Continuous porosity characterization: Metric-scale intervals in heterogeneous sedimentary rocks using medical CT-scanner

Abstract

Although computed tomography (CT-Scanning) has been regularly applied to core analyses in petroleum geology, there is still a need to improve our ways to document porosity and porosity distribution in the entire pore scale spectrum, from the tens of nanometer to the meter-scale. Porosity imaging is particularly crucial for complex and heterogeneous rocks such as hydrothermally altered and fractured carbonates. The present work proposes a improved method using medical-CT to reliably estimate reservoir porosity. An in-house core-flooding setup allowed to analyse several individual core samples, scanned simultaneously (dry and saturated), as well as continuous core sections up to 1.5 m long. Without any prior knowledge of samples, three-dimensional alignment and subtraction of the two data sets (dry and saturated states) results in the generation of 3D porosity matrices. The methodology tested on a large set of reference core material shows a strong correlation between conventional gas porosimetry techniques and porosity from CT-scan. The added value of the porosity measurements by CT-scan is, first of all, the generation of 3D images of pore network, allowing to assess spatial attributes of macropores, their distribution and connectivity. Secondly, the CT-scan method also provides continuous porosity profile at the millimetric scale. Both developments are crucial for the understanding of reservoir rock properties.

Identification of Common Minerals Using Stoichiometric Calibration Method for Dual‐Energy CT

“…A possible improvement of this stoichiometric method could reside in increasing the exposure time or to acquire repeated scans in order to improve the signal‐to‐noise ratio (e.g., Larmagnat et al., 2019), especially when very dense minerals, reducing the number of photons reaching the detectors, are present.…”

Tomographic reconstruction strategies for nondestructive testing with a commercial CT scanner

“…The X-ray tube can be operated in the range of 70-140 kVp. This platform is used for several non-medical applications, including material characterization with dual-energy techniques Fortin et al (2013); Larmagnat et al (2019); Martini et al (2021); Di Schiavi Trotta et al (2022).…”

Beam-hardening corrections through a polychromatic projection model integrated to an iterative reconstruction algorithm

“…Furthermore, the acquisition of high-Z and high density samples with reduced artifacts is also advantageous in the field of geology, such as porosity characterization in rocks with a CT scanner [31]. The presented algorithm can potentially deal with low and highly attenuation materials, such as water and dense rocks, improving the desired characterization by removing the bias caused by beam-hardening artifacts.…”