充填型单缝煤岩水力脉动解堵试验研究
摘要: 煤层气开采过程中,产生了大量的煤粉。煤粉聚集于裂隙中,成为影响煤层气渗透性能的重要因素之一。利用室内自行研制的可调频脉动水力压裂系统及预制充填型单缝的煤岩,开展不同频率条件下水力脉动解堵试验,研究脉动作用下解堵水压演化过程和解堵效果。试验结果表明:水力脉动解堵压力演化过程可分为三个阶段:压力上升阶段、压力下降阶段和压力波动稳定阶段。脉动作用下解堵压力阀值比定常流作用下更低、压降持续时间更短、压降幅值更小。定常流作用下煤粉运移集中在压力下降阶段,脉动压力作用下煤粉在压力下降阶段和压力波动稳定阶段均有运移,但煤粉总的运移量和定常流作用下的相当。脉动作用和定常流作用下径向渗透主要发生在压力上升至压力峰值阶段,但脉动流的解堵时间短,则滤液渗透半径小,储层伤害小。在3Hz的频率条件下,解堵效果最好,且其解堵压力阀值较低,解堵路径最为平直,压裂液渗流半径最小。
Experimental study on unblocking of coalbed with single-slit filling by pulse hydraulic fracturing
- Available Online:
2020-12-11
Abstract: During the process of coalbed methane extraction, a large amount of coal powder is produced. And coal powder accumulates in the fissure, which is one of the important factors to affect the permeability of coalbed methane. The unblocking test of coalbed under different frequency conditions is carried out by using the self-developed hydraulic fracturing system with adjustable frequency pulsation and the prefabricated samples with single-slit filling, to study the evolution process of the unblocking pressure and the unblocking effect under the pulse action. The results show that the evolution process of unblocking pressure can be divided into three stages: pressure rise phase, decline phase and pressure fluctuation stability phase; And compared to steady flow the pressure threshold under the pulse action is lower, the pressure drop duration is shorter, and the pressure drop amplitude is smaller. The coal powder has been transported in the pressure drop stage and the pressure fluctuation stable stage under the pulsating flow, while coal migration is concentrated in the pressure drop stage under the steady flow, and the total migration volume of coal powder in the two condition is equivalent ; The fluid infiltration along the radial direction mainly occurs the duration of the pressure rise to the peak pressure, the filtrate penetration radius is smaller due to shorter unblocking time under the pulsating flow, and the reservoir damage is small.Under the condition of 3 Hz, the unblocking effect is the best, and the plugging pressure threshold is lower, the unblocking path is the most straight, and the fracturing fluid seepage radius is the smallest.