Boring or penetrating the earth – With signaling – indicating – testing or measuring – Tool position direction or inclination measuring or...
Reexamination Certificate
1999-01-14
2001-01-30
Pezzuto, Robert E. (Department: 3671)
Boring or penetrating the earth
With signaling, indicating, testing or measuring
Tool position direction or inclination measuring or...
C175S024000, C175S076000
Reexamination Certificate
active
06179066
ABSTRACT:
BACKGROUND OF THE INVENTION
1.Field of the Invention
The present invention relates generally to measurement-while-drilling systems and more particularly to a stabilization system on a drill string that improves the quality of formation evaluation measurements.
2. Background of the Art
To obtain hydrocarbons such as oil and gas, a drilling assembly (also referred to as the “bottom hole assembly” or the “BHA”) carrying a drill bit at its bottom end is conveyed into the wellbore or borehole. The drilling assembly is usually conveyed into the wellbore by a coiled-tubing or a drill pipe. In the case of the coiled-tubing, the drill bit is rotated by a drilling motor or “mud motor” which provides rotational force when a drilling fluid is pumped from the surface into the coiled-tubing. In the case of the drill pipe, it rotated by a power source (usually an electric motor) at the surface, which rotates the drill pipe and thus the drill bit.
Bottom hole assemblies generally include several formation evaluation sensors for determining various parameters of the formation surrounding the BHA during the drilling of the wellbore. Such sensors includes sensors for measuring the resistivity, dielectric constant, water saturation, porosity, permeability, density and other properties of the formation surrounding the wellbore. Such bottom hole assemblies also include devices to determine the BHA inclination and azimuth, pressure sensors, temperature sensors, gamma ray devices, and devices that aid in orienting the drill bid a particular direction and to change the drilling direction. Acoustic and resistivity devices have been proposed for determining bed boundaries around and in some cases in front of the drill bit.
One or more stabilizers are disposed on the drilling assembly to stabilize the drilling assembly against excessive vibrations of the drilling assembly caused by the cutting action of the drill bit. Stabilizers are usually pads that extend outward from the drilling assembly and come in contact with the borehole. Independently operated pads or ribs that can selectively apply force to the borehole inside have been proposed for altering the drilling direction, i.e., for geosteering the drill bid for directional drilling.
However, certain measurements relating to the formation evaluation parameters, such as nuclear magnetic resonance (“NMR”) measurements, are very sensitive to any distortion of the magnetic field in the formation, which occur due to the movement of the magnets caused by normal vibrations of the BHA, even when commonly known multiple stabilizers are used. It is thus desirable to have a stabilization system that would automatically stabilize at least a section of the drill string containing sensors whose quality of measurement are susceptible to vibrations below a predetermined level during the drilling of the wellbore. The present invention addresses the above-noted need and provides a stabilization system for measurement-while-drilling sensors.
SUMMARY OF THE INVENTION
The present invention provides a drilling assembly with a stabilization system that stabilizes at least a section of the drilling assembly as a function of one or more downhole measured parameters or parameters of interest. One or more sensors carried by the drilling assembly measure the desired parameters of interest and a control system controls the stabilizer system in response to one or more determined parameters of interest to provide desired stabilization of a section of the drilling assembly. Measurement-while-drilling sensors whose measurements are affected by the parameters of interest are preferably disposed in the stabilized section.
In one embodiment, the stabilization system includes at least two axially spaced apart stabilizers. Each such stabilizer includes a plurality of independently adjustable members that radially extend from the drilling assembly to exert force on the wellbore inside. A control circuit processes the signals from the sensors and in response thereto causes a power unit to independently adjust the force applied by the adjustable members so as to maintain a parameter of interest below a predetermined value. The measurement-while-drilling sensors take measurements while the stabilization system is activated, which may be during the drilling of the wellbore or during retrieval of the drilling assembly from the wellbore. In an alternative embodiment, the stabilization system includes only one stabilizer that may contain a plurality of independently adjustable members.
A packer element of sufficient length that exerts force on the wellbore inside may be used as the extendable member of the stabilizer. One or more such packers may be used to stabilize the desired section of the drilling assembly or the drill string. In, yet another embodiment, the stabilization system may use one or more passive stabilizers, wherein a spring, a retractable plunger or piston arrangement or any other device continuously urges an extendable member against the wellbore inside to provide the desired stabilization.
REFERENCES:
patent: 5339036 (1994-08-01), Clark et al.
patent: 5341886 (1994-08-01), Patton
patent: 5507353 (1996-04-01), Pavone
patent: 5603386 (1997-02-01), Webster
patent: 0594419A1 (1994-04-01), None
patent: 2305196A (1996-09-01), None
Nasr Hatem
Oppelt Joachim
Wisler Macmillan M.
Baker Hughes Incorporated
Madan Mossman & Sriram P.C.
Pezzuto Robert E.
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