A high-efficiency static mixer was installed at the inlet of a desalter vessel at a Saudi Aramco gas-oil separation plant (GOSP) under an initiative to field trial new technologies to enhance crude quality of low water and salt content, and to optimize wash water consumption used in the desalting. This paper describes a high-efficiency static mixer assessment through Computational Fluid Dynamics (CFD) modeling and an extensive field trial. The technology, which is the first of its kind implemented in Saudi Aramco, is a compact wafer style mixer with a specially designed orifice plate. Enhanced turbulent mixing of wash water with wet crude oil improves desalting efficiency, resulting in lower desalter outlet salt-in-crude concentration and/or reduced wash water consumption. The compact design of the mixer and the restricted lengths of upstream and downstream straight run piping requirements makes this mixer ideal for installation in congested areas without the adequate space for conventional spool static mixers. The high- efficiency static mixer produced a 17% reduction of wash water consumption after installation downstream the conventional mixing valves and upstream the desalter inlet at the Saudi Aramco facility while maintaining the salt-content at 5-6 pounds per thousand barrels of crude oil. A total saving of more than 8½ million gallons of wash water was achieved during the nine month field trial. Further analysis by Saudi Aramco, including CFD modeling, identified the potential to improve mixer performance and gain further reductions in wash water rates by optimizing the mixer location.

Objectives/Scope: A Saudi Aramco facility is forecasted to process crude from an adjacent oil field. Additionally, the forecasted produced water rates and injection pressure are anticipated to increase. This requires pump upgrades thatincrease power consumption. Moreover, the produced water, normally reinjected into the reservoir, needs to be redistributed through upgraded headers to align with the overall reservoir management strategy. A hydraulic assessment was conducted to determine the ideal balance through optimization of capital expenditures and forecasted operating expenses. Methods, Procedures, Process: The study was conducted using a hydraulic model of the pipeline network and produced water pumping system. Several scenarios of pump stages and disposal header configurations were simulated. Pump discharge pressure can be manipulated by increasing the number of stages. Alternatively, the existing disposal water injection network can be upgraded by replacing with larger lines, looping and or rerouting of injection headers. Based on the scope of each upgrade, capital costs and forecasted operating expenditures were quantified. Results, Observations, Conclusions: Technical solutions through a hydraulic assessment was developed to achieve the ideal balance through optimization of capital expenditures and operating expenses. A 15% reduction in forecasted energy consumption was achieved by reducing the required discharge pressure from the salt water injection pumps. A major capital cost avoidance was also accomplished because of the proposed modification. Moreover, additional operational flexibility is provided, allowing for the facility to inject into other flanks as required, to reduce injection header pressure and fulfill reservoir management strategy. Further optimization will be explored in the future, as water injection redistribution to other flanks are introduced. Novel/Additive Information: This study was conducted using detailed hydraulic assessmenttools that were used to determine the optimum facility designrequired to achieve the overall water injection strategy for the field. It includes hydralic modeling with Geographic Information System(GIS) capabilities, which considers the impact of the elevation profile on the hydraulics.

Summary The use of chemical demulsifiers in the treatment of crude oil emulsions is an essential step in processing facilities worldwide. Each production facility requires specific demulsifier reformulations as the crude characteristics change. The assessment of candidate demulsifiers before online field trials is currently done with bottle tests. Such tests are manual, based on water dropout visually measured by operators. The development of a method that can automatically determine the speed and amount of water dropout without the laborious need to manually record water separation would significantly decrease human error. Pulsed field gradient nuclear magnetic resonance (PFG-NMR) is used as a classification tool to qualitatively rank the efficiency of different demulsifiers in breaking Arabian Light emulsions. This imaging method can evaluate demulsifier action based on the emulsion characteristics; for example, rate of sedimentation and coalescence and formation of a dense packed zone (rag layer). The results are validated against field trials performed in gas-oil separation plants (GOSPs) at two Saudi Arabian facilities. There was good agreement between the PFG-NMR method and field trials. The results were found to correspond to the water dropout in the first stage of crude oil treatment in processing plants (production traps).

The Modulated AC/DC Crude Desalting technology was successfully commissioned at several Saudi Aramco facilities. Enhancements to desalting performance and optimization of plant operating expenditures were realized. Benefits of the Modulated AC/DC Desalting technology, installation and operational best practices and a comparison to conventional AC technology is shared in the paper. The conventional AC desalting technology was replaced with the Modulated AC/DC Crude Desalting technology at some Saudi Aramco facilities. After the successful commissioning, the performance of the new units was tested in one of these facilities to identify operating limits, such as maximum water cut and minimum demulsifier injection at the production header, in which the stable operation is sustainable. A comparison of the performance of the technology compared to that of previous conventional AC desalting technology was conducted through analysis of grid/plate voltage stability, demulsifier injection rate, wash water rates and crude quality parameters. Some enhancements to the process were also introduced which resulted in realizing additional benefits. The technology resulted in several benefits, including: (1) A reduction in the required demulsifier injection rate during the testing period compared to the same time period from the previous year, leading to significant cost savings; (2) Ability to maintain normal operations beyond the design water cuts of the facility; (3) No major grid outages since installation; (4) Additional data that can be used to diagnose separation performance as each transformer provides a number of feedback signals to DCS that are good indicators of the separation process. Based on the observations and analysis, the Modulated AC/DC Crude Desalting Technology has several advantages over the conventional AC Crude Desalting Technology in regards to crude desalting performance and process stability. The Modulated AC/DC Crude Desalting technology at Saudi Aramco was the first installation in Saudi Arabia for Arab Light crude oil. The paper captures Saudi Aramco’s experience and best practices that other companies can find beneficial in their efforts to maintain crude quality and reduce operating expenditures.

Objectives/Scope A field trial was conducted for deoiling produced water at a Saudi Aramco GOSP. The objective of the field trial was to prove the concept of the centrifugal separator and test its capabilities to deoil produced water at varying feed rates and inlet concentrations. Methods, Procedures, Process The centrifuge was fed from the common water outlet line of a gravity water oil separator. Samples were taken for oil-in-water measurement using ASTMD7678. The testing covered various flowrates and inlet concentrations, which were adjusted by manipulating upstream conditions. Several parameters were used to determine the adequacy: Outlet oil-in water content (expected significantly less than 50 mg/l) and sufficiently high separation efficiencies to achieve the specification Unit downtime due to trip and failure of the unit and due to filter/screen cleaning and replacement Results, Observations, Conclusions The feed rate was adjusted by manipulating a valve at the inlet of the separator. A sample at the inlet and outlet of the separator was taken at each flowrate and condition as per the test guideline. It was noticed that inlet oil-in-water concentrations to separator were mostly on-spec, with only a few of them above 100 mg/l, as a result of temporarily lowering the dehydrator interface level for the the trial. The following observations can be made based on the test run data: The outlet oil-in water met the spec, far exceeding expectations Oil in water removal efficiency varied significantly, varying from 65-90% depending on rate and inlet concentration There were no issues in terms of unit downtime related to trips and filter/screen plugging Novel/Additive Information This was the first trial for a Saudi Aramco field. The process was applied to a facility with tight emulsions and a challenging environment that requires a highly efficient deoiling process, which the centrifugal separation has proven to be. Potential applications for produced water treatment and waste water handling can be derived from the field trial result.