Study and Application of a High Efficiency Liquid Pipe Freeing Agent in Pakistan

Black Magic is a widely used pipe freeing agent in Pakistan. Problems existed with the use of this pipe freeing agent include long time of preparation, weighting agents in the pipe freeing slurry which are easy to settle, poor compatibility of the Black Magic with drilling fluids used and low success rate of pipe freeing operations. A new high efficiency pipe freeing agent, ZL SPOT, was selected to solve these problems based on three evaluation parameters, say, degree of mud cakes broken down by the pipe freeing agent, time spent penetrating the mud cakes and extreme pressure friction coefficient. By studying the effects of oil/water ratio, pipe freeing agent and viscosifier on the break-down and penetration of the mud cakes, a weighted pipe freeing slurry was formulated with 0^# diesel oil, ZL SPOT, water and organophilic clay. Laboratory experimental results showed that for unweighted pipe freeing slurry, at a concentration of the pipe freeing agent between 1% and 2.5%, the extreme pressure friction coefficient was 0.069, time for 100 mL pipe freeing slurry to penetrate the mud cakes was only 15 min, and after soaking in the pipe freeing slurry, mud cakes were obviously developed with fracture network on the surfaces, indicating the ZL SPOT is superior to the dry pipe freeing agent Black Magic. For weighted pipe freeing slurry, addition of solids into the slurry greatly affects the efficiency of freeing a stuck pipe. However, when the concentration of the ZL SPOT was increased to 8%, the mud cakes were developed with fracture network after being soaked in the pipe freeing slurry. When stood still for 16 h at 120 ℃, the pipe freeing slurry with its density between 1.32 g/cm³ and 1.80 g/cm³ showed no signs of barite settling. When mixed with water based drilling fluid at a ratio of 1∶1, the pipe freeing slurry basically did not affect the rheology and filtration rate of the drilling fluid. This liquid pipe freeing agent has been successfully used on two wells drilled in Pakistan, proving its pipe freeing ability. Field operation with this pipe freeing agent is easy, and the application of this pipe freeing agent will popularize in the future.