静态压裂增透低渗煤层基础实验研究
发布时间：2018-10-21 10:15
【摘要】：在我国的煤系地层中贮存有丰富的煤层气。煤层气资源在能源领域是一种良好的清洁能源,热值高且燃烧后无有害气体产生。煤层气的主要成分是甲烷,煤层中甲烷的异常涌出会造成瓦斯事故的发生。如果甲烷直接向空气中排放,则会产生温室效应。因此合理利用煤层气资源不仅有利于能源的充分利用,还可以起到保护环境的目的,同时又可以避免瓦斯事故的发生实现煤矿的安全生产。我国的煤层普遍具有非均质性、渗透率低、瓦斯含量高的特点,这些特点使得直接预抽瓦斯难度大,因此提高高瓦斯低透气性煤层的渗透率已经成为制约矿井瓦斯抽采的瓶颈。静态爆破技术又称为无声爆破,是利用静态爆破剂与水混合后膨胀所产生的膨胀压作用于药孔孔壁使其胀裂的一种技术。静态爆破技术具有无飞石、无爆声、无冲击波和爆破震动等优点,且操作简单、安全性高,在低渗煤层致裂增透应用方面拥有良好的前景。本文提出运用静态压裂技术实现低渗煤层增透的目的,对静态压裂增透低渗煤层进行了基础实验研究。本文主要分析了静态压裂的原理及压裂过程中各阶段的应力作用情况;自制了静态压裂剂,在确定组分的基础上通过正交试验初步得出了静态压裂剂的最优配比;设计实验研究了钻孔形状、环境温度、生石灰粒径、水的酸碱度对静态压裂剂致裂效果的影响规律。本文得到以下主要结论:(1)静态压裂剂的致裂原理是膨胀源Ca O与水发生水化反应生成Ca(OH)2,水化过程中压裂剂体积增大产生膨胀压作用于孔壁。在自由状态下Ca O的水化并不能产生膨胀压,只有在受限条件下才会有膨胀压。压裂过程分为弹性阶段和非弹性阶段。以圆形孔为例,弹性阶段径向应力恒为压应力,环向应力为拉应力,钻孔周围各处应力相同。当膨胀压增大到一定值时,压裂过程进入非弹性阶段,在该阶段钻孔周边部分区域会出现微裂纹,该区域为损伤区。型煤的开裂和裂纹扩展方向沿着损伤区最大微裂纹产生的方向。(2)静态压裂剂的主要组分应该包括膨胀源、减水剂、缓凝剂、胶结剂等,具体成分为生石灰、萘系减水剂、葡萄糖酸钠、硅酸盐水泥,通过正交试验优选出的最佳配比为:生石灰:萘系减水剂:葡萄糖酸钠:硅酸盐水泥=90:3:5:7。通过XRD测试发现,静态压裂剂从膨胀压产生到膨胀压完全释放的过程中,膨胀压增速是变化的,前期增速快后期增速较慢。(3)钻孔形状会对静态压裂剂致裂效果产生影响。当钻孔为非圆孔时,在钻孔边缘尖点附近会形成应力集中区域,随着膨胀压的升高,型煤会在该应力集中区域率先出现开裂,裂纹沿着尖点方向扩展延伸。(4)环境温度、生石灰粒径、水的酸碱度都会对静态压裂剂致裂效果产生影响。环境温度对型煤的开裂效果具有显著的影响,20-50℃间随着环境温度的升高型煤的开裂时间逐渐缩短。生石灰的粒径过大将导致静态压裂剂的压裂效应无法完全释放,用粒径为6-18目的生石灰配制静态压裂剂其压裂性能最佳。使用碱性水配制的静态压裂剂其压裂性能优于酸性水,但当碱度达到一定值时,随着碱性的提升压裂性能开始下降,当水的PH为8时压裂效果最优。
[Abstract]:Rich coal-bed gas is stored in coal-bearing strata in China. the coal bed gas resource is a good clean energy in the energy field, the heat value is high, and no harmful gas is generated after combustion. The main component of coal bed gas is methane, and the abnormal emission of methane in coal seam can cause gas accident. If methane is directly discharged into the air, the greenhouse effect will be generated. Therefore, the reasonable utilization of the coal bed gas resources is not only beneficial to the full utilization of energy, but also the purpose of protecting the environment, and meanwhile, the safety production of the coal mine can be realized by avoiding the occurrence of gas accidents. The coal seam of China is generally characterized by non-homogeneous property, low permeability and high gas content. These characteristics make the direct pre-extraction gas difficult, so the permeability of high gas and low permeability coal seam has become the bottleneck restricting mine gas extraction. The static blasting technique is also called silent blasting, which is a technique for expanding the pore wall of the medicine hole by using the expansion pressure generated by the expansion of the static blasting agent and water. The static blasting technology has the advantages of no flying rock, no explosion sound, no shock wave and blasting vibration and the like, and has the advantages of simple operation and high safety, and has good prospect in the application of low-permeability coal seam-induced cracking and thickening. In this paper, the purpose of using static fracturing technology to realize the permeability of low-permeability coal seam is put forward, and the basic experimental study is carried out on the static fracturing and permeability-increasing low-permeability coal seam. In this paper, the principle of static fracturing and the stress action of each stage in fracturing process are analyzed. The static fracturing agent is self-made, and the optimum proportion of static fracturing agent is obtained by orthogonal experiment on the basis of determining the composition. Effect of lime particle size and pH value on cracking effect of static fracturing agent. The main conclusions are as follows: (1) The crack principle of static fracturing agent is that Ca (OH) 2 is generated by hydration reaction between the expansion source Ca O and water, and the volume of the fracturing agent in the hydration process is increased to generate the expansion pressure acting on the pore wall. The hydration of the Ca O in the free state does not produce an expansion pressure, and only