Integration of SIP and MIP methods for pore-size distribution in carbonate rocks

Abstract

Carbonate rocks exhibit the extreme form of heterogeneity among the sedimentary set of rocks, in terms of texture and contain different types of pore spaces ranging from nm to cm (Mousav et al., 2013). The complexity of carbonate reservoirs increases due to depositional processes and the diagenetic alteration immediately following the deposition through burial and even continuing today. Due to this chemical and physical transformation, the porosity, permeability, pore types and pore-throat structures are highly affected. The movement of reservoir fluids i.e., oil, gas, and water happen through the rock’s pore framework only. Therefore, the knowledge of pore size distribution and their interconnectivity is crucial of subsurface flow characterization. There are many laboratory methods to determine the pore size distribution e.g., Mercury Intrusion Porosimetry (MIP), Nuclear Magnetic Resonance (NMR) micro-computed tomography (μ-CT). But each method has its limitation. In this paper, we have used spectral induced polarization (SIP) method to determine relaxation time and pore size distribution in carbonate rocks because SIP method is sensitive to the pore size, grain size, pore throat distribution in the rock. For the proof of concept, we are presenting the sensitivity of SIP method in texturally and mineralogically heterogeneous carbonates. The implications were well founded in the high conductivity values measured in the homogeneous sample versus the low conductivity values measured in the heterogeneous sample. The pore size distribution in these materials seems very well recovered using the Warburg decomposition.