LAUSR

Lost circulation is one of the most troublesome and costly problems encountered in drilling. This problem is magnified while drilling in deeper, depleted and complex reservoirs. Based on the nation of preventive treatment, the paper intends to present a novel hydraulic tool with a purpose of lost circulation control while drilling. The hydraulic energy of swirling jet is employed in this tool to push the granules in drilling fluid into the fractures, and “an artificial borehole wall” is formed to enhance the pressure-bearing capacity of leakage formation. Moreover, a computing model for flow rate allocation of the tool is developed. The result of comparison experiment on plugging effectiveness manifests that plugging effectiveness with the use of hydraulic tool is much better than that without the tool. The maximal pressure-bearing capacity of experimental core is increased to 8.3 MPa under the experimental circumstances, which demonstrates that the hydraulic tool can provide an effective preventive treatment for lost circulation. Furthermore, field tests of the hydraulic tool are conducted in deep wells and depleted reservoirs. The statistical results validate that the plugging effectiveness can be improved greatly by employing the tool, and the pressure-bearing capacity of formation in depleted reservoir is increased to 11.6 MPa.