Raising the Bar: Why an Industrial Standard for Testing Hydraulic Sealability of Well Abandonment Materials in Laboratory is Essential for Well Integrity

Abstract

Abstract Advances in the properties of OPC and new materials (i.e., mechanical strength, rheological properties, etc.) have shifted the R&D focus towards sealing capability of plugging materials at interfaces between the material and its adjacent medium. The objective of this paper is to outline the importance of new standards for studying hydraulic sealability of barrier materials, with emphasis on interface analysis. This work reviews different procedures used to study hydraulic sealability of barrier materials. Reviewing current standards and procedures for testing and qualifying zonal isolation materials indicates that the focus is mainly on the bulk properties of cement, such as expansion/shrinkage, permeability, and mechanical strength. The benefits of these standards are to provide reproducible results, consistent testing procedures and prevent misunderstandings about behavior of hardened cement in laboratory and field operations. However, interfaces are complex and cannot be tested with current standards, meaning that mechanical properties alone cannot indicate hydraulic sealability. The review process also includes non-setting materials further indicating the need for updated standards. Per today, there is published work on sealability testing on the barrier material interfaces, either towards the surrounding rock or towards the casing. This is of particular importance due to more emerging well types such as CCS, hydrogen storage, geothermal wells, and purpose based well integrity and plug and abandonment. A thorough review of sealability test setups indicates that different research groups have designed setups with similar features, but with variations on scale dimensions, testing protocol and so on. This, in combination with the availability of modern measurement technologies, offers the possibility of enhanced understanding of barrier sealability. As no standards currently describe a uniform testing procedure, direct comparison of results is thus inaccurate, putting the reproducibility and reliability of analyses at risk. Our observation shows that possible considerations for standardization include understanding the effect of dimensional scales, the sequence in the procedure, the duration of testing, the type of casing steel or rock, and the type of invasion fluid besides the amount of released heat of setting material. Therefore, it is highly beneficial that current standards are updated to include sealability analysis, and updates for new and alternative materials, such as geopolymers, settled barite, and metal alloys.