The Study Of Natural Gas Hydrate Formation During Deepwater Drilling

As a result of increased deepwater drilling, Gas-hydrate formationduring deepwater offshore drilling become a well-recognized operationalhazard. Plugging the blowout preventer (BOP) stack, choke, and kill lineswith hydrates can cause a serious well-control problem. Researching theformation and mitigation of hydrate in drilling fluids is important for thedeepwaterdrillingoperations.Water activity is not equal to 1.0 in drilling fluids. Based on theinfluence of mud components to hydrate formation, the calculation of wateractivity considers the interact of salt ions, alcohol and water. Van derWaals-Platteeuw model is applied to predict the forming conditions of gashydrate in rich water, The result of the calculation is reasonable, so it canoffersreferencefortheinhibitionofgashydratein-situ.By the traits of heat transfer in a well,the one-dimension transientmathematical model of static temperature and the two-dimension transientmathematical model of circulating temperature have been built according tothe basic theorem of the heat transfer. In the light of the characteristic of thetwomodels,theycanbesolvedbythedigitalapproximationproceduresandthe principles of finite difference separately; According to therelative software, we analyze the sensitive parameters of circulating temperatureinwell.Compile the software using Borland C++ Builder6.0, combining thehydrate formation P-T conditions and the wellbore P-T conditions, thenanalyze the affect of the drilling parameters to the hydrate formation.Keeping the temperature of drilling fluid, improving the properties ofdrilling fluid or injecting the hydrate inhibitors can solve the hydrateproblems.