Comparison Study of Capillary Pressure Curves Obtained Using Traditional Centrifuge and Magnetic Resonance Imaging Techniques

The current study is a market validation trial of the new Magnetic Resonance Imaging (MRI) method for acquiring capillary pressure. This study is meant to evaluate the methodology and workflow on site with CoreLab in Houston, TX. This study compares gas-water capillary pressure results measured using a traditional centrifuge method and the new MRI based method. Traditional centrifuge capillary pressure measurements require the fluid(s) to reach equilibrium at many different speeds. This is very time consuming as each equilibrium step can take a couple of days. A new method, trademarked by Green Imaging Technologies (GIT) as GIT-CAP (GIT CAPillary pressure), centrifuges the core plugs then directly measures the water saturation distribution in the core plug using magnetic resonance imaging. The measured water saturation together with the known centrifugal force directly leads to a capillary pressure curve. Traditional MRI methods have difficulty in relating the detected signal intensity to water or oil saturation. This is because traditionally the MRI image intensity depends on the environment of hydrogen atoms. In this work, we use a new MRI method, one dimensional centric scan Single-point Ramped Imaging with T1 Enhancement (SPRITE), in which the detected signal is directly proportional to the amount of water or oil present. The new technique measures the capillary pressure curve more quickly and accurately. It is also 3-5 times faster due to the fact that only two to three centrifuge speeds are required (versus 7-10). In some rock types, this reduces the measurement duration from many weeks to days. The new technique is also potentially more accurate as it directly measures the water saturation in the rock instead of relying on a calculation using a measurement of the expelled water. The current study focuses on gas-water systems comparing traditional centrifuge capillary pressure measurements with the new MRI based method.