ASS-1屏蔽暂堵钻井完井液体系的实验研究

THE EXPERIMENT STUDY OF ASS-1 DRILLING AND COMPLETION FLUID SYSTEM OF BRIDGE PLUG IN LABORATORY

根据现场实际钻井过程,在实验室模拟ASS-1钻井完井液体系对储层岩芯进行动、静态伤害,岩芯渗透率平均恢复率可达到89%,经高压气体反向驱排之后恢复率可以提高到93%,滤饼的脱落压力小于1.0MPa,表明该体系只对储层产生轻微伤害,暂堵颗粒与储层孔隙直径相匹配,变形材料与暂堵剂、储层等配伍性良好,还可以通过储层自身压力实现解堵;岩芯从伤害端切除长约1cm后,岩芯渗透率的恢复率大幅度上升,平均可达137%,表明钻井液对岩芯的伤害深度在1cm以内;最后对岩芯不同部位通过电镜扫描,发现岩芯内部孔隙或喉道内没有任何固相颗粒侵入,进一步证明ASS-1体系的暂堵保护只发生在岩芯表面。研究认为,ASS-1钻井完井液体系选用适当粒度级别的碳酸钙作为暂堵剂是合理的,暂堵只是在井壁表面,达到了保护储层的目的,并且进一步拓宽了ASS-1体系的使用范围。

According to practical drilling on site,in laboratory the average recovery rate of core permeability can be up to 89% and its recovery rate is improved to 93% after nitrogen penetrates adversely the core damaged statically and dynamically by ASS-1 drilling fluid system.The pressure less than 1.0 MPa at which the mud cake lifts off shows that the temporary plugging is cleaned up easily by pressure on oil formation or gas formation without other methods.It also demonstrates that the size of temporary plugging particle conforms with the size of capillary in formation and soft material content with plugging agent or chemical in formation makes the damage to formation of ASS-1 system very light.After the section of the core long about 1 cm is cut off from damaged end,the permeability increases sharply,up to average 137% and which shows that the depth of damage is less 1 cm.At last,it is found that there is no immerging particle in the lacuna of core and ASS-1 drilling fluid system only plugs the lacuna at the surface of cores by scan electronic microscope (SEM).The studies above suggests that the choice of carbonate calcium as temporary plugging Particle is reasonable and effective and the plugging on formation happens only on the wall of well to protect formation from damage in the course of drilling and the using area of ASS-1 drilling fluid system can be extended to the field of drilling.