Scheme Research On Depressurization Mining Technology In Offshore Gas Field

CNOOC finds some big gas field in south of China Sea,especially along the HaiNan island.Due to the facility far away from onshore,the produced gas was deliver to downstream costumer via subsea pipeline.With the continued development of gas fields,usually in the middle or late stage of the gas field production,the gas reservoir pressure is drop dramatically along with the increasing of the production life,in another hand,the gas production capability reduced rapidly accordingly.To satisfy the downstream customer gas demand and the owned requirement for the enhance oil recovery,this paper study the general condition of the gas reservoir,upon underground gas reservoir energy continued reducing,and other underground adjusting well measure effect is not obvious.Based on the limited space of the offshore platform,this paper designed one offshore gas field depressurization mining technical seheme,which united the underground reservoir engineering and gas processing engineering,worked on the ground process facility.The core technology is the compressor rotor revamp modification,to implement the gas field overall depressurizaiton mining,furthermore,apply gas ejector technical scheme,archive the gas field partial well further depressurization mining.Meanwhile,the scheme optimize the subsystem such as produced water process and condensate process,manage to maximize the usasge of existing equipment and minimum the site process modification.Concern on the overall and auxiliary system engineering,including process,equipment,automation and overall technical modification,thereby,lower the overall wellhead pressure and individual well production pressure,archive gas field depressurization expoitation and production.Eventually increase the production capability of gas field,extend the gas field economic production period and enhanced the overall recovery rate of gas field,therefore,has positive meaning and reference to common problem of the offshore aging gas field development and production.On the other hand,during the scheme design,accord to the national and CNOOC energy conservation requirement,design flash tank lower fuel gas recover plan,which save large amount energy,yielding better economic benefits as well.