Crude Oil-water Flow Research Articles

Two-Phase Crude Oil-Water Flow Through Different Pipes: An Experimental Investigation Coupled with Computational Fluid Dynamics Approach.

The present study deals with two-phase non-Newtonian pseudoplastic crude oil and water flow inside horizontal pipes simulated by ANSYS. The study helps predict velocity and velocity profiles, as well as pressure drop during two-phase crude-oil-water flow, without complex calculations. Computational fluid dynamics (CFD) analysis will be very important in reducing the experimental cost and the effort of data acquisition. Three independent horizontal stainless steel pipes (SS-304) with inner diameters of 1 in., 1.5 in., and 2 in. were used to circulate crude oil with 5, 10, and 15% v/v water for simulation purposes. The entire length of the pipes, along with their surfaces, were insulated to reduce heat loss. A grid size of 221,365 was selected as the optimal grid. Two-phase flow phenomena, pressure drop calculations, shear stress on the walls, along with the rate of shear strain, and phase analysis were studied. Moreover, velocity changes from the wall to the center, causing a velocity gradient and shear strain rate, but at the center, no velocity variation (velocity gradient) was observed between the layers of the fluid. The precision of the simulation was investigated using three error parameters, such as mean square error, Nash-Sutcliffe efficiency, and RMSE-standard deviation of observation ratio. From the simulation, it was found that CFD analysis holds good agreement with experimental results. The uncertainty analysis demonstrated that our CFD model is helpful in predicting the rheological parameters very accurately. The study aids in identifying and predicting fluid flow phenomena inside horizontal straight pipes in a very effective way.

Capacitance probe for water holdup measurement in crude oil-water flows

Water holdup in crude oil-water flows is a crucial parameter to identify flow patterns or monitor the flow process in oil production. It has been increasingly important to accurately predict water holdup. Due to the simple structure and robust performance, capacitance probes have been widely used in experimental research and industrial application. In this paper, we proposed a water holdup measurement device based on a capacitance probe for crude oil-water flows. The measurement principle lies in the fact that the output capacitance is proportional to the part of the probe immersed in water. It was found that when inserted into crude oil, the surface of the probes will absorb hydrocarbons and form an oil film covering the probes. The formed oil film will reduce the sensitivity of the output capacitance to the water layer height. The thicker the film the lower the sensitivity. We examined the parameters that affect the thickness of the formed oil film and found that the thickness is mainly dependent on temperature and water holdup. The higher the temperature the thinner the formed oil film. The reason is that an increase of temperature leads to a decrease of viscosity. In addition, as the temperature approached about 50 ​°C, the thickness is nearly unchanged. As for the water holdup, at low temperatures the effect is considerable. At relatively high temperatures, the effect is minor and can be neglected. The experimental results showed that the capacitance probes have the highest sensitivity at about 50 ​°C. We designed and manufactured a prototype of the measurement device. The probes were inserted with heating wires to heat the crude oil near the probes and the current was controlled by an integrated circuit to maintain the temperature at about 50 ​°C. The field test showed that the natural gas entrained in the production fluids caused the device to under-predict the water holdup. After gas-liquid separation, the prediction errors were within ±6%.

Experimental investigation on phase inversion point and flow characteristics of heavy crude oil-water flow

The phase inversion point is of great significance for drag reduction in the flow of heavy crude oil. In this study, we used 25-mm inner diameter (ID) stainless steel pipes to investigate the oil-water flow characteristics of four heavy oils at five temperatures (90, 85, 80, 75 and 70 °C). The effects of temperature, velocity, and oil viscosity on the phase inversion point of heavy oil-water flow were studied. The viscosity of the experimental oil ranges from 358 to 4995 mPa·s. The phase inversion model of Yao and Gong (2006) was modified to fit high-viscosity oils. The proposed model was verified with pipe flow experimental data from various heavy oilfields. This study found that the effect of temperature on the phase inversion point of heavy crude oil is almost negligible. The flow pattern with the largest pressure drop during heavy oil-water flow is Int, and the flow patterns with a smaller pressure drop include semi-Anw, Anw, and DAnw. The water content at the inversion point of heavy oil-water flow is mostly between 45% and 70%. As the viscosity increases, the water fraction at the inversion point decreases. A high velocity helps the water maintain a continuous phase. The occurrence of phase inversion requires the mixture velocity to be maintained above a specific value, which should be high enough for the flow pattern to transition to semi-annular flow.

