Turbidite Facies Analysis Through Integration of Electrical Images with Openhole Logs, Mudlogs and Map Data, Red Oak Field, Oklahoma, U.S.A.

Xu, Chunming¹, Thomas Cronin², Brad Steer², Thal Mcginness², Thomas Pickens¹ (1) Schlumberger, Houston, TX (2) BP, Houston, TX

Integration of electrical borehole images with openhole logs, mudlogs, and map data has been carried out over the Red Oak and Fanshawe Formation intervals (Middle Atoka) in the study area. This analysis records a clastic intra-slope transition from a well-amalgamated channel facies (Red Oak) upwards through an overlying canyon cut-and-fill facies (Fanshawe). Ten wells with image and/or dip data were analyzed and integrated into the study. The resultant re-interpretation of the area has led to an updated geologic model and a better understanding of current and potential reservoir intervals.

The Red Oak Sands are dominated by well-amalgamated channel facies. The relative lack of lobe and levee facies is probably due to sandy channel amalgamation in a restricted fair­way. Borehole images reveal well-defined internal inclined-bedding bounded by erosional amalgamation surfaces in the sand units. In contrast to the current cross beds in fluvial channels, the azimuth statistics of these inclined-bedding in turbidite channels are widely scattered.

Fanshawe sands are dominated by finer grained and less amalgamated sheet turbidites. The thick section of thin parallel-laminated sandy silts seen in borehole images are either a levee-lobe component of a large single channel system, or sheet turbidites of continuous hyperpycnal flows. The best reservoir sands in the Fanshawe are associated with debris flows on the top of the sequence. The methodology developed in this project to extract and interpret turbidite elemental information from different wireline logs may provide valuable insights for more expensive deepwater exploration projects.