A new class of drilling fluid has been developed and proved to be extremely effective in increasing the leakoff pressure in permeable formations. A simple laboratory test is described to assess the limits of potential increase of leakoff pressure in the field. This paper describes some fundamental issues regarding fracture and leakoff pressures for well construction purposes and then shows how the increase in leakoff pressure can be achieved with the use of this new drilling fluid. Some case histories are presented in which the fluid has proven to increase the leakoff pressure effectively, and a comparison is made with drilling fluids traditionally used, highlighting the limitations of the current fluids to effectively deliver what the industry really needs. Several applications are presented in which an increase in leakoff pressure can hugely reduce the costs and risks of the wells.

Keywords:
permeable formation, nif sm, wellbore design, new drilling fluid, new class, drilling fluid formulation, invasion, noninvasive property, well control, wellbore integrity
Subjects:
Wellbore Design, Pressure Management, Drilling Fluids and Materials, Reservoir Characterization, Wellbore integrity, Well control, Drilling fluid selection and formulation (chemistry, properties), Drilling fluid management & disposal
Copyright 2002, Society of Petroleum Engineers
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