الملخص الإنجليزي
During SmartWater injection of carbonates, wettability alteration is the main mechanism contributing to incremental oil recovery. Apart from the SmartWater composition, level of dilution and the underlying mechanisms, "injection scheme" is of a great importance when developing a field scale flooding project. The pivotal target of this thesis is to evaluate the efficiency of SmartWater injection by deploying tertiary SmartWater "shock slug" injection within the periods of water flooding.
At the first stage, genuine reservoir brine was 10 times diluted and its composition was modified by adding MgSO4.7H20 (2.65 g/ml). Three different slugs of SmartWater, i.e., 0.5, 1 and 2 pore volumes were determined to be injected into the core. For continuous SmartWater injection, after the initial water flooding, SmartWater was injected until no further oil recovery observed. As for SmartWater shock slug injection, core samples were water flooded with the original high salinity water to reach the residual oil saturation. Subsequently, SmartWater was injected for the selected shock slug sizes followed by the high salinity water injection. The contact angle was measured under standard condition by generating a sessile drop of oil on the carbonate surface submerged in the brine environment. The pH of the injection fluids was measured during contact angle and coreflood tests. XRD was utilized to analyze mineralogy of the core samples. The SmartWater composition was analyzed by IC and optimized by assessing contact angle data.
XRD analysis on the rock revealed that the rock sample was dominantly (> 98%) composed of calcite with a negligible degree of quarts (< 2%). Contact angle measurements and pH evaluations were employed to examine the effect of the SmartWater on the wettability alteration.
As depicted in the photos generated from contacted angle measurements, SmartWater was capable of altering the wettability towards the more water-wet state. The pH of the Smartwater was increased after it was kept in contact with the oil aged rock for two weeks.
Core flooding results indicated that tertiary injection of larger slug size of SmartWater as a shock led to a higher incremental oil recovery. This is mainly due to more effective ionic exchange which leads to wettability alteration during SmartWater injection. It was observed that 1 PV of Smart Water shock slug can increase the incremental recovery by 10% while continues SmartWater injection yielded 13% extra recovery in the same condition. Initial runs for 2PV slug size demonstrated a substantial incremental recovery compared with the continuous smart water injection. This shows that 2PV slug can produce as much as the continuous SmartWater flood. Results showed that the newly proposed technique i.e., employing Smart Water Shock slug injection in tertiary mode followed by water flooding, leads to a significant amount of production in comparison with continues injection of SmartWater under the same circumstances. Implementing Smart Water "shock slug" injection, the Smart Water injection time is reduced down to 1-2 PV injection, which without sacrificing on oil recovery, makes the process financially viable.
