Mechanical Properties of Mississippian Rocks

Pouyan Ebrahimi Lialekol, Priyank Jaiswai, Sandip Harimakar, and James Puckette

The Mississippian carbonate reservoirs in the US belong to petroleum system of Silurian Devonian-Mississippian age. Although identified as prolific hydrocarbon resource, they have proven difficult to develop. They are generally developed through lateral drilling and fracking. Field engineers have often observed that the rock's response to fracking varies greatly in the Mississippian reservoirs. Concepts that have worked successfully in siliciclastic or even shale reservoirs do not appear to be directly applicable to these systems. The exact dependencies of frack response in the Mississippian are poorly constrained. Probable reasons include rapidly changing size and shapes of pores, facies-dependent intermittent transition from anisotropic to isotropic behavior, lithology driven heterogeneity, etc. We have put a series of Mississippian rock samples under compression testing and observed their stress-strain relationship. The samples varied from chert dominated to calcite dominated compositions. Preliminary results indicate that massive carbonates can more ductile than chert. However, chert-dominated samples appear to be readjusting their matrix over a larger range of strain rates between the inception and completion of rock failure. In presence of fractures, strain rates between the inception and completion of rock failure have a very narrow range. In Tripolites, fractures seem to be accumulating the boundary of chert and limestone. The stress-strain charts can provide basic geomechanical parameters such as Young's modulus and Poission's Ratio which can then be related to the seismic velocities. 

AAPG Search and Discovery Article #90176©AAPG Mid-Continent Meeting, Wichita, Kansas, October 12-15, 2013