准噶尔盆地砂砾岩储层压裂液损害及保护措施

Damage of Sandy Conglomerate Reservoirs in Dzungar Basin by Fracturing Fluids and Measures for Protection of the Reservoir Damage

针对准噶尔盆地玛湖凹陷区上乌尔禾组砾岩储集层压裂开采过程中储层损害等问题,在分析准噶尔盆地砂砾岩上乌尔禾组玛湖1井区储集层基本特征的基础上,开展了压裂液破胶液与地层水流体配伍性及固相颗粒堵塞评价、储层敏感性评价、毛细管自吸及黏土矿物水化膨胀评价实验,分析了储层损害的主要因素;对防膨抑制剂,仿生双疏压裂液助排剂进行了优选;此外,还建立了储层敏感性损害智能化定量预测技术。研究结果表明,准噶尔盆地砂砾岩上乌尔禾组玛湖1井区储层损害主要因素是蒙脱石吸水膨胀损害、强毛细管自吸损害、固相颗粒堵塞损害、水敏和弱酸敏性损害。优选出的4%聚醚胺抑制剂膨胀量在1.28 mm,2%仿生双疏助排剂的助排效率在88.54%以上;2%聚醚胺和2%双疏压裂液体系的岩心自吸量为1.38 mL,膨胀量为1.42 mm,返排率达到86.2%;建立的储层敏感性损害智能化定量预测技术的预测精度在85%以上,形成了一套适合准噶尔盆地玛湖砾岩储集层保护体系。

Formation damage has long been a problem existed in producing through fracturing the conglomerate reservoir in the upper Wuerhe formation in Mahu sag, Dzungar basin. Based on the analysis of the basic characteristics of the upper Wuerhe conglomerate reservoirs in the Mahu-1 block in Dzungar basin, laboratory experiments were performed to evaluate 1) the compatibility between the fluid from fracturing fluid after gel breaking and the formation water, as well as the plugging of reservoir formations by solid particles;2) the sensitivity of the reservoir to various damaging factors;and 3) capillary imbibition and the swelling of clay minerals though hydration. Main factors contributing to the reservoir damage were analyzed. In the laboratory evaluation experiments, the clay swelling inhibitor and the biomimetic amphiphobic fracturing fluid cleanup additives were selected.In addition, an intelligent quantitative prediction technology for reservoir sensitivity damage was also established. The study results showed that the main factors contributing to the damage of the sandy conglomerate upper Wuerhe formation in the Mahu-1 block in Dzungar basin include swelling of the montmorillonite caused by water absorption, strong capillary imbibition, solid particle blocking, water sensitivity and weak acid sensitivity. In laboratory swelling test with 4% polyetheramine solution, the cores only swelled by 1.28 mm, the cleanup efficiency of the biomimetic amphiphobic cleanup additive was at least 88.54%. The amount of the fluid(2% polyetheramine plus 2% amphiphobic fracturing fluid) absorbed by the cores was 1.38 mL, resulting in a length of swelling of 1.42 mm, and the ratio of the back flowed fracturing fluid was 86.2%. Using the intelligent quantitative prediction technology, the precision of the sensitivity prediction can be as high as more than 85%. All these study results together formed a set of technology for protecting the conglomerate reservoirs in the Mahu block in Dzungar basin.