Schlumberger Technology Corporation

Payam Tabrizi

Robert Freedman

Vivek Anand

Daniel Catina

Krishnamurthy Ganesan

Anatoly Dementyev

Yi-Qiao Song

Martin D Hurlimann

Nicholas J Heaton

Soumyajit Mandal

Douglas W Grant

Gabriela Leu

Ricardo Y Torres

Van D M Koroleva

A method for measuring one or more properties of a formation includes applying a magnetic field to a subterranean formation using a downhole tool. A radiofrequency signal is transmitted into the subterranean formation that is exposed to the magnetic field. The radiofrequency signal induces a transverse magnetization in the subterranean formation, and the transverse magnetization induces an initial voltage signal in the downhole tool. The initial voltage signal is amplified using a first amplifier in the downhole tool such that the first amplifier outputs a first amplified voltage signal. The first amplified voltage signal is introduced to an input of the first amplifier, such that the first amplifier amplifies the first amplified voltage signal and outputs a second amplified voltage signal.

Active damping for NMR logging tools

The Larmor frequency for an in situ nuclear magnetic resonance (NMR) tool is determined and used to acquire NMR data. An NMR tool is provided and placed in situ, for example, in a wellbore. An initial estimate of the Larmor frequency for the in situ NMR tool is made and NMR data are acquired using the in situ NMR tool. A spectral analysis is performed on the NMR data, or optionally, the NMR data are digitized and a discrete Fourier transform (DFT) is performed on the digitized NMR data. The modal frequency of the spectral analysis or DFT is determined, and the Larmor frequency for the in situ NMR tool is determined using the modal frequency. The NMR tool is modified to transmit at the determined Larmor frequency and then used to acquire further NMR data.

Determining the Larmor frequency for NMR tools

A nuclear magnetic resonance (NMR) measurement system for high pressure and temperature measurements on fluids is disclosed. The system has a sensor assembly that includes a sample holder having a body formed from a non-magnetic metal and defining an interior cavity for receiving a fluid sample, a frame member disposed in the interior cavity of the sample holder, an antenna coil disposed in the interior cavity about the frame member, an inlet that allows the fluid sample to enter the interior cavity, an outlet that allows for the fluid sample to be flushed from the interior cavity, and a magnet assembly having a central bore in which the sample holder is disposed. Adjacent to the sample holder are pulsed field gradient coils for performing diffusion measurements. The system further includes pulse sequencer circuitry that supplies signals to the antenna coil. When the interior cavity of the sample holder is filled with the fluid sample, the antenna coil and the frame member are at least partially submerged in the fluid sample, and the antenna coil obtains NMR measurements of the fluid sample in response to the signals. Related methods and apparatuses are also disclosed herein.

System and method for obtaining nuclear magnetic resonance measurements on reservoir fluids for prediction of fluid properties

Determining the larmor frequency for NMR tools

Growing community of inventors

Missouri City, TX, United States of America

Payam Tabrizi