Downhole magnetic dipole antenna

Details Downhole magnetic dipole antenna Downhole magnetic dipole antenna

1999-09-30

2001-06-19

Wong, Don (Department: 2821)

Communications: radio wave antennas

Antennas

Including magnetic material

C343S787000, C340S854600

Reexamination Certificate

active

06249259

ABSTRACT:

FIELD OF THE INVENTION
This invention is directed to a magnetic dipole antenna for use downhole in gas and oil wells. The invention also includes a well bore system which includes the downhole magnetic dipole antenna.
BACKGROUND OF THE INVENTION
The technology of drilling gas and oil wells has advanced significantly in recent years. Part of this advancement involves new and improved techniques for drilling non-vertical (i.e. horizontal and other directional) wells. One advantage of horizontal and other directional drilling is that it enables a greater portion of the well bore to be exposed to gas or oil-producing strata, which tend to be disposed more horizontally than vertically. This enables more gas or oil to be produced from the directional well, than from a similar vertical well.
When drilling non-vertical well bores, it is common practice to use downhole sensors to measure the orientation of the well bore. The well orientation information gathered during drilling must be transmitted to the surface. Conventional downhole sensors used to measure well orientation include a three-axis accelerometer used to measure roll and inclination of the well bore, and a three-axis magnetometer (which functions as an electronic compass) to measure the well bore azimuth. Information on the well bore has been transmitted to the surface of the earth using a wireline, a measurement while drilling (MWD) mud pulser, or an electric dipole.
The conventional transmission methods and devices have certain disadvantages. Wireline systems, which use a coaxial high strength cable to connect the downhole sensors to the surface, require the use of a wireline truck. Wireline trucks are expensive, both to buy and operate. Also, the wireline must be cut and reconnected to enable the insertion of drill pipe at the surface as the well is drilled down.
MWD methods require changing the downhole fluid dynamics to propagate pressure pulses to the surface. The pressure pulses are used to encode the downhole information. MWD systems are expensive to buy and operate, and do not work well in some formations which the circulation is lost or poor.
The electric dipole transmission method creates a downhole dipole by electrically isolating a portion of the drill pipe and impressing a voltage across it. This method is relatively simple and inexpensive. However, the technique does not work when there is a moderately conducting formation above the dipole, which shorts the dipole signal. Also, this technique cannot be used inside casing, because casing shorts out the signal.
Magnetic dipole antenna transmission has been proposed to eliminate the above shortcomings but has yet to be perfected for practical usage.
Thus, there is a need or desire for a technique for transmitting downhole data to the surface via a magnetic dipole antenna which is relatively simple and inexpensive, provides strong signal and which can be used in a wide variety of environments.
SUMMARY OF THE INVENTION
The present invention is a method and apparatus for transmitting downhole data to the surface using a magnetic dipole. The magnetic dipole has the advantages of the electric dipole technique of being simple and inexpensive to use. Yet the magnetic dipole eliminates the disadvantage of short circuiting in certain environments.
The magnetic dipole includes an elongated metallic cylinder composed of laminations with high magnetic permeability, and an excitation coil wound around the cylinder. The cylinder can be fastened around a drill pipe for mechanical strength, wrapped with excitation coils and covered with a thin protective sleeve. The sleeve is preferrably split longitudinally when composed of a conductive material. The dipole is preferably about as long as a section of drill pipe, e.g. ten meters, because this increases its strength.
The dipole can be energized by a supply of electricity removed from the dipole location by several dipole lengths. The supply of electricity can be at, above or below the earth's surface, and can be connected to the dipole by an electric transmission wire. At least one orientation sensor capable of measuring well bore orientation (e.g. inclination and azimuth) is provided in electronic communication with the dipole.
Data on the well bore can be transmitted to the surface by energizing the dipole and employing phase shift key (PSK), or other known modulation techniques. The dipole can be energized with a frequency of about 2 to about 10 Hz, and preferably about 3 Hz for instance. The magnetic downhole transmission power and duration can be enhanced over standard battery pack power by employing a downhole hydraulic power generator.
Magnetic signals from the dipole can be detected at the top of the bore hole using a magnetic field sensor. More than one sensor can be used for increased accuracy to reduce environmental noise and increase range.
With the foregoing in mind, it is a feature and advantage of the invention to provide a magnetic dipole antenna for improved downhole monitoring of the orientation of a well bore during drilling of a gas or oil well.
It is also a feature and advantage of the invention to provide an improved method for monitoring the orientation of a well bore during drilling of an oil or gas well.
It is also a feature and advantage of the invention to provide a well which includes an improved magnetic dipole antenna in a downhole location.
The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are intended to be illustrative rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.


REFERENCES:
patent: 3967201 (1976-06-01), Rorden
patent: 4536714 (1985-08-01), Clark
patent: 4637480 (1987-01-01), Obrecht et al.
patent: 4691203 (1987-09-01), Rubin et al.
patent: 4800385 (1989-01-01), Yamazaki
patent: 4812812 (1989-03-01), Flowerdew et al.
patent: 4980682 (1990-12-01), Klein et al.
patent: 5103177 (1992-04-01), Russell et al.
patent: 5130706 (1992-07-01), Van Steenwyk
patent: 5331331 (1994-07-01), Wu
patent: 5491488 (1996-02-01), Wu
patent: 5757186 (1998-05-01), Taicher et al.
patent: 5914598 (1999-06-01), Sezginer et al.
patent: 5923167 (1999-07-01), Chang et al.

Affiliated with

Also associated with

Rating

Downhole magnetic dipole antenna does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Downhole magnetic dipole antenna, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Downhole magnetic dipole antenna will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2480557