The Effect of Solvent based Nanofluid Flooding on Heavy Oil Recovery

摘要

The objective of this study is to investigate the effect of solvent based nanofluid flooding followed bywaterflooding on heavy oil recovery performance and sweep efficiency improvement in unconsolidated oil-wet porous media.The sweep efficiency improvement is correlated with in-situ emulsion generation duringsuch displacement and is monitored with a CT scanner.Partially hydrophobic silica NPs with proper interface affinity was firstly synthesized,and subsequentlydispersed in toluene along with a surfactant to prepare the solvent based nanofluid.The solvent basednanofluid was then injected into an oil saturated sandpack at different slug sizes and further chased bybrine to investigate the sweep efficiency improvement through possible emulsification.To investigate thebeneficial effect of NPs,the aforementioned flooding was compared against conventional solvent floodingfollowed by waterflooding.The displacement patterns were monitored with a CT-scanner to assess the heavyoil recovery performance in the absence or presence of the solvent based nanofluid.The fluid density profiles during solvent based NF flooding followed by waterflooding were extractedfrom CT-scan images and compared against conventional solvent flooding followed by waterflooding toassess potential sweep efficiency improvement.The results revealed an increase in sweep efficiency duringsolvent based NF flooding followed by waterflooding.This was related to the creation of in-situ emulsion atthe water-diluted oil interface due to the presence of NPs and surfactant in diluted oil.Unlike conventionalsolvent flooding where post water created several fingers through porous media,the water phase in solventbased nanofluid flooding was able to displace all the lower resistance paths created by the solvent basednanofluid.Moreover,chase water was able to recover almost all of the solvent in solvent based NF flooding,which is essential for the process to be economically viable.In general,the presence of solvent based NFwas found to be effective in re-distributing the preferential water flow paths in to a more uniform front,which suppressed the fingering in turn and resulted in later water breakthrough,better sweep efficiency,and higher oil recovery.The proposed solvent based nanofluid flooding has not been tested so far as a heavy oil recoverytechnique.Unlike conventional solvent flooding which can suffer from high residual solvent towaterflooding,this technique revealed negligible residual solvent upon waterflooding.Moreover,it wasfound to be effective in sweep efficiency improvement and heavy oil recovery compared to conventionalsolvent flooding.