Computer Techniques for the Zoning and Correlation of Well‐logs*

Abstract

H O Y L E , I . B . 1986, Computer Techniques for the Zoning and Correlation of Well-logs, Geophysical Prospecting, 34,648-664.This paper reviews computer techniques used in the automatic zoning and correlation of well-logs. Prior to correlating, well-logs are to be segmented-or 'zoned ' -so as to delineate sections that have similar properties. Techniques discussed include statistical methods such as variance tests and Student's t-test, linguistic analysis, the use of Walsh functions and spectral analysis.Well-log correlation, which may be between traces from diffebent wells or between traces from the same hole (as in dip logs), is used in basin studies and the determination of structural dip. A variety of methods are reviewed including conventional time and frequency correlation, sequence slotting, pattern recognition and frequency analysis. Future directions for investigation are proposed.

Depth imaging and velocity calibration by 3D adaptive tomography *

“…Thus, we have to increase the window size which is used to average the logs, although we then lose the accuracy that would be necessary for a reflectivity tie. Hoyle (1986) reviewed a number of techniques for matching the two resolution scales, most of which share the philosophy of adapting the time windows to the data features. For example, we may mention statistical zoning (e.g.…”

A Geostatistical Well Correlation Method That Can Identify Faults

“…where Dist(1,2) is the distance between well 1 and well 2, and se is the estimated shift, se(1,2) = so (1,2). In general, we cannot locate a fault with only two wells unless the fault cuts through a well.…”

“…but is still at an early conceptual stage (Hoyle, 1986). The major difficulty is in attempting to correlate small scale features associated with a particular layer or the top of a particular zone.…”

Correlation of Boreholes through Well Logs: Application to the Western Sector of Madrid

“…Moreover, in this type of basin, changes in layer thickness and the lack of lateral continuity of strata are frequent, even if they are found within the same sedimentary environment. This results in a lack of homogeneity between sedimentary episodes, even leading to the inversion of sedimentary sequences and the appearance of geological discontinuities [ 14 , 15 ]. In these basins, the lateral extension of the layers are typically a few hundred meters; thus, when the distance between boreholes is greater, several characteristics of the well logs associated with the layers are not maintained laterally.…”

“…For years, it has been possible to perform layer correlations between well logs made in relatively close boreholes. Therefore, the division of well logs into stretches, as defined above, is the best solution to achieve this objective, which, to date, has no definitive solution [ 14 , 26 , 27 , 28 , 29 , 30 ].…”