Abstract This paper is the second part of a two-part series introducing a new and innovative managed temperature drilling technique for thermal wellbore strengthening of challenging oil and gas wells. It describes the development of heat-releasing (“exothermic”) coated particles designed to release heat at exactly the right circulating time to increase near-wellbore formation temperature and thermal stress in potential lost circulation zones, such as depleted reservoir zones in deepwater wells. The increase in thermal stress directly elevates the near-wellbore tangential stress, which translates into an increase in the effective fracture gradient. This may lower the risk of lost circulation, and also improve the chance of successfully cementing casing and achieving zonal isolation. In the latter application, a treatment can be executed as an integral part of the cement job by using it in an extended spacer train for mud displacement, pumped directly prior to cement placement to thermally strengthen a formation. The coated exothermic particles, which were based on the hygroscopic calcium and magnesium salts with chlorine and bromine, were designed such that they could release their “payload” via an extended time-release mechanism, to ensure that the heat release reaches the appropriate target location in the wellbore at exactly the right time. The chemical candidate systems were found to effectively heat up the wellbore and increase temperature up to 90 °C. This, in turn, will elevate the fracture gradient by several hundred psi, depending on formation properties. The particles need to be transported to the target formation and their reaction products need to be carried away from the target formation by a suitable carrier fluid that can handle the exothermic dissolution of a large amount of salt without any instability. Details regarding the formulation and testing of non-coated and coated particles and their carrier fluid are discussed here, as well as considerations for field application of thermal wellbore strengthening. The developed managed temperature drilling technique, enabled by the chemical system described here, can be used to minimize lost circulation events and associated well trouble time and cost during drilling, cementing and completion operations.

中文翻译：

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通过控温钻井加强热井筒——第二部分：化学系统设计和实验室测试

摘要 本文是由两部分组成的系列文章的第二部分，介绍了一种新的和创新的控温钻井技术，用于对具有挑战性的油气井进行热井筒加固。它描述了散热（“放热”）涂层颗粒的开发，这些颗粒旨在在正确的循环时间释放热量，以增加潜在的漏失区（例如深水井中的枯竭储层区）的近井眼地层温度和热应力。热应力的增加直接提高了近井眼切向应力，这转化为有效裂缝梯度的增加。这可以降低井漏风险，并提高成功固井和实现层位隔离的机会。在后一个应用程序中，处理可以作为水泥作业的一个组成部分来执行，方法是将其用于泥浆置换的扩展间隔系列，在水泥放置之前直接泵送以热强化地层。涂层放热颗粒基于吸湿性的钙和镁盐与氯和溴，设计成可以通过延长的时间释放机制释放其“有效载荷”，以确保热量释放到达适当的目标位置在正确的时间在井筒中。发现化学候选系统可有效加热井筒并将温度升高至 90 °C。这反过来又会使裂缝梯度升高数百 psi，具体取决于地层特性。颗粒需要被输送到目标地层，并且它们的反应产物需要通过合适的载液从目标地层带走，该载液可以处理大量盐的放热溶解而没有任何不稳定性。此处讨论了有关非涂层和涂层颗粒及其载液的配方和测试的详细信息，以及热井筒强化现场应用的注意事项。开发的受控温度钻井技术由这里描述的化学系统启用，可用于在钻井、固井和完井作业期间最大限度地减少漏失事件和相关的井故障时间和成本。