Publications

Dual Gradient Drilling (DGD) makes offshore drilling easier. In DGD the wellbore is drilled with two different density drilling fluids, seawater till seafloor and a heavier drilling fluid beyond. This ultimately results in the same bottom hole pressure as conventional drilling fluid at total depth. The objective is to adjust bottom hole pressure within required range without changing the density of the drilling fluid. DGD is a form of managed pressure drilling (MPD) which has enhanced safety, improved environmental performance, reduced drilling cost and risk, improved well integrity and productivity and enhanced exploration performance and predictability. DGD removes the effect of water depth and makes offshore drilling equivalent to land drilling. However, DGD still has issues regarding the pressure requirement to decrease hydrostatic pressure at the return line which is the main point of DGD.  New Dual Gradient Drilling concepts tries to overcome this problem by combining the basic idea of gas lift by placing the compressor for dilution fluid on the surface (to ease maintenance and reduce cost) and the use of valves with mandrels that are placed along the mud return line, an additional fluid lines are installed to carry the lighter fluid from surface to gas lift mandrel which is installed along the return line.