Study of water wetting in oil-water flow in a small-scale annular flume

Proper characterization of the phase wetting regime (water wet or oil wet) in two-phase oil-water flow can lead to optimized measures for pipe integrity management and save cost. In previous work it was demonstrated that not only the physicochemical properties of the produced oil and water have an important impact on flow patterns, but also the wettability of the pipe surface can favor or hamper the contact with water. Since the wettability of steel pipes can be altered by the chemical composition of the oil and water phases, and due to the wide diversity of the chemical composition of produced crude oils and water, as well as different chemicals injected in production systems (e.g., corrosion inhibitors, scale inhibitors, de-emulsifiers), it is important to perform phase wetting experiments in dynamic conditions using representative fluids and pipe material. This study presents an experimental assessment of the phase wetting regime of oil-water flow using a small-scale annular flume of 5 l capacity, which is advantageous as a potential testing tool for crude oil-water flows compared to regular multiphase flow loops. A model oil and brine were used as experimental fluids and three different materials (carbon steel, stainless steel and a polyester plastic) were used to analyze the effect of flume surface wettability on the phase wetting regime. The results indicate that the annular flume is a promising low-cost tool to test dynamic phase wetting and dispersed flow of petroleum-water systems qualitatively as well as quantitatively. Moreover, basic hydrodynamic assessment of the annular flume flow was performed to evaluate available criteria to predict the stability of fully dispersed flow.

Experimental Investigation on Hydrodynamics of Two-Phase Crude Oil Flow in Horizontal Pipe With Novel Surfactant

The hydrodynamic entrance length, pressure drop analysis, viscosity, and fully developed velocity profile in horizontal pipe for crude oil with and without water and surfactant were studied in a 2 in ID horizontal pipe of length 2.5 m experimentally. Hydrodynamic entry length and fluid characteristics have been examined by varying temperature, water fraction, and flow rates. Temperature was varied by 25–40 °C, flow rates 40–60 LPM, and water 0–15% v/v and Madhuca longifolia from 500 to 2000 ppm. Triton X-100 was mixed with water to increase the emulsion capability during crude oil–water flows. The results showed significant influence of water, flow rate, and temperature on the hydrodynamic entry region length, pressure drop, viscosity, and velocity profiles along with natural surfactant. Pressure drop was reduced by 93.75%, 94.18%, and 93.02% with 15% water and 2000 ppm surfactant at 40 °C for 40 LPM, 50 LPM, and 60 LPM, respectively. Viscosity of the crude oil during flowing is greatly influenced by water and addition of surfactant. After addition of 2000 ppm surfactant and 15% water at 40 °C, viscosity reduced by about 94%. Hydrodynamic entry region length increased from 0.0354 to 0.2014 m, 0.0368 to 0.2336 m, and 0.0384 to 0.2641 m during transportation of crude oil after addition of 2000 ppm surfactant and 15% water at 40 °C for 40 LPM, 50 LPM, and 60 LPM flow, respectively.

