INVESTIGATION OF PHYSICAL PROPERTIES OF HYDROCARBONS IN UNCONVENTIONAL MUDSTONES USING TWO-DIMENSIONAL NMR RELAXOMETRY
SPEAKER: Z. Harry Xie, Core Laboratories LP
Speaker Bio: Zonghai ‘Harry’ Xie is NMR Senior Advisor at Core Laboratories. He received his PhD in Physics from the University of Kent at Canterbury, UK, in 1994. Dr. Xie has spent several years working as Product Specialist to develop and support laboratory NMR products (MARAN product line) at Resonance Instruments Ltd, UK. He has also spent time at Bruker as Senior Applications Scientist in the Time Domain NMR division USA, Technical Director of the Time Domain products for Asia Pacific, and General Manager of Bruker Optics China. Dr. Xie has been focusing on developing new NMR techniques and petrophysics models for unconventional tight rocks since he joined Core Lab in November 2012. He is the current president of NMR SIG of SPWLA.
Authors: Z. Harry Xie and Zheng Gan, Core Laboratories LP, Houston, TX, USA
There are two identical sessions:
of organic matter properties is crucial in characterization of unconventional
plays. It is always a challenge for petrophysicists to differentiate and
quantify mobile and immobile hydrocarbons in unconventional mudstones. High
frequency (22MHz) NMR for unconventional rock core analysis has gained industry
acceptance for its high efficiency and high sensitivity to measure very small
volumes of fluids and solid hydrocarbons in tight rocks. Previous work has
revealed that one-dimensional (1D) NMR T2 method is insufficient to study
organic matters in fresh core samples due to overlapping T2 signals from both
hydrocarbons and water. Co-existence of structurally bound water and solid
hydrocarbons in shales leads to short T2’s in microseconds range, and further
complicates the situation. In this work, we present the first detailed analysis
method using the two-dimensional (2D) NMR T1-T2 mapping techniques to study
physical properties of hydrocarbons in various shale rocks. Combined NMR pulse
sequences were used to acquire signals from solids and liquids that contain
hydrogen. The 2D T1-T2maps were further processed by removing the map regions
which are from water to obtain 1D T2 distributions for hydrocarbons only.
Measurements on mudstone core samples at various temperatures, from 22 °C to 90
°C, show that the relaxation time T2’s of hydrocarbon components increase with
temperature due to molecular mobility increasing but at different rates,
implying that hydrocarbons present in different environments (e.g., organic and
inorganic pores) within these tight core samples are undergoing different
thermal dynamics processes. T2 of each hydrocarbon component as a function of
temperature were analyzed to calculate the activation energy (Ea) based on the
Arrhenius equation for molecular kinetics, and producibility is then estimated
accordingly. This NMR method provides petrophysicists with a powerful way to
study hydrocarbons that are confined in organic matter such as bitumen and
kerogen to understand the mechanism of enhanced oil recovery (EOR) in
unconventional reservoirs. Furthermore, results from such NMR relaxometry
analysis and multiple-heating rate pyrolysis indicate that the combined
techniques are very promising for investigating producible estimates from the
free/adsorbed hydrocarbons present in source-reservoir intervals. Such an
alternative approach leads to an analytical protocol for the determination of
NMR cut-offs to quantify mobile and immobile hydrocarbons.
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