Experimental Study of Multiphase Flow Through One-Way Valves for SWEOR Concept

This thesis studies the efficiency of conical seat one-way ball-type valves, and the possibility of their usage in the frac-to-frac method in tight oil reservoirs through the single well enhanced oil recovery method. Thus, an injection valve that only allows flow from the tubing into the formation and a production valve that only allows flow from the formation into the tubing are tested to understand their performance by measure their leakages and rates needed to become functional. The experimental work was conducted using two test benches, a high-pressure (HP) test bench that was used to measure the leakage rates and closing rates of the valves, and a low-pressure (LP) test bench that allows to visualize the flow and measure and calculate the leakage through the valves. This second low-pressure test bench is useful to propose design improvements. The fluids used during these experiments were air and water, and the results were extracted through the Labview software. In the experiments using the HP test bench, the valves had a Silicon Nitride ball with a hex-hole lid that keeps the ball in place. In addition, thread seal tape was used to decrease possible leakage through the threading (between the valve body and the cell wall). Leakage rate tests were done at 50, 75, 100, 125, and 150 bar pressure difference. The tests’ durations varied between forty minutes and two hours. The results showed an increase in the leakage rate as the pressure was increased. The coefficient of variation of the leakage rates during the stabilization period was high for low leakage rates and were very low, for high leakage rates. Closing rate tests were performed in the HP test bench to determine the flow rate needed for the ball to be pushed into place, shutting the valve closed. Two closing rate tests were done for each valve and the average of the values obtained is reported. Leakage tests in the HP test bench were conducted on an injection and a production blind, to quantify the leakage through the threading. The values obtained were then compared against the results with the valves to back-calculate the leakage through the seal surface between the conus and the ball. One peculiar result is that he leakage through the production blind was higher than through the production valve; however, as the leakage rates were very low, it is believed that this may be caused by the thread seal tape that was applied differently in both tests. Regarding the LP transparent test bench, two types of experiments were conducted, an air-injection water-production cyclic experiment, and an air-injection zero-production cyclic experiment. In the first one, when injection starts, the air rate that causes the closing of the production valve is determined by visual inspection and subsequent check of the measurement loggings. The injection phase then continues until the tank reaches maximum possible pressure. Then, the production phase begins, water is sent through the production valve. During this phase, the air tank will depressurize, due to leakage of air through the injection valve. The leakage rate appeared (visually) to be higher when water production took place after the air injection phase, compared to when the tank leakage through the valve was left to take place by itself. It is believed that this is because in the first case the pressure differential across the valve is lower than for the second case. These tests allowed to visualize the leakage through the valves and understand the nature of the flow within the cell. After performing the experiments, the valves showed very positive results, having minimal leakage rates compared to the seal thresholds set by NORSOK (0.4 liters/min for water and 15 scfm for gas), proving that the current valves’ designs could qualify as a barrier between the formation and the rest of the production system. Finally, the aim of this work is to provide a completion technology that is simple and cost-effective for usage in the single well enhanced oil recovery through the frac-to-frac method in tight oil reservoirs, which allegedly has a better performance than the Huff-n-Puff method