Cyclostratigraphy: Recognition of Climate Forcing Stratigraphic Cycles from Well Logs of the MITI Sanriku-Oki Borehole, Offshore Northeast Japan
The MITI Sanriku-Oki borehole was drilled in 1999 to a depth of 4,500 meters to explore offshore natural gas resources derived from the Cretaceous and the Oligocene coal and coaly shale. The borehole site is located 857 meters deep below the sea level and about 60 km offshore northeast Japan. The author has been investigating sequence stratigraphic, sedimentological, and geochemical reconstruction of coals in this area. As a part of the collaboration, a time series frequency analysis of wireline log data was applied to evaluate a sequence stratigraphic framework in the reservoirs of the MITI Sanriku-Oki by using $B!H (BCycloLog. $B!I (B In the frequency analysis, GR log data was processed using Maximum Entropy Spectral Analysis (MESA). In MESA, the prediction error calculation is conducted to evaluate the degree of deviation or best fit. The prediction is based on an assumed pattern of cycles within the data series. Based on the prediction error calculation, Prediction Error Filter Analysis (PEFA) calculates the position and amplitude of breaks in the frequency successions or breaks in the phase of each cycle present within the total frequency. Finally, the integration of one set of PEFA values is carried out to produce an Integrated Prediction Error Filter Analysis (INPEFA) curve. Based on biostratigraphy the MITI Sanriku-Oki is aged in the late Santonian to the late Early Miocene, which can be related with third order eustatic cycles. By analyzing all available data these cycles are further subdivided into smaller cycles related with forth sea-level changes.
Advances in Geologic and Seismic Modeling
2004 AAPG International Conference and Exhibition Technical Program