Abstract: In this invention a new interpretation methodology has been developed. A pore structure model is used to compute the relaxation behavior. This model is then used as the kernel of a best-fit inversion scheme against the measured data, in contrast to inverting for a T.sub.2 distribution that relies on regularization. Parameters of the model are obtained by "best fitting" the model with the data. The method considers a geometrical or physical model comprising both intergranular and intragranular porosity (microporosity). The NMR relaxation is computed by one of the several methods. The model is compactly represented by a set of physical parameters that are iterated upon until a match with relaxation data is obtained in the best fit sense. The result is obtained in terms of these physical parameters, and then integrated with other types of measurements.

Abstract: Single point optical probes for measuring three-phase characteristics of fluid flow in a hydrocarbon well and methods of processing signals generated by the probe are disclosed. A probe having a single fiber optic is coupled to a light source and apparatus for detecting reflectance and fluorescence. Light is delivered to the tip of the probe where it either is internally reflected in the probe or exits the probe and illuminates the fluid (liquid) ambient the probe tip. If the fluid at the probe tip is oil, the light exits the probe, illuminates the oil, and causes the oil to fluoresce. If the fluid is water, no fluorescence occurs. If the fluid is gas, at least some light is internally reflected in the probe. A detection system including at least one beam splitter and fluorescence and reflectance detectors is provided in conjunction with the probe. Preferably, the fluorescence detector is coupled to the fiber optic by a wavelength division multiplexer.

Abstract: After an oil well has been drilled, lined and cased, and is producing, it may be desirable in situ (either at the wellhead or downhole) to measure, and log (record), the rate at which fluid, and its several distinct components, is flowing out of the geological formations through which the bore has been drilled and is passing into and up the casing. A useful type of detector system for this purpose is an optical probe (31), and the invention proposes a novel design of probe which has a doubly-angled tip, there being measured the light totally internally reflected at the interface (37), which depends on the ratio of the refractive indices of the probe tip and fluid component in which it is immersed.