Cleanout of proppants, cuttings and fines in well construction and production phases are typical of oilfield operations. To make these processes successful, extensive research efforts have been done on the development of (i) equipment such as concentric pipe, tubing-operated pump-to-surface bailer and coil tubing with jetting; (ii) engineering operation control and software simulation such as conventional high-rate circulation, reverse circulation, three-segment hydraulic modeling; and (iii) carrier fluids with suspension capabilities. The development of equipment is generally expensive, and often operation limited. Software simulation and control of operation parameters are normally not able to achieve the expected cleanout effectiveness due to the process complexity. Development of novel fluid systems is the only way forward to simplify the cleanout puzzle, and extensive research has been done to improve the efficiency of carrier fluids. The most commonly used fluids are brines, drilling fluids, foams and viscous polymer fluids.
The paper describes the laboratory development of a novel viscoelastic surfactant-based cleanout fluid system and its successful field application. This fluid has several advantages over conventional polymer systems. Viscoelastic surfactant systems are non-damaging to the reservoir, has excellent suspension capacity, adjustable density for hydrostatic head and low friction.