Rheological and Emulsification Behavior of Xinjiang Heavy Oil and Model Oils

Transparent model oils are commonly used to study the flow patterns and pressure gradient of crude oil-water flow in gathering pipes. However, there are many differences between the model oil and crude oils. The existing literatures focus on the flow pattern transition and pressure gradient calculation of model oils. This paper compares two most commonly used model oils (white mineral oil and silicon oil) with Xinjiang crude oil from the perspectives of rheological properties, oil-water interfacial tensions, emulsion photomicrographs and demulsification process. It indicates that both the white mineral oil and the crude oils are pseudo plastic fluids, while silicon oil is Newtonian fluid. The viscosity-temperature relationship of white mineral oil is similar to that of the diluted crude oil, while the silicon oil presents a less viscosity gradient with the increasing temperature. The oil-water interfacial tension can be used to evaluate the oil dispersing ability in the water phase, but not to evaluate the emulsion stability. According to the Turbiscan lab and the stability test, the model oil emulsion is less stable than that of crude oil, and easier to present water separation.

Pressure Drop and Water Holdup of Malaysian Crude Oil and Water Two-Phase Flow in Pipes

Understanding the pressure drop and water holdup of crude oil-water flow in a pipe is crucial to many engineering applications. Free water in contact with the pipes wall can cause erosion or corrosion problems. An experimental research was conducted at the Malaysia Petroleum Resources Corporation Institute for Oil and Gas, Universiti Teknologi Malaysia to study the pressure drop and water holdup of the Malaysian waxy crude oil-water flowing in a closed-loop system at ambient condition through a 5.08 cm ID stainless steel horizontal pipeline. In the research work, water cuts were varied from 0 - 90% with mixture velocities ranging from 0.1 0.8 m/s. The research works comprised fluid characterization, pressure drop, and liquid holdup measurement.The investigations proved that pressure drop increased with flow rates, while the water holdup was found to have decreased slightly at higher water cuts due to the presence of emulsion in the crude oil a challenge when using a waxy crude oil in a two phase flow system. The experimental results can be used as a platform to understand better a more complex case of liquid-liquid two phase flow.

Flow Pattern Map of Malaysian Crude Oil and Water Two-Phase Flow in a Pipe System

Water produced along with the crude oil during production and transported together in a pipeline is a common occurrence in a petroleum production system. Understanding the behavior of crude oil-water flow in a pipe is crucial to engineering applications such as design and operation of flow lines and wells, and separation systems. Presently, there was no two phase flow study done on the Malaysian waxy crude oil-water. Therefore, a research work was conducted at the Malaysia Petroleum Resources Corporation Institute for Oil and Gas, Universiti Teknologi Malaysia to study the flow pattern of the Malaysian waxy crude oil-water flowing in a closed-loop system at the ambient condition through a 5.08 cm ID stainless steel horizontal pipeline. The research works comprised fluid characterization and flow pattern observation using a video camera camcorder. Five flow patterns have been identified, namely stratified wavy flow, stratified wavy with semi dispersed flow at interface and oil film, dispersion of water in oil and oil continuous with emulsion, dispersion of oil in water with water continuous, and the newly found semi dispersed flow with semi emulsion at interface and thin oil film. The experimental results could be used as a platform to understand better a more complex case of gas, oil, and water flow in a pipeline, which is of utmost importance in designing optimum surface facilities.

Applicability of Emulsion Viscosity Models to Crude Oil Emulsion

The rheology behavior of waxy crude emulsion is an important basic information on safeguard research of crude oil-water flow. The non-newtonian characteristics of apparent viscosity of three kinds of waxy crude emulsions were studied experimentally around condensation point; three apparent viscosity forecasting models were evaluated by least-square regressions based on experimental data of shear balance and the average absolute deviation was taken as the measurement of fitness of a model to experimental data. It is concluded that the Pal-Rhodes model, whose relative deviation can be as high as 80%, is the worst forecasting model, but it need the least experiment data to obtain model parameters, only water cut was needed. Elgibaly model has the best forecasting results, the average absolute deviation of forecasting results of three waxy crude emulsions under the condition of different temperature, water cut and shear rate were all less than 15%, but compared with the other two models, Elgibaly model needs the most parameters.