A new vertical oil storage system based on oil-water exchange method for a deepwater floating production system was investigated experimentally. The system mainly consists of a storage tank, water tank, upper tank, lower tank, oil pumps and pipes. Two kinds of oils (light oil and heavy oil) were investigated in the experiment. 12 oil/water exchange tests and 18 dynamic tests were carried out. The Oil/water exchange test simulates oil-water exchange progress. A special oil/water separation device was designed to separate stored oil from the water by the use of density difference between oil and water. The oil content in the discharged water at different locations was measured in terms of PPM. The cycle time of oil/water exchanges was also investigated. The aim of the dynamic test is to find out if there is significant disturbance or sloshing at the oil/water interface due the motion of the floater. The storage tank was placed on the 3-DOF sloshing equipment. Sloshing tests were done for 50% and 75% filling level. During the experiment, the oil/water separation device was set on the oil/water interface to reduce the disturbance.
Main finding from the experiment are:
The oil content of in the discharged water is less than 50ppm, which meet the oily wastewater discharge standards of offshore petroleum development industry (GB 4914-85).
Compared with light oil, the oil content in the water seems larger for the heavy oil in the oil/water exchange tests.
The device of upper and lower tanks can reduce the oil content in the water.
In the dynamic tests, no matter there is oil/water separation box or not, there is no significant disturbance at the oil/water interface.
