Reduced energy losses during transportation of drilling fluid by Platform Supply Vessels

Abstract

The object of research is the process of drilling fluid transportation by Platform Supply Vessels. The subject of research is the energy losses when pumping drilling fluid from a platform supply vessel to an oil platform. The research was carried out on a vessel with deadweight of 3840 tons. It has been experimentally established that for a drilling fluid with an initial density of 1272 kg/m3 for transportation within 6–48 hours, the following changes in rheological characteristics occur: – a layer with a density of 1235–962 kg/m3 is formed on the surface of the cargo tank; – a layer with a density of 1283–1422 kg/m3 is formed in the bottom part of the tank; – sedimentation resistance decreases by 3.89–47.82 %. A variant of modernization of the drilling fluid transportation system by installing additional circulation pumps providing forced circulation of the drilling fluid between cargo tanks is proposed. Additional circulation of the drilling fluid with an initial density of 1272 kg/m3 for transportation within 6–48 hours ensures that the rheological characteristics are maintained in the following range: – density on the surface of the cargo tank 1270–1232 kg/m3; – density in the bottom of the tank 1288–1338 kg/m3; – decrease in sedimentation resistance 1.42–7.92 %. Similar results were established for drilling fluid with an initial density of 1323 kg/m3 and 1188 kg/m3. To reduce energy losses, the process of unloading the fluid onto the oil platform is proposed to be performed at the completion of the technological process of unloading the vessel. At the same time, due to a decrease in draft and an increase in the height of the freeboard of the vessel, the static component of the pressure and hydraulic losses of the cargo pump decrease. A set of studies for drilling fluids with different initial density (1272 kg/m3, 1188 kg/m3, 1323 kg/m3) confirmed that when using additional X-shaped drilling fluid circulation: – relative performance of cargo pumps increases from 37–57 % to 88–96 %; – the time of pumping the drilling fluid from the vessel to the oil platform is reduced from 7.1–8.5 to 3.3–3.8 hours. The presented results confirm the expediency of using additional X-shaped circulation of the drilling fluid to reduce energy losses during transportation by Platform Supply Vessels.