Method and apparatus for borehole fluid influx detection

#(1) Field of the Invention

#The present invention relates to exploration for sources of hydrocarbon fuel and particularly to enhancing the safety of oil and gas well drilling procedures. More specifically, this invention is directed to apparatus and methods for detection of the infusion of gas into a borehole and especially to apparatus and methods for a gas infusion detection system which is continuously operable during drilling for blowout protection.

#(2) Description of the Prior Art

#Referring now to the several Figures of the drawings, wherein like reference numerals refer to like elements in the several Figures:

#FIG. 1 is a generalized schematic view of borehole drilling apparatus employing the present invention;

#FIG. 2 is a schematic view of a downhole energy source;

#Referring to FIG. 1, a drilling apparatus has a derrick 10 which supports a drill string or drill stem, indicated generally at 12, which terminates in a drill bit 14. As is well known in the art, the entire drill string may rotate, or the drill string may be maintained stationary and only the drill bit rotated. The drill string 12 is made up of a series of interconnected pipe segments, with new segments being added as the depth of the well increases. The drill string is suspended from a moveable block 16 of a winch 18 and crown block 19, and the entire drill string of the disclosed apparatus is driven in rotation by a square kelly 20 which slideably passes through and is rotatably driven by the rotatable table 22 at the foot of the derrick. A motor assembly 24 is connected to both operate winch 18 and drive rotary table 22.

#The lower part of the drill string may contain one or more segments 26 of larger diameter than the other segments of the drill string. As is well known in the art, these larger diameter segments may contain sensors and electronic circuitry for preprocessing signals provided by the sensors. Drill string segments 26 may also house power sources such as mud driven turbines which drive generators, the generators in turn supplying electrical energy for operating the sensing elements and any data processing circuitry. An example of a system in which a mud turbine, generator and sensor elements are included in a lower drill string segment may be seen from U.S. Pat. No. 3,693,428 to which reference is hereby made.

#Drill cuttings produced by the operation of drill bit 14 are carried away by a mud stream rising up through the free annular space 28 between the drill string and the wall 30 of the well. That mud is delivered via a pipe 32 to a filtering and decanting system, schematically shown as tank 34. The filtered mud is then drawn up by a pump 36, provided with a pulsation absorber 38, and is delivered via line 40 under pressure to a revolving injector head 42 and thence to the interior of drill string 12 to be delivered to drill bit 14 and the mud turbine in drill string segment 26.