松软煤层穿层钻孔水力压裂实验研究

分析了煤层水力压裂增透的原理,设计了两个穿层钻孔(一个压裂对象为构造软煤,另外一个为软煤的坚硬顶板)的压裂方案,在淮北矿业(集团)有限责任公司临焕煤矿进行了现场试验,采用压裂后钻孔瓦斯抽采浓度与流量等指标考察压裂效果.试验表明,水力压裂对松软煤层效果甚微.针对这一问题,提出了对松软煤层的坚硬顶板进行压裂以达到对该煤层卸压增透的目的,现场结果表明松软煤层顶板压裂能大幅增加松软煤层的渗透率,增强瓦斯抽放的效果.     

顺煤层定向长钻孔水力压裂煤层增透技术及试验研究

为了提高顺煤层钻孔瓦斯抽采效果,在分析井下煤层水力压裂技术发展现状及其增透机理的基础上,结合定向长钻孔施工技术与煤层水力压裂增透强化抽采技术,提出了顺煤层定向长钻孔裸孔坐封、水力压裂增透技术工艺。鉴于赵固二矿二1煤层中等偏硬、厚度大、瓦斯含量高等特征,选择该矿井二1煤层进行长钻孔整体压裂试验。结果表明:采用煤层长钻孔孔内封隔器裸孔坐封方式能够满足赵固二矿水力压裂煤层段密封需要;注水压裂过程压力上升平稳,泵压和流量达到设计要求;工具串回收过程无塌孔和卡阻现象,顺层长钻孔孔内封隔器裸孔坐封和压裂工艺达到预期目标;整体水力压裂影响半径最大达到38 m(单侧),压裂钻孔百米钻孔瓦斯抽采量比常规顺层钻孔有了较大提升。     

低渗厚煤层水力压裂增渗技术研究与应用

为增强保安煤矿15#低渗厚突出煤层的透气性,提高穿层钻孔瓦斯的抽采效果,改善煤矿生产接替困难的现状,采用工业试验和数值分析相结合的方法,对低渗厚煤层的水力压裂增透技术及工艺进行试验研究。结果表明:15#煤层水力压裂影响半径高达40m,透气性显著增强,抽放浓度提高3倍以上,抽放纯量提高4倍以上,掘进速度提高2.5倍以上;形成了一整套包括压裂参数设计、压裂钻孔封孔、注水压裂增透、压裂效果考察、煤巷条带瓦斯抽采、煤巷掘进等适合阳泉矿区厚煤层的水力压裂增渗技术。     

煤矿井下水力压裂产能主控因素研究

为提高煤储层的透气性,将地面油气开采的水力压裂技术引入煤矿井下进行煤层气的抽采和瓦斯治理。通过对影响煤矿井下水力压裂效果的煤层及煤层气赋存特征、压裂工艺等进行样本统计分析,确定储层透气性、煤体结构、布孔方式是影响煤矿井下水力压裂效果的主控因素,注入液量、注入压力、煤层埋深等因素对其影响较小。研究成果可对煤矿井下水力压裂设计提供参考。     

煤矿井下水力压裂增透抽采瓦斯存在问题分析及对策

在分析总结我国煤矿井下水力压裂增透抽采已有研究成果的基础上,从理论基础、装备水平、技术工艺等方面探讨了井下钻孔水力压裂取得的成绩与不足,认为目前煤矿井下水力压裂增透抽采理论与技术多借鉴于石油气、煤层气开采的相关研究成果,尚没有完全形成以煤层瓦斯赋存特征、采掘应力场、裂隙场、流场的动态变化特征和井下瓦斯抽采特点等为基础的、特色鲜明的煤矿井下水力压裂理论及技术体系。据此,提出了相应对策:大力发展瓦斯抽采地质学,研究水力压裂前、中、后地应力和水力裂缝演化规律及瓦斯抽采的动态响应特征;进一步提高煤矿井下水力压裂的钻孔、封孔、压裂、测试等相关的设备水平;以缝网改造为煤矿井下水力压裂技术的发展思路,结合井下"三场"动态变化特征,有的放矢进行水力压裂设计,丰富内涵,扩展外延;大力发展井下与地面联合水力压裂抽采瓦斯及煤气共采等理论与技术。为煤矿井下水力压裂的推广应用提供一定的借鉴。     

