深水水基钻井液低温流变性调控用温敏聚合物研制及作用机理研究

The high viscosity, high shear stress and poor rheology of current deepwater drilling fluids are one of the bottlenecks in deepwater drilling, and no controlling method has been developed so far. This project will design and synthesize a series of low molecular weight temperature sensitive polymers (TSP), in order to construct a temperature sensitive system of polymer/bentonite aggregate. The hydrophilicity andζpotential of the aggregate should increase at low temperature, and the matric structure between the aggregate and drilling fluid additives should be weaken, so that the effective control to the rheology of deepwater drilling fluid can be achieved. With the help of experiments and molecular simulation, the influence of molecular structure, temperature, mineralization and pH on interaction forces, adsorption energy and capacity between the TSP and bentonite will be studied at multi-scales, the key factors controlling the hydrophilicity andζpotential of the aggregate will be specified, the relationship of matric structure's strength and the interaction between aggregate and additives will be explained, and the controlling mechanism of TSP to low temperature rheology of deepwater drilling fluid will be revealed. The findings will help with the development and perfection of the (low temperature) rheological theories and controlling technique of bentonite colloidal-suspending fluid systems, and provide a theoretical and experimental base for the development of flat rheological water-based deepwater drilling fluids and safe drilling.

深水水基钻井液低温黏度高、切力大，流变性差，是制约深水油气安全高效开发的技术瓶颈之一，至今缺乏有效的调控手段。本项目拟设计并合成系列低分子量温敏聚合物，构建对温度敏感的聚合物/黏土聚集体。低温时，聚集体的亲水性增强，ζ电势增大，削弱聚集体与钻井液处理剂之间的网架结构，从而实现对深水钻井液流变性的有效调控。通过实验和分子模拟，多尺度研究分子结构、温度、矿化度、pH值对温敏聚合物与黏土之间的作用力、吸附能、吸附量等的影响规律，明确影响聚集体ζ电势和亲/疏水性质的关键因素，阐明聚集体与处理剂之间的相互作用与体系网架结构强度的关系，揭示温敏聚合物对钻井液低温流变性的调控机理。研究结果有助于拓展和完善黏土胶体悬浮液体系（低温）流变学理论和调控技术，为建立“恒流变性”深水水基钻井液体系、提高深水钻井安全提供理论支撑和实验研究基础。

深水钻井过程中，井筒温度随水深增加而降低，随地层深度增大而快速上升，钻井液循环过程需经历“低温-高温-低温”交替变化，致使其黏度、切力等流变参数调控困难，特别是含膨润土相水基钻井液体系，严重时甚至影响深水油气钻井安全。温度敏感型聚合物可以随温度变化而改变分子构象，随之改变其亲疏水特性，从而对钻井液内膨润土颗粒与聚合物之间的网状结构做出调控。针对深水“低温-高温”大温差环境对含膨润土相水基钻井液流变性的影响，通过分子结构设计，引入不同敏感温度和亲/疏水性官能团，优化合成反应条件，研发了不同敏感温度和不同亲/疏水性质的新型温敏聚合物。通过改变环境温度、矿化度、pH值等参数，揭示了LCST型温敏聚合物的环境响应特性。新研制的聚合物均具有较强的温度敏感效应，且合成工艺简便易行，具有良好的应用前景。利用分子模拟技术与室内实验，分别从分子层面和实验层面揭示了温敏聚合物调控深水水基钻井液低温流变性的作用机理，形成了包含温敏聚合物-膨润土-水的“氢键网络”结构，为钻井液流变性调控提供了理论依据。实验结果证明新研制的LCST型温敏聚合物能够显著改善深水水基钻井液低温流变性，在2-90 ℃范围内钻井液黏度和切力波动幅度相对较小，并且具有良好的抗温、耐盐性能。最后，依据温敏聚合物的温度响应特征，构建了“恒流变”深水水基钻井液体系，实现了含膨润土相深水水基钻井液流变性的有效调控，可满足2-150 ℃深水深层钻井工程对水基钻井液性能的要求。