fault, where displaced man-made structures give overall slip rates (1–1.9 cm/year), only slightly lower than those calculated for the western portion (1.4–2.3 cm/year). After an initial rapid motion during the first days of the 2002–2003 eruption, movement of the western portion of the PFS decreased dramatically, while parts of the eastern portion continued to move. These data suggest a model of spreading of the eastern flank of Etna along the PFS, characterized by eruptions along the NE Rift, instantaneous, short-lived, meter-scale displacements along the western PFS and more long-lived centimeter-scale displacements along the eastern PFS. The surface deformation then migrated southwards, reactivating, one after the other, the NNW–SSE-trending Timpe and Trecastagni faults, with displacements of ~0.1 and ~0.04 m, respectively. These structures, along with the PFS, mark the boundaries of two adjacent blocks, moving at different times and rates. The new extent of the PFS and previous activity over its full length indicate that the sliding eastern flank extends well below the Ionian Sea. The clustering of seismic activity above 4 km b.s.l. during the eruption suggests a deep décollement for the moving mass. The collected data thus suggests a significant movement (volume >1,100 km³) of the eastern flank of Etna, both on-shore and off-shore.Editorial responsibility: R. Cioni     

Block-supported cataclastic flow within the upper crust

Recent work from portions of the Sevier fold-thrust belt that have deformed primarily within the elastico-frictional regime, demonstrates that cataclastic flow can be subdivided into two types: matrix- and block supported. The two types may operate simultaneously within the same deforming material. However, their activity can vary spatially, temporally and across scales. Although block-supported cataclastic flow is a critical process in upper crustal deformation, it continues to be largely ignored and/or misunderstood, primarily because established concepts and definitions for cataclastic flow are chiefly based on matrix-supported cataclastic flow. Here, block-supported cataclastic flow is examined to better understand cataclastic flow in general and to explore its relationship with matrix-supported cataclastic flow.     

Laboratory Studies on Property Changes in Surrounding Clays Due to Installation of Deep Mixing Columns

This paper has identified six major factors causing property changes in surrounding soils during and after installation of deep mixing columns: soil thixotropy, soil fracturing, cement penetration and diffusion, cementation, consolidation, and heating. Laboratory tests were performed to investigate the effects of soil thixotropy, soil fracturing, and cementation in a soft marine clay, Ariake clay. Laboratory tests were conducted to evaluate property changes in surrounding clays due to installation of deep mixing columns. Test results showed that an influential zone of property changes existed in surrounding clay ranging from the edge of the columns to the distance of about twice the radius of the columns. Within this influential zone, water content decreased as samples neared the columns, while pH values and electric conductivity increased. Test results also showed that undrained shear strengths of the surrounding clays decreased during mixing but regained after a 7-day curing period and continued increasing during 28 days in this study.