METHOD OF BOREHOLE IMAGING

摘要

1. Method of detecting significant events intersecting a borehole from an image of the borehole wall, which image comprises a two-dimensional array of numbers, each number being the magnitude of a relevant borehole parameter at a point defined by the circumferential direction and the depth, which method comprises the steps of: (a) converting the image into a three-dimensional orientation space consisting of a stack of two-dimensional images, wherein each two-dimensional image is obtained by applying an edge-detecting or line-detecting filter to the image with a particular orientation of the filter; (b) selecting a parameter relation that represents the intersection of an event with the borehole wall, wherein the intersection is characterized by n parameters; (c) creating an n-dimensional parameter space consisting of numbers as a function of the n parameters, wherein each number is a measure of the support in the orientation space for an intersection characterized by the parameters that pertain to that number; (d) selecting in the parameter space a set of the largest numbers, wherein the parameters that pertain to each of these largest numbers represent well supported intersections with the borehole wall; and (e) presenting the intersections pertaining to the set of the largest numbers as a list of data representing significant events. 2. Method according to claim 1, wherein step (d) further includes the steps of: d1) selecting k intersections having a high support to form a set of k candidate intersections and sorting the set by support; d2) storing the parameters that represent the candidate intersection having the largest support in an array of intersections; d3) removing the data pertaining to the candidate intersection having the largest support from the orientation space; d4) recalculating the support in the orientation space for the remaining candidate intersections to obtain a reduced set of candidate intersections, sorting the reduced set by support, and adding the parameters that represent the candidate intersection having the largest support to the array of intersections; d5) repeating steps d3) and d4) for all candidate intersections to obtain an ordered set of intersections; and d6) selecting from the ordered set of intersections the k-i intersections having the largest support, and presenting the k-i intersections as a list of data representing significant events, wherein i can be any number less than k. 3. Method according to claims 1 and 2, wherein step (d) further comprises determining for every point in the orientation space that belongs to a well-supported candidate intersection a support set comprising those orientations for which the support is larger than a threshold value times the support of actual orientation of the well-supported candidate intersection; and removing the candidate intersection from the list of candidate intersections if the number of elements in the support set is relatively large compared to the number of filter orientations.