The tool of claim 11, wherein the one or more parameters comprise at least one of an azimuthal gamma angle, a maximum gamma ray detection level, a minimum gamma ray detection level, an average gamma ray detection level, and an anisotropy.ġ3. The tool of claim 10, wherein one or more parameters regarding a gamma ray distribution are determined using the approximation and measurements taken while the tool is at a position along the wellbore.ġ2. The tool of claim 2, wherein an approximation of the geometric figure is determined as a function of a roll angle.ġ1. The tool of claim 2, wherein the geometric figure used to approximate the estimated set of gamma ray detection levels of each detector comprises one of a circle, an ellipse, an oval and a cardioid.ġ0. The tool of claim 7, wherein a ratio of the distance divided by the radius provides an estimate of an anisotropy of the gamma ray distribution.ĩ. The tool of claim 6, wherein a sum of the radius and the distance is an estimate of a maximum gamma ray detection value during the rotation, a difference of the radius minus the distance is an estimate of a minimum gamma ray detection value during the rotation, an angle between the offset direction and a gamma ray detection vector is an estimate of an azimuth gamma angle of the gamma ray detector corresponding to the gamma ray detection vector, and the offset direction is an estimate of a direction of highest gamma ray intensity of a gamma ray distribution detected by the plurality of gamma ray detectors.Ĩ. The tool of claim 5, wherein the plurality of gamma ray detectors comprises three or more gamma ray detectors, the circle being defined by the three or more gamma ray detection vectors having a common origin and pointing in directions that are generally equally spaced circumferentially from one another, the circle having a radius and a center that is offset from the common origin by a distance along an offset direction.ħ.
The tool of claim 4, wherein the geometric figure used to approximate the estimated set of gamma ray detection levels of each detector comprises a circle.Ħ. The tool of claim 2, wherein the geometric figure approximates the estimated set of gamma ray detection levels of each detector of the plurality of gamma ray detectors expected during a hypothetical rotation of the body about the center axis while the body is substantially stationary in a direction along the wellbore.ĥ.
The tool of claim 2, wherein each detector of the plurality of gamma ray detectors has a direction of maximum gamma ray sensitivity with the direction having a non-zero component perpendicular to the center axis, the non-zero components of the plurality of gamma ray detectors spaced circumferentially about the center axis.Ĥ. The tool of claim 1, wherein the geometric figure approximates an estimated set of gamma ray detection levels of each detector of the plurality of gamma ray detectors.ģ. A wellbore survey tool comprising: a body having a center axis, the body configured to be placed within a wellbore a plurality of gamma ray detectors within the body and a controller configured to: receive signals from the plurality of gamma ray detectors, the signals being indicative of a gamma ray detection level of each detector of the plurality of gamma ray detectors, and determine a geometric figure in response to the signals from the plurality of gamma ray detectors.Ģ.
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