To measure the phase behavior of a fluid in a porous medium such as a tight gas shale, one illustrative method involves: (a) loading the fluid into a sample cell containing the porous medium; (b) setting a pressure and a temperature for the fluid in the sample cell; (c) applying an RF pulse sequence to the fluid in the sample cell to acquire an NMR signal; (d) deriving from the NMR signal an NMR parameter distribution that depends on the pressure and the temperature; (e) determining whether a fluid phase is present based on the NMR parameter distribution; (f) repeating operations (c) through (f) to determine the presence or absence of the fluid phase at multiple points along a pressure-temperature path that crosses a phase boundary; and (g) providing an estimated location of the phase boundary based on the presence or absence of the fluid phase at said points.

A container has a sample installation unit and an NMR circuit therein, and is connected to a bearing gas supply path and a drive gas supply path for supplying gas to the inside of that container. This container is also connected to an exhaust path that exhausts the gas from the inside of the container. The exhaust path has a pressure control valve as an adjustment mechanism for adjusting the pressure in the container.

Snap-in bushings are disclosed that enable sealing of sample chambers in MAS-NMR rotors for high pressure and/or high temperature operation that enhance pressure limits up to about 400 bar and temperature limits up to at least about 250 C.

Nuclear magnetic resonance (NMR) gas isotherm techniques to evaluate wettability of porous media, such as hydrocarbon reservoir rock, can include constructing a NMR gas isotherm curve for a porous media sample gas adsorption under various pressures. A hydrophobic or hydrophilic nature of the porous media sample can be determined using the NMR gas isotherm curves. A wettability of the porous media sample can be determined based on the NMR gas isotherm curve. The wettability can be determined for porous media samples with different pore sizes. In the case of reservoir rock samples, the determined wettability can be used, among other things, to model the hydrocarbon reservoir that includes such rock samples, to simulate fluid flow through such reservoirs, or to model enhanced hydrocarbon recovery from such reservoirs.

Nuclear magnetic resonance (NMR) gas isotherm techniques to evaluate wettability of porous media, such as hydrocarbon reservoir rock, can include constructing a NMR gas isotherm curve for a porous media sample gas adsorption under various pressures. A hydrophobic or hydrophilic nature of the porous media sample can be determined using the NMR gas isotherm curves. A wettability of the porous media sample can be determined based on the NMR gas isotherm curve. The wettability can be determined for porous media samples with different pore sizes. In the case of reservoir rock samples, the determined wettability can be used, among other things, to model the hydrocarbon reservoir that includes such rock samples, to simulate fluid flow through such reservoirs, or to model enhanced hydrocarbon recovery from such reservoirs.

An NMR apparatus includes a depressurizing device for depressurizing an NMR probe, a gas supply device for supplying gas into the NMR probe to thereby pressurize the NMR probe, and a control device. The control device alternately repeats depressurization of the NMR probe, using the depressurizing device, and pressurization of the NMR probe, using the gas supply device. This replaces the gas in the NMR probe.

Preparations of a highly coherent diamond nitrogen vacancy (NV.sup.) and a diamond anvil are provided. A graphite is used as a carbon source, a diamond is used as a crystal seed, aluminum/titanium is used as a nitrogen remover, and a single crystal diamond is synthesized under a high temperature and a high pressure, and high-pressure-high-temperature (HPHT) annealing is performed on the synthesized diamond; after the annealing, multiple NV.sup.s are generated in <100> and <311> crystal orientation growth regions from scratch, while native NV.sup.s in a <111> crystal orientation growth region are disappeared; and the <100> and <311> crystal orientation growth regions do not contain defects related to ferromagnetic elements. The high-density and highly coherent NV.sup.s are produced under nondestructive conditions, and the diamond anvil with controlled NV.sup. depths are prepared to achieve a precise detection of the NV.sup. at a pressure above 60 GPa.

Nuclear magnetic resonance (NMR) gas isotherm techniques to evaluate wettability of porous media, such as hydrocarbon reservoir rock, can include constructing a NMR gas isotherm curve for a porous media sample gas adsorption under various pressures. A hydrophobic or hydrophilic nature of the porous media sample can be determined using the NMR gas isotherm curves. A wettability of the porous media sample can be determined based on the NMR gas isotherm curve. The wettability can be determined for porous media samples with different pore sizes. In the case of reservoir rock samples, the determined wettability can be used, among other things, to model the hydrocarbon reservoir that includes such rock samples, to simulate fluid flow through such reservoirs, or to model enhanced hydrocarbon recovery from such reservoirs.

A core holder for a reservoir rock core sample for MR or MRI measurement including a casing and a chamber internal to the core holder, an inlet and an outlet in the core holder for circulating a confining fluid in the chamber, a sample housing in the chamber for containing the core sample, the sample housing including an inlet and an outlet in the sample holder for circulating fluid to and from the sample, and a membrane for isolating the sample from fluid contact with the confining fluid but permitting fluid pressure to be exerted on the sample when the confining fluid is pressurized, the space in the chamber not occupied by the sample housing defining a void space, an RF probe in the void space and at least partially surrounding the sample housing, whereby confining fluid introduced into the chamber circulates in the void space around the RF probe.

A method (and corresponding system) that characterizes a porous rock sample is provided, which involves subjecting the porous rock sample to an applied experimental pressure where a first fluid that saturates the porous rock sample is displaced by a second fluid, and subsequently applying an NMR pulse sequence to the rock sample, detecting resulting NMR signals, and generating and storing NMR data representative of the detected NMR signals. The application of experimental pressure and NMR measurements can be repeated over varying applied experimental pressure to obtain NMR data associated with varying applied experimental pressure values. The NMR data can be processed using inversion to obtain a probability distribution function of capillary pressure values as a function of NMR property values. The probability distribution function of capillary pressure values as a function of NMR property values can be processed to determine at least one parameter indicative of the porous rock sample.