The Geochemical And Pore Structural Characterization Of Shale Oil Reservoir From The Second White Specks Formation In The Western Canada Sedimentary Basin

Based on the data derived from Rock-Eval pyrolysis,X-ray diffraction,low—temperature nitrogen adsorption,argon ion mill-scanning electron microscopy and extractable organic matter gas chromatographic mass spectrometry(GC-MS)analysis of the Second White Specks(2WS)Formation core samples from 9 wells in the Western Canada Sedimentary Basin,this paper discusses the geochemical characteristics and pore structures of shale oil reservoirs.GC-MS analysis of saturated hydrocarbon shows that short-chained n-alkanes(n-C9—n-C19)are the dominated compound class,steranes are dominated by ???20R C27 sterane and relatively low content of oleanane occurs in terpanes.The organic matter origin is dominated by algae and plankton.Maturity has a little impact on Pr/Ph,which basically records the environmental re-ox conditions during deposition.The relationship between dibenzothiophene/ phenanthrene and pristane/phytane indicates that the depositional environmentlithofacies of the 2WS Formation vary largely from east to west.Strong reducing environment occurs in the east of Alberta,weak reducing environment in the mid-west and relatively strong reducing environment in the west.As pyrolysis products in the lab usually contain large amount of polar,high-molecular compounds,hydrocarbon potential obtained from current mass balance model has been over-estimated.A new method of dead carbon calibration is used to reconstruct the original organic carbon content and original hydrocarbon potential of matured-high matured source rocks in the 2WS Formation.Shale oil reservoirs study show that the pore structure mainly consists of medium pore,followed by a certain amount of micro and macro pores.There are five pore types in the studied samples which include interparticle pores between clay minerals,organic nanopores,microcracks,secondary denudation pores and mineral intercrystal pores,which provide space for shale oil storage.The porosity of shales is mainly affected by mineral composition,thermal maturity changes,organic richness and bitumen content.The cumulative pore volumes of different pore sizes generally increase with higher quartz content.And notable variations were found for bitumen content,which blocks pores and reduces the porosity.While pyrite has high macro pore proportion,its existence is unfavorable for the development of pores.Based on the established standard,only a few samples contain commercial production required quantity and shale oil production potential is limited.