Download: Seismic can be relevant in shales
A novel interpretation and characterization of an Eagle Ford shale play used geometric, mechanical, and full-azimuth seismic attributes.
Shale plays have become one of the important sources of hydrocarbons, both domestically and globally. Due to their unique nature, shale plays have demonstrated challenges to geoscientists in reservoir E&P. In searching for the sweet spots of a shale formation, geoscientists must rely on seismic data, microseismic data, core data, well data, and a wealth of other technologies to characterize and model what is frequently a highly heterogeneous formation. The defining factors of a sweet spot include rock properties such as brittle/ductile quality, in situ stress, and total organic content.
Project review
The Eagle Ford shale is located in the Western Gulf Basin and trends across South and East Texas. This Cretaceous formation is the source rock for the Austin Chalk oil and gas formation. The seismic data cover about 340 sq km (130 sq miles) across Karnes and Live Oak counties and was acquired by Seitel. The seismic survey is in the primary production zone of a wet gas/condensate window. There are two existing wells inside of the seismic survey. The seismic data were processed through full-azimuth prestack depth migration with continuous azimuth reflection angle gathers as the primary outputs.
Objectives
Shales are frequently highly heterogeneous in nature. Seismic data, with properly preserved amplitudes and sampled in the angle domain, contain information related to lithology and rock properties. Properly processed and analyzed, the seismic data are not only relevant in prospect identification but also are an important data source for well planning in a shale play. The objectives of this study are:
- To observe shale heterogeneity by examining and analyzing different seismic attributes such as frequency- dependent attributes, structural attributes, and trace shape attributes;
- To determine and map the shale brittleness using rock mechanical attributes such as Poisson’s ratio and Young’s modulus; and
- To estimate stress and its orientation by deriving, evaluating, and integrating amplitude versus angle versus full azimuth (AVA(Z)) and residual moveout attributes.
The Full article was published in E&P magazine April 2012. You can download a copy here ›
