Umesh Prasad

Regional In-Situ Stress Mapping: An Initiative for Exploration & Development of Deep Gas Reservoirs in Kuwait.

KOC has undertaken an initiative to generate a regional in situ stress map for 23 Kuwait oil and gas fields using the data from more than 400 wells. Key objectives of this project are to integrate all available well data sources from these fields to derive the in situ stress orientation and also to create an interactive digital stress map supported by sub-surface structural geological data including formation seismic horizons, faults and well markers with the help of visualization software. In this way, the outcome of this project is available as an interactive geomechanical knowledge base which can be viewed at regional scale. The results of this project indicate that the maximum principal stress azimuth in Cretaceous formations is consistent with the regional Zagros tectonics and it is more or less uniform N45° (±10°) E direction even across major fault systems. However the sub-salt Jurassic formations exhibit high variability in stress orientation across faults as well as in the vicinity of fracture corridors. In addition to the patterns seen in stress orientation, the geomechanical models from each field exhibited that the Gotnia Salt is mechanically decoupling the highly stressed, strong, Jurassic formations from shallower, relatively lower stressed and weaker Cretaceous formations. It was also found that these stress anomalies in Jurassic formations coincide with associated fault and fracture corridors which appear to be critically stressed. Characterizing critically stressed fractures at the wellbore scale provided an understanding of possible permeable fracture sets that could contribute to gas flow. This paper discusses detailed results of the regional stress distribution patterns including innovative criteria developed to manage quality control of stress orientation data, correlation between stress anomalies and structural geological elements in Kuwait and also covers insights developed for exploration and development strategies of deep gas reservoirs in Kuwait.

Improved Method for Estimating the Strength of Carbonate Rocks

A substantial number of underground formations penetrated during oil and gas well drilling operations consist of carbonate rocks, limestones and dolomites. Knowledge of their strength can help drill bit and mud weight selection, drilling performance prediction, wellbore stability analysis, and even casing point selection.