Schlumberger Technology Corporation

Edmund John Fordham

Jonathan Mitchell

Andrew Clarke

Denise E Freed

Ravinath Kausik Kadayam Viswanathan

John E Edwards

Lukasz Zielinski

Yuesheng Cheng

Marie Ann Giddins

Christopher Lenn

Paul Naccache

Shi Su

A coreflood experiment may be modeled by generating a three dimensional computer simulation model of a core plug and modeling within the three dimensional computer simulation model one or both of a fluid introduction element or a fluid extraction element of a core holder used in the coreflood experiment. Once generated, the model may be loaded and used when running a simulation to model a heterogeneous distribution of fluid flow proximate one or more faces of the core plug.

Modeling of fluid introduction and/or fluid extraction elements in simulation of coreflood experiment

Methods for improved interpretation of NMR data acquired from industrial samples by simultaneously detecting more than one resonant nucleus without removing the sample from the sensitive volume of the NMR magnet or radio frequency probe are disclosed. In other aspects, the present disclosure provides methods for robust imaging/analysis of spatial distribution of different fluids (e.g., 1H, 23Na, 19F) within a core or reservoir rock. NMR data may be interpreted in real-time during dynamic processes to enable rapid screening, e.g. of enhanced oil recovery techniques and products and/or to provide improved interpretation of well-logs. Measurements of resonant nuclei other than 1H may be performed in the laboratory or downhole with a NMR logging tool. In other aspects, the present disclosure describes a novel kernel function to extract values for underlying parameters that define relaxation time behavior of a quadrupolar nucleus.

Methods for interpreting NMR data

A porous material with liquid in the pores is examined by submerging the material in a bathing liquid, possibly a perfluorocarbon, which is immiscible with the liquid in the pores, is non-wetting towards the material, is immiscible with and differs in density from any liquid on the outside of the material, and does not contain a resonant element found in the bathing liquid. This bathing liquid displaces fluid from the surface of the porous material but not the liquid in the pores. Nuclear magnetic resonance signals from liquid in the pores give a measurement of pore volume. Volume of bathing liquid displaced by the porous material gives the bulk volume and porosity can be derived from these measurements. Sample preparation is minimal and a benchtop spectrometer can be used, making the method practical for examination of drill cuttings from a borehole while drilling.

Determining properties of porous material by NMR

A pressurizable holder for a sample to be examined by NMR, comprises a pressure retaining nonmagnetic tube surrounding a radio-frequency coil which in turn surrounds a space for the sample. The pressure retaining tube is formed of (i) nonmetallic electrically insulating material such as a ceramic or (ii) nonmetallic electrically insulating matrix material reinforced with electrically insulating filaments such as glass fiber, or (iii) non-metallic electrically insulating matrix material reinforced with electrically conductive filaments configured so that conductivity is anisotropic. There is good coil filling factor without constraint on wall thickness of the pressure retaining tube. Avoidance of isotropically conductive material inhibits eddy currents when an NMR spectrometer's magnetic field gradient coils are switched on and off. The tube resists hoop stress from internal pressure. Longitudinal stress is resisted by structure connecting end pieces at the ends of the pressure retaining tube.

Sample holder for use in NMR

An apparatus and method for NMR analysis of a plurality of core samples includes a core holder () that holds a core sample under pressurized conditions. A radio frequency coil () disposed about the core holder () generates a pulsed-mode magnetic field component over a sample volume occupied by the core sample. A support structure is removably secured to the respective core holder. A permanent magnet (A,B) has an open configuration such that it is removably disposed into a position within the support structure about the radio frequency coil and the core holder. The open configuration allows the same permanent magnet to be used for NMR analysis of a plurality of core samples without the need for depressurizing the respective core holder and disassembling the core holder and corresponding load frame for each core sample. It also allows multiple core samples to be prepared for NMR analysis while separated from the NMR measurement apparatus.

NMR analysis of a core sample employing an open permanent magnet removable from a core holder

Apparatus for examining a fluid-containing porous sample, by a combination of centrifuging to move fluid into, out of, and/or within the sample and NMR to monitor the amount of fluid present at locations within the sample has a magnet system to provide a magnetic field; and a centrifuge rotor comprising a holder () for the sample and mounted to move the sample within the magnetic field. The apparatus preferably includes gradient coils () superimposing a magnetic field gradient onto a field provided by magnets (). At least one radio-frequency coil () is located on the centrifuge rotor in a positionwhich surrounds the sample in the holder. The coil axis is transverse to the magnetic field and field gradient when measurement is made. Consequently NMR measurement of the distribution of fluid in the sample can be made while the centrifuge is in motion.

