To evaluate the effectiveness of polyacrylamide (PAM), polyvinylpyrrolidone (PVP) and polyethylene oxide (PEO) as draft reducing agent for water. This research project aimed to evaluate the effectiveness of using polyacrylamide (PAM), polyvinylpyrrolidone (PVP) and polyethylene oxide (PEO) as drag reducing agents in water pipeline systems by studying the effect of volume and concentration on drag reduction in pipelines. This is evidenced by the decrease in pressure drop and increase in resistance reduction and flow throughput.
Overall, PAM is the most effective DRA compared to PVP and PEO, with drag reduction up to 42.5% and flow throughput increased to 36%. By increasing the volume and concentration of drag reducing agents, the drag reduction is increased, thereby minimizing the pressure loss across the pipeline system.
Project Background
In many cases, it is desirable to increase the injection water flow instead of drilling another injection well to maintain the reservoir pressure, as the latter is very expensive. Therefore, flow improvers for injection water will be the most economical way to increase the flow rate.
Problem Statement
Objectives
Scope of Study
Relevancy and Feasibility of Project
Introduction
Drag reduction
Drag Reducing Agents (DRA)
Al-Wahaibi, et al (2007) and Derrule (1974) state that there was a greater drag reduction in rough pipes, where turbulence increases, than in smooth ones. Thus, we can conclude that pipe roughness, fluid velocities, and pipe diameter are some of the factors that contribute to the turbulent environment in pipes, and adding a high molecular weight polymer to the system results in a high drag reduction. A good dispersion of DRA will ensure optimal dissolution of the liquid in the pipeline, thereby achieving a high drag reduction.
The effectiveness of DRA can be evaluated by determining the magnitude of the reduction in resistance at a given concentration and flow rate. The percent drag reduction (%DR) is defined at a given flow rate as the difference between the pressure drop of the untreated fluids (ΞP, as a baseline) and the pressure drop of the fluid containing the DRA (ΞP DRA) divided by the baseline pressure drop.
Mechanism of DRA
A section of the laminar substrate, called the "streak", will occasionally move up to the buffer zone. As the streak enters the buffer zone, it will begin to vortex and oscillate, moving faster as it gets closer to the turbulence core. Eventually, the streak becomes unstable and breaks up as it sheds fluid into the core of the flow.
Drag-reducing polymers interfere with the cracking process or inhibit the formation of turbulent cracks and turbulence, or at least reduce the degree of turbulence, and in turn reduce drag or pressure loss. The drag-reducing polymers somehow extend into the flow, absorbing the energy in the streak and thereby preventing the turbulent outburst.
Water-Soluble DRA
Polyacrylamide (PAM)
It is widely known that polyacrylamide (PAM) and related derivatives are the most preferred polymetric water soluble DRA in the oil industry for water injection. Polyacrylamide DRAs are highly effective in water injection systems because only 10-30 ppm of polymer is required to achieve significant pressure drop (Kelland, 2003).
Polyvinylpyrrolidone (PVP)
Polyethyleneoxide (PEO)
Research Methodology
Experimental Details
A steel beam is placed under the water tank to support the tank and place it about 2m off the ground to facilitate the flow of water based on gravity and potential energy. A ball valve is installed between the water tank and the flexible hose to control the flow of water to the pump; in the open or closed position. The pump will provide additional energy for the flow of water through the piping system.
A liter of DRA solution is poured into the injection chute and the valves will act as a check to ensure that the DRA will flow into the pipes and mix well with the tap water before the pressure drop is measured. As the DRA can easily degrade under high shear forces, the injection point is located 1.5 m behind the pump to ensure that the DRA maintains its structure and can function effectively. This inlet length is important to ensure that the turbulent flow is fully developed and the DRA has reacted with the tap water before the pressure drop is measured.
Throughout this section, it is assumed that the fully turbulent flow regime has been reached and the DRA polymer has reacted with the tap water and the pipe wall. The sump tank is used to collect the volume of 36L tap water passing through the pipeline. The flow rate and pressure drop at the end of the water pipe are recorded.
Then, turn the pump back on and open valve 1 to allow fluid to flow into the pipeline. The time required for the passage of 36 liters of water through the pipeline and the pressure of the system is recorded using a stopwatch and camera. Before proceeding with concentration and the next type of polymer, the pipeline system is rinsed with tap water twice.