under restricted conditions there will be an expansion pressure. The fracturing process is divided into elastic stage and non-elastic stage. According to the circular hole, the radial stress in the elastic phase is the compressive stress, the stress of the ring is tensile stress, and the stress around the borehole is the same. when the expansion pressure is increased to a certain value, the fracturing process enters a non-elastic stage, and micro-cracks appear in the area of the peripheral part of the drilling hole at the stage, and the area is a damaged area. The cracking and crack propagation direction of briquette is along the direction of the maximum micro-crack in the damage zone. (2) The main components of static fracturing agent should include expansion source, water reducing agent, retarder, cementing agent and the like, and the concrete components are quick lime, water reducing water reducing agent, sodium gluconate and silicate cement. Sodium gluconate: Portland cement = 90: 3: 5: 7. By means of XRD, the expansion and pressure increase of static fracturing fluid from the expansion pressure to the full release of the expansion pressure is changed, and the growth rate is slower in the early stage. (3) The drilling shape will have an effect on the fracturing effect of static fracturing agent. When the drilling hole is a non-circular hole, a stress concentration area is formed near the edge tip of the drilling hole, and as the expansion pressure increases, the briquette can lead to crack in the stress concentration area, and the crack extends along the direction of the tip point. (4) The influence of ambient temperature, lime particle size and pH value of water on the cracking effect of static fracturing agent will be affected. The environmental temperature has a remarkable effect on the cracking effect of the briquette, and the cracking time of the briquette is gradually shortened at 20-50 DEG C with the increase of the ambient temperature. The fracturing effect of the static fracturing agent can not be completely released after the particle size of the calcined lime is too small, and the fracturing performance of the static fracturing agent is optimized by using the calcined lime with the grain diameter of 6-18 meshes. The fracturing performance of static fracturing agent prepared by using alkaline water is superior to that of acid water, but when the alkalinity reaches a certain value, the fracturing effect is optimal when the PH of water is 8.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD712.6
本文编号：2284796
[Abstract]:Rich coal-bed gas is stored in coal-bearing strata in China. the coal bed gas resource is a good clean energy in the energy field, the heat value is high, and no harmful gas is generated after combustion. The main component of coal bed gas is methane, and the abnormal emission of methane in coal seam can cause gas accident. If methane is directly discharged into the air, the greenhouse effect will be generated. Therefore, the reasonable utilization of the coal bed gas resources is not only beneficial to the full utilization of energy, but also the purpose of protecting the environment, and meanwhile, the safety production of the coal mine can be realized by avoiding the occurrence of gas accidents. The coal seam of China is generally characterized by non-homogeneous property, low permeability and high gas content. These characteristics make the direct pre-extraction gas difficult, so the permeability of high gas and low permeability coal seam has become the bottleneck restricting mine gas extraction. The static blasting technique is also called silent blasting, which is a technique for expanding the pore wall of the medicine hole by using the expansion pressure generated by the expansion of the static blasting agent and water. The static blasting technology has the advantages of no flying rock, no explosion