低浓度瓜胶压裂液储层损害特征及评价方法

Characteristics and evaluation method of low concentration guar-based fracturing fluid formation damage

瓜胶压裂液的伤害一直是人们关注的热点,高尚堡油田深层属于中孔低渗、中等偏强水敏性储层,储层填隙物微结构疏松,通过分子量、粒径分布等残胶分析手段,结合静态驱替、动态驱替实验,结果表明:一方面,由于过氧化物破胶剂不能彻底降解瓜胶分子量和形成的残渣引起吸附滞留伤害;另一方面,由于储层本身的疏松微结构“杂基”,造成颗粒运移伤害;针对中等偏强水敏储层,现有的工作液可预防水敏伤害。从宏观上表征出该低浓度瓜胶压裂液配方对高尚堡深层聚合物吸附滞留基质伤害率为25%~30%,水敏伤害占9.7%,少量的颗粒运移伤害,并通过核磁共振、微观结构论证了残胶中未完全降解的聚合物呈粒状、絮状吸附滞留在岩石颗粒和黏土颗粒表面,从而造成大吼喉数量减少,并且残渣及残胶相互缠结主要吸附滞留在岩芯入口端,远端逐渐减少。

The guar-based fracturing fluid formation damage mechanism is the focus.The deep layer of Gaoshangpu oil field is medium porosity,low permeability and strong water-sensitive reservoir whose interstitial matter is loose.By measuring molecular weight,size distribution,static displacement and dynamic displacement,it is stated that the adsorption retention formation damage is related to residue and molecular weight which is not degradable by peroxide.It is also stated that the particle migration formation damage is related to loose matrix.Finally,the medium-high water sensitive reservoir is prevented by the fluid available.Adsorption retention formation damage proportion is 25%-30%,caused by polymer in the low concentration guar fracturing fluid,water-sensitive formation damage proportion is 9.7%,a little particle migration formation damage.It is demonstrated that the polymer which is not completed degradable is adsorbed on the surface of rock and clay particle granularly and cotton-shapedly.Because of above,the quantity of big pore throats is reduced.The residue and residual gel are mainly adsorbed in the entry of drill core,the content of far-end is gradually decreasing.