上向穿层钻孔水力冲孔卸压增透技术研究

为考察水力冲孔卸压增透技术的消突效果,在潘二煤矿A组煤底抽巷穿层钻孔中进行试验。在煤层段每米冲孔时间不低于60min条件下,单孔冲出煤量约2.0t/m,可形成直径约1.3m孔洞,水力冲孔后钻孔周围的卸压范围显著增加,钻孔瓦斯抽采量提高3倍,透气性系数由原来0.19m2/(MPa2.d)提高到1.71m2/(MPa2.d),钻孔流量衰减系数降为冲孔前的1/3,有效影响半径达到5m,降低了瓦斯突出潜能和危险性,卸压增透效果明显。     

超高压水力割缝强化抽采瓦斯技术研究

水力割缝是一种重要的强化瓦斯抽采增透技术,现已开始在低透气性突出煤层应用。为了进一步考察其实际效果,选取新集二矿1煤组220112工作面底抽巷实施了100 MPa超高压水力割缝试验。试验结果表明:割缝后,瓦斯抽采纯量平均0.77 m3/min,是未割缝钻孔的瓦斯抽采纯量(0.34 m~3/min)的2.26倍;1煤层组瓦斯抽采钻孔抽采30、60天的抽采有效半径为5 m、7.5 m,极限抽采半径为8 m,相比水力冲孔、未割缝钻孔抽采有效半径显著增加,超高压水力割缝强化抽采瓦斯技术具有广泛的应用前景。     

CO_2致裂增透技术的抽采半径考察研究

为了提高在某矿15号煤层穿层钻孔瓦斯抽采效率和缩短瓦斯抽采达标时间,利用CO_2致裂增透技术对瓦斯抽采钻孔致裂作用进行抽采半径考察,通过对煤层致裂增透前后的瓦斯抽采效果进行对比分析可知三组不同瓦斯抽采半径的最优抽采钻孔间距,最终确定瓦斯抽采半径。现场试验表明,CO_2致裂增透技术条件下,三组瓦斯抽采半径致裂孔的布置方式,1.5m瓦斯抽采半径能有效缩短抽采达标时间,提高瓦斯抽采率。     

深部高瓦斯低透突出煤层水力化增透技术模拟分析及试验研究

本文以淮南矿区低透气性煤层为试验区,考察钻孔采取水力化措施,形成水力增透理论。水力冲孔后,储层内孔隙压力发生很大变化,导致地应力场的变化,并在钻孔的煤孔段形成较大的圆柱体状的洞穴,煤体卸压范围扩大,裂隙入渗进一步扩大,透气性增强。在对淮南潘二矿 A 组煤工作面进行水力冲孔试验,取得了较好的效果,抽采半径增加 1.25 倍,抽采量增加 2.68 倍,煤体的透气性系数增加到原来的 2.5 倍,衰减系数只有原来的 1/3,降低了煤层的突出危险性,保证了安全生产。     

双关键层跨煤组远程卸压增透效应试验研究

以潘二煤矿11223工作面远程卸压4~#煤为研究背景,采用物理模拟、FLAC~(3D)流固耦合模拟及现场工程实测相结合的方法,对远程被保护层4~#煤卸压增透区分布特征及关键层破断影响卸压瓦斯抽采效果机制进行分析.结果表明:1)卸压瓦斯抽采量极值点间距与上位关键层周期断裂步距吻合,而下位关键层破断对卸压瓦斯抽采没有直接影响,上位关键层周期断裂步距对远程卸压瓦斯抽采峰位具有一定预测作用;2)经压实变形后,被保护层膨胀变形和渗透率在煤层倾斜方向呈双峰形态,其量值为在中下部最大,中上部次之,中部最小;3) 4~#煤实测膨胀变形达到1.26%,卸压瓦斯抽采率为69.59%,煤层渗透率扩大2 149倍,证明该工程地质条件下3~#煤远程卸压4~#煤具有可行性.     

Guiding-controlling technology of coal seam hydraulic fracturing fractures extension

Aiming at the uncontrollable problem of extension direction of coal seam hydraulic fracturing, this study analyzed the course of fractures variation around the boreholes in process of hydraulic fracturing, and carried out the numerical simulations to investigate the effect of artificial predetermined fractures on stress distribution around fractured holes. The simulation results show that partial coal mass occurs relatively strong shear failure and forms weak surfaces, and then fractures extended along the desired direction while predetermined fractures changed stress distribution. Directional fracturing makes the fractures link up and the pressure on coal mass is relieved within fractured regions. Combining deep hole controlling blasting with hydraulic fracturing was proposed to realize the extension guiding-controlling technology of coal seam fractures. Industrial experiments prove that this technology can avoid local stress concentration and dramatically widen the pressure relief scope of deep hole controlling blasting. The permeability of fractured coal seam increased significantly, and gas extraction was greatly improved. Besides, regional pressure relief and permeability increase was achieved in this study.     

