Presenter
Meysam Nourani from Stratum Reservoir AS, Stavanger, Norway
Co-authors
Øyvind Espedal (Stratum Reservoir AS), Sveinung Frafjord (Stratum Reservoir AS), Jone Bråstein (Stratum Reservoir AS), Hans-Erik Rodvelt (Stratum Reservoir AS), Izaskun Zubizarreta (Indar Ltd) and Stefano Pruno (Stratum Reservoir AS)
Abstract
- Introduction – Motivation
Mercury injection capillary pressure (MICP) analysis at ambient conditions is an important laboratory method for characterizing pore-throat structure, capillary pressure, and seal capacity in very low-permeability rocks. For caprock evaluation, reliable MICP measurements are particularly important because the capillary entry pressure and high-pressure intrusion behavior provide key information on the ability of the rock to resist intrusion by a non-wetting phase. These properties are directly relevant to subsurface containment applications such as geological CO2 storage, underground gas storage, and hydrocarbon trapping. However, conventional MICP procedures can be inefficient for very tight caprocks, where long equilibration times and very high pressures are required. This study evaluates an optimized MICP approach aimed at improving testing efficiency without compromising capillary-pressure measurement quality, while minimizing extended high-pressure stabilization periods that can increase wear and operational stress on the intensifier system.
- Procedure – Methods
A series of MICP experiments was conducted on adjacent pieces of the same caprock material using different equilibrium-control strategies, mercury intrusion rates, and pressure-step designs. A conventional procedure based on a fixed equilibrium time at each pressure step was compared with constant intrusion-rate approaches designed to allow equilibration time to vary according to the actual intrusion response of the sample. Different intrusion rates were evaluated to determine whether slower injection produced measurable improvements in the resulting capillary-pressure curves. In addition, the standard pressure schedule was compared with a modified schedule incorporating additional measurement points in the high-pressure range, where mercury invasion of the smallest connected pore throats predominantly occurs in very tight caprocks.
- Results/Observations – Key Findings
The different testing approaches produced essentially the same capillary entry pressure, indicating that the main limitation of the conventional fixed-time procedure is not entry-pressure determination but inefficient distribution of equilibration time. Below the mercury entry pressure, equilibrium was generally achieved within approximately 20–120 s. Once mercury began invading the pore system, the required equilibration time increased markedly, typically to 350–650 s and, in some cases, to more than 1,000 s. The constant-rate approach responded naturally to this behavior by reducing unnecessary waiting at lower capillary pressures while allowing additional time during active pore filling. Comparison of the investigated intrusion rates showed that the higher rate provided virtually the same mercury intrusion response as the slower rate, while requiring less total analysis time. Increasing the density of pressure steps in the high-pressure region also improved definition of the intrusion curve and pore-throat distribution.
- Conclusion – Lessons and Implications
The results show that a constant intrusion-rate approach combined with an enhanced high-pressure pressure schedule provides a more efficient and physically representative MICP procedure for very tight caprock samples. The optimized method preserves reliable determination of capillary entry pressure, achieves near-equilibrium intrusion behavior, and improves resolution in the pressure range most relevant to the smallest connected pore throats. At the same time, it avoids unnecessarily long equilibration periods and improves overall laboratory efficiency. Developing MICP procedures specifically suited to caprock is important because seal-capacity interpretation depends strongly on accurate characterization of high-pressure intrusion behavior. A robust caprock-focused MICP workflow can therefore strengthen laboratory assessment of sealing performance and provide more reliable petrophysical input for evaluating subsurface storage and containment systems.
Supporting document (download from Google Drive)
Biography
Meysam Nourani is a reservoir engineering and Special Core Analysis (SCAL) specialist who bridges advanced scientific research with real-world energy challenges. As a SCAL Project Manager at Stratum Reservoir in Stavanger, Norway, he brings five years of industry experience at the company, supported by a strong international academic and research background. He holds a PhD in Petroleum/Reservoir Engineering from Sharif University and has completed five years of postdoctoral research at two renowned institutions: NTNU in Norway and GEUS in Denmark. His expertise spans advanced reservoir characterization, enhanced oil recovery (EOR), innovative SCAL methodologies, and their evolving applications in carbon capture, utilization, and storage (CCUS). Combining scientific depth with practical insight, Meysam is passionate about pushing the boundaries of core analysis, transforming complex reservoir data into meaningful insights, and contributing to smarter, more sustainable energy solutions.