Abstract
Massive lost circulation is a major and costly drilling problem. The drilling community needs a single fluid which can be pumped through the drill bit, curing losses instantly. This paper describes a novel shear-sensitive plugging fluid designed to gel rapidly after passing through the bottom hole assembly (BHA) in normal drilling operations, thus curing massive mud losses.
This fluid is based upon what is termed a ‘loose’ invert emulsion. The continuous phase provides an encapsulation medium for a crosslinker. The internal phase of the fluid consists of a high concentration of a polymer and the interfacial tension between the two phases is maintained by a concentration of a lipophilic surfactant.
The pressure drop experienced by the fluid as it passes through the BHA triggers the inversion of the emulsion to a direct emulsion. This inversion releases the encapsulated crosslinker into the water phase. The result is a rigid gel which can be designed to generate a solid structure from one to ten minutes after passing through the BHA. The set time is virtually independent of temperature.
This paper describes the perceived mechanism, placement and data from field trials demonstrate the potential of the fluid under difficult conditions.
