Mud level monitor

In apparatus for well drilling according to the rotary method in which liquid base drilling fluid is pumped down the bore of the well being drilled, through the drill bit and back up the well bore, apparatus for monitoring the level of drilling fluid in the return line comprising:

• an open window in the top of the return line,
• said line being positioned with the windowed portion above the level of the fluid in the path of drilling fluid from said floor to the reservoir,
• an ultrasonic transducer mounted above the window,
• means for activating said transducer to send a beam of ultrasound from the transducer to the air-drilling fluid interface in the fluid return line,
• means to measure the transit time of the beam from the window to the interface and back to the window to give information as to the level of the interface in the line,
• means to generate timing signals during such transit,
• countdown accumulator means connected to the last said means to countdown with said signals during such transit to give information as to the height of the air-drilling fluid interface in the return line,
• means to compare the count in the accumulator with a predetermined count,
• means to give an alarm when the accumulator count departs from the datum count by a predetermined amount, and
• means to record the accumulator count and turn off the alarm and reset the datum count equal to the accumulator count.

In well drilling according to the rotary method in which drilling mud is pumped down the bore of the well being drilled, through the drill bit and back up the well bore to a return line extending laterally from the well bore and thence to a reservoir from which it is again pumped, the method of monitoring the drilling mud comprising:

• with the return line leveled to within X degrees of horizontal, where X is the cone angle of a beam produced by a sonar transducer, flowing the drilling mud in the return line at a normal rate sufficient to leave an air space above the level of the drilling mud in the return line, and
• measuring the level of drilling mud in the return line by sonar employing said transducer placed out of the path of mud flow in said return line, above and directed through a window in the top of the return line, at a height low enough for the beam reflected from the air-mud interface when at lowest level to pass through the window, and high enough to allow the transducer's natural oscillation following a transmission burst to die out before reception of the burst reflection from the air-mud interface when at highest level,
• the path of travel, between said transducer and said window, of acoustic bursts emitted by the transducer during said measuring, being shielded from the air outside the return line without reflecting the beam as the burst travels from transducer to window nor impeding the flow of mud through said return line,
• whereby mud flowing in said return line will tend to equilibrate the air temperature in said path without escape of drilling mud or interference with such measuring.

Level sensing apparatus comprising:

• an imperforate shield tube, narrower than it is long and open at one end,
• an electro-acoustic ultra-sonic transducer mounted at the other end of the tube and positioned to beam ultra sound inside the tube toward the open end of the tube,
• said apparatus being useful for sensing the mud level in the return line in a well drilling system employing the rotary method in which mud is pumped down the bore of a well being drilled, through the drill bit and back up the well bore to a return line extending laterally from the well bore and thence to a reservoir from which it is again pumped,
• said apparatus being characterized by:
• (1) said open end of the tube being adapted to be secured to such return line in fluid tight communication with a window therein,
• (2) said transducer producing a beam directed toward said open end of the tube, which beam is narrower than said open end, avoiding reflections of said beam from the sides of the tube as it travels from said transducer inside said tube and out said open end,
• (3) said transducer having a radius less than the radius of the open end of said tube by a distance R, and
• (4) said transducer producing a beam having a cone angle x where (1) tan (x/2) is less than R, (1) being the length of the tube from the transducer to the open end of the tube.

Apparatus for monitoring drilling mud employed in well drilling by the rotary system, said apparatus comprising:

• a sonar transducer for producing and acoustic beam,
• a lateral mud return line,
• said line being positioned within X degrees of horizontal where X is the cone angle of the beam of said sonar transducer,
• said line having an open window in the upper side thereof, and
• an air filled tube extending transversely of the line with one end of the tube in open communication with the line through the window,
• the axis of said tube being perpendicular to the line axis,
• said transducer being positioned in the other end of said tube to direct its beam through said window without the beam reflecting from the sides of the tube,
• the width of said beam where it passes through the open end of said tube being narrower than said open end of said tube.