煤层气水平井筒煤粉迁移特征实验研究

发布时间：2018-02-11 06:19

本文关键词： 煤层气钻屑捞砂水平井启动流量压差流型　出处：《西安科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：煤层具有低抗拉强度、抗压强度、弹性模量和高泊松比的特性。煤层气井在钻井、排采过程中由于压力波动、气液冲刷、机械碰撞等外力作用,不可避免地会产生煤粉,煤粉产出对煤层气的排采有有利的一面,适量的煤粉排出,可以疏通流体运移通道,有利于煤层流体导通,扩大压降范围,增大煤层气井的控气面积,提高煤层气井的产气量。但是当煤粉产出量过大时,就会产生不利的影响。一方面,压力波动或者排水强度过大会导致煤粉激动,煤粉随液相或者气相一起运移。当流速降低或者遇到狭窄不能通过的缝隙,煤粉便沉降淤积在该处,会降低原始裂隙和支撑裂隙的导通能力,导致储层渗透性下降。另一方面,由于水平井在钻进时是略有起伏式的,和液相一同进入水平井段的煤粉,当运移至上行井段,若液相流速不足以搬运抬升煤粉,煤粉便逐渐淤积在井筒中。造成不同程度的阻塞井筒,有可能造成水平井报废。运移至排水泵位置的煤粉,可能会导致埋泵现象。煤粉堵塞泵吸入口,致使阀门关闭不严,大幅度降低水泵功效。有时会形成黏稠胶状物进入泵内,对泵筒和柱塞造成磨损,泵效降低,甚至造成卡泵现象,导致排采过程中频繁检泵。为此,有必要确定煤粉启动的条件和规律,为控制排采速度提供依据,进而防止发生埋泵,卡泵等排采事故,延长检泵周期。通过实验模拟钻屑样和捞砂样在水平井中的运动得到如下认识:不同粒径的钻屑煤粉的启动运移规律基本相同。相对而言捞砂样的运移规律更为复杂。但是这两种煤样随着液相流量的增加,遵循静止-滑动-滚动-层移-悬移的运移状态变化规律。与钻屑样相比,粒径较小时,捞砂样运移需要的流量值较小,这是由于捞砂样磨圆度好,易于滚动。粒径较大时,由于捞砂样中的沙粒密度大,钻屑样相对更好启动。改变模拟管道的倾角,则启动流量也会发生相应的变化。随着管道下倾加剧,煤粉启动流量变小,倾角越大,启动越困难。在确定的管道倾斜角度下,随着粒径增大,煤粉的启动流量增加。用一次函数对启动流量和煤粉粒径之间的关系进行拟合,拟合度较高。一次函数对启动流量和倾角间关系的拟合度也很好,这说明通过一次函数可以较好的预测不同粒径和管道倾角下的煤粉启动流量。气相加入后,管道中为三相介质相互作用状态,气相对水流的扰动作用很强,煤粉很容易就悬浮起来随水流开始运移。管道一旦有角度,气液比越大,气相的扰动作用就越强,煤粉的运移效率随之增加。管道的流量与压差直接相关,压差越大流量越大,两者关系用一次函数拟合度高。研究的最后建立了液固两相流、气液固三相流煤粉启动-运移模型,可大概预测不同粒径煤粉在特定水平井倾角下的启动流量,以及不同气液比对应的压差。
[Abstract]:Coal seam has the characteristics of low tensile strength, compressive strength, elastic modulus and high Poisson ratio. Coal powder will inevitably be produced in coalbed methane wells due to pressure fluctuation, gas-liquid scour, mechanical collision and other external forces. The output of pulverized coal has a beneficial effect on coal bed methane production. Proper amount of pulverized coal can dredge the passage of fluid transfer, which is beneficial to the flow conduction of coal seam, the expansion of pressure drop range, and the increase of gas control area of coalbed methane wells. Increase the gas production of coalbed methane wells. But when the production of pulverized coal is too large, there will be adverse effects. On the one hand, pressure fluctuations or excessive drainage intensity will lead to pulverized coal agitation. Pulverized coal moves along with liquid or gas phase. When the flow rate decreases or the narrow gap cannot pass, the pulverized coal settles and silts there, which reduces the conductivity of the original fracture and the supporting fissure, and results in the decrease of reservoir permeability, on the other hand, Because the horizontal well is slightly undulating during drilling, the pulverized coal that enters the horizontal well with the liquid phase, when transported to the upstream section, if the liquid flow velocity is not sufficient to carry the raised pulverized coal, The pulverized coal gradually silts up in the wellbore, causing various degrees of blockage in the wellbore, which may cause the horizontal well to be abandoned. The pulverized coal transported to the position of the drainage pump may lead to the phenomenon of burying the pump. The pulverized coal will block the suction port of the pump and cause the valve to close insufficiently. Reduce pump efficiency by a large margin. Sometimes a viscous glue will enter the pump, causing wear and tear to the pump cylinder and plunger, reducing pump efficiency and even causing pump jam phenomenon, leading to frequent pump inspection in the process of discharging and mining. For this reason, It is necessary to determine the conditions and rules of pulverized coal starting, to provide the basis for controlling the drainage speed, and to prevent the occurrence of mining accidents, such as burying pump and stuck pump, etc. Through the experimental simulation of the movement of cuttings and sand samples in horizontal wells, we can get the following understanding: the starting and migration laws of different diameter cuttings drilling coal powder are basically the same, and relatively speaking, the migration laws of dredged sand samples are more regular. But these two kinds of coal samples increase with the liquid flow rate, It follows the law of movement state variation of static, sliding, rolling, layer moving and suspended moving. Compared with the sample of drilling debris, the flow rate of the sand sample is smaller than that of the sample of drilling. This is due to the fact that the sand sample has good grinding roundness, is easy to roll, and when the particle size is larger, Because the sand density in the dredged sand sample is high, the drilling sample is better to start up. If the inclination angle of the simulated pipeline is changed, the starting flow rate will change accordingly. With the downdip of the pipeline increasing, the starting flow rate of pulverized coal becomes smaller and the inclination angle is larger. The more difficult it is to start, the more difficult the starting flow rate of pulverized coal increases with the increase of particle size under the fixed inclined angle of the pipeline. The relationship between the starting flow rate and the particle size of pulverized coal is fitted by the first function. The first function has a good fit for the relationship between the starting flow rate and the inclination angle, which indicates that the starting flow rate of pulverized coal under different particle size and pipe inclination angle can be well predicted by the first order function. In a three-phase medium interaction state, the disturbance between gas and water flow is very strong, and pulverized coal is easily suspended to start moving with the water flow. Once the pipe has an angle, the greater the gas-liquid ratio, the stronger the disturbance of the gas phase. The flow rate of pipeline is directly related to the pressure difference, the greater the pressure difference is, the greater the flow rate is, the higher the fitting degree is with the primary function. Finally, the liquid-solid two-phase flow is established. The gas-liquid-solid three-phase pulverized coal starting-migration model can be used to predict the starting flow rate and the pressure difference of different gas-liquid ratio under certain horizontal well inclination angle.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD712

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