Experimental Study on Oil Base Mud Loss Control with Gel LCM

Loss of oil base mud downhole is diffcult to stop in feld operation and causes great economic loss. An oil base mud loss control method is presented to effciently control oil base mud loss. This method uses gel lost circulation material (LCM) to control oil base mud loss. In selecting additives for gel LCM, a gelling agent NJZ was found to have good solubility in diesel oil and had good gelling capacity. NJZ reacted very well with a crosslinking agent JLJ to form high quality gels. It did not form good gel with the crosslinking agent AlCl₃f 6H₂O and NaOH. Highest gel strength was obtained by reacting a 10.0% NJZ solution with 4.0% crosslinking agent solution under the action of an emulsifer EHJ. The formulation of the gel LCM was optimized by orthogonal experiment, and the effects of temperature, pH and shearing on gel strength were analyzed. Laboratory experiment has shown that the gel LCM can be used the way cement LCM is used, and can be squeezed in multiple times. Compared with water base gel LCM, this oil base gel LCM worked better in stopping mud loss and has good high temperature stability; it had high gel strength even at 120℃, and was able to tolerate a pressure gradient of 1.05 MPa/m.