Method for curve correlation

Claim 1

A method for generating a geophysical dipmeter log of a subsurface formation surrounding a borehole, comprising the steps of: a) lowering a dipmeter logging tool having at least three geophysical sensors at angular positions displaced from the longitudinal axis of said tool and equally spaced apart around said axis to an initial borehole depth within said borehole, b) positioning each of said sensors against the wall of said borehole, each of said sensors producing a signal which changes in accordance with a geophysical property change of said formations, c) traversing said logging tool through an initial borehole depth interval, d) recording changes in said geophysical property in correlation with depth, e) selecting a first window along a first geophysical recording for said initial borehole interval, f) selecting a second window along a second geophysical recording for said initial borehole interval, g) determining a first reference line along said first geophysical recording within said first window representing a first amplitude position along said first geophysical recording, h) determining a second reference line along said second geophysical recording within said second window representing a second amplitude position along said second geophysical recording, i) offsetting one of said geophysical recordings in amplitude with respect to the other of said geophysical recordings such that said first and second reference lines coincide, j) determining common areas of said geophysical recordings with coinciding reference lines, k) incrementally shifting said first geophysical recordings through said first window and repeating steps (e)-(j) following each incremental shift, l) comparing the common areas of said geophysical recordings determined in steps (i) and (j) following each of said incremental shifts to identify a maximum value for said common areas, m) determining the maximum correlation of said first and second geophysical recordings from positions of said geophysical recordings within said first and second windows yielding the maximum value of said common areas. n) traversing said logging tool through a plurality of borehole depth intervals along said borehole, o) repeating steps (d)-(m) for each of said plurality of depth intervals as said logging tool traverses said borehole, and p) generating a dipmeter log representative of the dip of said subsurface formation with depth from said determined maximum correlations of said geophysical recordings.

Claim 2

A method for generating a geophysical dipmeter log of a subsurface formation surrounding a borehole, comprising the steps of: a) lowering a dipmeter logging tool having at least three geophysical sensors at angular positions displaced from the longitudinal axis of said tool and equally spaced apart around said axis to an initial borehole depth within said borehole, b) positioning each of said sensors against the wall of said borehole, each of said sensors producing a signal which changes in accordance with a geophysical property change of said formations, c) traversing said logging tool through an initial borehole depth interval, d) recording changes in said geophysical property in correlation with depth, e) selecting a first window along a first geophysical recording for said initial borehole interval, f) selecting a second window along a second geophysical recording for said initial borehole interval, g) determining a first reference line along said first geophysical recording within said first window representing a first amplitude position along said first geophysical recording, h) determining a second reference line along said second geophysical recording within said second window representing a second amplitude position along said second geophysical recording, i) offsetting one of said geophysical recordings in amplitude with respect to the other of said geophysical recordings such that said first and second reference lines coincide, j) determining common areas of said geophysical recordings with coinciding reference lines, k) incrementally shifting said first geophysical recordings through said first window and repeating steps (e)-(j) following each incremental shift, l) comparing the common areas of said geophysical recordings determined in steps (i) and (j) following each of said incremental shifts to identify a maximum value for said common areas, m) determining the maximum correlation of said first and second geophysical recordings from positions of said geophysical recordings within said first and second windows yielding the maximum value of said common areas. n) traversing said logging tool through a plurality of borehole depth intervals along said borehole, o) repeating steps (d)-(m) for each of said plurality of depth intervals as said logging tool traverses said borehole, and p) generating a dipmeter log representative of the dip of said subsurface formation with depth from said determined maximum correlations of said geophysical recordings.