滑溜水在页岩储集层的吸附伤害及控制措施

滑溜水在页岩储集层的吸附伤害及控制措施

郭建春;李杨;王世彬

【摘要】The slick-water polymer adsorption damage and control measures in shale were examined using a shale pack model of the Ordovician Wufeng Formation-Silurian Longmaxi Formation in the Changning block of the Sichuan Basin.The adsorption law of slick water under different displacement time,concentrations,pH values and temperatures of polymer were tested by traditional displacement experiment and UV-Vis spectrophotometer.The adsorption equilibrium time was 150 min,the amount of adsorption was proportional to the concentration of the polymer,and the maximum adsorption concentration was 1 800 mg/L.With the increase of pH value,the adsorption capacity decreased gradually,the adsorption capacity increased first and then decreased with the increase of temperature,and the adsorption capacity was the largest at 45 ℃.The adsorption patterns of polymers on shale were described by scanning electron microscopy and magnetic resonance imaging.It is proved that the adsorption of polymer on shale led to the destruction of the network structure of anionic polyacrylamide molecules,and the shale adsorption conformation was characterized qualitatively.Finally,according to the adsorption law and adsorption mechanism,it is proposed to reduce the adsorption quantity of polymer on shale surface by using hydrogen bond destruction agent.The effects of hydrogen bond destruction on four kinds of strong electronegative small

molecules were compared,the hydrogen bond destroyer c was the best,which lowered the adsorption capacity by 5.49 mg/g and recovered permeability to 73.2％.The research results provide a reference for the optimization of construction parameters and the improvement of slickwater liquid system.%基于四川盆地长宁区块奥陶系五峰组—志留系龙马溪组页岩充填模型,研究滑溜水中聚合物在页岩中的吸附伤害及控制措施.利用驱替实验并结合紫外分光测试,得到了滑溜水中的聚合物在不同时间、浓度、pH值和温度下的吸附规律:吸附平衡时间为150 min;聚合物浓度越高吸附量越大,极限吸附浓度为1 800 mg/L;随pH值增大吸附量呈逐级递减趋势;吸附量随温度先增后减,45℃时吸附量最大.通过电镜扫描、核磁共振成像描述了聚合物在页岩上的吸附形态,证明聚合物吸附会导致阴离子聚丙烯酰胺分子网络结构破坏,且对页岩的吸附构象进行了形貌表征.根据页岩与聚合物间的吸附规律和吸附机理,认为用氢键破坏剂可以降低聚合物在页岩表面的吸附量.对4类电负性较强的小分子物质进行氢键破坏效果对比,氢键破坏剂c效果最佳,可使吸附量降低5.49 mg/g,渗透率恢复至73.2％.研究成果可为优化施工参数和改进滑溜水液体体系提供借鉴.

【期刊名称】《石油勘探与开发》

【年(卷),期】2018(045)002

【总页数】6页(P320-325)

【关键词】页岩;水力压裂;滑溜水;聚合物;页岩吸附;解吸附

【作者】郭建春;李杨;王世彬

【作者单位】油气藏地质及开发工程国家重点实验室西南石油大学,成都610500;

油气藏地质及开发工程国家重点实验室西南石油大学,成都610500;油气藏地质及

开发工程国家重点实验室西南石油大学,成都610500

【正文语种】中文

【中图分类】TE357.12

0 引言

页岩储集层为典型的低孔低渗储集层[1-3]，水力压裂是高效开发此类资源的关键

技术[4-5]。在页岩压裂过程中，滑溜水压裂液体系使用率超过80%[6-7]。但滑溜水黏度低、携砂性能差，为提高支撑剂的输送能力，施工排量比常规压裂明显增大，导致施工摩阻剧增[8-11]。因此滑溜水中的降阻剂（一般采用阴离子聚丙烯酰胺）是压裂施工的重要保障之一[12-14]。但是阴离子聚丙烯酰胺中的亲水基团与页岩

中的含氧基团会形成化学键，进而在岩石裂缝壁面和基质孔隙中发生吸附滞留，导致压裂形成的油气流动通道减小甚至堵塞，严重制约压裂改造效果[15-17]。

目前，针对常规储集层压裂的保护技术主要是减小压裂液浓度、缩短施工时间以及降低聚合物相对分子质量等[18-22]。而页岩储集层孔喉半径与聚合物分子都属于

纳米级别，这将导致裂缝与基质的渗透率伤害增大[23-24]。

本文以四川盆地长宁区块奥陶系五峰组—志留系龙马溪组页岩为研究对象，研究

滑溜水中聚合物在页岩中的吸附规律和影响因素，并结合吸附形态的微观分析，提出降低页岩储集层吸附伤害的控制措施。

1 页岩吸附伤害测试

常规滑溜水体系中降阻剂主要成分是阴离子聚丙烯酰胺，为验证页岩是否会吸附该类聚合物，首先将页岩样品制作成0.21～0.30 mm（70～50目）的页岩颗粒装