自降解聚合物堵漏剂的合成与应用

Synthesis and Application of a Self-Degradable Polymeric Lost Circulation Material

钻井液漏失问题是长期存在于钻井作业中并且一直未能得到较好解决的技术难题,目前常用的聚合物凝胶堵漏材料存在承压能力低、吸水膨胀量小、抗温抗盐性差、不能自降解等缺点。为此优选了合成自降解聚合物堵漏剂的单体,通过正交实验确定了最佳合成条件,合成了自降解聚合物堵漏剂。该堵漏剂刚开始遇水膨胀率较小,能够快速进入裂缝部位产生封堵,随着时间的延长,体积不断膨胀,在裂缝处形成嵌压式封堵层,提高堵漏剂在裂缝性漏失层的滞留能力和封堵层的抗剪切强度。实验结果表明,该堵漏剂饱和吸水量最大可达156.9 g/g;21 d的降解率超过90%。在聚磺钻井液体系中分别加入5%的自降解堵漏剂和其它现有的几种堵漏剂后,针对3~5 mm的锲形裂缝,自降解堵漏剂钻井液体系承压压力可达17.5 MPa,堵漏效果明显优于现有堵漏剂;利用3 mm的裂缝性岩心模拟地层条件进行动态损害实验评价,岩心渗透率恢复值达到90%,且油气层保护效果良好。现场应用表明,该钻井液堵漏体系能够对裂缝型漏失地层实现良好的封堵,具有一定的应用前景。

Oil and gas well drilling have long been faced with a technical difficulty-mud loss,and this problem still remains unresolved.Polymer gel lost circulation material(LCM),a kind of LCM commonly used today,has several deficiencies such as low pressure bearing capacity,small expansion after water absorption,poor high temperature and salt resistance as well as inability to self-degrade etc.To deal with these problems,a self-degradable polymer LCM was synthesized with carefully selected monomers at optimum conditions determined by orthogonal experiment.This degradable LCM,when first in contact with water,has low rate of expansion,and is thus easy to enter quickly into the fractures where a plugging layer is formed.The LCM forming the plugging layer continuously swells with time and forms in the fractures an embedded plugging layer,thereby increasing the retention ability of the LCM in the loss zones and the shear strength of the plugging layer.Experimental results show that the saturated water adsorption capacity of this LCM can be as high as 156.9 g/g,and the degradation rate of the LCM after 21 d exceeds 90%.In laboratory experiment,polymer sulfonate drilling fluid samples were treated with 5%of this LCM and several other LCMs presently in use and were then tested on a 3-5 mm wedge-shaped fracture tester,the drilling fluid treated with the new degradable LCM has a pressure bearing capacity of 17.5 MPa,significantly higher than those of the other LCMs.In dynamic damage experiment conducted at simulated formation conditions,rock cores with 3 mm fractures were used to evaluate the ability of the self-degradable LCM to resist formation damage.The experimental results show that the permeability recovery of the cores flooded with the new self-degradable LCM treated drilling fluid was 90%,indicating that the new self-degradable LCM causes very slight formation damage.In field application,the polymer sulfonate drilling fluid treated with the self-degradable LCM is able to successfully plug the fractures through which the mud is lost,proving that the LCM has good application prospects.