Abstract

In the pipeline transportation of crude oil, the addition of drag reducers can effectively reduce the flow friction of crude oil and increase the transportation volume. This article combines the application examples of drag reducers in extending oil pipeline transportation to illustrate the drag reducing and transportation increasing effects of pipeline drag reducers in crude oil transportation.

When crude oil is transported through pipelines, the presence of frictional resistance in the pipeline restricts its flow, resulting in a decrease in pipeline transportation efficiency and an increase in energy consumption.The injection of drag reducing agents can effectively reduce the frictional resistance of fluids in pipelines and improve their transport capacity without changing the operation mode of pipelines.Pipeline drag reducer is a polymer additive that can reduce fluid flow friction and increase transport capacity. It plays a very important role in increasing transport capacity, energy conservation, and improving economic benefits of pipelines.

1.Mechanism of Pipeline Drag Reducing Agent

During the transportation of crude oil in pipelines, as the pipeline friction increases, the laminar flow of crude oil will gradually decrease, while the turbulent flow will increase.There are many vortices in crude oil that are in a turbulent state, and these vortices gradually decrease. The smaller the scale of the vortex, the greater the viscous loss of energy. The energy of the vortex will eventually be lost by the viscous force of the fluid and converted into heat. Therefore, crude oil in a turbulent state requires a large amount of pipeline transportation energy.The central area of the pipeline is the turbulent core area, where most of the fluid inside the pipeline is located. Only a small portion of the liquid near the pipe wall moves in laminar flow, and there is a transitional buffer zone between the two.Drag reducer is a method that changes the motion state of oil molecules near the pipe wall (transition buffer zone) to move in the same direction, in order to expand the existing laminar flow zone, reduce energy consumption, and decrease frictional losses, in order to achieve the goal of reducing drag and increasing transport.At the same time, the vortices at all levels in the turbulent state of crude oil transfer energy to the drag reducing agent molecules, causing them to undergo elastic deformation and store energy.Afterwards, the drag reducing agent molecules return the energy obtained to the oil molecules to maintain the necessary energy for the normal transportation of crude oil, achieving the purpose of drag reduction. It is worth noting that drag reducers only have a drag reducing effect when crude oil is in a turbulent state.

2.The Drag Reduction and Transportation Enhancement Effect of Crude Oil Pipelines after the Application of Drag Reducing Agents

The drag reduction and increase of drag reducing agents are: drag reduction - reducing the flow friction of crude oil, reducing the pressure loss along the pipeline, thereby reducing the power consumption of the pump, saving energy, and can be replaced with a lower head pump for oil transportation, while keeping the original delivery volume unchanged.Increased transmission - Under the condition of unchanged original pressure, the transmission volume increases due to the reduction of crude oil flow friction; In most cases, the use of drag reducers is to increase the pipeline's throughput, which is achieved due to the drag reducing effect.

The use of drag reducing agents to reduce drag or increase transmission does not require the expansion of the existing pipeline engineering scale, the addition of pump stations or the construction of pipeline double lines, or the replacement of oil transportation equipment to achieve the goal of improving pipeline transportation capacity.With the increasing demand for oil and gas and the growing production capacity of oil and gas producing areas, there will be further requirements for the transportation capacity of pipelines.Adding new transportation pipelines requires a longer construction period. In this case, using drag reducing agents to increase the pipeline's transportation capacity is the best choice, which can quickly and easily achieve the goal of reducing or increasing transportation.In addition, pipelines transporting oil and gas may experience defects or thinning due to corrosion from surrounding soil and internal fluids, significantly reducing their pressure resistance. The use of drag reducers can effectively reduce frictional pressure drop, achieve safe transportation, and extend the service life of pipelines.

3.Application Examples of Drag Reducers in YANCHANG Petroleum Pipeline Transportation

Pipeline drag reducers, due to their superior drag reduction and transmission performance, have been applied in many oil pipelines worldwide, covering major oil production areas.When added in small amounts, drag reducers can significantly reduce fluid flow resistance, especially in crude oil pipelines. The emergence of polymer drag reducers can effectively solve the difficulties of long-distance pipeline transportation and save a lot of resources, so drag reducers are most commonly used in crude oil transportation.This article uses examples of the application of drag reducers in extending the transportation of oil pipelines to illustrate the drag reducing and transportation increasing effects of drag reducers.

The maximum designed annual transportation capacity of the YANCHANG Dingbian Jingbian crude oil pipeline is 1 million tons. In recent years, due to the increase in crude oil production at the Dingbian oil production plant, the oil transportation equipment and design flow rate have been unable to balance the production and transportation contradictions. In order to overcome the industrial contradictions caused by the imbalance of the production and transportation chain and to connect with upstream and downstream production, the Dingbian Jingbian oil transmission station has adopted the method of adding drag reducers to long-distance pipelines to take into account the problem of regional production and transportation development imbalance, striving to achieve the smooth completion of annual production tasks.

The first station of Dingbian Jingbian oil transportation completed the debugging of the drag reducing agent equipment at 21:00 on June 17, 2008, and began to add drag reducing agent. The main pump motor was running at 50Hz, and the injection volume of drag reducing agent was 12L/h.After adding drag reducers, the effect of increasing crude oil transportation volume is significant.As of 3:00 pm on June 25th (accumulated 186 hours of operation with added and removed drag agents), the total injection volume of drag agents is 2032L, and the transported crude oil volume reaches 29917.2 tons. The long-distance pipeline before adding and removing drag agents can complete a total of 22302 tons of oil transportation in 186 hours (calculated at a flow rate of 118t/h), with an additional transportation of 7615.2 tons and an increase rate of 34.15%;As of 9:00 on June 27th (accumulated 228 hours of operation with added or removed inhibitors), the amount of crude oil transported has reached 36542.3 tons, an increase of 9284.3 tons compared to the previous long-distance pipeline oil transport of 27258 tons with added or removed inhibitors, with an increase rate of 34.06%.

In 2010, the annual oil transportation volume of the Dingbian Jingbian line increased to 1.56 million tons. Through nearly a year of operation practice, the addition of drag reducers not only provided the possibility to achieve the annual oil transportation task of 1.56 million tons, but also ensured the smooth and safe operation of the long-distance pipeline.Due to the application of drag reducing agents, the intermediate station can achieve a process flow of one pump to the end and all over the station, greatly reducing operational risks and improving safety index.The use of drag reducers has economic benefits and achieves energy conservation and increased transmission; Has safety and environmental benefits, reducing operational risks; At the same time, it also has other social benefits, effectively alleviating the problem of imbalanced industrial chain in mining and transportation.

Since the first use of pipeline drag reducers on the Dingbian Jingbian line in 2008, pipeline drag reducers have been continuously applied until today, resulting in considerable economic benefits for increased transmission.Our company first participated in the bidding project for the addition of drag reducing agents on the Dingbian Jingbian line in May 2016 and successfully won the bid. The DOD-E500 drag reducing agent produced has been continuously applied to this pipeline since then until today.

4.Conclusion

Through the analysis of the application example of pipeline drag reducers in the YANCHANG petroleum Dingbian Jingbian crude oil transportation process, and comparing the crude oil transportation volume before and after adding drag reducers, it can be seen that the addition of drag reducers in pipelines is small and the drag reduction effect is significant, which can effectively increase the oil transportation volume of pipelines, reduce oil consumption, and bring significant economic and social effects.With the continuous improvement of oil production capacity and the expansion of refinery scale, drag reducing agent transportation technology will be widely applied in pipeline transportation of oil products.