Enhancement of petrophysical workflows with digital rock analysis
William Godoy, Santiago Drexler, Vitor Silos, Milena Siqueira and Jonas Toelke
Morro do Chaves coquinas are highly complex carbonate rocks. They present heterogeneous pore system and matrix, challenging the standard methods to provide a correct reservoir quality evaluation. Digital Rock Analysis (DRA) workflow combines the X–ray computed microtomography (μCT) 3D imaging methods and modeling in multi-scale fluid flow numerical simulations to better understand reservoir variability and productivity.
The coquinas from Morro do Chaves Formation studied in this project are considered analogous to the Pre-salt Itapema and Coqueiros Formations. From nano- to micro-scale, we performed multi-resolution integrated DRA analyses to support Lattice Boltzmann-based numerical fluid flow simulations for complex carbonate rocks. The main objective of this research project was a multi-scale approach for heterogeneous carbonate rocks, including multimodal systems evaluation, and two-
phase fluid flow numerical simulations in order to study the effects of different resolutions on important parameters such as irreducible water saturations and residual oil saturations.
Three (3) samples were selected and several μCT acquisitions with different voxel sizes were performed. Information from higher resolution models were incorporated in lower resolution models to correctly address the effects of smaller pores and micro-fractures. Several laboratory measurements – Mercury Injection Capillary Pressure (MICP), thin section analysis, and special core analysis (SCAL) – supported the digital results.
The digital activities performed involved porosity and absolute permeability estimates, pore characterization, digital SCAL, and upscaling methodologies. Capillary pressure curves could be compared with experimental ones, stating the effects of multi-scale approach to better predict the fluid flow dynamics in these challenging samples. Relative permeability curves were generated numerically based on DRA. The results show that the multi-resolution approach in different scales
improves the estimate of fluids distribution within these coquinas pore systems. Rigorous quality control steps must be performed to obtain quality results.
