Abstract: In some embodiments, apparatus and systems, as well as methods, may operate to irradiate a portion of a geological formation (94) with neutrons in a neutron burst generated by a switchable electronic source (84), to measure (with one or more detectors (86) a flux of gamma rays to provide a measured flux, at least a portion of the gamma rays being generated by the neutrons, and to determine one one or more of a neutron porosity, a density, and/or a photoelectric factor of the geological formation based on the measured flux.

Abstract: Apparatus, methods for forming the apparatus, and methods for operating the apparatus provide a value for a formation property or a borehole property from measurements obtained in a well. The value may be generated from determining a weighted average of the value for the formation property or the borehole property using both values corresponding to different azimuths and weights corresponding to different azimuths.

Abstract: Apparatus, methods for forming the apparatus, and methods for operating the apparatus provide a modular unit of hardware to make measurements in a well. The modular unit may include a housing arranged for placement in a drill-string element, where the housing includes a sensor and is structured such that the housing is transferable to another drill-string element without a calibration of the sensor during or after the transfer. The drill-string elements associated with the transfer may be of different sizes.

Abstract: In some embodiments, apparatus and systems, as well as methods, may operate to acquire borehole standoff data (321), segregate the standoff data into a plurality of azimuthal bins (363), derive a plurality of diameters from the standoff data in the bins, determine an average borehole diameter from the plurality of diameters (367), calculate a standard deviation from the average borehole diameter (375), and compute a caliper measurement (383), a major elliptical axis length, and a minor elliptical axis length based on the average borehole diameter and the standard deviation (387).

Abstract: We disclose density measurement methods that are accurate over an extended range of standoff distances. One method embodiment includes: a) obtaining a standoff distance, a near detector count rate, and a far detector count rate; b) determining a formation density measurement using near and far detector count rates when the standoff distance is less than a predetermined value; and c) determining the formation density measurement using just the far detector count rate and the standoff distance measurement when the standoff distance is greater than the predetermined value. The method may further include calculating a calibration parameter when the standoff distance is less than the predetermined value. The calibration parameter serves to calibrate a standoff-based correction to the far detector count rate, enabling accurate formation density measurements at large standoff distances. The measurements are made with a rotating logging tool, causing the standoff distance to cycle between large and small values.

Abstract: A distance measurement device and method for measuring a distance between two reference points comprising a housing, a base, and a flexible member curving therebetween. The flexible member housing end is allowed to slide in a slide track in the housing. The housing also comprises sensors that detect the position of the flexible member housing end relative to the housing. The distance measurement device measures the distance between the two reference points by engaging the first reference point with the housing and engaging the second reference point with the flexible member apex. As the distance from the housing to the flexible member apex changes, the flexible member housing end slides in the housing slide track. There is a unique correlation between the location of the flexible member housing end and the distance to flexible member apex, and thus the second reference point.

Abstract: A distance measurement device and method for measuring a distance between two reference points comprising a housing, a base, and a flexible member curving therebetween. The flexible member housing end is allowed to slide in a slide track in the housing. The housing also comprises sensors that detect the position of the flexible member housing end relative to the housing. The distance measurement device measures the distance between the two reference points by engaging the first reference point with the housing and engaging the second reference point with the flexible member apex. As the distance from the housing to the flexible member apex changes, the flexible member housing end slides in the housing slide track. There is a unique correlation between the location of the flexible member housing end and the distance to flexible member apex, and thus the second reference point.

Abstract: We disclose density measurement methods that are accurate over an extended range of standoff distances. One method embodiment includes: a) obtaining a standoff distance, a near detector count rate, and a far detector count rate; b) determining a formation density measurement using near and far detector count rates when the standoff distance is less than a predetermined value; and c) determining the formation density measurement using just the far detector count rate and the standoff distance measurement when the standoff distance is greater than the predetermined value. The method may further include calculating a calibration parameter when the standoff distance is less than the predetermined value. The calibration parameter serves to calibrate a standoff-based correction to the far detector count rate, enabling accurate formation density measurements at large standoff distances. The measurements are made with a rotating logging tool, causing the standoff distance to cycle between large and small values.

Abstract: Fluid property sensors and associated methods of calibrating sensors in a well provide enhanced well monitoring and control. In one described embodiment, an external venturi flowmeter is utilized to determine a flow rate of fluid from a zone into a tubing string, independent of flow into the tubing string of fluid produced from any upstream zone. In another described embodiment, a gamma ray fluid density sensor utilizes a unique combination of gamma ray sources and detectors to determine a density of fluid flowing through a tubing string. In yet another embodiment, external tubing string sensors are used to determine properties of fluid from a zone into a tubing string, independent of flow into the tubing string of fluid produced from any upstream zone. In still another embodiment, sensor systems for multiple independently produced zones are calibrated.

Abstract: Fluid property sensors and associated methods of calibrating sensors in a well provide enhanced well monitoring and control. In one described embodiment, an external venturi flowmeter is utilized to determine a flow rate of fluid from a zone into a tubing string, independent of flow into the tubing string of fluid produced from any upstream zone. In another described embodiment, a gamma ray fluid density sensor utilizes a unique combination of gamma ray sources and detectors to determine a density of fluid flowing through a tubing string. In yet another embodiment, external tubing string sensors are used to determine properties of fluid from a zone into a tubing string, independent of flow into the tubing string of fluid produced from any upstream zone. In still another embodiment, sensor systems for multiple independently produced zones are calibrated.

