Online Journal for E&P Geoscientists

Muzaffar, Asif ^*1; Al-Shammery, Matter ¹; Ali, Syed S.²; Sprague, Ronald ¹
(1) Reservoir Characterization Department, Saudi Aramco, Dhahran, Saudi Arabia. (2) Geological and Interpret Application Division (GIAD), Saudi Aramco, Dhahran, Saudi Arabia.

A workflow was developed to underscore the overall risks associated with drilling and planning development wells for a single reservoir layer contained within a larger reservoir complex. Deterministic Common Risk Segment (CRS) mapping was adopted to highlight the risks. Maps for basic parameters such as porosity, permeability, reservoir thickness, lost circulation zones and faults were produced over the entire field using log data from seven hundred sixteen wells, core data from thirteen wells, and 3D seismic data. Additional maps of reservoir pressures and seismic attributes, such as curvature and impedance, were produced over a smaller area of the field. Each of the parameter maps was converted to a discrete map using a cut-off value for that parameter. Each discrete map was assigned a value of one (1) for risk and zero (0) for no risk. The final summation risk maps were produced by combining the discrete parameter maps. These maps were then further simplified and redefined into areas of high, medium, and low risk. Two summation risk maps were created: one over the entire field using fewer parameters, and another over a smaller area with additional parameters. The larger map, with fewer parameters, was validated using ten new wells. This validation resulted in an 80% predictive success. The map generated using the additional parameters, over the smaller field area, resulted in a 100% predictive success for four new wells.

The workflow also includes sensitivity testing of various parameters to determine the main risk drivers. This workflow can be adapted to any mature or semi-mature field, where a statistically valid number of wells and 3D seismic data are available.