Systems and methods for guiding the drilling of a horizontal well

The present application is a continuation-in-part of co-pending U.S. application Ser. No. 10/998,781, filed Nov. 30, 2004, entitled “Method and System for Precise Drilling Guidance of Two Wells (expected U.S. Pat. No. 7,475,741), the disclosure of which is incorporated by reference herein in its entirety.

The invention relates generally to systems and methods for guiding the drilling of a horizontal well and, more specifically, to systems and methods for guiding the drilling of a horizontal well into an intersection with a vertical well.

Directional drilling, or slant drilling, is typically utilized to drill non-vertical wells. Directional drilling is utilized in a wide variety of applications, including oil drilling, utility installation drilling, and in-seam drilling. In some applications, directional drilling is utilized to intersect an existing vertical well with a horizontal well. Various techniques and methods are typically utilized in an attempt to accurately intersect the vertical well with the horizontal well that is being drilled.

One conventional technique that is utilized is to rely on directional surveys in an attempt to place the horizontal well in close proximity to a vertical target well. However, this technique may often be ineffective due to errors in the surveying of the two wells and the land survey at the surface.

Other conventional techniques utilize various sensors that are intended to assist in the guiding of the intersection of the horizontal well with a vertical well. The sensors may be situated either in the drilling assembly of the horizontal well with a signal source in the existing vertical well or, alternatively, in the existing vertical well with a signal source in the drilling assembly of the horizontal well. However, many of these conventional techniques may also include small but inherent errors in determining the intersection of the vertical and horizontal wells. Errors in estimating the positions of both the vertical and horizontal wells can accumulate as drilling and surveying progresses. Eventually, the additive errors impacting the path or trajectory may be so large as to prevent a desired near intersection of the two wells.

Additionally, it can be difficult to accurately determine a range or distance between a horizontal well that is being drilled and a target vertical well utilizing the prior art techniques. A failure to accurately determine the range or distance often leads to failed intersections or poor intersections between the two wells. A poor determination of range or distance may prevent a driller that is guiding the drilling of the horizontal well from being able to plan and take corrective maneuvers in steering the drilling of the horizontal well. Thus, without an accurate determination of range or distance, a driller may not be able to correct the direction of the drilling of the horizontal well in order to intersect a vertical well.

Furthermore, there is also often a need to drill a second well adjacent an existing well. For example, a pair of horizontal wells may be drilled to extract a natural resource from a deposit of the resource. The two wells may be utilized for different purposes. For example, an upper well may be utilized to inject steam into a subterranean deposit of a resource while the lower well collects the resource from the deposit. The pair of wells may often be positioned within a few meters of each other along the length of the lateral such that the wells may be utilized in conjunction with one another. As with intersecting a vertical well with a horizontal well, when drilling a second horizontal well adjacent an existing horizontal well, it can be difficult to accurately determine a range or distance between the existing well and the well being drilled.

Accordingly, there is a need for improved systems and methods for guiding the drilling of a horizontal well in order to intersect a vertical well. There also exists a need for improved systems and methods for guiding the drilling of a horizontal well adjacent an existing horizontal well.

According to one aspect of the invention, a method is provided for guiding the drilling of a horizontal well. A current is provided in at least one conductor positioned in a target vertical well. A magnetic field generated by the current is measured at a drilling assembly that is drilling the horizontal well. A direction from the drilling assembly towards the target vertical well is determined based at least in part on the measured magnetic field. A distance from the drilling assembly to the target vertical well is determined based at least in part on the measured magnetic field. The determination of the distance also includes at least one gradient.

According to another aspect of the invention, a system is provided for guiding the drilling of a horizontal well. The system can include at least one conductor, one or more sensors, and a control unit. The at least one conductor is positioned in a target vertical well. The at least one conductor carries a current signal. The one or more sensors are associated with a drilling assembly that is drilling the horizontal well. The one or more sensors measure the intensity of a magnetic field generated by the current signal. The control unit receives the intensity measurements from the one or more sensors. The control unit determines a direction from the drilling assembly towards the target vertical well based at least in part on the received intensity measurements. The control unit determines a distance from the drilling assembly to the target vertical well based at least in part on the received intensity measurements. At least one gradient calculation is utilized to determine the distance from the drilling assembly to the target vertical well.

Other aspects of the invention will become apparent from the following description taken in conjunction with the following drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

FIG. 1 is a schematic diagram of one example intersection of a vertical well by a horizontal well in accordance with an illustrative aspect of the invention.

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