Schlumberger Technology Corporation

Yuesheng Cheng

Abdel Kharrat

Robert Freedman

Krishnamurthy Ganesan

Denise E Freed

John E Edwards

Edmund John Fordham

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

The viscosity &#x3b7; (in centipoise) of a heavy oil sample is determined according to an equation of the form ln where T is the temperature of the heavy oil, Tis the logarithmic mean of the Tdistribution of the sample obtainable from nuclear magnetic resonance (NMR) measurements, c'=1.0&#xb1;0.05, c&#x2033;=1.0&#xb1;0.04, &#x3b7;is the glass transition temperature viscosity of the heavy oil and a function of T, and C1 is a variable which is a constant for the heavy oil and is a function of T. Both C1 and &#x3b7;are considered functions of certain NMR values associated with the heavy oil sample, with &#x3b7;and C1 preferably estimated by empirically fitting data to the equations ln T=a&#x2032;+b&#x2032; ln &#x3b7;and ln T=a&#x2033;+b&#x2033;C1, where a&#x2032;, b&#x2032;, a&#x2033; and b&#x2033; are constants.

Methods for determining in situ the viscosity of heavy oil using nuclear magnetic resonance relaxation time measurements

Viscosity of heavy oil is determined in situ in a formation by making nuclear magnetic resonance (NMR) measurements in the formation, and then calculating viscosity according to an equation of the form where T is the temperature of the heavy oil sample, &#x3b7; is the viscosity, Tis the logarithmic mean of the Tdistribution spectrum of the sample, and a, b, and c are non-zero constants. Typically, constant b has a value between 5 and 7 and constant c has a value between &#x2212;0.7 and &#x2212;0.5.

Methods for determining in situ the viscosity of heavy oil

A method for determining a wax appearance temperature of a fluid includes obtaining nuclear magnetic resonance (NMR) measurements of the fluid at a plurality of temperatures; deriving a NMR parameter from each of the NMR measurements; and determining the wax appearance temperature by analyzing the NMR parameter as a function of temperature. An apparatus for detecting wax appearance in a fluid includes a sample cell for holding a fluid for nuclear magnetic resonance (NMR) measurements at a plurality of temperatures; a temperature measuring device disposed proximate the sample cell; a magnet for polarizing molecules in the fluid in the sample cell; at least one radiofrequency (RF) coil for generating pulses of magnetic field and for detecting NMR signals; and circuitry for controlling and measuring the temperature of the fluid in the sample cell and for obtaining NMR measurements.

NMR measurement of wax appearance in fluids

A method for estimating a concentration of a substance in a test sample of formation fluid, comprising measuring an NMR parameter of a first sample of formation fluid to obtain a first measurement, adding a known quantity of the substance to the first sample to produce a modified sample, measuring the NMR parameter of the modified sample to obtain a second measurement; and determining a relation between the concentration of the substance and a function of the NMR parameter using the first and second measurements and the NMR parameter of the substance.

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Edmonton, Canada

Yuesheng Cheng