Pore System Changes During Experimental Polymer Flooding in Ben Nevis Formation Sandstones, Hebron Field, Offshore Eastern Canada

Abstract

Experimental polymer flooding was conducted in Ben Nevis (BN) Formation sandstones from Pool 1, Hebron Field, first heavy oil field offshore Eastern Canada and the effects are investigated as part of an ongoing study aimed at identifying polymers that can be applied to this field. The study focuses on the potential of this enhanced oil recovery (EOR) method on sandstones with interconnected pore networks and relatively low permeability (200 – 600 mD). Polymer floods consisted of selected partially hydrolyzed polyacrylamide and the biopolymer Guar Gum. The mineralogy and texture of the sandstones were studied before and after the injection by both optical microscopy and scanning electron microscopy and mineral liberation analysis (SEM-MLA), and quantification was completed using digital image analysis. The studied cores were sampled from the exploration wells in Pool 1, Hebron Field and mainly consist of fine to very fine grained sublitharenites with similar mineralogy but different textures (homogeneous vs. heterogeneous). The results obtained from the flooded core sandstone samples indicate a porosity increase and a qualitative permeability rise. Intergranular clay matrix detachment and partial removal from the rock sample (due to polymer flooding input/release drag) are the main processes that explain the porosity increase. Carbonate cements were relatively stable and no substantial changes were observed. Additional textural changes observed were minor and consisted of variations in the roughness of grain-pore contacts, pore shape and aspect ratio. Primary texture of the rock subjected to polymer flooding injection is an important factor and seems to enhance textural/mineralogical changes in heterogeneous systems. These results simulate the polymer flooding injection nearest to the production well and indicate that, in this environment, where the polymer flood pushes out the oil and brine fluids and interacts with rocks, some mineralogical/texture re-adjustments take place. Possible porosity and permeability increases could facilitate the polymer flooding but textural re-adjustment could also affect the rock physical properties; thus affecting the oil recovery.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015