Abstract: A centralizer for use in oil well wireline toolstrings comprising a central mounting rod and floating spring mechanisms between which a number of jointed centralizer arms are connected. The jointed centralizer arms have a section with a concave profile disposed near to their pivot points so that a closing force acting on the arms acts at a greater distance from the pivot, thereby increasing the closing moment and making the centralizer easier to draw into a borehole with a narrow cross-section. The floating spring mechanisms also have a linkage to the presser plate of the spring such that an axial force pulling the centralizer apparatus into a borehole is transferred directly into a force on the spring, thereby reducing the opening moment the springs exert on the centralizer arms.

Abstract: A wireline logging sonde for sensing fluid properties in a bore hole. The sonde has a main body and a plurality of sensor capsules mounted peripherally to the main body on fingers. A sensor element is located in each sensor capsule. The sensor elements receive power by inductive coupling from the main body and transmit data signals at radio frequencies back to the main body.

Abstract: An improved centralizer apparatus for use in oil well wireline toolstrings comprising a central mounting rod (20) and floating spring mechanisms (30, 90) between which a number of jointed centralizer arms (120, 140) are connected. The jointed centralizer arms (120, 140) have a section with a concave profile (64, 84) disposed near to their pivot points (50) so that a closing force acting on the arms (60, 80) acts at a greater distance from the pivot, thereby increasing the closing moment and making the centralizer easier to draw into a borehole (200) with a narrow cross-section. The floating spring mechanisms also have a linkage (99) to the presser plate (98) of the spring (96) such that an axial force pulling the centralizer apparatus into a borehole is transferred directly into a force on the spring (96), thereby reducing the opening moment the springs exert on the centralizer arms, making them easier to close.

Abstract: A wireline logging sonde (10) for sensing fluid properties in a borehole has a main body (12) and a plurality of sensor capsules (30) mounted peripherally of the main body on fingers (22, 24). The sensor capsules transmit data signals at radio frequency to the main body, and are powered from the main body by inductive coupling. The need to provide pressure-proof wire connections between the main body and into the sensor capsules is thus completely avoided.

Abstract: A method and apparatus is disclosed for avoiding problems caused by a logging tool sticking in a borehole and subsequently accelerating when it becomes free. Such problems give rise to measurement errors and loss of data, particularly when the tool is in the vicinity of ground discontinuities where the data is especially valuable. In accordance with the method and apparatus, data is stored in the tool as it is moved within the borehole, the data being stored in a manner which varies in accordance with any difference between the actual motion of the tool in the borehole and the apparent motion of the tool as measured at the surface. The stored data is transmitted from the tool to the surface at a rate within a transmission bandwidth capacity of a communication link. According to one arrangement, means are provided for shifting the writing position of data entered into a memory, the shifting means being responsive to an error signal related to any difference between the actual and apparent motions of the tool.