| dc.description.abstract | Reactive nature of steam and clay minerals may lead to formation damage and flow assurance issues. This dissertation presents experimental investigation of oil recovery and changes in petrophysical properties as a function of mineralogy and amount of injected steam.
Sandpacks with fixed amounts of quartz, calcite, dolomite, kaolinite, and montmorillonite were prepared to identify mineral reactions, their conditions, and effects of these processes on porosity and permeability. Rock mixtures were aged in HP/HT cells. Sandpacks with quartz, calcite, feldspar, kaolinite, smectite, and illite were prepared for investigation of oil recovery factors in steam injection experiments. Porosity and permeability of the initial and steamed sandpacks were determined using CT scan and coreflooding respectively. Composition of the collected liquid samples was analyzed using ICP-OES. Rock morphology and pore-space configuration were studied using SEM-EDS, and mineralogy was analyzed using XRD.
Sandpacks without clay minerals were found to be the least prone to formation damage associated with steam injection. Silica dissolution/precipitation reaction resulted in 5% permeability reduction and 1-2% porosity reduction. Mixtures of quartz, kaolinite and carbonate minerals (calcite or dolomite) after steam injection lost 11-22% of permeability and 2-7% of porosity. Kaolinite fines were shown to be mobilized during steam treatment. Aging of these mixtures for 10 days at 400°F and 1,000 psi lead to formation of swelling smectite clay (Ca montmorillonite). Steam injection in montmorillonite-rich sandpacks caused up to 84% permeability loss and up to 8% porosity loss. This was explained by clay swelling and porebridging. Microporous network that filled the pores significantly restricted the flow.
Oil recovery factors for 100% quartz case was determined to be 65 wt%. Calcite- and feldspar-rich sandpacks produced 56 and 61 wt% of oil respectively. Sandpacks with clay fractions have shown the lowest oil recovery – 39, 29, and 28 wt% for kaolinite-, smectite-, and illite-rich samples respectively. Feldspar-rich sandpack demonstrated signs of structural destruction and fines release. Steam interaction with illite-rich sandpacks caused formation of amorphous silica.
Obtained results characterize petrophysical changes and formation damage mechanisms caused by hydrothermal alterations and identify oil recovery factors of sandpacks containing minerals with different structures and properties. | |
