The forward and reverse transportation simulation model was established by using SPS simulation software to simulate the forward and reverse operation process of A?Sai crude oil pipeline at low throughput. The change law of the oil temperature along the pipeline during the process of forward and reverse transportation is studied. The results show that the oil temperature along the pipeline decreases gradually under the steady state of forward transportation. The oil temperature drops first and then increases at the beginning of the reverse transportation, and then drops gradually after reaching the steady state.The oil temperature at the reverse inlet station decreases first and then increases slightly, and finally tends to be stable. The lowest temperature of crude oil in the process of forward and reverse transportation is the arrival temperature when the remaining crude oil is completely pushed out of the pipeline. In addition, the influence of inverse throughput on oil temperature drop during the inverse transportation was analyzed. The higher the inverse throughput is, the higher the lowest oil temperature in the process of inverse transportation is, and the faster the stable state of inverse transportation reaches. The temperature change of forward and reverse transportation obtained by SPS simulation analysis can provide certain basis for making the forward and reverse transportation scheme of A?Sai pipeline.
The crude oil produced by oil wells contains sediment, scale and other particles, which are deposited together with the wax in the process of crude oil pipeline transportation. It leads to a decrease in pipeline throughput, and may cause pipeline blockage and affect the safety of transportation in severe cases.The yield stress test and microscopic characteristic experiments show that there is a critical scale containing ratio in wax deposits of the influence of calcium carbonate scale on the strength of wax deposits. And it is found that the wax deposits containing scale will increase the breaking force on the wax layer and the pigging efficiency of the pig through the indoor pigging experiment of polyethylene pipeline. Based on the data of pigging experiment, a prediction model of pigging efficiency was established by using the π theorem. The model was validated by indoor experiments and third?party literature experimental data.
Most of the oil fields in China have entered the middle and late stage of exploitation, and the well produced fluid has a high water content. FRP pipes are widely used in surface gathering system of oilfield because of their excellent corrosion resistance. At the same time, in order to save heating energy, low?temperature transportation process can be used to transport high water?cut crude oil, but the possible adhesion problem of crude oil is a serious threat to system safety.Therefore, it is important to investigate the interfacial properties of FRP pipe wall/crude oil to reveal the adhesion mechanism of low?temperature transportation of crude oil with high water?cut. The interfacial properties of crude oil on the FRP surface and stainless steel surface were investigated based on the contact angle apparatus. In the aqueous phase, the contact angle of oil droplet on the solid surface increased with decreasing temperature, and the contact angle of oil droplet on the FRP surface is larger than that on the stainless steel surface. The interfacial tension of oil droplet increased with decreasing temperature in the aqueous phase, and compared to the stainless steel surface, the adhesion work of oil droplet on the FRP surface is lower. And the cohesion work of oil droplet decreased with increasing temperature in the aqueous phase. Crude oil is not easy to adhere to the FRP pipe in the gathering system, FRP pipe is more conducive to the implementation of low?temperature transportation process.
As a universal low temperature gathering and transportation boundary condition,the wall sticking occurrence temperature (WSOT) has been widely promoted and applied in the oilfield in the late stage of high water cut development. When the oil gathering temperature is higher than the WSOT, the pipeline operates smoothly, otherwise the pressure drop of most pipelines increases significantly, but some of the pipeline pressure drop changes are not obvious. Through the field cooling experiment, it was found that in the process of the oil gathering temperature gradually decreasing to 6,8,10 ℃ and 12 ℃ below the gel point, the wellhead back pressure has experienced four stages of smooth operation, small fluctuation, low frequency large fluctuation and high frequency large fluctuation, and there are several "restart" processes in the pipeline when the gathering temperature is too low. At the same time, the gas injection experiment under different gas?oil ratio was further carried out, and the results show that when the gas?oil ratio is 40,80,160 m3/t, the pipeline can run stably at the gathering temperature 3,4 ℃ and 6 ℃ lower than the WSOT.