An Innovative Approach for Pore Pressure Prediction and Drilling Optimization in the Abnormally Sub-Pressured 'Deep Basin' of the Western Canada Sedimentary Basin

Up to now, an indirect method to predict pore pressure under sub-pressured conditions has not been reported in the literature. In this thesis, an innovative approach is presented for estimation of pore pressure and drilling optimization of wells drilled in the abnormally sub-pressured Deep Basin of the Western Canada Sedimentary Basin (WCSB). The procedure starts with detailed evaluation of five wells drilled in township T65-R09W6 that covers the study area. Pore pressure was calculated using Eaton method from sonic logs (Eaton, 1975), and Eaton method from the modified D exponent (Rehm and McClendon, 1971), which proved to be the most effective for abnormal sub-pressured conditions over a variety of methods tested.;The combination of a rollercone bit code IADC 547 and at least 0.73 horsepower in the bit per square inch (HSI) provides the best quality of cuttings from the tight gas Nikanassin Group. This is of paramount importance for increasing accuracy in the quantitative determination of permeability and porosity from cuttings particularly in those tight gas reservoirs where the amount of cores is very limited.;It is concluded that wells in the sub-pressured study area of the Deep Basin of the WCSB can be drilled efficiently with 7 bit runs reaching larger rates of penetration than achieved in practice so far, while at the same time reducing bit wear, controlling wellbore stability problems and recovering good quality drill cuttings.;Although the methodologies developed in this thesis concentrate on township T65-R09W6 we anticipate that they can be extended to other sub-pressured formations with similar geologic characteristics in the Deep Basin of the WCSB and elsewhere.;The drilling optimization procedure was carried out using the Apparent Rock Strength Log (ARSL); next, optimization of individual sections in each well was carried out to determine the optimum operational parameters for the lowest net drilling time. Special attention was focused on the tight gas Nikanassin Group for selection of the most suitable drilling parameters that increase the quality of drill cuttings.