Abstract: A method for magnetic ranging includes switching an electromagnet deployed in a target wellbore between at least first and second states and acquiring a plurality of magnetic field measurements at a magnetic field sensor deployed on a drill string in a drilling wellbore while the electromagnet is switching. The magnetic field measurements may be sorted into at least first and second sets corresponding to the first and second states of the electromagnet. The first and second sets of magnetic field measurements are then processed to compute at least one of a distance and a direction from the drilling well to the target. The electromagnet may be automatically switched back and forth between the first and second states independently from the acquiring and sorting of the magnetic field measurements.

Abstract: A method for determining a list of survey points for a drilling well includes a feedback loop in which one or more measured parameters are compared with computed or derived parameters. The computed parameters are typically obtained from other/additional measurements. For example, in one exemplary embodiment of the invention, a magnetic least distance vector determined via magnetic ranging is compared with a geometric least distance vector computed from conventional borehole surveying measurements. Estimates of the drilling well azimuth and/or inclination may be adjusted to yield a good agreement between the magnetic and geometric least distance vectors. Exemplary embodiments of the present invention advantageously provide for a substantially real-time determination of a definitive well path for a drilling well as well as a substantially real-time relative placement of the drilling well with respect to a target well.

Abstract: A relative error model is used to compute a relative uncertainty in the position of a first well with respect to a second well. This relative uncertainty may be computed in real time during drilling and may be used in making subsequent steering decisions during drilling. Moreover, an absolute uncertainty in the position of a first well may be obtained by combining an absolute uncertainty in the position of a second well and the relative uncertainty in the position of the first well with respect to the second well.

Abstract: Methods for determining the distance and relative axial position between twin and target wells are disclosed. In one exemplary embodiment the magnitude and direction of the interference magnetic field vector are processed to determine the distance and the axial position. In another exemplary embodiment, a change in direction of the interference magnetic field vector between first and second longitudinally spaced magnetic field measurements may be processed to determine the distance and axial position. In still another exemplary embodiment of the invention, a component of the magnetic field vector aligned with the tool axis may be measured in substantially real time during drilling and utilized to determine the distance between the two wells. Embodiments of this invention improve the accuracy and/or the frequency of distance determination between twin and target wells.

Abstract: A method for determining a list of survey points for a drilling well includes a feedback loop in which one or more measured parameters are compared with computed or derived parameters. The computed parameters are typically obtained from other/additional measurements. For example, in one exemplary embodiment of the invention, a magnetic least distance vector determined via magnetic ranging is compared with a geometric least distance vector computed from conventional borehole surveying measurements. Estimates of the drilling well azimuth and/or inclination may be adjusted to yield a good agreement between the magnetic and geometric least distance vectors. Exemplary embodiments of the present invention advantageously provide for a substantially real-time determination of a definitive well path for a drilling well as well as a substantially real-time relative placement of the drilling well with respect to a target well.

Abstract: Methods for determining the distance and relative axial position between twin and target wells are disclosed. In one exemplary embodiment the magnitude and direction of the interference magnetic field vector are processed to determine the distance and the axial position. In another exemplary embodiment, a change in direction of the interference magnetic field vector between first and second longitudinally spaced magnetic field measurements may be processed to determine the distance and axial position. In still another exemplary embodiment of the invention, a component of the magnetic field vector aligned with the tool axis may be measured in substantially real time during drilling and utilized to determine the distance between the two wells. Embodiments of this invention improve the accuracy and/or the frequency of distance determination between twin and target wells.

Abstract: A method for surveying a subterranean borehole is provided. The method includes determining tool face angles at first and second longitudinal positions in the borehole. The method further includes processing the tool face angles to determine a change in borehole azimuth between the first and second positions. Exemplary embodiments of this invention provide a direct mathematical solution for the change in azimuth and therefore provide for improved accuracy and reliability of azimuth determination (as compared to the prior art) over nearly the entire range of possible borehole inclination, azimuth, tool face, and dogleg values.