新型自降解堵漏剂封堵裂缝与保护储层特性评价

在裂缝性储层钻进过程中，既要封堵储层裂缝，还要兼顾完井后可解堵。针对常用暂堵类材料无法自降解，且封堵储层承压不足等问题，分析了一种新型环保自降解堵漏剂SDPF，并借助承压强度实验、傅里叶红外光谱仪、热重分析和扫描电镜（SEM）观测等方法，探讨了新型自降解堵漏剂SDPF的降解作用机理、承压堵漏和自解堵保护储层效果。实验结果表明，新型自降解堵漏剂SDPF在25 MPa下的承压破碎率小于5%；随温度升高其自降解率增大，酸性和碱性环境可促进其自降解作用，无机盐不影响其自降解作用。以SDPF为架桥颗粒，协同其它可酸溶堵漏材料，实验优化出适用于微米级和毫米级裂缝的自降解堵漏体系，该体系的封堵承压能力可达7.5 MPa ；泥饼清除和岩心返排恢复实验表明，自解堵后的岩心渗透率恢复值为85%以上，具有较好的承压堵漏与自解堵保护储层效果，可望解决裂缝堵漏与储层保护难以兼顾的技术难题。 

Evaluation on the Ability of a New Self-Degrading Lost Circulation Agent to Plug Fractures and Protect Reservoirs

When drilling in fractured reservoirs, consideration has to be given to both the plugging of the fractures to control mud losses and the removal of the plugging agents after completion of the well. Conventional temporary plugging agents do not degrade by itself and do not have enough strength to withstand the formation pressures of the reservoirs. A new environmentally friendly self-degrading lost circulation agent SDPF was analyzed for its performance as a lost circulation material (LCM). The self-degrading mechanisms, ability to control mud losses under pressure and reservoir protection by self-removal of SDPF were investigated through pressure bearing test and with Fourier infrared spectrometer, thermogravimetric analyzer (TGA) and scanning electron microscope (SEM). Experimental results have shown that under 25 MPa, the percentage of SDPF that was broken under pressure was less than 5%. The percentage of self-degrading increases with temperature, acidic and basic conditions help accelerate the self-degrading of SDPF, and inorganic salts play no role in the self-degrading of SDPF. A self-degrading mud loss control slurry was formulated with SDPF as the bridging particles and other acid-soluble materials as synergy materials. Micrometer and millimeter sized fractures can be plugged with the slurry, and fractures plugged with the slurry can withstand pressures up to 7.5 MPa. Experiment on the removal of mud cakes and core flowback have shown that rock cores after self-removal of the slurry had percent recovery of permeability of at least 85%. These experimental results have proved that the mud loss control slurry formulated has the ability to control mud losses under pressure and good performance in reservoir protection by self-removal. The development of the new self-degrading LCM is expected to solve mud losses into fractured reservoirs and reservoir protection, two problems that have been difficult to solve simultaneously previously.