Reservoir reconstruction technologies for coalbed methane recovery in deep and multiple seams

Multiple coal seams widely develop in the deep Chinese coal-bearing strata. Ground in situ stress and coal seam gas pressure increase continuously with the increase of the mining depth, and coal and gas outburst disasters become increasingly severe. When the coal is very deep, the gas content and pressure will elevate and thus coal seams tends to outburst-prone seams. The safety and economics of exploited firstmined coal seams are tremendously restricted. Meanwhile, the multiple seams occurrence conditions resulted in different methane pressure systems in the coal-bearing strata, which made the reservoir reconstruction of coal difficult. Given the characteristics of low saturation, low permeability, strong anisotropy and soft coal of Chinese coal seams, a single hydraulic fracturing surface well for reservoir reconstruction to pre-drain the coalbed methane(CBM) of multiple seams concurrently under the different gas pressure systems has not yet gained any breakthroughs. Based on analyses of the main features of deep CBM reservoirs in China, current gas control methods and the existing challenges in deep and multiple seams, we proposed a new technology for deep CBM reservoir reconstruction to realize simultaneous high-efficiency coal mining and gas extraction. In particular, we determined the first-mined seam according to the principles of effectiveness and economics, and used hydraulic fracturing surface well to reconstruct the first-mined seam which enlarges the selection range of the first-mined seam. During the process of mining first-mined seam, adjacent coal seams could be reconstructed under the mining effect which promoted high-efficiency pressure relief gas extraction by using spatial and comprehensive gas drainage methods(combination of underground and ground CBM extraction methods). A typical integrated reservoir reconstruction technology, ‘‘One well for triple use", was detailed introduced and successfully applied in the Luling coal mine. The application showed that the proposed technology could effectively promote coal mining safety and simultaneously high-efficiency gas extraction.     

Phenomenon of methane driven caused by hydraulic fracturing in methane-bearing coal seams

The methane concentration of the return current will always be enhanced to a certain degree when hydraulic fracturing with bedding drilling is implemented to a gassy coal seam in an underground coal mine. The methane in coal seam is driven out by hydraulic fracturing. Thus, the phenomenon is named as methane driven effect of hydraulic fracturing. After deep-hole hydraulic fracturing at the tunneling face of the gassy coal seam, the coal methane content exhibits a ‘‘low-high-low" distribution along excavation direction in the following advancing process, verifying the existence of methane driven caused by hydraulic fracturing in methane-bearing coal seam. Hydraulic fracturing causes the change of pore-water and methane pressure in surrounding coal. The uneven distribution of the pore pressure forms a pore pressure gradient. The free methane migrates from the position of high pore(methane) pressure to the position of low pore(methane) pressure. The methane pressure gradient is the fundamental driving force for methane-driven coal seam hydraulic fracturing. The uneven hydraulic crack propagation and the effect of time(as some processes need time to complete and are not completed instantaneously) will result in uneven methane driven. Therefore, an even hydraulic fracturing technique should be used to avoid the negative effects of methane driven; on the other hand, by taking fully advantage of methane driven, two technologies are presented.     

Progress on the hydraulic measures for grid slotting and fracking to enhance coal seam permeability

A method of hydraulic grid slotting and hydraulic fracturing was proposed to enhance the permeability of low permeability coal seam in China. Micro-structural development and strength characteristics of coal were analysed to set up the failure criterion of coal containing water and gas, which could describe the destruction rule of coal containing gas under the hydraulic measures more accurately. Based on the theory of transient flow and fluid grid, the numerical calculation model of turbulence formed by high pressure oscillating water jet was used. With the high speed photography test, dynamic evolution and pulsation characteristics of water jet water analysed which laid a foundation for mechanism analysis of rock damage under water jet. Wave equation of oscillating water jet slotting was established and the mechanism of coal damage by the impact stress wave under oscillation jet was revealed. These provide a new method to study the mechanism of porosity and crack damage under high pressure jet.Fracture criterion by jet slotting was established and mechanism of crack development controlled by crack zone between slots was found. The fractures were induced to extend along pre-set direction,instead of being controlled by original stress field. The model of gas migration through coal seams after the hydraulic measures for grid slotting and fracking was established. The key technology and equipment for grid slotting and fracking with high-pressure oscillating jet were developed and applied to coal mines in Chongqing and Henan in China. The results show that the gas permeability of coal seam is enhanced by three orders of magnitude, efficiency of roadway excavation and mining is improved by more than 57%and the cost of gas control is reduced by 50%.     

