微纳米井壁强化技术在长宁“大坝东”区域的应用

长宁公司“大坝东”区域受构造作用、岩性组分等因素影响，龙马溪组微裂缝发育，原生孔径主要分布在0.05～2 μm之间，地层稳定性差，钻进过程阻卡严重，单纯通过上提钻井液密度，未能有效控制井眼垮塌，且钻井现场的封堵类添加剂属于微米级，缺乏纳米级封堵添加剂，不能有效封堵纳米级孔缝，同时不利于形成渗透率更低的封堵层，阻缓井筒压力向地层传递。引入纳米级石墨烯封堵剂，补全钻井液微观固相级配，配合地质力学建模，确定合理的密度，匹配性能调控工艺，形成微纳米井壁强化技术。在宁209H69平台现场应用过程中，钻井液性能稳定，全井段无事故复杂，平均井眼扩大率不大于8%，井径规则，有效地预防了井眼垮塌。 

Borehole Wall Strengthening with Micron and Nano Materials in “Dabadong” Area of Changning

The Longmaxi formation in Changning is highly developed with microfractures because of the tectonic action in the “Dabadong” area and the formation rock components. The sizes of the primary pores are distributed in a range of 0.05-2 μm. The formation stability is very poor and overpull and resistance have been frequently encountered during drilling. Increase in mud weight only cannot control wellbore instability. The drilling fluids presently in use only contain micron-sized plugging agents and are unable to effectively plug the nanometer pores. The lack of nanometer plugging agents cannot help form low permeability plugging layers to hinder the transmission of borehole pressure into the formations. By introducing a nanometer graphene plugging agent, the drilling fluid has both micron-sized and nano-sized plugging agents. Furthermore, the mud weight was determined through geomechanics model. With all these technologies and mud property control, the borehole wall was strengthened. Application of the borehole wall strengthening technology in the well Ning-209H69 showed that the properties of the drilling fluid were stable, no downhole troubles were encountered in the whole drilling process, the average percent hole enlargement was less than 8%, and the borehole wall collapse was effectively eliminated.