Device for and method of sensing conditions in a well bore

Means for continuously monitoring drilling fluids in a well bore adjacent the drilling fluid return line comprising:

• a continuous radiative source mounted adjacent the return line to emit a radioactive signal across the well bore;
• means for detecting said radioactive signal being positioned opposite said source and wherein the magnitude of any detected signals is inversely related to the density of the drilling fluids;
• electrical conduit means mounted with said detecting means for electrically transmitting any detected signals indicating the density of such drilling fluids;
• metering means mounted with said electrical means for indicating the absence of drilling fluids, and if such drilling fluids are present, for indicating the density of such drilling fluids;
• a well head structure positioned over the well bore at the surface, said well head structure defining a passage communicating with said well bore, said well head further defining an outlet communicating with said passage for removing the drilling fluids from the well bore during drilling operations and a fill inlet communicating with said passage for adding drilling fluids to the well bore, and
• said detecting means mounted with said well head structure for indicating when the level of the drilling fluids is beneath the outlet which indicates the loss of drilling fluid circulation.

A method of sensing and correcting a condition of drilling fluid downhole in a well bore, comprising the steps of:

• emitting a radioactive signal from a radioactive source positioned at the surface of the well bore across the well bore and a drilling pipe positioned therein;
• detecting said radioactive signal with apparatus positioned opposite the radioactive source;
• measuring the intensity and frequency of occurrence of each detected signal with electrical apparatus;
• providing an electrical signal from said electrical apparatus indicating the presence or absence of drilling fluids at the surface of the well bore;
• and
• adding drilling fluid to said well bore in response to electrical detection of a predetermined absence of drilling fluid at the surface of said well bore.

A method of sensing and correcting a condition of drilling fluid downhole in a well bore, comprising the steps of:

• emitting a radioactive signal from a radioactive source positioned at the surface of the well bore across the well bore and a drilling pipe positioned therein;
• detecting said radioactive signal with apparatus positioned opposite the radioactive source;
• measuring the intensity and frequency of occurrence of each detected signal with electrical apparatus;
• providing an electrical signal from said electrical apparatus indicating the presence or absence of drilling fluids at the surface of the well bore;
• emitting a gamma ray signal from said radioactive source, mounting an ion chamber opposite said source at the surface of the well bore, and mounting a gamma ray detector with said chamber for providing an electrical signal in proportion to the intensity and frequency of occurrence of each detected signal;
• and
• using the provided electrical signal to activate a pump when the absence of drilling fluids at the surface of the bore hole is indicated, said pump adding drilling fluids to the well bore when activated.