In miscible shear, one of the most important parameters to investigate is the minimum miscibility pressure (MMP). Several oil samples with varying wax content have been experimented to obtain the pressure at which the IFT approaches zero, also known as MMP. However, the experiment failed to obtain one of the sample's MMP due to technical difficulties.
I would also like to express my gratitude to my family, who gave me emotional and financial support during the entire project. 26 Figure 23: Determination of MMP by extrapolating JFT vs pressure plot for 10% wax content waxy oil sample. 27 Figure 24: Determination of MMP by extrapolating 1FT vs pressure plot for 15% wax content waxy oil sample.
28 Figure 25: Determination of MMP by extrapolating JFT vs pressure plot for 20% wax content waxy oil sample. 29 Figure 26: Determine MMP by extrapolating 1FT vs pressure plot for 25% wax content waxy oil sample.
Introduction and Background
This will cause the reservoir to experience a sharp pressure drop, reducing the natural driving force, and the heavier components of the remaining oil will be difficult to move, in other words, decreasing mobility. As mentioned before, EOR methods are designed to recover residual oil stuck in the reservoir, and miscible gas displacement may prove to be a solution to this problem. Holm8 (1987) conducted a field test on Mead Strawn in 1964 to find out the effects of C02 miscible displacements on the recovery factor.
Therefore, it is imperative to work towards a better understanding of the effects of wax content on MMPofC02. According to Beckers (1997), primary recovery usually produces the lighter hydrocarbons while the heavier components remain. However, for this method to work, the tank pressure must be higher than the C02 MMP, otherwise the C02 will not be soluble in the oil.
Holm8 (1987) concluded that MMP is mostly influenced by temperature and the heavier fraction of the oil composition. Therefore, it is crucial that values of MMP for different percent wax content are obtained and further investigated to gain an understanding of the trend of C02 MMP with respect to wax content.
Objectives and Scope of Study
A sample of oil with different wax content will be prepared and then the MMP will be determined for each sample.
Literature Review
- Carbon Dioxide Miscible Displacement
- Minimum Miscibility Pressure
- Calculation Methods of Obtaining MMP
- Simulation Methods of Obtaining MMP
- Correlation Methods of Obtaining MMP
- Experimental Methods of Obtaining MMP
- Slim Tube Test
- Rising Bubble Analysis .................................................................................. I 0
- Surface and Interfacial Tension
- Waxy Oil
Forward contact experiment is done by changing the oil to a new oil sample after each repetition, but the gas from the previous repetition is used again in the next repetition. Reverse contact experiment is done in contrast to the forward contact experiment, whereby the gas remains the same while the oil is the same oil from the previous experiment. After the gas and oil have reached equilibrium, the gas will be brought to another cell containing a fresh sample of oil and the oil will be brought to another cell containing a fresh sample of gas.
The pressure will be adjusted and the whole process is repeated until the key tie line in any cell is zero. This method is the accepted method of determining MMP in the oil and gas industry. The ultimate oil recovery will be plotted against operating pressure and the pressure corresponding to 100% recovery is taken as the MMP.
Finally, the MMP is defined as the pressure at the break of the recovery curves. According to Ayirala and Rao2, and Holm and Josendal9, it was found that a thin tube test can take up to several weeks and therefore this technique is time consuming. More recently, the micro thin tube test has appeared and the only difference is that it uses a much smaller tube to better represent the tight pore spaces.
They confirmed that the difference in bubble shape is mainly caused by the difference in 1FT between oil and gas. Researchers have concluded that relatively, the cost of RBA is less than the thin tube test. The test is considered qualitative because the result requires observing the change in the shape and appearance of the bubble.
Ayirala and Rao2 (2006) explained that the basic theory behind the method is that when mixing is achieved, the interfacial tension between oil and gas will become zero. In the middle of the liquid phase, a liquid molecule will be pulled in every direction, while at the interface of two liquids, there is an imbalance between the forces. With a calibrated and precise video lens system, the full shape of the drop is captured and analyzed by software.
Then the Laplace equations of the analysis are solved numerically over its complete form to obtain !FT. Due to the composition, wax will precipitate out of the oil if the cloud point is reached.
Methodology
Waxy Oil Sample ................................................................................................... l8
Because UTP does not have a cooling bath necessary to properly determine the wax content of the crude oil sample, the experiment is conducted using a synthetic oil sample. White mineral oil, also known as paraffin oil (CAS is used to control wax as the only manipulated variable. The experiment should continue until no more drop of oil can be formed on the needle due to the limitations of the equipment; the maximum pressure allowed to obtain 1FT is 2800 psi.
There is already a new machine in UTP that is specifically used to determine MMP which is a micro slim tube machine. Measuring 1FT with IFT 700 requires the density of the fluids at the pressure and temperature used in the investigation because bulk density is one of the variables used to calculate IFT. However, density of waxy oil will change greatly with temperature; it experiences small density changes with respect to pressure.
Assuming negligible changes in density over pressure changes and negligible temperature change over the reservoir, the density of oil sample will be measured only at the reservoir temperature. Clean the tube and pump with a large amount of toluene and dry with ethanol until no bubbles or liquids can be observed. Below are the procedures to obtain 1FT measurement and consequently MMP using a readily available machine called 1FT 700.
The valve for C02 gas to flow from the liquid tank to the liquid cell chamber is opened. Using the 1FT 700, which is a 1FT measuring device, it is impossible to obtain a zero IFT reading because, as explained earlier, 1FT is a measure of the strength of the barrier between the two fluids. If 1FT is zero, there will be no barrier to separate the two fluids from mixing with each other. Figure 19 shows a picture of iFT 700.
Key Milestone
Gantt chart
Results and Discussions
Density Measurement
Using the attached equation b) ExceL, the pressure when 1FT becomes zero is calculated and taken as MMP. At I 0% wax content, only 3 pressure points were produced. wax content course, there was not enough C02 to run the experiment, so it was only possible to achieve 1 FT for pressure up to 1500 psig. In order to stay on schedule, the 0% wax sample I trial was postponed due to limited time and machine failure, and a 10% wax repeat was never performed. A line of best fit was obtained using Excel. Using the equation provided by Excel, the pressure when 1fT becomes 1cro is calculated and taken as MMP.
Using the Excel equation, the pressure when 1FT becomes 7ero is calculated and taken as MMP. A series of trials should be continued until a pressure is reached where a stable drop of oil can no longer be produced. To follow the plan, sample I 0% was moved back to be run again after all other samples had been run.
As a result, the time allocated to run the experiments for the 15% oil sample was cut in half. In the I0 table below, the MMP obtained by experiment is shown in Figure 27 excluding the I0% wax sample. A suitable method for the determination of C02-waxy oil MMP using an experimental approach using the Vanishing Interfacial Technique was determined.
From the experiments conducted and by analyzing SMP obtained from an oil sample with a wax content of 5% and an oil sample with a wax content of 15%, the conclusion is that with increasing wax content. Due to the success of this project, engineers now know that over time the reservoir pressure must be increased to remain above the increasing MMP. If the tubing was sturdier, JFT could be obtained for pressures above 3000 psig and thus better results could be obtained for oil samples with higher wax content.
34;On JFT Measurements 10 Estimation of Minimum Mixing Pressures", paper SPE 30786 presented at the SPE Annual Technical Conference and Exposition. 34;'Analysi~ o.l Rising Bubble Experiments to Determine Minimum Mixing Pressure", paper SPE 30786 presented at the SPE Annual Technical Conference and Exposition, Dallas, October 22-25 (1995).
IFT Measurements
- Problems Encountered
Paraffin Weight Calculation
