The Development and Field Testing of Novel Online Salt-in-Crude Oil Measurement Method and Analyzer - A Systematic Approach to Technology Qualification

Abstract

Abstract 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 &amp; 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.</jats:p