A Multivariate Analysis on the Influence of Indigenous Crude Oil Components on the Quality of Produced Water. Comparison Between Bench and Rig Scale Experiments

Abstract

A matrix of 30 crude oils have been analyzed to investigate if there is any correlation between the physiochemical properties of the crude oils and the quality of the produced water. As an approach to study produced water quality, oil. and brine water (3.5 wt%) have been mixed together, and transmission profiles from the separation process have been investigated by means of Turbiscan LAb. The Turbiscan LAb enables the study of stability of colloidal dispersions without any dilution or modification of the sample. The oil-in-water emulsions (30:70) were made by mixing oil and water at low speed to be sure that they separate within a short period of time. Drop size distributions were investigated for all crude oil emulsions by using a Coulter Counter (COULTER Multisizer II). The correlations between transmission profiles and crude oil characteristics were made by using principal component analysis (PCA), a method that helps visualize the most important information contained in a data set and find combinations of variables that describe major trends. A Vortoil K-liner hydrocyclone connected to a mixing rig has been used to separate oil and water in larger scale experiments. The objective with these experiments was to compare the results with separation experiments done at bench scale. Six crude oils have been investigated at the separation rig, and both droplet size distribution and dispersed oil concentration have been performed. The main conclusions from this work are that Turbiscan LAb is a suitable technique to study the separation of oil-in-water with good reproducibility. The results from the multivariate data analysis show that the crude oils group according to if they are light or heavy and according to if they get high or low transmission. From the larger scale experiments it has been shown that the droplet sizes, oil/water density differential, and viscosity have a significant impact on separation efficiency.

Influence of the Crude Oil and Water Compositions on the Quality of Synthetic Produced Water

“…Furthermore, the volume contribution of drops larger than 10 µm was negligible. The increased polydispersity in the emulsions, when the viscosity of the dispersed phase was higher, agreed with other reports 20,46 , even though the measurements were done subsequent to two hours of gravity separation.…”

“…The interfacial activity of components in the crude oils will be affected by these parameters and can lead to increased emulsion stability and problems with separation [17][18] . It has been shown that the interfacial properties can influence the coalescence of oil droplets 19 and the stability of oilin-water emulsions [20][21] . Once in contact with an aqueous phase, water-soluble hydrocarbons in the crude oil will partition into the water phase [22][23][24] , adsorb at the gas-water interfaces and influence the oil removal efficiency by gas flotation [25][26] .…”

“…Typically, crude oil is characterized by physical properties, such as density and viscosity, and chemical properties, such as total acid and base numbers and SARA (saturates, aromatics, resins, asphaltenes) composition. The interfacial activities of the components in crude oils are affected by these parameters and can lead to increased emulsion stability and problems with separation. , It has been shown that the interfacial properties can influence the coalescence of oil droplets and the stability of oil-in-water emulsions. , Once in contact with an aqueous phase, water-soluble hydrocarbons in the crude oil partition into the water phase, − adsorb at gas–water interfaces, and influence the efficiency of oil removal by gas flotation. , The characteristics of the produced water also depend on properties such as pH, , ionic strength, and the presence of divalent ions …”

Microfluidic Investigation of Crude Oil Droplet Coalescence: Effect of Oil/Water Composition and Droplet Aging

“…A stirring tank was used by Angle et al, who followed the change in size distributions of toluene-diluted heavy oil in water emulsions upon variation of different parameters. ,, Some studies also attempted to correlate the crude oil composition with the water quality after separation. Silset et al conducted bench- and technical-scale experiments with a large matrix of oils to map the relation between the crude oil properties and the separation performance . Eftekhardadkhah and Øye investigated the effect of the crude oil and water composition on the concentration and interfacial activity of the dissolved components in PW .…”

“…Silset et al conducted bench-and technical-scale experiments with a large matrix of oils to map the relation between the crude oil properties and the separation performance. 28 Eftekhardadkhah and Øye investigated the effect of the crude oil and water composition on the concentration and interfacial activity of the dissolved components in PW. 29 Their study showed good correlation between the water quality and the presence of certain heteroatom-containing groups in crude oils.…”