Iranian Journal of Oil & Gas Science and Technology
Volume:9 Issue: 1, Winter 2020

The influences of several operating factors on the viscosity of the Isfahan refinery waxy crude oil sample are studied through conducting some rheological shear rotational tests. The Taguchi design method is adopted to determine the impact of factors such as shear rate, temperature, cooling rate, wax content, and asphaltene content on the viscosity of the waxy crude oil. The results show that temperature with a contribution of 53.61% is the most influential factor. The wax content, shear rate, and asphaltene content have a contribution of 20.86, 14.75, and 3.11% respectively. The cooling rate does not have a statistically significant effect on the viscosity. The results of the rheological oscillatory tests confirm that the temperature and wax content change the viscoelastic properties of the waxy crude oil completely. An increase in the wax content from 12 to 22 wt.% raises the wax appearance temperature (WAT) from 19.1 to 34.9 °C and improves the gel point from 13 to 34.1 °C. By decreasing the temperature or increasing wax content, the viscoelastic nature of the oil sample changes from a viscoelastic fluid to a viscoelastic solid.

The current work investigates the performance of a single-stage, bench-scale system using a spray dryer to treat produced water. The produced water is generated in three large reservoirs of Ahvaz, Maroon, and Mansouri fields, which have different compositions but the same high total dissolved solids (TDS) and total organic carbon (TOC). The results of this study indicate that the newly developed bench scale rig is able to reduce the amount of TDS in the water produced in Ahvaz, Maroon, and Mansouri reservoirs to 98.78, 98.65, and 98.90, and TOC decreases the three types of the produced water to zero. Investigating the effect of independent parameters on the performance of this system using response surface methodology shows that the most effective parameters affecting the efficiency of the produced water treatment system are the entering carrier gas temperature (TGIT), the flow rate of the produced water (QL), the carrier gas flow rate entering the spray dryer (QG), and the atomizer pore size (d). Additionally, the optimal conditions are obtained as follows: TGIT = 113.7 °C, QL = 20.8 cc/min, QG = 59.9 m3/hr., and d = 0.03 mm.

Nowadays, the increasing demand for energy in the world is one of the main concerns for energy supply. In fact, the required energy can be obtained by increasing the production rate of fossil fuels such as oil and natural gas. However, improving the efficiency of the equipment and facilities might have a significant impact on production from hydrocarbon resources. With respect to this subject, the optimization of separation facilities will be a simple and economic choice to increase the amount of the liquid obtained from production units all over the world. One of the parameters which have a noticeable effect on the yield of the production units is the separator pressure. Also, there are other factors such as heptane plus fraction properties, well head pressure, and ambient temperature which can change the optimum separator conditions. In this study, the influence of crude oil properties on the number of stages and pressure of each separator is investigated. The result shows that the most important property of the feed which has the greatest influence on the conditions of separators is the percentage of heptane plus fraction in crude oil. Therefore, a method for the estimation of the number of separators based on the percentage of C7+ component is developed. Moreover, the threshold of heptane plus fraction for selecting the optimum number of separator stages was observed to be around 30% in the feed composition. Hence, three separators and a stock tank can separate samples with a C7+ molar fraction lower than 30%, but two separators and a stock tank are needed for samples with a heptane plus fraction higher than 30%. Finally, the results indicate an increase of about 1.3% in the oil production for the new optimization method compared to the constant-ratio method.

Separation of nitrogen from a gaseous mixture is required for many industrial processes. In this study, the adsorption of nitrogen on zeolite 4A was investigated in terms of different adsorption isotherm models and kinetics. An increase in the initial pressure from 1 to 9 bar increases the amount of adsorbed nitrogen from 6.730 to 376.030 mg/(g adsorbent). The amount of adsorbed nitrogen increased from 7.321 to 40.594 mg/(g adsorbent) by raising the temperature from 298 to 333 K at a pressure equal to one bar; however, it then dropped to 15.767 mg/(g adsorbent) when temperature decreased to 353 K. Increasing the amount of the adsorbent from 1 to 4 g decreased the specific adsorption from 67.565 to 21.008 mg/(g adsorbent) at a temperature of 298 K and a pressure of 3 bar. Furthermore, it was found that the nitrogen adsorption experimental equilibrium data are consistent with Sips and Langmuir-Freundlich models. The highest overlap was achieved through second order and Ritchie’s models.

Separation of suspended droplets in a fluid flow has been a great concern for scientists and technologists. In the current study, the effect of the surface roughness on flow field and the performance of a gas-oil cyclone is studied numerically. The droplets and the turbulent airflow inside the cyclone are considered to be the discrete and continuous phases respectively. The Reynolds stress model (RSM) is employed to simulate the complex, yet strongly anisotropic, flow inside the cyclone while the Eulerian-Lagrangian approach is selected to track droplet motion. The results are compared to experimental studies; according to the results, the tangential and axial velocities, pressure drop, and Euler number decrease when the surface roughness increases. Moreover, the cyclone efficiency drops when the vortex length decreases as a result of a rise in surface roughness. The differences between the numerical and experimental results become significant at higher flow rates. By calculating the impact energy of droplets and imposing the film-wall condition on the walls, splash does not occur.

The Khaviz oil field located in Dezful embayment is one of Iran’s southwest oil fields. In this study, a total of 28 cutting samples from Kazhdumi formation (well No. KZ1, Khaviz oil field) were subject to geochemical investigation using Rock-Eval pyrolysis for the first time. The results of pyrolysis indicated that Kazhdumi source rock has significant hydrocarbon production potentiality and already entered the oil generation window. As inferred from the diagram of OI versus HI, Kazhdumi source rock contains organic matter type II kerogen deposited in paralic environment with anoxic to suboxic conditions. Using the diagram of S2 versus TOC, the absorbed carbon content, neutral carbon, and active carbon were calculated to be 0.42, 0.39, and 2.43 wt.% respectively.

Production strategy from a hydrocarbon reservoir plays an important role in optimal field development in the sense of maximizing oil recovery and economic profits. To this end, self-adapting optimization algorithms are necessary due to the great number of variables and the excessive time required for exhaustive simulation runs. Thus, this paper utilizes genetic algorithm (GA), and the objective function is defined as net present value (NPV). After developing a suitable program code and coupling it with a commercial simulator, the accuracy of the code was ensured using a synthetic reservoir. Afterward, the program was applied to an Iranian southwest oil reservoir in order to attain the optimum scenario for primary and secondary production. Different hybrid water/gas injection scenarios were studied, and the type of wells, the number of wells, well coordination/location, and the flow rate (production/injection) of each well were optimized. The results from these scenarios were compared, and simultaneous water and gas (SWAG) injection was found to have the highest overall profit representing an NPV of about 28.1 billion dollars. The application of automated optimization procedures gives rise to the possibility of including additional decision variables with less time consumption, and thus pushing the scopes of optimization projects even further.