Previous Talks

Wednesday March 11, 2015

Impact of heterogeneity on in-situ stress of unconventional shale formations

Munir Aldin, MetaRock Laboratories


Hydraulic fracture stimulation is the single most important technology which unlocks vast unconventional resources. Hydraulic fracture design requires a good knowledge of subsurface stress regime, especially the anisotropic minimum in-situ stress profile to determine landing zone and fault type. Field injection tests such as micro-frac and mini-frac provide the best estimates but they are costly and often limited to a few formation layers. It is now common to obtain in-situ stress profile using sonic logs calibrated to field injection test data.

Log based in-situ stress determination assumes knowledge of rock’s elastic properties. For conventional sandstone, assumption of isotropy is reasonable, but for highly laminated and heterogeneous shale rock system, isotropic assumption proves inadequate. In finely laminated layers the sonic logs average over large intervals and might not provide full representation of the lithology variations. Laboratory core testing data enhances well logs and provides parameters necessary to illustrate anisotropy behaviour.  Lately, vertically transverse isotropic elasticity (VTI) is commonly invoked in stress estimation. VTI requires knowledge of 5 elastic parameters compared to only 2 for isotropic elasticity.

Methods to estimate these parameters in VTI model exist. The most challenging aspect is to determine the off-diagonal parameter (C13) in the elastic stiffness matrix. Here, we outline a coherent lab-based, deterministic approach to obtain all these parameters, combined with borehole sonic logs to derive minimum in-situ stress for shale rock systems. Novel acoustic sensors and measurement techniques have been developed to obtain velocity profiles on one single representative rock sample at multiple angles (0, 45, 90 degrees). The associated Biot coefficients in the vertical and horizontal directions can now be derived. The resultant stress profile shows great variability due to the rock’s heterogeneity. The experimental approach and comparison of results to field data will be presented

Speaker Biography

Munir Aldin began his career in 1990 with Shell Oil Company in special core analysis with a focus on GeoMechanics studies. After eight very constructive years, he went on to establish what is today, a very successful business venture MetaRock Laboratories in Houston. In 2010, he worked exclusively with Marathon Oil to provide experimental studies focusing on unconventional reservoirs. Recent accomplishments include the development of enhanced testing capabilities for unconventional studies related to flow and rock mechanics.

MetaRock Laboratories, Inc. provides testing systems and solutions within niche research areas in the Oil & Gas industry. Having personally designed and built numerous products, data acquisition and testing solutions, Munir is a hands-on leader who continually stresses innovation and spearheads R&D efforts.