Examining porous samples

Nuclear magnetic resonance apparatus for measuring properties of a fluid stream flowing within a pipeline has one or more magnet systems for applying magnetic field to the fluid stream and also has means for inducing and observing magnetic resonance within the fluid stream as it passes through a said magnetic field. The apparatus may also include a polarizing magnetic field upstream of the magnetic field in which resonance is observed. The fluid stream may be hydrocarbon from an underground reservoir. In order to guard against accumulation of magnetisable iron debris particles entrained in the fluid flow, the apparatus comprises one or more upstream traps having a magnetic field to attract and hold solid magnetizable material and an exit path for the removal of the solid magnetizable material so that it does not continue towards any polarizing field and the field where resonance is observed.

Trapping magnetizable particulates

A method of analyzing properties of a porous sample, typically a cylinder of porous rock, comprises centrifuging the sample while it contains at least one liquid, determining the distribution of at least one liquid in the sample by magnetic resonance imaging of the sample, and also determining the distribution of at least one magnetic resonance parameter, where the parameter is one of longitudinal relaxation time T, transverse relaxation time Tand diffusion coefficient D. Pore throat sizes can be determined from the distribution of at least one liquid in the sample and pore body sizes can be determined from the distribution of the magnetic resonance parameter enabling determination of a relationship between pore throat sizes and pore body sizes in the sample. This can be a relationship between individual values of pore throat size and an average of body sizes of pores having that individual pore throat size.

Magnetic resonance examination of porous samples

Properties of a porous solid sample, which may be a core of rock taken from below ground are carried out using apparatus which performs both nuclear magnetic resonance (NMR) and porosimetry measurements. The apparatus has a magnetproviding a magnetic field and a radio frequency coilfor transmitting and/or receiving electromagnetic radiation so as to bring about NMR in the magnetic field, a pressure vesselto hold a samplewithin the magnetic field, a supply of a non-wetting liquid connected to the vessel, means to apply pressure to the non-wetting liquid to force liquid into pores of the samplemeans to measure applied pressure of the non-wetting liquid and means to measure volume thereof taken up by the sample. The pressure of non-wetting liquid may be increased in steps, using intruded liquid volume at each step to give a measurement of pore throat size using NMR at each step to give a measure of pore size such as diameter of equivalent sphere. The non-wetting liquid may be mercury and NMR may observe the Knight shift of 99 Hg.

Examination of porosity by NMR and intrusion porosimetry

A laboratory NMR methodology (and corresponding laboratory apparatus) defines a sample volume. The method stores downhole tool data corresponding to a hydrocarbon-bearing sample collected from a given subsurface formation. The downhole tool data includes parameters pertaining to magnetic fields used by a downhole tool during a suite of NMR measurements of the given subsurface formation. The sample is positioned in the sample volume of the laboratory apparatus, which applies a static magnetic field in the sample volume. Furthermore, the laboratory apparatus applies a suite of NMR measurements to the sample volume to thereby determine a property of the sample. The NMR measurements of the suite each include a pulse sequence of oscillating magnetic field in conjunction with a pulsed-mode gradient field. The pulsed-mode gradient field is based on the stored downhole tool data corresponding to the sample. A laboratory NMR methodology for optimizing downhole NMR measurements is also described.

System for emulating nuclear magnetic resonance well logging tool diffusion editing measurements on a bench-top nuclear magnetic resonance spectrometer for laboratory-scale rock core analysis

NMR logging in a wellbore is used to monitor an oil reservoir during oil recovery by miscible displacement. Diffusivity distributions found by NMR logging indicate whether one or two phases are present and composition of residual oil. Operation of the oil recovery procedure may be maintained or modified in response to monitoring of the reservoir.

NMR logging of miscible displacement

System and method for emulating nuclear magnetic resonance well logging tool diffusion editing measurements on a bench-top nuclear magnetic resonance spectrometer for laboratory-scale rock core analysis

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Cambridge, United Kingdom

Edmund John Fordham