Reliance Industries Limited operates D1D3 deep water gas field in Krishna-Godavari basin in India. Water depth at well heads varies from 550 meter to 1150 meter. Horizontal Christmas trees (XMT) are installed on each well head. Hydrate inhibitor is continuously injected at Christmas tree to prevent hydrate formation occurring in the system during all operating conditions. For a properly designed system, hydrate formation should not be possible in normal operation. The only risk of hydrate formation is related to abnormal operating conditions. Hydrate management philosophy should be developed to address the risk of hydrate formation in all condition with minimum hydrate inhibitor injection.
There are always some uncertainties in measurements therefore some level of hydrate inhibitor overdosing is required. In this field Mono Ethylene Glycol (MEG) is injected to prevent hydrate formation. To optimize MEG injection, reliable water and MEG measurements are the important keys. Salinity of slug, pipeline network and different well head water depths are major driving factors to optimize MEG injection.
Hydrate curve is developed either with professional software like PVTsim or rocking cell apparatus in laboratory. In this field minimum required MEG percentage is calculated from PVTsim software. MEG optimization is continuous process and since inception of field, the level of overdosing is reduced from 80% to 15%. Wet Gas Flow Meter (WGFM) is installed on each XMT to measure water production. To verify WGFM water measurement from individual well, other methods of measurement were also developed. MEG injection valves are installed on each XMT which can measure the injection quantity. Correlation is established between different measurement techniques to consider most reliable and accurate value of water and MEG measurement which aided to optimize the MEG injection rates.
Analysis is done through software for some of wells, to find out the feasibility to stop continuous MEG injection in deep water pipeline network system. After this study, continuous MEG injection was stopped in one well. The paper will describe various steps of MEG optimization and level of confidence on hydrate management philosophy.