sound, no shock wave and blasting vibration and the like, and has the advantages of simple operation and high safety, and has good prospect in the application of low-permeability coal seam-induced cracking and thickening. In this paper, the purpose of using static fracturing technology to realize the permeability of low-permeability coal seam is put forward, and the basic experimental study is carried out on the static fracturing and permeability-increasing low-permeability coal seam. In this paper, the principle of static fracturing and the stress action of each stage in fracturing process are analyzed. The static fracturing agent is self-made, and the optimum proportion of static fracturing agent is obtained by orthogonal experiment on the basis of determining the composition. Effect of lime particle size and pH value on cracking effect of static fracturing agent. The main conclusions are as follows: (1) The crack principle of static fracturing agent is that Ca (OH) 2 is generated by hydration reaction between the expansion source Ca O and water, and the volume of the fracturing agent in the hydration process is increased to generate the expansion pressure acting on the pore wall. The hydration of the Ca O in the free state does not produce an expansion pressure, and only under restricted conditions there will be an expansion pressure. The fracturing process is divided into elastic stage and non-elastic stage. According to the circular hole, the radial stress in the elastic phase is the compressive stress, the stress of the ring is tensile stress, and the stress around the borehole is the same. when the expansion pressure is increased to a certain value, the fracturing process enters a non-elastic stage, and micro-cracks appear in the area of the peripheral part of the drilling hole at the stage, and the area is a damaged area. The cracking and crack propagation direction of briquette is along the direction of the maximum micro-crack in the damage zone. (2) The main components of static fracturing agent should include expansion source, water reducing agent, retarder, cementing agent and the like, and the concrete components are quick lime, water reducing water reducing agent, sodium gluconate and silicate cement. Sodium gluconate: Portland cement = 90: 3: 5: 7. By means of XRD, the expansion and pressure increase of static fracturing fluid from the expansion pressure to the full release of the expansion pressure is changed, and the growth rate is slower in the early stage. (3) The drilling shape will have an effect on the fracturing effect of static fracturing agent. When the drilling hole is a non-circular hole, a stress concentration area is formed near the edge tip of the drilling hole, and as the expansion pressure increases, the briquette can lead to crack in the stress concentration area, and the crack extends along the direction of the tip point. (4) The influence of ambient temperature, lime particle size and pH value of water on the cracking effect of static fracturing agent will be affected. The environmental temperature has a remarkable effect on the cracking effect of the briquette, and the cracking time of the briquette is gradually shortened at 20-50 DEG C with the increase of the ambient temperature. The fracturing effect of the static fracturing agent can not be completely released after the particle size of the calcined lime is too small, and the fracturing performance of the static fracturing agent is optimized by using the calcined lime with the grain diameter of 6-18 meshes. The fracturing performance of static fracturing agent prepared by using alkaline water is superior to that of acid water, but when the alkalinity reaches a certain value, the fracturing effect is optimal when the PH of water is 8.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD712.6
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