Flow Characteristics Of Water-Cut High Pour-Point Crude Oil Beneficiated With Flow Improver In Pipes

The water-cut hight pour-point crude oil is conventionally transported with hot water-mixing transportation process, which is of the hight energy consumption. In order to save energy and reduce the energy consumption, a flow improver was added into pipelines to decrease the oil transferring temperature. Through the theoretical analysis on the rheological characteristics of water-cut high pour-point crude oil and its flow in a circular pipe, and the laboratory experiments on the flow parameters and rheological characteristics in the pipelines on oil fields, in this dissertation, the optimal flow improver and its optimal concentration were screened out, and the flow characteristics of water-cut high pour-point crude oil added with the flow improver in pipelines were studiedFirst of all, the flow of water-cut high pour-point crude oil in a circular pipe was theoretically analyzed and the flow laws of the laminar flow and turbulent flow in the circulapr pipe of oil-water mixture were summarized. The fundamental theory about the measurement of the rheological properties of water-cut high pour-point crude oil was introduced. Thus a method was clearly developed for measurement of the flow parameters of water-cut high pour-point crude oil in a thin pipe and the rheological parameters with a rotating cylinder viscometer.Based on the fundamental theory about the measurement of the rheological properties of water-cut high pour-point crude oil, the rheological properties of the high pour-point crude oil and the water-cut high pour-point crude oil from Daqing oilfield were studied. Yield stress, viscosity and thixotropy properties of high pour-point oil and water-cut high pour-point crude oil were measured with the rheometer. The law of the effect of temperature, shear rate and water-cut on the yield value and apparent viscosity was obtained.Based on the parameters such as the phase inversion point of water-cut high pour-point crude oil emulsion, the temperature of the oil droplet coalescence, the quantity of condensate oil stuck on pipe wall, the demulsification performance of the flow improvers, and the temperature of condensate oil stuck on pipe wall, the optimal flow improvers were screened out. The flow improvers evaluated, namely the DODE series, can significantly reduce oil transferring temperature.In order to study the flow characteristics of water-cut high pour-point crude oil beneficiated with flow improver and to screen out the optimal concentration of the flow improver DODE, the indoor flow experiments on the water-cut high pour-point crude oil from Daqing Oilfield beneficiated with flow improver was carried out. Indoor flow experiments were carried out at different temperatures and at different concentrations of flow improver, using vertical pipes with three different diameters and the high pour-point crude oil from Daqing oilfield with a water-cut ranging from 30% to 90% as experiment medium.Based on the experimental results, rheological properties of water-cut high pour-point crude oil beneficiated with the improver DODE were studied with the theory of measurement on rheological parameters in thin pipe and Robinowitsch-Mooney equation. The results show that water-cut high pour-point crude oil beneficiated with flow improver can be regarded as a power law fluid and its flow index is less than 1, which means that it is shear-thinning fluid.Indoor restart experiments were carried out to explore the flow characteristics of water-cut high pour-point crude oil beneficiated with the flow improver DODE when oil transportation is restarted after shutdown. The law of the effect of concentration of flow improver, shutdown time, water-cut and diameters of pipes on the start-up pressure gradient was obtained.The experimental results show that the flow improver DODE can significantly decrease the start-up pressure gradient.The field experiments were carried out in 2331 wells,37 oil transfer stations and 10 oil puodction plants. The experimental results show that the flow improver DODE can improve the flow characteristics of water-cut high pour-point crude oil in pipes, decrease temperature of water mixed in oil well head, temperature in metering room and consumption of gas to transport a ton of oil, with good energy-saving effect.