Evaluation of Reservoir Formation Collapse in a Carbonate Gas Field in Abu Dhabi Using Coupled Reservoir Geomechanical Modeling

The objective is to investigate the possibility of formation collapse of the production zone, particularly within those severely depleted areas and associated well failure and completion integrity damage. This study also aims to assess other potential geomechanics-related risks due to early depletion, such as the risk for cap rock integrity and fault sealing capacity damage. Pore collapse is likely the main failure mechanism of high porosity formations under high level of depletion. The high porosity reservoir rock failure starts at compaction strain around 10 millistrain (1%) based on Lab rock mechanics core sample tests. The formation failure was identified according to both criterions (a) the computed formation total vertical strains being larger than the core sample failure strain (10 millistrain) and (b) plastic compressive strains development. The timing and location of plastic compressive strain development are consistent with the formation collapse indicated by the total compressive strain criterion. Large area of formation failure is unlikely to occur in Base case, but is likely to occur in weak formation scenario from 2020.