The Importance of Geohistory for SGR Threshold Calibration; A Case Study from Sarawak & Sabah Basins

Analysis of 470 drilled wells in Sarawak and Sabah basins- Malaysia; shows 41.87% of failures are related to seal and trap effectiveness. Sand against shale juxtaposition along fault plan is the primary mechanism of sealing ( Allan 1989 & Knipe et al 1997 ). However, fault rocks seal which get entrained in the faulting process can also act as a secondary sealing mechanism when sand juxtapose sand ( Fristad et al 1997 , Yielding et al 1997 & Yielding 2002 ). Shale Gouge Ratio (SGR) is a quantitative parameter that was first introduced to predict fault seal capacity by Fristad et al 1997 and Yielding et al 1997 . Later based on compilation of fault related seal and leak observations for the North Sea, Yielding (2002) presented the SGR minimum threshold required to have an effective seal. He also established an empirical relationship between SGR and across fault pressure difference which later incorporated buoyancy pressure data ( Bretan et al., 2003 ). These data and relationships have been incorporated and it is calibrated to the North Sea. We have now conducted SGR calibration for Sarawak & Sabah more accurately reflect the risk in fault dependent traps and probable range of HC column in these basins.