TY - THES

T1 - An enhanced oil recovery micromodel study with associative and conventional polymers

AU - Buchgraber, Markus

N1 - no embargo

PY - 2008

Y1 - 2008

N2 - Half of the recovery of the worldwide oil production is due to waterflooding projects. Mainly lighter oils with lower in situ viscosities are recovered by water flooding. Higher viscous oils suffer from unfavourable mobility ratios and, therefore, show unstable displacement. Viscous fingers cause an early breakthrough leaving a lot of bypassed oil behind them and having high watercuts early in their flooding life. By adding polymer into the injection water and, therefore, increasing the viscosity, the displacement process will have a more favourable mobility ratio and hence a more stable displacement. In addition, the effect of the plugging of high permeability paths so that bypassed areas get in contact with the displacement fluid, is desired. Polymer flooding has been done for almost 40 years with hydrolysed polyacrylamide or xanthan, which are referred to as conventional polymers. A new type of polymer, a so-called associative polymer, has been developed recently. It has a greater resistance against salinity and at the same concentration a higher viscosity than conventional polymers, which would reduce the costs of a polymer flooding project significantly. The purpose of this study is to improve the understanding of the immiscible displacement of conventional and associative polymer solutions with dead oil (250 cP). Forced imbibitions experiments were conducted to observe front stability, breakthrough-time and recovery and ultimate recovery for different polymer concentrations and polymers. Experiments were conducted in a micromodel which had geometrically and topologically the same homogenous pore space as Berea sandstone. It acts as an artificial reservoir and is an etched silicon wafer bonded with glass to build the flow channels. The main advantage compared to conventional core experiments is that the displacement process can be observed at meso and micro scale with a microscope without any CT-scanning tools. Records in form of high resolution photographs and videos describe the displacement process at micro and meso scale. Initial water saturation, water saturation at breakthrough, swept area at breakthrough and ultimate recovery are determined and calculated with digital analyses. Additional data recorded before and during experiments are oil and polymer viscosity, mobility ratios, shear rates for polymer solution in the micromodel, absolute and relative permeabilities, injection rate and pump pressure.

AB - Half of the recovery of the worldwide oil production is due to waterflooding projects. Mainly lighter oils with lower in situ viscosities are recovered by water flooding. Higher viscous oils suffer from unfavourable mobility ratios and, therefore, show unstable displacement. Viscous fingers cause an early breakthrough leaving a lot of bypassed oil behind them and having high watercuts early in their flooding life. By adding polymer into the injection water and, therefore, increasing the viscosity, the displacement process will have a more favourable mobility ratio and hence a more stable displacement. In addition, the effect of the plugging of high permeability paths so that bypassed areas get in contact with the displacement fluid, is desired. Polymer flooding has been done for almost 40 years with hydrolysed polyacrylamide or xanthan, which are referred to as conventional polymers. A new type of polymer, a so-called associative polymer, has been developed recently. It has a greater resistance against salinity and at the same concentration a higher viscosity than conventional polymers, which would reduce the costs of a polymer flooding project significantly. The purpose of this study is to improve the understanding of the immiscible displacement of conventional and associative polymer solutions with dead oil (250 cP). Forced imbibitions experiments were conducted to observe front stability, breakthrough-time and recovery and ultimate recovery for different polymer concentrations and polymers. Experiments were conducted in a micromodel which had geometrically and topologically the same homogenous pore space as Berea sandstone. It acts as an artificial reservoir and is an etched silicon wafer bonded with glass to build the flow channels. The main advantage compared to conventional core experiments is that the displacement process can be observed at meso and micro scale with a microscope without any CT-scanning tools. Records in form of high resolution photographs and videos describe the displacement process at micro and meso scale. Initial water saturation, water saturation at breakthrough, swept area at breakthrough and ultimate recovery are determined and calculated with digital analyses. Additional data recorded before and during experiments are oil and polymer viscosity, mobility ratios, shear rates for polymer solution in the micromodel, absolute and relative permeabilities, injection rate and pump pressure.

KW - Polymere Assoziative Polymere Polymerfluten Scheer Raten Viscosität EOR Viscous fingering Breakthrough time Polymer Adsorption

KW - polymer solution associative polymer conventional polymer shear rate viscosity viscous fingering polymer plugging polymer adsorbtion breaktrough time EOR

M3 - Master's Thesis

ER -