Wing rib telescopic while-drilling density logger

Abstract

The invention relates to the rib-expansible density logging while drilling apparatus for use in the petroleum drilling industry. A density detector pup joint and a gamma radioactive source are sealed and arranged on a drill collar. An expandable rib is arranged on the surface of the drill collar at position of a groove, and the groove and the density detector pup joint are arranged at an interval of about 120 degrees in a circumferential direction. The expandable rib relies on a piston assembly to extend outward under the action of pressure drop (difference between inner pressure and outer pressure) generated due to instruments such as a drill bit (and a motor) arranged at the lower part of the apparatus and presses the detector pup joint against a well wall on a corresponding side by using counterforce of the well wall to realize density measurement by the well wall. And when a pump stops, the expandable rib retracts under the action of a return spring. The rib-expansible density logging while drilling apparatus is applicable to various wells, ensures measurement by the well wall, overcomes influence of slurry, mud cake or complex well structure on measurement precision, improves underground safety and is applicable to logging while drilling and geosteering drilling.

Description

Technical field: [0001] The invention relates to a measuring-while-drilling instrument used in the oil drilling industry. In particular, the present invention relates to a density logging while drilling tool capable of reducing the impact of drilling the borehole. Background technique: [0002] In the petroleum industry, it is suitable for logging while drilling and geosteering drilling. The density logging tool while drilling is used to measure the porosity of the formation around the wellbore in real time during the drilling process, so as to find the target oil and gas formation and improve oil and gas recovery. [0003] A density logging tool usually consists of a gamma radiation source, two gamma detectors at different distances from the gamma radiation source and corresponding electronic circuits. Since the density logging is greatly affected by the borehole (such as mud and mud cake), the instrument is required to be close to the borehole wall for measurement, so tha...

AI Technical Summary

Problems solved by technology

When the diameter of a section of the wellbore increases due to the continuous erosion of the mud, there will be a gap between the gamma radiation source and the detector and the wellbore wall, and the mud will affect the measurement, resulting in measurement errors; If the hole diameter becomes smaller, the stabilizer part is likely to be stuck on the well wall, resulting in a pipe sticking accident. In severe cases, the instrument cannot be salvaged, and the radioactive source remains downhole to pollute the formation

[0007] Secondly, because the drill collar is not always in the center when it rotates downhole, but is approximately an irregular ellipse, and its motion trajectory is more complicated due to the influence of borehole changes, it cannot always ensure that the instrument sticks to the borehole wall for measurement. Therefore, even if the borehole instrument and software compensation calculation methods, etc., and the measurement accuracy cannot be guaranteed

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