New Insights into Microscopic Fluid/Rock Interaction: MR-CT Microscopy Approach
- Hyung Tae Kwak (Saudi Aramco) | James Joseph Funk (Saudi Aramco) | Ayman R. Al-Nakhli (Saudi Aramco) | Bruce John Balcom (University of New Brunswick)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 8-10 October, San Antonio, Texas, USA
- Publication Date
- Document Type
- Conference Paper
- 2012. Society of Petroleum Engineers
- 5.6.2 Core Analysis, 4.3.4 Scale, 5.5.2 Core Analysis, 4.1.2 Separation and Treating, 5.1 Reservoir Characterisation, 3 Production and Well Operations, 5.6.1 Open hole/cased hole log analysis, 1.6.9 Coring, Fishing
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In the current work, we propose a new suit of core analysis tools, called MR-CT Microscopy. Nuclear magnetic resonance combined with X-ray computed tomography improves the description of pore property changes as the result of core flooding with various types of fluids. With its ability to offer spatial fluid-rock interaction information with proper mineralogy quantification, MR-CT Microscopy offers a new opportunity to observe microscopic events within reservoir porous media without damaging the sample. To demonstrate the benefit of the proposed analytical tool, core flooding test were performed to investigate chemical stimulation treatment for a set of Upper Jurassic carbonate core plugs from Saudi Arabia.
The detailed understanding of physical and chemical alteration of pore system in porous media when specific types of fluids are introduced is essential to the success of petroleum reservoir management and production enhancement. Conventional methods, such as inflow-outflow methods and effluent analysis, do not adequately resolve spatial heterogeneity. In other words, conventional methods cannot provide the precise pictures of modifications of pore system by invaded fluids.
Recently, X-ray CT and NMR have been recognized as important tools to monitor physical and chemical alteration before, during and after core flooding tests (Vinegar 1986). The properties measured by these two techniques are complementary. X-ray CT provides pore structure images and mineral distribution by detecting bulk density (rb) and effective atomic number (Zeff) (Wellington et al. 1987; Shameem et al. 2004), while NMR provides fluid saturation by imaging nuclide concentration for a variety of nuclei. NMR also provides information about the fluid-rock interaction by measuring the longitudinal and transverse relaxation time, and diffusion constant of the nuclei of interest, mostly proton (1H) (Kenyon 1992; Kenyon 1997; Vinegar 1995).
Even with the obvious advantage of combining both techniques for reservoir rock studies, it has not been utilized widely due to the resolution incompatibility between them. Unlike X-ray CT, which provides microscopic pore structure images and local mineral distribution, conventional NMR techniques such as CPMG, do not provide spatial information of fluid-rock interaction. A recently developed phase-encode T2 mapping technique, Spin-Echo Single Point Imaging (SE-SPI), however, solves this problem by adding spatial encoding pulsed magnetic field gradients to the conventional CPMG pulse sequence (Petrov et al. 2011a; Petrov et al. 2011b). With the addition of this new NMR method, we propose a NMR-CT technique, called MR-CT microscopy. The proposed suite of core analyses provides a better knowledge of the physical and the chemical alteration occurring inside of the pore structure during fluid invasion. It combines spatial information of pore size distribution, fluid-rock interaction, saturation, and quantitative mineralogy determination along with detailed images of the pore system.
The technique has been applied to study the site specific fluid-rock interactions during specially designed chemical injection. The reactive heat and gas from the injected chemicals creates localized pressures that result in thermal and mechanical fractures. The spatial pore structure and fluid-rock interaction changes by this process have been monitored by the proposed MR-CT microscopy.
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