State of the Art Technology Development for Hydrocarbon and CCS Caprock In-Situ Stress Testing

ABSTRACT: Until recently the measurement of reservoir caprock and shale in-situ stress has mainly been limited to extended leak off tests (XLOTs) performed during drilling operations at casing or liner shoes. Whilst the wireline formation tester tool has been used for in-situ stress data acquisition for many years, the technique's application has been restricted to particular environments constrained by the fracture initiation, propagation & closure capabilities of the tool. Although many hardware & operational practice improvements have enhanced the technique's success rate, these solutions have not always been successful in shallow and non-conventional formations such as the caprocks that are present in frontier exploration areas of the Norwegian Continental Shelf (NCS). Two flowback solutions were developed to improve the reliability of the wireline formation tester tool. These allow fluid to flow out of the fracture across a fixed choke or at a controlled rate and thereby provide suitable conditions for interpretable fracture closure processes. The technology permits repeated measurements due to its ability to conduct multiple flowback cycles with downhole fluid recycling. These two independent flowback techniques have been deployed in several exploration and development projects on the NCS over several recent years. These developments, together with other operational practice & hardware optimizations, have made it possible for the wireline formation tester to measure fracture closure in low and non-permeable open hole environments. 1. INTRODUCTION Rock stress measurements in low permeable formations such as caprocks and shales provide critical input to hydrocarbon field developments as well as to carbon capture utilization and storage (CCUS) projects. The industry has traditionally acquired this data by performing (extended) leak-off tests (XLOTs) at casing shoes, which unfortunately aren't necessarily located there where the rock stress data is needed. Other stress testing methods, such as DFITs and minifrac tests, measure rock stress at the depth of interest by perforating a cemented casing, but these often require a tailored well design with associated time and cost implications.