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Well-Log Electrofacies Prediction of Middle and Upper Jurassic Carbonates, Saudi Arabia: A Case Study for Exploration Applications

Tang, David Z.*1; Rabiller, Philippe 2; Bakhiet, AbdelFattah 1; Gregory, Greg 1; Lawrence, Paul 1; Samsudin, Azman 1; Tan, Wenbin 1
(1) Exploration Resource Assessment, Saudi Aramco, Dhahran, Saudi Arabia. (2) Rabiller Geo-Consulting, Pau, France.

The Middle and Upper Jurassic formations contain both significant carbonate hydrocarbon reservoirs and world-class source rocks. To explore and assess the hydrocarbon resource potential in the Jurassic system, it is critical to reconstruct the regional stratigraphic framework, and define the fairways of reservoirs, source rocks, and seals by integrating core, well-logs, and seismic interpretations. This case study presents an integrated approach for predicting well-log electrofacies of the Middle and Upper Jurassic carbonates, and their exploration applications.

Core-based rock types were defined for selected Jurassic carbonate reservoirs by integrating core descriptions, thin-section petrography, core plug porosity/permeability, and mercury injection capillary pressure (MICP) data. Reservoir quality and sealing capacity were evaluated using capillary pressure data and pore-throat size distributions from a full spectrum of reservoir and seal facies. Core-derived reservoir and seal facies were then calibrated to well-log responses using the Multiple Resolution Graph-Based Clustering (MRGC) method for selected “Reference Wells” that were extensively cored and analyzed. The MRGC models were validated by comparing predicted electrofacies with core-derived rock types and lithofacies. The optimized model was used to predict electrofacies that represent rock types of varying reservoir quality and seal capacity for selected wells without core data (i.e. “Application Wells”). The predicted electrofacies of the reservoirs and seals were utilized for three key exploration applications: 1) high-resolution stratigraphic correlations and stratigraphic framework reconstructions based on vertical and lateral facies patterns, 2) calibrated seismic facies modeling of 3D seismic volumes, and 3) to map regional play elements such as reservoirs, source rocks, and seals. These are the essential building blocks for defining the Jurassic gross depositional environments, petroleum systems analysis, and hydrocarbon exploration prospectivity. This case study has demonstrated that this type of integrated approach can be applied for high-resolution stratigraphic analysis, calibrated seismic facies prediction, and play fairway mapping on both regional and sub-regional scales.

 

AAPG Search and Discovery Article #90141©2012, GEO-2012, 10th Middle East Geosciences Conference and Exhibition, 4-7 March 2012, Manama, Bahrain