BRIGE: Characterizing the Rheological and Microstructural Evolution of Oil Well Cement Slurries under Elevated Temperature and Pressure Conditions

背景：油井普遍存在分层隔离或密封不足的问题，由此可能引起许多安全、经济和环境方面的问题。失效的原因可以追溯到新油井水泥浆的放置。在一个称为过渡期的关键时期，水泥浆是静止的，由于水泥水化的发展，水泥浆从接近牛顿的流体演化为粘弹性固体。如果它既不能迅速形成足够的静凝胶强度，也不能迅速凝结，来自邻近地质地层的气体就会渗透到材料中。这使得水泥浆极易发生气体运移，从而在油井中形成永久的流体通道，并影响最终水泥环结构的密封性能。技术描述：拟议工作的目标是表征油井水泥浆的流变性，这些特性被认为是实现适当的分层隔离的关键，即胶凝。这将需要测量大变形和快速变形下的动态流动特性和静止时的线性粘弹性特性。所有的流变性测试都将严格注意温度和压力升高的影响，以模拟井下条件，以及剪切历史，以模拟不同的泵送条件。该方法将实施互补剪切和拉伸流变学技术，将样品置于动态和准静态载荷下，以监测模拟固井期间胶凝速度和静态凝胶强度的变化。流变学的一个重要补充是监测材料晶相和孔隙网络的变化，这将有助于深入了解流动行为和密封性能。这将通过同步加速器x射线衍射和x射线断层显微镜实时、原位微结构表征来完成。更广泛的意义和重要性：作为一种不断演变的复杂流体，新拌水泥基材料的热力学以及时间和剪切相关的流动行为提出了一个具有挑战性的表征问题。油井固井的特定领域是一个特别好的应用实例，在这种应用中，了解严酷条件下的新鲜状态和早期特性是至关重要的。拟议的活动将提高对油井水泥浆体在放置过程中的性能的了解，这有助于开发有效的配合比设计方法和模型。最终，这可以改善分区隔离，以提高产量和安全性，并减少油井作业对环境的负面影响。此外，研究中提出和开发的实验方法可能会扩展到所有类型的水泥基系统，应用范围很广。扩大代表不足的群体对工程学的参与：拟议工作的一个重要组成部分是扩大参与计划，该计划将侧重于通过直接参与大学预科、本科生和研究生级别的研究活动来支持妇女参与工程学。通过让女学生参与拟议的研究，PI将为她们提供影响该领域的机会，并随后给予她们在工程和科学领域追求学术或高级行业职业的信心和愿望。通过由外展计划办公室和哥伦比亚大学女性工程师协会当地分会协调的各种外联计划，PI将作为嘉宾演讲者参与，介绍拟议的工作并进行流变学方面的动手实验室演示。这将作为一种手段，传达她所在领域的跨学科性质，激发兴趣并招收学生。此外，国际学生联合会将鼓励她自己的学生参加外展计划，这样他们自己就可以继续充当榜样。作为这些项目本身的产物，国际工程促进会坚信这种涓滴方法是有效的。这项研究是通过工程教育和中心部门扩大参与工程计划的一部分--工程招揽中的扩大参与研究启动补助金--资助的。

Background:Insufficient zonal isolation, or sealing, is a prevalent issue in oil wells, from which many safety, economic, and environmental concerns can arise. And the origin of failure can be traced back to the placement of the fresh oil well cement slurry. During a critical period called transition time, the slurry is static and evolving from a near-Newtonian fluid to a viscoelastic solid due to the progression of cement hydration. If it does not either rapidly develop sufficient static gel strength or set, gas from adjacent geological formations will penetrate the material. This makes the slurry extremely susceptible to gas migration, which can result in permanent fluid channels in the well and compromise the sealing performance of the eventual cement sheath structure. Technical Description:The objective of the proposed work is to characterize the rheological properties of oil well cement slurries considered to be critical in achieving proper zonal isolation, namely gelation. This will entail measuring the dynamic flow properties under large and rapid deformation and the linear viscoelastic properties at rest. All rheological tests will be performed with rigorous attention to the effects of elevated temperatures and pressures to simulate down-hole conditions, and shear history to simulate different pumping conditions. The approach will be to implement complementary shear and extensional rheological techniques that place the sample under dynamic and quasi-static loading to monitor the evolution of rate of gelation and magnitude of static gel strength over the simulated cementing period. And an important complement to the rheology will be to monitor changes in the crystalline phases and pore network of the material, which will help provide insight into flow behavior and sealing performance. This will be done through synchrotron x-ray diffraction and x-ray tomographic microscopy for real-time, in-situ microstructural characterization. Broader Signficance and Importance:As a complex fluid that is continuously evolving, the thermomechanics and time- and shear-dependent flow behavior of fresh cement-based materials presents a challenging characterization problem. And the specific area of oil well cementing is a particularly good example of an application where understanding the fresh-state and early-age properties under severe conditions is critical. The proposed activities will improve understanding of the performance of oil well cement slurries during placement, which can help in the development of effective mix design methodologies and models. Ultimately, this can improve zonal isolation to increase production and safety, and reduce the negative environmental impact of oil well operations. Further, the experimental methodology proposed and developed in the study can potentially be extended to all types of cement-based systems for a wide array of applications. Broadening Participation of Underrepresented Groups in Engineering:An important component of the proposed work is the broadening participation plan, which will focus on supporting women in engineering through direct involvement in research activities at the pre-college, undergraduate, and graduate level. By engaging female students in the proposed research, the PI will present them with the opportunity to impact the field and subsequently give them the confidence and desire to pursue academia or advanced industry careers in engineering and science. And through various outreach programs coordinated by the Office of Outreach Programs and local chapter of Society of Women Engineers at Columbia University, the PI will participate as a guest speaker to present the proposed work and run hands-on lab demonstrations on rheology. This will serve as a means to convey the interdisciplinary nature of her field, invoke interest and recruit students. Further, the PI will encourage her own students to participate in outreach programs so that they, themselves, can go on to serve as role models. As a product of such programs herself, the PI firmly believes that such trickle down approaches are effective.This research has been funded through the Broadening Participation Research Initiation Grants in Engineering solicitation, which is part of the Broadening Participation in Engineering Program of the Engineering Education and Centers Division.