Design, synthesis and characterization of polymer gel systems for low-permeability oil reservoirs

The scope of this thesis is to design, synthesize and characterize an effective polymer gel system that aims to reduce the significant amount of wastewater encountered during oil and natural gas production and to provide a more efficient conformance control, and finally to bring a new design to the sector by proving its effectiveness with a pilot field study after determining its contribution through performance tests. In this context, for low permeability reservoirs where traditional gel applications are insufficient, it is aimed to create a gel form based on in-situ polymerization and subsequent cross-linking under high pressure (1.500 psi) and temperature (60℃) conditions approximately 1500 meters below the ground. The feasibility of the designed polymerization under all conditions that can be encountered in the reservoir was examined in both static and dynamic conditions with controlled experimental setups by scanning different pH (1 –14), salinity (0 –200.000 ppm), shear (2 – 200 s-1), temperature (40 – 60℃) and pressure (0 – 1.500 psi) ranges. As a result of controlled experiments, it was determined that the design in which acrylamide monomer is transformed into polyacrylamide (PAM) by free radical polymerization over persulfate-based thermal initiators and formed into a gel with metallic cross-linker is the most effective solution applicable in the field. After the polymerization kinetics and characterization studies were completed, flow tests were performed with plugs brought to reservoir conditions and permeability decreases were monitored. Subsequently, flooding tests reflecting the field conditions were performed on the core brought to oil-water saturation and aged at reservoir conditions for 6 weeks to test the gelation performance, penetration and blockage rate, permeability drop, and additional oil recovery (%17.0). CT Scan, SEM, EDS and thin section studies were performed to determine the placement and clogging ability of the gel in the rock. As a result of these findings, it was decided to move the study to a pilot field test in wells with different functions (production, wastewater injection, gas injection), chemical materials were procured and the operation was programmed and designed. A pilot field study was successfully carried out in 6 candidate wells identified as a result of extensive analysis and very ambitious results were achieved to effectively combat wastewater and increase oil recovery. An average 20% decrease in watercut of production wells and a 35% increase in sweeping pressure of injection wells were observed.