Early Kick Detection in an Oil and Gas Well

Abstract

An acoustic transducer on a downhole tool sends an acoustic wave through a sensor plate in contact with drilling fluid. Vibrations of the sensor plate are indicative of the impedance of the borehole plate that may be associated with gas influx. A processor analyzes the vibrations and uses an estimated Q of the vibrations to determine gas influx. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.72(b).

Description

CROSS-REFERENCES TO RELATED APPLICATIONS This application claims priority from U.S. Provisional Patent Application Ser. No. 60 / 839,602 filed on Aug. 23, 2006.BACKGROUND OF THE DISCLOSURE[0001]1. Field of the Disclosure[0002]This disclosure relates generally to oil and gas well logging tools. More particularly, this disclosure relates to tools and methods for identifying the influx of gas into the borehole in real-time during drilling operations.[0003]2. Description of the Related Art[0004]Exploration for hydrocarbons commonly includes using a bottomhole assembly including a drill-bit for drilling a borehole in an earth formation. Drilling fluid or “mud” used in the drilling may vary in density or “mud weight” for a number of reasons. Such variations can result from changes in the quantity and density of cuttings (particles of formation); changes in the “mud program” at the surface, changes in temperature, etc. Variations in mud density also occur when gas or liquid enter the borehol...

AI Technical Summary

Benefits of technology

[0009]One embodiment of the disclosure is an apparatus for detection of gas influx in a borehole fluid during drilling operations. The apparatus includes a bottomhole assembly (BHA) configured to be conveyed in a borehole. The BHA includes at least one transducer assembly which has a sensor plate in contact with the borehole fluid and a cavity disposed between a transducer and the sensor plate. The transducer is configured to generate acoustic vibrations in the sensor plate. The apparatus includes a processor configured to estimate from a signal indicative of the acoustic vibrations an impedance of the borehole fluid, and to use the estimated fluid impedance to provide an indication of the gas influx. The cavity may include a fluid having a known density and compressional velocity. The signal indicative of the acoustic vibrations may be provided by the transducer and/or a r

Problems solved by technology

Such influx of formation fluids may likely be the result of formation overpressures or abnormally high pressures.

Not only does the drilling rate decrease with a high overbalance of mud pressure versus formation pressure, but also lost circulation and differential pressure sticking of the drill pipe can readily occur.

More importantly, an underbalance of mud pressure versus formation pressure can cause a pressure “kick.” A well may kick without forewarning.

Balanced drilling techniques often require only a fine margin between effective pressure control and a threatened blowout.

Additionally, there are situations where underbalance is maintained to avoid formation damage so that it is important to detect inflow of formation liquids into the borehole.

All of these suffer from the drawback that the measurements are not available in real-time as they must wait for the bottom hole fluid to reach the surface.

A drawback of methods that make density measurements is that gas must be present in sufficient quantities to affect the density of the mud, so that dissolved gas that may be a precursor to a gas kick would not register with conventional density measuring devices.

They also require the use of a radioactive source—a safety hazard during drilling operations.

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