Perpustakaan Digital ITB

As oil and gas wells are being developed in deep water, hydrate formation in the production system has become a major concern. The risk of forming hydrates is greatest when the well is cold. During a production shut down, hot produced fluids become stagnant and are cooled by the surrounding cold water, resulting in gas hydrates. Flow rates can be reduced significantly or production could completely stop if hydrates occur. Additionally, hydrate formation can affect the ability to function valves located on the seafloor make it difficult to run wireline tools. Thermal insulation is one of the attractive ways for preventing hydrates. Thermal insulation systems help to avoid wax and hydrate precipitation by keeping the flowing fluids above the wax appearance temperature or hydrate formation temperature throughout the length of the production conduit. The typically involves filling the annulus completely or partially with a low thermal conductivity fluid in order to prevent heat loss. Using PVTsim and OLGA simulator, this study evaluated the effectiveness of thermal insulation in preventing hydrates by modeling steady state heat transfer in producing and shut-down conditions. The sensitivity studies of insulating materials, depth setting, thickness of insulator and flow rate were analyzed. This study provides a design of insulation system to keep the fluid temperature a minimum of 3oC above the hydrate formation temperature after 8 hour shut down period.