Method and apparatus for borehole fluid influx detection

Claim 1

Apparatus for detection of fluid influx in a borehole in which a drill string is positioned, the drill string cooperating with the wall of the borehole to define an annulus, and in which drilling fluid is circulated from the surface through the interior of the drill string and into the annulus back to the surface, the apparatus for detection of fluid influx including: means for generating a coherent energy signal at a downhole location and propagation said signal as a primary signal in the drilling fluid in said drill string and as a secondary signal in the drilling fluid in said annulus; means for detecting said primary signal; means for detecting said secondary signal; means for measuring the difference between at least one selected parameter of said primary signal with the same selected parameter of said secondary signal, wherein the entire drill string is a reference with which to make a differential comparison to the entire annulus; and means for determining changes in said measured difference between the selected parameter of said primary and secondary signals wherein fluid influx into the annulus is determined.

Claim 12

A method of monitoring a well drilling operation for the presence of fluid influx into the bore hole, the drilling operation comprising the use of a tubular drill pipe having a diameter which is less than the diameter of the borehole being formed wherein a generally annular space is defined between the drill pipe and the borehole, said monitoring being performed during the drilling of the borehole, the method comprising the steps of: pumping drilling fluid down the interior of the drill pipe, the drilling mud exiting at or near the base of the drill pipe and returning to the surface via the generally annular space between the drill pipe and borehole; modulating the flow of drilling fluid in the drill pipe at a point near the bottom of the borehole, the modulating of the drilling fluid flow producing pressure pulses therein; sensing the pressure pulses in the drilling fluid returning to the surface via the said annular space; measuring the difference between one selected parameter of the pressure pulses in the interior of the drill pipe with the same selected parameter of the pressure pulses in the annular space wherein the entire drill pipe is a reference with which to make a differential comparison to the entire annular space; and determining changes in said measured difference between the selected parameters of said primary and secondary signals wherein fluid influx into the annulus is determined.

Claim 13

A method of monitoring a well drilling operation for the presence of fluid influx into the bore hole, the drilling operation comprising the use of a tubular drill pipe having a diameter which is less than the diameter of the borehole being formed wherein a generally annular space is defined between the drill pipe and the borehole, said monitoring being performed during the drilling of the borehole, the method comprising the steps of: pumping drilling fluid down the interior of the drill pipe, the drilling mud exiting at or near the base of the drill pipe and returning to the surface via the generally annular space between the drill pipe and borehole; modulating the flow of drilling fluid in the drill pipe at a point near the bottom of the borehole, the modulating of the drilling fluid flow producing pressure pulses therein; sensing the pressure pulses in the drilling fluid returning to the surface via the said annular space; measuring the difference between one selected parameter of the pressure pulses in the interior of the drill pipe with the same selected parameter of the pressure pulses in the annular space wherein the entire drill pipe is a reference with which to make a differential comparison to the entire annular space; and determining changes in said measured difference between the selected parameters of said primary and secondary signals wherein fluid influx into the annulus is determined.