Study On Self - Repairing Material For Cementing Cement

Layers packer invalidation can be caused by the micro cracks of cement ring, which seriously affect the safety of exploration and development about oil and gas fields. As a new technology, the self-healing material is important theoretical research and engineering application value for solving the micro cracks.Methods to evaluate the self-healing properties of cement based on cement mechanical recovery rate first of all in order to evaluating the self-healing effect of self-healing materials. The flexural and splitting tensile strengths of cement should be both evaluated. If the flexural strength repair rate is higher than50%and splitting tensile strength the repair rate is higher than30%, cement will have a self-healing property. Then, methods to evaluate the self-healing properties of cement based on cement permeability, and the formula is [(Kbefore-Kafter)/Kbefore]×100%.The paper researched the effect of the application of the trigger type by oil, the trigger type by gas and thermal self-healing materials for cement slurry performance. The results show thatl) XJ cements are greatly influenced by temperature, and their mechanical properties are better at low temperatures and at high temperature instead;2) the mechanical properties of cement are improved contrast to pure cement under a low BX-1amount. And BX-1cement is sensitive to temperature;3) the mechanical properties of EVA cement decrease significantly when added amount.Self-healing performance of the trigger type by oil cement is evaluated through the permeability:1) the more XJ added, the better self-healing performance is. And its permeability decreased more than40%;2) the mechanism are capillary diffusion and surface adsorption, functional group, molecular chain swelling stretch of self-healing materials. These actions changed the internal environment of cement. Self-healing performance of the trigger type by gas cement is evaluated through the permeability:1) real-time permeability of BX-1cement declined by more than30%and the self-healing rate of was higher than50%;2) the mechanism is chemical precipitation reaction. Products can fill in internal gaps and cracks so that it ensures the integrity of the cement ring. Thermal self-healing cement is evaluated through the mechanical strength. The results show that:1) the more EVA, the self-healing rate of flexural strength and splitting tensile strength higher. And the results meet the conditions that the flexural strength repair rate is higher than50%and splitting tensile strength the repair rate is higher than30%;2) the mechanism is EVA will flow when the the temperature is higher than the melting point. At this time, EVA will fill the gaps and cracks for repairing cement. The interface structure and performance between EVA and cement are changed.The paper prepares and screenings for three kinds of self-healing material and studies the effects on the properties of the slurry application. Their self-healing performances and mechanisms are preliminary proven, which is beneficial to scientific design and the use of self-healing cement slurry. The results of the study will provide theoretical guidance for self-healing materials selection and self-healing cement development, and can be directly applied to annulus channeling prevention and control of oil and gas wells. The study of cementing self-healing cement slurry has important application value.