مجله پژوهش نفت
پیاپی 119 (مهر و آبان 1400)

In this study, foam is used to treat production wells of heterogeneous reservoirs that produce high amounts of gas. For this purpose, a numerical simulation study is designed in which foam is injected through the perforations that produce large amounts of gas to block the gas path and allow much more oil to be produced simultaneously from the rest of the perforations. For this purpose, three synthetic sectors are simulated in such a way that in the first one a large volume of injected gas is produced from the upper perforations of the production well, in the second one from the middle perforations and in the third one from the lower perforations. Then, in each of these three sectors, foam injection rate and treatment scenarios are optimized. The results show that the location of gas entry to the production well, which depends on the reservoir heterogeneity, plays a key role in selection of the best treatment scenario and optimal parameters. This has led to introduce a protocol for treatment of production wells with a high amount of gas oil ratio (GOR). Finally, in order to validate this protocol, a real sector of a heterogeneous carbonate reservoir located in south of Iran that has high amounts of GOR is simulated and by following the protocol, foam injection parameters including foam injection rate, treatment scenarios, foam injection/oil production sequence and the depth of packer set are optimized and treated which reduced the GOR by 60%.

Low salinity water injection (LSWI) is an emerging and effective enhanced oil recovery (EOR) technique because of its recovery performance, low cost, and environmentally friendly compared to other EOR approaches. However, low salinity water effects and their governing mechanisms in carbonates were not fully understood. According to the literature, the present of anhydrite mineral can play a positive role in low salinity in carbonates. In this study, to investigate the present of anhydrite mineral, the wettability alteration was measured in a wide range of salinity by flotation technique. The flotation results show that the wettability modified toward a more water-wet state by decreasing salinity and in-active ions.  Rock wettability was slightly altered by deionized water that could be due to dissolution of anhydrite that provide SO4-2 ions consequently electrical charge reduction of the rock surface. It was then aimed to examine the effectiveness of the low salinity brines in core flood experiments. The results of core flooding experiments indicated that 25 times diluted sea water extracted 4.9 % extra oil production in tertiary mode following by formation water, sea water, and 10 times diluted sea water. This brine in secondary mode produced 2.3 % of OOIP more than sequentially injection of brines. Based chemical element analysis using ICP-OES method, multi-component ion exchange and mineral dissolution are responsible for wettability alteration to more water-wet.

The increasing pollution of water and soil in today›s industrial activities becomes a real problem in the world. In the meantime, oily wastewater has adverse effects on surface and underground waters, agricultural products and soil quality. The purpose of this study was to reduce or eliminate pollutants present in the effluent of one of the vegetable oil plants to prevent the accumulation of oily materials in environment. In this regard, effectiveness of using coagulants and coagulant aids as water and oil separation process has been investigated. This method is based on the changing of operational variables such as pH, alkalinity and concentrations of coagulant and coagulant aids. Thus, optimal conditions for effective water and oil separation were determined. Test samples were prepared from a vegetable oil plant. Poly aluminum chloride as coagulant and different coagulant aids have been used. The basic method was jar test in which, the different concentrations of coagulant, coagulant aids, pH and Alkalinity were considered. The best results were achieved at 10 ppm for poly-aluminum chloride as coagulant, 0.3 ppm for Gfloc-C125 as a coagulant aid with alkalinity amount of 75 ppm. The results showed that at optimal condition, the quantities of turbidity, oil, COD and Total Suspended Solids (TSS) for wastewater was decreased 89.4%, 98.8%, 62.6% and 97.9% respectively. The results were in a good accordance with environmental standards for plant irrigation.

Among the flow measurement technologies, the ultrasonic cross-correlation flowmeter (UCCF) has received much attention due to its high accuracy, performance independency from sound speed and no pressure drop. In industrial plants, due to space constraints and equipment special arrangement, the flowmeter is not always located at the ideal position. Under these conditions, the calibration factor plays an important role in increasing the accuracy of the flow measurement. The calibration factor is the function of the flow Reynolds number, the straight pipe length at the upstream of the flowmeter and the roughness of the pipe. In present study, with the aid of CFD simulation and using Reynolds Stress Model (RSM), the air flow inside the pipe was simulated in range of Reynolds number from 3.16×104 to 3.16×105. Then, with the aid of UCCF analytical model, the effect of the mentioned parameters including flow Reynolds number, the straight pipe length at the upstream of the flowmeter and the roughness of the pipe, on the performance of the UCCF were investigated. The simulation results show that the changes in shape and curvature of velocity profile inside the pipe has an important role in analyzing and interpretation of the changes in calibration factor. As the flow Reynolds number increases, the velocity profile at the pipe section becomes flatter, so the calibration factor increases. The results also demonstrate that as the flow moves inside the pipe (prior to fully developed length), the curvature of the velocity profile increases firstly and then decreases. In contrast, the calibration factor decreases firstly and then increases. It was also concluded that by changing the pipe material from carbon steel to cast iron and increasing the pipe roughness, the velocity profile becomes more rounded, so the calibration factor decreases.

Sulphate reducing bacteria (SRB) have been identified in oil reservoirs since 1920s. They reduce sulphate to sulphide resulting in production of hydrogen sulphide. H2S is a corrosive, toxic and flammable gas which causes operational and capital costs for oil industry. Classification of microbial activity as the main source of H2S generation in flooded reservoirs is followed by the increasing number of water-based EOR projects in the few last decades. Failure in precise prediction of reservoir souring onset in the reservoir may lead to severe health and safety issues. Once the prediction and simulation phase is accomplished, appropriate mitigation method should be selected. However, many simulators capable of considering the reservoir souring are available, urgent need to quick prediction of this phenomenon looks necessary. A novel souring screening approach is presented to investigate the souring potential using simple information. Comparing the reservoir conditions with the required criteria for microbial activity is the main idea of this method. In addition, some new methods to mitigate the souring effects are proposed. The most inspiring method is to utilize (per) chlorate group to inhibit bacterial activity.

Because of increasing demand for oil and gas, it is necessary to properly manage the production in oil fields which can be performed through optimization. Azadegan Oil Field has a large volume of oil reserves shared with Iraq and requires special attention. The main goal of this paper is to introduce and develop mathematical modeling for Azadegan oil field to optimize the oil production using Real-Time Production Optimization (RTPO). Therefore, 13 wells were considered in Manifold No. 7 of Azadegan Oil Field. Due to the nonlinearity nature of oil production and pressure drop equations in production facilities, Mixed Integer Linear Programming (MILP) was examined to convert nonlinear equations to the linear ones. By solving the equations simultaneously, optimum wellhead pressures were obtained to achieve maximum oil production. The results showed a 27.7% increase in oil production.