Net to Gross Estimation of S-field Using Well-log and ۳D Seismic Data: A Malay Basin Case Study

Net- to-gross (NTG or N/G) is a measure of sand or pay in the overall reservoir interval. It is used as one of the parameters for reserves calculation. In the conventional method, N/G is estimated from lithofacies models; however, that method becomes highly uncertain as the distance away from control well increases. As such in this study, well log data and seismic are combined to better map N/G and hence improve static models and reserves calculations. In that quest, conventional log analysis is carried out to ascertain the reservoir of interest and its associated petrophysical parameters. It followed then by elastic properties generation and subsequently sensitivity analysis in cross-plots to discriminate reservoir sands from the caprock shales. Additionally, the delineated reservoir on the well logs is mapped on seismic data to get its areal extent as an input to inversion. Finally, Simultaneous inversion is carried out to generate the elastic parameters determined in feasibility analysis followed by probabilistic neural net application to predict the best combination of elastic properties for N/G prediction and subsequently N/G volume and maps generation.

Keywords:

Net-to-gross Estimation , Elastic Properties , Reservoir Characterization , Malay Basin