Abstract: Methods and apparatus for the characterization of formation fluids are disclosed. A downhole tool disposed in a borehole penetrating a subterranean formation obtains a NMR measurement, effects a change in a characteristic of the formation fluid, and obtains another NMR measurement subsequent to the change. Alternatively, the downhole tool effects a radial gradient of a characteristic of the formation and obtains NMR measurements at two or more selected radial distances from the wellbore wall. A parameter representative of the subterranean formation or the formation fluid is further determined from the NMR measurements.

Abstract: Methods and apparatus for the characterization of formation fluids are disclosed. A downhole tool disposed in a borehole penetrating a subterranean formation obtains a NMR measurement, effects a change in a characteristic of the formation fluid, and obtains another NMR measurement subsequent to the change. Alternatively, the downhole tool effects a radial gradient of a characteristic of the formation and obtains NMR measurements at two or more selected radial distances from the wellbore wall. A parameter representative of the subterranean formation or the formation fluid is further determined from the NMR measurements.

Abstract: The present invention relates to a method and apparatus for determining the wettability of a porous media, such as bone, plant, food, wood or molecular sieves, etc., having two or more fluids. The method of the present invention correlates a diffusion-relaxation calibration function representative of at least one fluid in the porous media with a 2-D function developed using diffusion-editing to determine wettability of the porous media.

Abstract: The present invention relates to a method and apparatus for determining the wettability of a porous media, such as bone, plant, food, wood or molecular sieves, etc., having two or more fluids. The method of the present invention correlates a diffusion-relaxation calibration function representative of at least one fluid in the porous media with a 2-D function developed using diffusion-editing to determine wettability of the porous media.

Abstract: The present invention relates generally to a nuclear magnetic resonance apparatus and method for substantially eliminating the effects of phase coherent acoustic ringing in borehole logging. A series of cycles of measurement pulse sequences are applied to the formation surrounding the borehole. Each pulse sequence includes an RF excitation pulse and several RF refocusing pulses. Spin echoes are received that contain spurious ringing signals from the excitation and refocusing pulses. Spin echo signals from corresponding spin echoes of each cycle are combined and substantially cancel the spurious ringing from the excitation and refocusing pulses of the pulse sequences.

Abstract: There is provided a method of accurately estimating the permeability of sedimentary rock formations from well logging data. The method involves a short relaxation time strategy with the identification of the key k-Lambda parameter S/V.sub.p, which is the surface-to-pore ratio. The inverse of T.sub.2 is related to this ratio by the surface relaxivity, .rho.2. The k-Lambda estimator is given by: ##EQU1## where: .DELTA.V.sub.1 represents the volume elements of the T.sub.2 distribution and the sum over i=1 to n represents some set of early to later volume elements; and V.sub.p is the total pore volume.

Abstract: An NMR pulse sequence for use in a borehole logging tool includes a series of CPMG pulses according to:T.sub.r -90.degree..sub..+-.x -(t.sub.cp -180.degree..sub.y -t.sub.cp -echo.sub.j)where j is the index of CPMG echoes gathered, T.sub.r is wait time, t.sub.cp is the Carr-Purcell spacing. This pulse sequence is used to determine Bound Fluid Volume (BFV) which is subtracted from total porosity to yield Unbound Fluid Volume (UFV) of a formation surrounding the borehole. Measuring the BVF, the amount of rapidly relaxing fluid (less than 50 ms), is more efficient than measuring UFV (up to 2 secs), and is insensitive to motion of the logging tool.