Sequence Stratigraphy Correlated to Geomechanics Characterization of the LaLuna Formation: Is It a Shale?

Abousleiman, Younane¹; Emilio, Torres Parada; O'brien, Neal; Slatt, Roger M.; and Tran, Minh H.
¹[email protected]

An outcrop-based study is being conducted on the upper Cretaceous LaLuna Formation, from the southern and middle parts of the Middle Magdelana Valley, Colombia to assess unconventional resource shale potential. Numerous outcrop samples have been collected from the Galembo calcareous shale member, the Pujamana claystone/chert member, and the Salida black shale member. Detailed sequence stratigraphy and geochemistry are the main focus of this research, however, geomechanical properties are also being evaluated, and are discussed here. Mineral composition of 8 selected samples shows a wide range of: quartz 10-94wt.%, calcite 0-90wt.% and illite 0-32wt. %. TOC 0.15-11.9wt.% and ‘visual porosity’ is in the range 5-20%.

Geomechanics characterization using the mineralogy and nano-structure modeling approach (Ulm & Abousleiman, 2006) revealed similarity between poromechanical parameters (i.e. Young’s modulus, Poisson’s ratio, and Biot’s pore pressure coefficient) measured perpendicular to the formation lamination and those measured parallel to it. The results, thus, indicate a very low degree of anisotropy LaLuna shale at the sample scale. This mechanical characteristic of LaLuna shale is unlike other resource shales which are observed to be highly anisotropic due to multi-nano porosities and microstratification. If this difference mechanical characteristic at the sample scale is also observed in larger stratigraphic scale, then precautions must be taken during drilling and well completion. Reservoir stimulation techniques such as hydraulic fracturing in this low anisotropic LaLuna shale formation may exhibit a behavior that is not similar to other highly anisotropic and microstratified shale plays such as the Woodford shale, Barnett shale, etc.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013