STUDY ON THE EFFECT OF VOIDS ON RESTART PUMPING OF GELLED CRUDE OIL IN PRODUCTION PIPELINE

Waxy crude oil can be found in many parts of the world for exploration and production purposed. The crystallisation of waxy crude oil during the transportation through pipeline may cause problems. The waxy crude oil may gel up during the platform shutdown and thus causes blockage in the pipeline. At a very high temperature at which it can reach up to 90°C especially in the reservoir, the waxy crude oil behaves as Newtonian fluid. When the temperature starts to decrease while flowing in the production pipeline, wax will form upon reaching the limit of Wax Appearance Temperature (WAT) as a result of cooling due to the low seabed temperature. The problem becomes more serious as the crude oil gelled up and clogs the pipeline as the temperature decreases and reaches the pour point temperature. Restarting the flow would be a problem because when the crude oil becomes gelled, it would be hard to initiate the flow of the oil and might damage the pipeline due to the gelled up crude oil that cannot be transported. The equation that has been used to calculate the restart pressure has be over predicted as it does not consider the compressibility characteristic of the crude oil. The gas voids formation during the transportation may also affect the compressibility of the oil. The objective of this work is to determine the effect of gas voids on the restart pressure the flow of gelled crude oil. The effect of gas voids was observed and compared by having the original sample and the second sample that is injected with air. The compressibility test was done to both of the sample. From the study it is shown that the gelled crude oil can be compressible and the pressure applied also affect the movement of the crude oil. The compressibility factor for the injecting air sample is higher compared to the original sample as it is the result of voids formation. The compressibility factor of the gelled crude oil from original sample (Sample 1) and injecting air (Sample 2) was 0.001 and 0.003 respectively for every 0.5 bar pressure applied.