Interpretation and Fracture Characterization of Early-Cretaceous Buda Limestone Formation Using Post-Stack 3D Seismic Data in Zavala County, Texas

摘要

The Buda Limestone is a naturally fractured Early Cretaceous carbonate formation in south Texas which unconformably underlies the Eagle Ford Shale. Matrix porosity of the Buda is less than 6%, therefore natural fractures improve the potential for commercial hydrocarbon production from this tight limestone formation. This presents a challenge for producers to identify these zones using well log and post stack 3D seismic data typically available to medium or small exploration companies. This project provides a workflow based on well log analysis tied to seismic acoustic impedance (AI) inversion to locate areas of probable natural fractures.;Acoustic impedance inversion was performed across a 42 square mile 3D seismic survey. The AI data shows low AI shadow zones on the down thrown side of faults. Post stack geometric seismic attributes such as coherence, maximum and minimum curvature were analyzed in the anomalous AI areas, along with physical seismic attributes such as instantaneous amplitude and instantaneous frequency. This study indicates that a combination of acoustic impedance inversion and seismic attributes can identify areas of enhanced natural fracturing within the Buda Limestone interval.