Research Of Equivalent Circulation Density For Dual Gradient Drilling Operations Under High Temperature And High Pressure Envionment

with the increasing demand for oil energy in China,coupled with the difficulty in finding land and shallow water oil and gas resources,people gradually concentrating on deep water area.However,the narrow density window problem is the root of all deep water drilling difficulties.And the development of dual-gradient drilling technology solves the problem very well.Dual gradient drilling as a form of control pressure drilling technology,to deal with the problem of deep water drilling shows great prospects.However,with the increasing of water and well depth,geological conditions becomes more complex,there is the phenomenon of high temperature and high pressure,such as the south China sea,is one of the three high temperature and high pressure area of the world.When drilling these kind of wells,fluid properties such as density and rheological property changes,which affect the bottom hole pressure and the hydraulic parameters optimization.In this paper,by analyzing the principles of the dual-gradient drilling technology,combined with high temperature and high pressure conditions,select the high temperature and high pressure calculation model of drilling fluid density,analyze rheological parameters under HTHP environment,based on the general pipe flow equation to calculate the circulating pressure loss accurately.Taking the Riserless Drilling as an example,the paper analyzes the equivalent circulating density along with the change of well depth under three different geothermal gradient,mapped the circulating pressure profile,and base on the maximum bit hydraulic horsepower principle to calculate the drilling hydraulic parameters,in order to ensure the safe and efficient dual gradient drilling.