Electromagnetically determining the relative location of a drill bit using a solenoid source installed on a steel casing

Abstract

Electrically powered electromagnetic field source beacons installed in a reference well in combination with a down-hole measurement while drilling (MWD) electronic survey instrument near the drill bit in the borehole being drilled permit distance and direction measurements for drilling guidance. Each magnetic field source beacon consists of a coil of wire wound on a steel coupling between two lengths of steel tubing in the reference well, and powered by an electronic package. Control circuitry in the electronic package continuously 'listens' for, and recognizes, a 'start' signal that is initiated by the driller. After a 'start' signal has been received, the beacon is energized for a short time interval during which an electromagnetic field is generated, which is measured by the MWD apparatus. The generated magnetic field may be an AC field, or switching circuitry can periodically reverse the direction of a generated DC electromagnetic field, and the measured vector components of the electromagnetic field are used to determine the relative location coordinates of the drilling bit and the beacon using well-known mathematical methods. The magnetic field source and powering electronicpackages may be integral parts of the reference well casing or may be part of a temporary work string installed therein. Generally, numerous beacons will be installed along the length of the reference well, particularly in the important oil field application of drilling steam assisted gravity drainage (SAGD) well pairs.

Description

Background of the invention [0001] This application claims the benefit of U.S. Provisional Application No. 60 / 810,696, filed June 5, 2006, and U.S. Provisional Application No. 60 / 814,909, filed June 20, 2006, the disclosures of which are incorporated by reference included here. [0002] The present invention is directed generally to methods and apparatus for tracking the drilling of a borehole at greater depths in the subsurface, and more particularly to a method of determining the relative position of a reference well to the borehole being drilled by beacons located on the reference borehole casing. [0003] The difficulties encountered in tracking and steering borehole drilling intended to traverse, bypass or penetrate reference wells at great depths below the earth's surface on precisely defined paths are well known. Such guidance is required, for example, when it is desired to construct complex underground "piping systems" for the extraction of underground gas, oil or bit...

AI Technical Summary

Problems solved by technology

[0004] In general, while perforation steering has made great strides over existing wells, particular problems arise in situations where existing technology is insufficient to provide precise control over a situation

For example, problems arise when one wants to locate and either avoid or traverse a specific well of interest in a scene involving many other wells