PETROPHYSICAL MODELLING IN SHALE SAND LAMINATIONS USING THOMAS STIEBER TRIANGLE

Abstract

In subsurface geological formation, a lot of uncertainties lies in rock property estimation due to the existence of under-resolved strata. This is primarily due to use of low resolution conventional logging suites for acquiring borehole records. A simple example is laminated shaly-sand reservoir. The shoulder bed effects in such alternating/sandwich sequences do not allow the conventional logs signals to be fully developed to represent its true value of the measurement in these thin laminas. The ability to characterize only an average of multiple beds often results in significant underestimation of oil and gas in the reservoir. In this work I used both routine petrophysical analysis and Thomas-Stieber analysis for evaluation of Vshale, porosity, and saturation. I presented the work flow in a way that it explains the intricate processes of segregating the structured, the dispersed and the laminated shale volume using simple GUI interfaces that asks for obvious inputs. The results shows that Thomas Stieber analysis produces porosity values which are distinctly improved from the porosities value obtained from routine analysis. Similarly the results obtained for water saturation (Sw) using laminated porosities shows distinct values then the once obtained from routine analysis.