Mechanical rock properties prediction in Niger DELTA

New empirical correlations connecting rock strength and compressibility to accompanying petrographic and petrophysical data have been developed using a database of core-derived mechanical properties measurements. These empirical data are translated into predictive methods for determining mechanical qualities from geophysical wire-line records using automated fitting procedures. 600 triaxial compressive strength experiments of sandstone-to-shale lithotypes, as well as 275 uniaxial and hydrostatic compaction tests of siliciclastic reservoir rocks, are included in the database (unconsolidated sands to tight gas sandstones). Shear strength is calculated using lithotype (arenite, wacke, or shale) porosity and normal stress magnitude; Mohr-Coulomb cohesion and internal friction angle are calculated using porosity and total clay weight fraction; and pore volume compressibility is calculated using elastic moduli. The Cam clay elastoplastic constitutive model’s observed trends in material characteristics provide some restrictions for simulating the commencement of pore collapse and the evolution of rock compressibility with fluid pressure reduction under uniaxial strain boundary conditions.