Abstract: Fluid property sensors and associated methods of calibrating sensors in a well provide enhanced well monitoring and control. In one described embodiment, an external venturi flowmeter is utilized to determine a flow rate of fluid from a zone into a tubing string, independent of flow into the tubing string of fluid produced from any upstream zone. In another described embodiment, a gamma ray fluid density sensor utilizes a unique combination of gamma ray sources and detectors to determine a density of fluid flowing through a tubing string. In yet another embodiment, external tubing string sensors are used to determine properties of fluid from a zone into a tubing string, independent of flow into the tubing string of fluid produced from any upstream zone. In still another embodiment, sensor systems for multiple independently produced zones are calibrated.

Abstract: Fluid property sensors and associated methods of calibrating sensors in a well provide enhanced well monitoring and control. In one described embodiment, an external venturi flowmeter is utilized to determine a flow rate of fluid from a zone into a tubing string, independent of flow into the tubing string of fluid produced from any upstream zone. In another described embodiment, a gamma ray fluid density sensor utilizes a unique combination of gamma ray sources and detectors to determine a density of fluid flowing through a tubing string. In yet another embodiment, external tubing string sensors are used to determine properties of fluid from a zone into a tubing string, independent of flow into the tubing string of fluid produced from any upstream zone. In still another embodiment, sensor systems for multiple independently produced zones are calibrated.

Abstract: A method for calibrating a logging tool that is exposed to an external energy spectrum, comprising the steps of: (a) providing a stabilization source that emits a stabilization signal having a known energy; (b) providing a receiver that receives a total spectrum that comprises the sum of the external energy spectrum and the received stabilization signal; (c) discerning the stabilization signal in the total spectrum by the steps of: calculating the centroid of the area under the total spectrum; adjusting the gain of the tool on the basis of the calculated centroid; dividing a portion of the spectrum that includes the known energy level of the stabilization peak into a number of windows of equal width, with an equal number of windows on either side of the stabilization peak energy; using the count rates in each of the windows to calculate a value D.sub.n that is proportional to the n.sup.

Abstract: An improved formation density logging tool is provided that is effective in cased holes. The improved tool utilizes four detectors which generate four signals enabling the operator to calculate the four unknown variables of interest: formation density, cement thickness, cement density and casing thickness. By providing a means for calculating cement thickness, cement density and casing thickness, a more accurate calculation of formation density is provided. Further, by providing a means for calculating cement thickness, cement density and casing thickness, a more accurate neutron-porosity measurement can be made when the density tool is used in combination with a neutron tool. The tool comprises improvement over currently-available two-detector density tools which are normally useful only in open holes.

Abstract: The invention relates to an apparatus and method for verifying the operability of neutron detectors and associated pulse generating circuits in a neutron logging tool prior to committing the tool to the well borehole. The method comprises the steps of exposing the neutron detectors to a source or sources of gamma rays, determining the rate of detected gamma rays by counting detector output pulses, and comparing the detected rate to an expected value thereby to verify the operations of the detectors. In the apparatus in accordance with the invention, the gamma ray source(s) may be contained inside the tool near or mounted on the detectors themselves. In an alternate embodiment, the gamma ray source(s) may be externally applied to the tool at the surface during verification procedures.

Abstract: An improved formation density logging tool is provided that is effective in cased holes. The improved tool utilizes three detectors: a first detector for primarily compensating for the casing; a second detector for primarily compensating for the cement; and a third detector for providing formation information. The tool provides an improvement over currently-available two-detector density tools which are normally useful only in open holes. It is anticipated that the tool provided herein will be useful in both open and cased holes.

Abstract: A standoff compensation system is disclosed for use in an LWD system implementing gamma density and/or neutron porosity measurements. An acoustic transducer is provided to measure the standoff distance between the logging tool and the borehole wall. The present invention includes a downhole processor for determining a weighting factor for the density and/or porosity measurements based upon the measured standoff distance. The weighting factor can either be calculated by the downhole processor according to a predetermined weighting function, or can be retrieved from a pre-calculated look-up table in ROM. The processor then multiplies the weighting factor by the count data from the sensor to determine a weighted count value. The weighted count values are accumulated during an averaging period and normalized, so that a single normalized count value can be generated and either stored in downhole memory, used immediately, or transmitted by telemetry to the surface.

Abstract: This disclosure sets out a method for applying a temperature correction to calculations that employ measurements made with scintillation detectors. Temperature measurements are made at or near the scintillation detectors and utilized in corrections employing measurements made with the scintillation detectors to obtain quantities that are relatively independent of temperature.

Abstract: A fluid density measuring tool is set forth, a structure having a shielded sonde supporting a radiation source having a characteristic gamma ray emission pattern preferably in all directions of azimuth, and a cooperative first detector is disclosed. Ports aligned with the first detector and source preferably limit the gamma ray pathway primarily to the fluid surrounding the tool. Additional detectors are included, and they measure gamma radiation which involves a surrounding casing and other materials about the well. This provides sufficient measurement data enabling one to sort the data and thereby determine the bulk density of the fluid in the well.

Abstract: A method for laboratory measurement of lithology factor L related to the photoelectric absorption properties of a rock sample for use in lighology determinations. By definition L=(.sigma..sub.T- .sigma..sub.C)/.sigma..sub.C where .sigma..sub.C is the Compton cross section .sigma..sub.T is the total photoelectric cross section of the sample which includes the binding-energy corrected Compton cross section and the Rayleigh photoelectric cross sections. A low-energy source of gamma radiation sensitive to photoelectric absorption and a high energy source of gamma radiation that has a significantly different sensitivity to photoelectric absorption are employed and the attenuation of radiation from each source is measured. With the low energy source, radiation count rates N.sub.L and N.sub.Lo obtained for measuring attenuated radiation with the sample present and with the sample absent, respectively, and similar count N.sub.H and N.sub.Ho are obtained for the high energy source.