Regional In-Situ Stress Prediction in Frontier Exploration and Development Areas: Insights from the First-Ever 3D Geomechanical Model of the Arabian Plate

Abstract

In this paper, we present results from the first-ever 3D geomechanical model that supports pre-drill prediction of regional in-situ stresses throughout the Arabian Plate. The results can be used in various applications in the petroleum industry such as fault slip-tendency analysis, hydraulic fracture stimulation design, wellbore stability analysis and underground carbon storage. The Arabian tectonic plate originated by rifting of NE Africa to form the Red Sea and the Gulfs of Aden and Aqaba. The continental rifting was followed by the formation of collisional zones with eastern Turkey, Eurasia and the Indo-Australian Plate, which resulted in the formation of the Eastern Anatolian fault system, the fold-thrust belts of Zagros and Makran, and the Owen fracture zone. This present-day plate tectonic framework, and the ongoing movement of the Arabian continental lithosphere, exert a first-order control on the of in-situ stresses within its sedimentary basins. Using data from published studies, we developed a 3D finite element of the Arabian lithospheric plate that takes into account interaction between the complex 3D plate geometry and present-day plate boundary velocities, on elastic stress accumulation in the Arabian crust. The model geometry captures the first-order topographic features of the Arabian plate such as the Arabian shield, the Zagros Mountains and sedimentary thickness variations throughout the tectonic plate. The model results provide useful insights into the variations in in-situ stresses in sediments and crystalline basement throughout Arabia. The interaction between forces from different plate boundaries results in a complex transitional stress state (thrust/strike-slip or normal/strike-slip) in the interior regions of the plate such that the regional tectonic stress regime at any point may not be reconciled directly with the anticipated Andersonian stress regimes at the closest plate boundary. In the sedimentary basin east of the Arabian shield, the azimuths of the maximum principal compressive stresses change from ENE in southeast to ~N-S in northern portions of the plate. The shape of the plate boundary, particularly along the collisional boundaries, plays a prominent in controlling both the magnitude and orientations of the principal stresses. In addition, the geometry of the Arabian shield in western KSA and variations in the sedimentary basin thickness, cause significant local stress perturbations over 10 – 100 km length scales in different regions of the plate. The model results can provide quantitative constraints on relative magnitudes of principal stresses and horizontal stress anisotropy, both of which are critical inputs for various subsurface applications such as mechanical earth model (MEM) and subsequently wellbore stability analysis (WSA). The calibrated model results can potentially reduce uncertainties in input stress parameters for MEM and WSA and offer improvements over traditional in-situ stress estimation techniques.