Tool for Experiment
The plot of %DR vs. concentration and %FI vs. concentration for PAM, PVP, and PEO is shown.
Material for Experiment
Chemicals for Experiment
Gantt Chart
Variables
For PAM, the pressure drop increased as the concentration was increased from 400 ppm to 600 ppm, which is 8.5 psi to 10 psi. After 600 ppm the pressure drop decreases steadily as the concentration is further increased to 800 ppm and 1000 ppm. For PEO, there is only a small change in pressure drop for all concentrations, and the pressure drop increases as concentration increases.
Then the pressure drop increased with increasing concentration at 1000ppm up to 9.625psi. This may be due to the fact that the system has reached the optimal concentration of DRA and further increasing the concentration does not affect the drag reduction. Therefore, having less pressure drop after adding DRA to the system, higher drag reduction is expected to be achieved.
The trend plots for all three polymers are similar to the drag reduction plots. It is expected that this research project could provide an understanding of the drag reduction concentration effect and the most effective drag reduction polymer. Flow characteristics such as pressure drop, drag reduction (%DR), flow rate increase (%FI) and flow rate were studied with DRA concentration of 400ppm, 600ppm, 800ppm and 1000ppm.
This is evidenced by a decrease in pressure drop and an increase in drag and flow rate reduction as shown in Figures 14, 15 and 16. From this experiment it is known that different type of polymer will give different results in terms of their flow rate as the concentration increases according to the trend reducing resistance and increasing flow. In fact, the addition of a small amount of DRA that can cause such a reduction in resistance and an increase in flow can be very fascinating from an economic point of view.
To test the rheological properties of the polymer; its shear degradation and elasticity so that a better understanding of the effect of these properties on drag reduction is known. J., βMechanical Degradation of Drag Reduction Polymers and Additives: A Review,β Drag Reduction in Fluid Flows, Ellis Horwood Limited.
Assumptions
Experiment Calculation
Flow rate result can be obtained by dividing the constant volume of water by the different time it takes for the water to reach at constant point in the drainage tank. From the experiment conducted, below is the data showing the results of the experiment.
Discussions
- Average Pressure Drop
- Drag Reduction (%DR)
- Flow Throughput Increase (%FI)
- Average Flow Rate
The smallest total pressure drop achieved is 7.75 psi by adding 1000 ppm PAM to the system as more polymer molecules are available to suppress the turbulent eddies. The equation shows the relationship between the pressure drop measured by adding DRA and without DRA (base case). The highest resistance reduction for PEO is at 400 ppm, which is 35%, and further increased concentration caused a decrease in resistance reduction to 28%.
The study flow increase shows that the capacity of the pipelines to transfer a volume of fluid increases as the resistance decreases. PAM gives the highest result in average flow and the trend fluctuates; with the highest flow rate of 800 ppm, which is 48.6 gpm. The average flow rate decreased as the concentration was increased for PEO polymer with the highest flow rate at 400 ppm (34.2 gpm) and the smallest flow rate at 1000 ppm (29.2 gpm).
For PVP, the average flow rate increases steadily but in small proportion with increasing polymer concentration, which is from 39.2 gpm to 40.2 gpm. Since the drag force is removed or suppressed by the addition of DRA, the flow rate is higher as the fluid can flow easily. PAM gives the most positive effect to the system by having smaller pressure drop and higher drag reduction, flow increase and flow rate compared to PVP and PEO.
This result can be explained by discussing the properties of the polymer itself, especially the molecular weight and structure of the polymer. It is clearly shown that the high molecular weight polymer will give smaller pressure drop, better drag reduction, higher throughput and higher flow rate. This may be one of the contributing factors to the PEO's reduced effectiveness.
Limitations
Errors
Entrance Length
Drag Reduction (%DR)
Flow Throughput Increase (%FI)
DRA concentration
It is assumed that the fluid in the pipe is delivered in the full diameter of the pipe. The injection point is designed to be 90o from the pipeline system so that once the valve is opened, the DRA will flow directly in the direction of the fluid flow and react accordingly to reduce the frictional energy losses. i) Average pressure drop. The reaction time of the person in charge to stop the stopwatch precisely at 36L water volume may contribute to the error.
Liberatore, M.W., Baik, S., McHugh, A.J., Hanratty, T.J., "Turbulent Drag Reduction of Polyacrylacmide Solutions: Effect of Degradation on Molecular Weight Distribution," Journal of Non-Newtonian Fluid Mechanics.
