Oil level sensor system and method for oil wells

Claim 1

A system for controlling production in an oil well wherein the oil well comprises a cased borehole, tubing within said cased borehole, a pump at the lower end of the tubing arranged to pump oil into said tubing, sucker-rods extending down into said tubing for mechanically activating said pump, means for causing reciprocation of the sucker-rods; a controller for activating the means for causing reciprocation; first sensing means secured to the outer surface of the tubing near the lower end thereof comprising a radioactive source spaced from a radioactivity detector such that oil at that level will fill the said space, means associated with said radioactivity detector for counting the output of the detector and establishing an "off signal" when the frequency of the output is indicative of no oil in the said space; means for converting the "off signal" into a sonic signal directed up the borehole; an electrical power supply for energizing means for sensing, means for counting and means for converting; receiving means at the top of the borehole for detecting the acoustical representation of the "off signal" and transmitting it as an electrical signal to said controller whereby said controller stops the means for causing reciprocation.

Claim 2

A system for controlling production in an oil well wherein the oil well comprises a cased borehole, tubing within said cased borehole, a pump at the lower end of the tubing arranged to pump oil into said tubing, sucker-rods extending down into said tubing for mechanically activating said pump, means for causing reciprocation of the sucker-rods; a controller for activating the means for causing reciprocation; first sensing means secured to the outer surface of the tubing near the lower end thereof comprising a radioactive source spaced from a radioactivity detector such that oil at that level will fill the said space, means associated with said radioactivity detector for counting the output of the detector and establishing an "off signal" when the frequency of the output is indicative of no oil in the said space; means for converting the "off signal" into a sonic signal directed up the borehole; an electrical power supply for energizing means for sensing, means for counting and means for converting; receiving means at the top of the borehole for detecting the acoustical representation of the "off signal" and transmitting it as an electrical signal to said controller whereby said controller stops the means for causing reciprocation.

Claim 4

The system according to claims 1 or 2 wherein the radioactive source comprises Cesium 137.

Claim 5

The system according to claims 1 or 2 wherein the first and second sensing means comprising a digital circuit for analyzing the frequency of the radioactivity and for generating a signal indicative of the presence or not of oil at the level of the detector.

Claim 7

The system according to claims 1 or 2 wherein the acoustical signals produced by the first and second sensors are of different frequencies.

Claim 8

The system according to claims 1 or 2 wherein the electrical power supply is rechargeable and means are provided for charging the power supply, said recharging means comprising a spring biased element that reciprocates in response to a change in pressure in the production tubing with each pump cycle, means attached to said element for causing relative movement of the magnetic field and a pick up coil in which the charging current is induced.

Claim 12

A method for controlling production in an oil well wherein the oil well comprises a cased borehole, tubing within said cased borehole, a pump at the lower end of the tubing arranged to pump oil into said tubing, sucker-rods extending down into said tubing for mechanically activating said pump, means for causing reciprocation of the sucker-rods comprising the steps for: sensing radioactivity emitted from a first radioactive source near the lower end of the tubing and generating an "off signal" when the frequency of the radioactivity is indicative of no oil at the level of the radioactive source; converting the "off signal" into a sonic signal directed up the borehole; detecting the acoustical representation of the "off signal" at the well head and stopping the reciprocation of the sucker-rods in response to said "off signal".

Claim 13

A method for controlling production in an oil well wherein the oil well comprises a cased borehole, tubing within said cased borehole, a pump at the lower end of the tubing arranged to pump oil into said tubing, sucker-rods extending down into said tubing for mechanically activating said pump, means for causing reciprocation of the sucker-rods comprising the steps for: sensing radioactivity emitted from a first radioactive source near the lower end of the tubing and generating an "off signal" when the frequency of the radioactivity is indicative of no oil at the level of the radioactive source; converting the "off signal" into a sonic signal directed up the borehole; detecting the acoustical representation of the "off signal" at the well head and stopping the reciprocation of the sucker-rods in response to said "off signal".