Abstract

On the basis of coal-bed methane particularity in China, the pressure, penetration and water-bearing are low. Generally, an extra straight well is needed for the coal-bed methane horizontal wells. And the straight well is connected to the horizontal wells for the entry of rod pump etc to drain water and collect gas. For the connection spot of the vertical well and horizontal well is less than 0.5m in diameter, the connection goal can not be achieved by conventional wellpath measurement. Based on the features of horizontal well, a suit of remote needle technique and relevant equipment is invented, which is used to guide the intersection between horizontal wells and the vertical well. The theoretical principle is rotating magnetic field orientation. By processing the real-time collection data of rotating magnetic field, the distance and angular deviation of drilling direction can be calculated to locate the drill bit and the vertical cavity, and connect the horizontal well and vertical well.

In this paper, wellpath measurement and controlling model, method of remote needle technique, and theory of needle equipment were elaborated. This technique has been applied successfully to six horizontal wells in Chinese coal-bed methane basin, such as Ordos basin. All intersections were finshed once only. In the field application, 60m distance away from the cavity can be precisely located for leading connection, the signal of magnetic field is distinct. By the improvement of the model, the system possessees the capability of measuring well deflection to guide the nitersection in 3D. The success of applying needle technique to Ordos basin demonstrates that the established measurement model of needle can be used for the intersection of coal-bed methane horizontal wells, and positioning accuracy of needle equipment satisfy the field demand.

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