Two-dimensional NMR Logging and Field Test Results

摘要

Recent advances in two dimensional NMR (2DNMR) technologies have extended the NMR logging applications to perform in-situ fluid typing, oil saturation, and oil viscosity determination, in addition to the more conventional usage of NMR logs. We have recently deployed such 2DNMR technology to various oil fields. Using a set of CPMG echo train data with different echo spacing and wait time acquired by commercially available NMR logging tools and a global inversion algorithm for relaxation-diffusion (GIRD), we were able to obtain a relaxation-diffusion 2D (RD2D) NMR map as a function of depth. This is a map which represents the hydrogen population as a function of both T2 relaxation time and diffusion coefficient. Using either synthetic or experimental data of mixed oil-water samples, we have resolved oil and water peaks based on the contrast in their relaxation times and diffusion coefficients. RD2D NMR logging was also performed in real open-hole wells by MRIL as well as CMR stationary logging. The RD2D log derived from GIRD successfully resolved oil and water saturations. RD2D log combined with core measurements, GR, neutron/density logs also provide a self-consistent interpretation on the whole mud invasion. From our laboratory and field test results, it is clear that 2DNMR techniques greatly increase the accuracy of fluid typing and saturation determination. The T2-diffusion correlation information can be used to determine pore size distribution, perform fluid saturation typing, and estimate in-situ oil viscosity simultaneously. These techniques can also be applied to explore internal magnetic field gradient and characterize the droplet size distribution of emulsion, measure the gas/oil ratio, monitor the alteration of wettability caused by oil-based mud filtrate or chemical surfactants used in oil recovery operation and determine the properties of heavy oil.