脉冲参数对致密储层水力压裂起裂压力影响

Effect of pulse parameters on hydraulic fracturing initiation pressure of tight reservoir

为揭示脉冲参数对致密储层水力压裂起裂压力的影响规律,基于流固耦合理论,建立致密岩脉冲水力压裂数学模型和有限元模型,并利用ABAQUS中的CDP模型对脉冲水压作用下射孔眼周围岩体损伤情况进行模拟计算,分析脉冲赋值及波形对起裂压力的影响规律.计算结果表明:在脉冲循环载荷作用下,射孔面损伤呈现出损伤累积效应,随脉冲次数增加,射孔面损伤值逐渐增加;脉冲幅值越大,裂缝起裂所需循环次数越少;脉冲幅值相同时,正弦形脉冲作用下射孔面损伤最大,其次为三角形脉冲和矩形脉冲.因此,可通过脉冲循环加载累积致裂达到降低起裂压力的效果.研究结论为降低致密储层起裂压力和改造成本提供新思路.

In order to reveal the influence law of pulse parameters on the hydraulic fracturing initiation pressure of tight reservoir,based on the fluid solid coupling theory,the mathematical model and finite element model of tight rock pulse hydraulic fracturing are established.The rock mass damage around the perforation under the action of pulse water pressure is simulated and calculated using the CDP model in ABAQUS,and the influence law of pulse assignment and waveform on the initiation pressure is analyzed.The calculation results show that under the action of pulse cyclic load,the perforation surface damage gradually accumulated,with the increase of the number of pulses,the perforation surface damage value increases gradually.The larger the pulse amplitude,the fewer cycles are required for fracture initiatate;As the pulse amplitude is the same,the perforation surface damage under sinusoidal pulse is the largest,followed by triangular pulse and rectangular pulse.Therefore,using damage accumulation effect of pulse cyclic loading can reduce the initiation pressure.The research conclusion provides a new idea for reducing the initiation pressure and reconstruction cost of tight rock.