鄂西渝东区东岳庙段页岩气压裂实践与分析

前期评价表明,江汉油田部分区块页岩气富集、地质条件优越,其中鄂西渝东区被评为中石化南方Ⅰ类区块,具有巨大的勘探开发潜力。鄂西渝东区东岳庙段的页岩气压裂实践证明缝网压裂技术在工艺上是可行的,陆相东岳庙段页岩储层地层压力系数高、天然裂缝发育,有利于页岩气的大规模缝网压裂改造。微地震裂缝监测结合施工曲线有助于分析压裂过程中具体现象,但应加强裂缝监测手段及精度提升研究,加强数据的校核及干扰的排除以提高监测结果的可靠性。     

Hydraulic drill hole reaming technology with large flow and draining of coal mine gas

This paper takes Zhaozhuang mine in Shanxi province as an example to study the technology of hydraulic reaming drill hole for improving the gas extraction. The influence of the physical properties of coal seam on the hydraulic reaming drill holes and the draining of coal mine gas were analyzed and discussed for different coal structure areas, and the following conclusions were made. Hydraulic drill hole reaming has had a positive impact in Zhaozhuang Mine, and can improve the efficiency of gas extraction to different degrees. The water jet pressure used in hydraulic drill hole reaming mainly depends on the structure of the coal. When the coal seam basically becomes integrated, the critical water jet pressure increases, the discharge becomes relatively easy to achieve, the blocking effect on the gas extraction decreases, and the gas extraction significantly increases after the reaming process. When the coal seam is broken, the critical water jet pressure decreases, the discharge becomes difficult to achieve, the blocking effect on the gas extraction becomes obvious, and the gas extraction changes slightly after reaming.     

吐哈盆地沙尔湖地区煤层气钻完井适用技术探讨

在剖析美国圣胡安盆地煤层气空气钻井、裸眼洞穴完井技术及优势的基础上,确定了低煤阶煤层气钻井及裸眼洞穴完井的煤储层条件等,并以吐哈盆地沙尔湖地区低煤阶煤层气为主要研究对象,利用类比法及地质统计法,具体分析了吐哈盆地沙尔湖地区的煤储层厚度、含气量、渗透率、井壁稳定性及储层压力条件等．研究表明,沙尔湖地区煤层厚度大,储层物性好,井壁稳定性好,可采用低成本空气钻井及裸眼完井技术提高钻井效率,保护煤储层,提高煤层气采收率．     

Effect of ground stress on hydraulic fracturing of methane well

Most of the coal reservoirs in China are of low-permeability, so hydraulic fracturing is widely used to improve the permeability in the extraction of gas by ground drilling. The ground stress around the well was analyzed by using theory of elasticity. The pressure when the well fractured is formulated and the effect of ground stress on pressure is discussed. The effect of ground-stress-differences on hydraulic fracturing was analyzed by using the numerical software RFPA2D-Flow in reference to the tectonic stress in Jincheng coal area. The results show that: 1) the position where initial fracture appears is random and fracture branches emerge when the fractures expand if ground stresses in any two directions within a horizontal plane are equal; 2) otherwise, the fractures expand in general along the direction of maximum ground stress and the critical pressure decreases with increasing ground-stress-differences and 3) the preferred well-disposition pattern is diamond shaped. The preferred well spacing is 250 m×300 m. This study can provide a reference for the design of wells.     

义18井区泥页岩裂缝油藏储层改造方式优选

针对胜利油田渤南油田义18井区中孔特低渗泥页岩油藏的生产特点和水力裂缝的渗流特征,运用油水井储层改造优化设计系统软件,以采油量、注水量为目标对压裂和酸化两种储层改造方式的各项工艺参数进行模拟．根据模拟结果,对其进行评价和分析,优选出压裂是义18井区最适合的储层改造方式．     

用常规黑油模型模拟煤层气开采过程

流体在煤层中的传输机理由两部分组成,气体在煤内表面解吸,并通过基岩和微孔隙扩散进入裂缝网络中。若岩块表面甲烷气体的释放速度比气,水相在煤层割理中的流动速度快得多,那么在模拟煤层气开采过程时,解吸动能可以不考虑,根据这个假设可认为：在给定压力下煤层吸附的甲烷气体量类似于相应压力下溶解在原油中的气体量,煤层中的朗格缪尔等温曲线可视为常规黑油油藏中的溶解气油比曲线。若将煤层表面的吸附气作为不流动油中溶解气来处理,那么可用常规黑油模型描述煤层气,而不需要对模型源码做会何修改,基于上述思路,用黑油模型模拟煤层气开采过程,并与用煤层气模拟软件（COMETPC）的计算结果进行了比较,趋势非常接近。