Regional In-Situ Stress Mapping: An Initiative for Exploration & Development of Deep Gas Reservoirs in Kuwait.
Authors: Perumalla Satya , Al-Fares Abdulaziz , Husain Riyasat , Mulyono Rinaldi , Al-Ammar Nada , Al-Kandary Ahmad , Singh Hemant , Al-Naeimi Reem , Prasad Umesh , Scheele Erik , Barton Colleen 
Published: March 2015

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.

Introduction and Objectives

Mapping of sub-surface structures and in situ reservoir properties have been in practice by explorationists for more than a century. The structural maps and profiles provide understanding of geological history and conditions that are essential for play evaluation. Many conventional oil & gas fields in the world have been explored and developed and many are at a mature state. However, limited data are available to map the present day in situ stresses in these fields, as typical conventional exploration techniques assume theoretical stress estimations based on a regional understanding of tectonic history related to the evolution of a particular field structure. Occasionally, seismic attributes have been used to complement these geological estimates. Consequently, there has been little appreciation of the influence of in situ stresses on exploration and development strategies. More recently, it has been realized that geomechanics plays a key role in various ways from exploration through field development including wellbore stability analysis (for improved drilling experience) to reservoir geomechanical analysis (for optimization of production).