A new class of drilling fluid has been developed and proved tornbe extremely effective in increasing the leakoff pressure inrnpermeable formations. A simple laboratory test is described tornassess the limits of potential increase of leakoff pressure in thernfield. This paper describes some fundamental issues regardingrnfracture and leakoff pressures for well construction purposesrnand then shows how the increase in leakoff pressure can bernachieved with the use of this new drilling fluid. Some casernhistories are presented in which the fluid has proven tornincrease the leakoff pressure effectively, and a comparison isrnmade with drilling fluids traditionally used, highlighting thernlimitations of the current fluids to effectively deliver what thernindustry really needs. Several applications are presented inrnwhich an increase in leakoff pressure can hugely reduce therncosts and risks of the wells.
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