Sediment cyclicity from well logs. In

Abstract: The application of wireline well logs to the recognition and interwell correlation of sediment cyclicity is governed by the resolving powers of the different logging tools relative to measured sedimentation rates and cyclic periodicities. These variables, which are not always well defined, give rise to diverse capabilities of well logs in recording and correlating cyclic events. It is therefore important hat criteria be established for the successful application of wireline logs in cyclostratigraphy, especially when a succession reflects everal lithoperiodicities due to climate forcing. Quantification of these criteria leads to the introduction of a log association parameter (LAP) to compare the effective cyclic resolutions of different logging tools in diverse geological environments. This parameter relates edimentation rates andtool vertical resolutions to the targeted time-periods of cyclicity. It is tool- and site-specific but is independent of formation lithology and chemistry. High LAP values, above the critical evel of unity, suggest a strong cyclic resolution. Similar supracritical LAP values for (different) logs in different boreholes imply a high degree of potential interwell correlation. The benefits of a LAP-based approach are evident from illustrative examples, even at this preliminary stage. Fiel