The Development of Novel Micro-foam Milling and Sand-washing Technology

Many problems often happen during workover in Bohai oilfield, such as that heavy leakage, difficult fishing, and slow washover footage. To overcome these problems, a new kind of environment friendly washover and sand cleaning fluid has been developed on the basis of foam drilling theory. Compared with the traditional temporary blocking solution, this kind of fluid is more preferable, with low viscosity, small shearing force, high sand-carrying capacity, low circular friction, easy to dissolve and no blocking pump. With this kind of fluid, it is not necessary to break the glue in the latter. The composition is 0.5%BH-VIS+3%FPJ-I2+3%XJW-0H-2%YS-A. With microbubble as dispersed phase, low viscosity glue solution as continuous phase, this kind of fluid has good effect in sand cleaning and fluid loss reducing due to the high sand holding capacity of foam as well as double plugging capacity of foam and biopolymer. This technology has been used successfully in Bohai oilfield, which is guarantee for smooth workover operation.