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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).

International audience; The current practice for crude oil demulsifier selection consists of pre-screening of the best performing demulsifiers followed by field trials to determine the optimum demulsifier dosage. The method of choice for demulsifier ranking is the bottle test. As there is no standard bottle test method, there are different methodologies reported in the literature. In this work, a new approach to bottle test and field trial was described which improved significantly the selection and dosage of the demulsifier. The bottle test was optimized by measuring an accurate mass of demulsifier. This method produces repeatable results. This bottle-test methodology was benchmarked against field trial results performed in oil processing plants. The field trials were also improved to avoid the accumulation effect of demulsifier, when optimizing their dosage. The field data for the optimization of demulsifier dosage was analyzed mathematically; and a graphical method to determine the optimum range is described.

This paper describes a new approach to online monitoring salt content in crude oil. An extensive experimental study was conducted in the laboratory on different crude oil types, to evaluate accuracy and repeatability of the new method in comparison with the existing standard, the ASTM D3230. Following the successful laboratory study, an industrial prototype based on this new method was designed, installed in a production facility, and tested for 6 months. Maintaining crude oil production rate and quality are the primary targets of any oil producer. Salt (defined here summarily as a mixture of Na, Mg, and Ca chlorides) is one of the undesirable crude oil contaminants that affects crude oil quality. Salt is mostly entrapped in the micron-sized water droplets carried out from the last separation vessel of oil production facilities. While measuring salt content per the existing ASTM D3230 standard offers no difficulty in laboratories, implementation of online measurements remains very challenging. Commercial analyzers based on the ASTM D3230 mix crude oil with three different solvents (Xylene, Methanol, and Butanol) and measure the mixture conductivity. Due to their numerous moving parts, commercial online analyzers’ reliability is low and maintenance is difficult and costly. Additionally, procurement, storage, and handling of these highly flammable, toxic, and low boiling point chemicals are not practical in remote areas or offshore production sites. Saudi Aramco Research & Development Center and Saudi Aramco Oil Operation worked jointly to simplify the measurement protocol by replacing the three hazardous solvents with a relatively harmless single solvent. This solvent is very stable and has a high boiling point; consequently, it can be stored in large quantities, which significantly reduces the frequency of replenishments and limits the operator’s exposure to chemicals. The application of the new single solvent method has multiple advantages: ∘It reduces moving parts and complexity, and hence the fabrication and maintenance costs of industrial online analyzers.∘It reduces solvent consumption, as the solvent/crude oil mixture ratio is 50/50, in comparison with ASTM D3230 ratio of 90/10, thus further reducing the operating costs.∘It increases salt content in the measurement cell because of higher crude oil to solvent ratio, thus improving accuracy.∘It can be implemented by simple modifications to existing commercial analyzers.