STUDY AND APPLICATION OF UNBALANCED AND ECCENTRIC INCLINING PREVENTION DRILLING TOOL

The existence of high formation dip and difficult deviation control in new exploration area of Daqing oilfield had great effect on drilling speed and increased drilling cost.The unbalanced and eccentric inclining prevention drilling tool can produce centrifugal force when it rotates downhole, the centrifugal force can keep the stabilizer at the heavy side of its unbalanced section close to borehole wall. This causes revolution of drilling tool and overcomes the deviation resulted from self-rotating bit. The centrifugal force is directly proportional to the second power of rotary speed. The higher the rotary speed is, the larger the centrifugal force can be produced. The tool can be used for inclining prevention, angle holding and angle dropping. It is of simple structure and easy installation. And it can solve the technical anticollision problem for straight section of directional cluster well. The tool can also be used in soft to middle-hard formation with high dip. The determination of its eccentriclty, the optimization of drill assembly structure and proper selection of WOB and rotary speed played a key role on inclining prevention drilling and increasing penetration rate. In the field test of 12 wells, deviation angle was controlled within 1°. This met the requirement of the deviation angle less than 1° at the kickoff point in directional cluster wells.