Several new approaches to the deepwater dual gradient drilling were developed,including subsea mudlift drilling,riserless drilling,and dual density drilling.

Method of bottom hole pressure,temperature and drilling fluid density measurement while drilling;

By combining with formatting density logging,we calculated parameters of rock elasticity and intensi- ty using multi-pole array acoustic logging,and performed for- rnation stress analysis to determine breakdown pressure and drilling fluid density.

Then breakdown pressure,caving pressure and drilling fluid density can be obtained,which will act as references for drilling design to guide safe drilling.

Well drilling in a salt formation is a problem in drilling,while accurately establishing the mud density and undersaturation is the key for solving the problem.

This principle is different from the traditional one described on most textbooks in China and abroad that the mud density is designed according to the highest pore pressure of a section to be drilled.

On the base of core experiment,the basic parameters that influence the collapse are calculated,and mud density for the stability of wellbore wall is determined.

Dual Gradient Drilling (DGD) is also known as Dual Density Drilling, which is a new type of drilling technology for deepwater drilling.

Hollow sphere dual gradient drilling is a new deepwater drilling technology, which is developed by Maurer technology inc.

In order to solve the problems associated with complex operation environment and geology conditions during deepwater drilling process, dual gradient drilling technology has been researched and developed by the international petroleum industry.