Technologies to Mitigate Geomechanical Challenges of Deepwater Resource Development

ABSTRACT: Deep-water fields offer substantial opportunities due to their high reservoir quality, leading to significantly higher production rates and reserves per well compared to shallow-water fields. However, deep-water environments present unique engineering and geoscience challenges, particularly related to geomechanics. One of the key sub-surface characteristics of deep-water fields is mechanically weak formations, a result of the reduced lithological column being replaced by seawater. This translates to lower vertical stress, while pore pressure remains similar to shallow-water fields. These conditions pose several geomechanical challenges that impact drilling, completion, reservoir production, and overall reservoir management. Common issues in deep-water fields include drilling losses, sand production, and limited injectivity for pressure maintenance. This paper assesses various technologies used to mitigate these risks and highlights that approaches successful in shallow-water fields may not directly translate to deep-water environments. Specifically, the methodologies discussed address four key areas of deep-water geomechanics: wellbore stability in low fracture gradient formations, sand production and prevention in unconsolidated formations, water injectivity in low minimum horizontal stress environments, and reservoir geomechanics for simulation modeling and production forecasting. For wellbore stability, stress mapping and careful well trajectory selection are essential to avoid collapse or fracturing during drilling. Sand production prevention in weak, unconsolidated formations requires optimized proppant selection and advanced completion techniques. Water injectivity is constrained by the risk of fault activation, necessitating precise control of injection rates to prevent fault slippage. Finally, incorporating geomechanics into reservoir simulation models improves production forecasting by accounting for stress-induced changes in reservoir properties such as porosity and permeability. This paper presents workflows, methodologies, and engineering solutions derived from actual field applications, offering a practical assessment of how to overcome the geomechanical challenges of deep-water developments. 1. INTRODUCTION Deepwater environments present a unique set of geomechanical challenges due to the significant replacement of overburden rock with seawater, as depicted in Figure 1. This reduction in overburden results in lower vertical stress on the reservoirs in deepwater fields, as shown in Figure 2. Compared to shallow water fields, this shift in stress has far-reaching impacts on the subsurface characteristics and influences all stages of deepwater drilling and development. In particular, three key geomechanical challenges must be addressed: (i) drilling through formations with low fracture gradients, (ii) producing hydrocarbons from unconsolidated formations, and (iii) injecting water into formations with low minimum horizontal stress.