Geothermal well integrity has proven to be of high importance, especially because the geothermal life span is expected to be longer than that of conventional oil and gas wells. Recent studies have demonstrated that cement-casing interfacial bonding is a classical well failure in such wells, but field measurements do not correlate with the simulations. We believe that this discrepancy is due to limitations of the simulation itself, which in most cases assumes a free movement of the casing after the interfacial bonding has been exceeded. Since the casing is cemented using a complex hardware package such as centralizer and other cementing components, the free movement of the casing is only possible when no-cement exists behind the casing. This paper proposes a novel experimental method to understand cement strength properties other than the standardized unconfined cement strength (UCS). The novel setup allows the measurement of interfacial bonding strength between cement and casing and the pure cement shear strength. The later becomes an important parameter as the interaction between casing couplings and cement will show. In the past, standard cement bending tests were designed to measure cement shear, but the value obtained from such tests is not relevant for the geothermal in situ casing-cement interaction, and thus the need for a new testing method arose. The new method is capable to mimic the interaction between the casing connection edges and the cement. We believe that the results presented within this paper will help engineers to validate their numerical simulations and to optimize the geothermal well design which will result in the increase of the well integrity for the life of the geothermal well.

Horizontal wells with multiple transverse fractures were defined as the key well architecture and completion strategy oriented to develop clastic tight gas accumulation otherwise impossible to be developed with vertical wells. However, a detailed evaluation during early deployment indicates the need for an integrated subsurface platform (ISP) covering geophysics, geology and geomechanics, to support well placement, well orientation and hydraulic fractured design. Detailed subsurface characterization was used to build the ISP. Geomechanical logs estimated using the drilling data, as wells as, wireline logs are used to define engineered completion strategies. The ISP provide us with three dimensional properties maps capturing lithogical, petrophysical and geomechanical properties distribution, this allow the identification of the properties anisotropy coveing key variables including, elastic properties, in-situ stress variation, stress rotation across the field and stress anisotropy, thecombination of the predicted stimulated reservoir volume and the dynamic model, both part of the ISP, were used to access potential production forecast for selected well locations. The ISP support the identification of geological sweet spot to definelanding zones and optimizing the hydraulic fracturing to improve the production performance. We will discuss how the geomechanical evaluation provides us the spatially varying stress magnitude and stress orientation and strain across the tight reservoir units. The use of the geological and geomechanical data within the ISP can be used to estimate geomechanical half lengths that are used to improve fracture design. We will also discuss how completion optimization and number of perforation clusters can be defined to maximize gas production based on a better understading of the special variation of petrophysical, geomechanical and lithological properties across reservoir units. The described integrated subsurface platform can be used to help optimize horizontal well placement, well orientation and fracture completion design. It will be discussed the procedures and process of integration geophysical, geological and geomechanical reservoir properties into the ISP, as well as, how this was used to support the continuous development of these tight gas accumulation in Oman.