Sandwich: Log Evaluation In Laminated Shaly Sands

SUMMARY Formation evaluation from well logs in laminated shaly sands has often suffered from lack of proper models, and in many cases led to underestimation of oil or gas in place. Shell Research have developed a technique that allows consistent analysis of formations with laminated, dispersed and structural shale, leading to better quantification of oil and gas volumes in place. Present research is concentrating on further calibration of the model input parameters by core and highresolution logs such as borehole imaging logs. The present paper shows results of application of the model to the oil fields in Sarawak Shell Berhad (SSB) in Malaysia. The results show increases in the hydrocarbon volumes of up to 40%, as compared to the previous conventional analysis. Higher increases were obtained in environments with higher amount of laminated shale. The main benefit of application of the SANDWICH model was the increased confidence in the volumes of oil and gas in place in laminated shaly sands. This was achieved through reduction of the uncertainty in the log derived inputs to volumetrics. As a result, the reduced uncertainty has helped to reconcile reservoir production with oil in place, and it will improve further development planning such as redevelopments and re-completions.