Quantitative strata calibration method based on the reflection coefficient proportions

Strata calibration is the foundation of stratigraphic interpretation and reservoir analysis. Current used calibration methods qualitatively compare geological interfaces with wave peaks, troughs, and other features, thus emphasizing the depth-time relationship of geological interfaces. These methods associate geological interfaces with specific wave peaks, troughs, or zero-crossing points but fail to reflect lateral changes in stratigraphy. This results in significant errors and insufficient interpretation. The present study proposes a method for calculating the contribution ratio of the reflection coefficients. Based on the calibration of the synthetic seismic records, the reflection coefficient sequence of the geological interfaces was computed using sonic travel time and density curves from well logging. Subsequently, the contribution ratio of each reflection coefficient to the specified wave peaks or troughs was calculated based on the seismic waveforms. This established a quantitative relationship between the seismic waveforms and the composition of the reflection coefficients and their amplitude contributions. Through the analysis of this quantitative relationship, a correspondence between geological interfaces and wave peaks or troughs with well seismic traces was established. The target stratigraphic level in the seismic data was then correlated with the reflection interface that had the maximum contribution ratio to determine the sensitive phase corresponding to the stratigraphic boundary interface. By selecting the sensitive phase, it was possible to track and analyze the lateral variations in the target stratigraphic level and lithology more accurately. The application of this method to the Shasan Lower Sandstone of the Shengtuo exploration area in the Shengli Oilfield improved the accuracy of sandbody interpretation, increasing the drilling matching rates from 75% to 92%. This indicates the broad potential applicability of the proposed method for the seismic interpretation of reservoir development.