Method and apparatus for transmitting information in a borehole employing signal discrimination

For use in conducting measurement operations in drill holes, the method of obtaining useful information by selectively filtering data signals carrying said information from mixed signals representing a mixture of said data signals and of interfering signals which tend to obscure said information, wherein said interfering signals have characteristic shape, said method comprising:

• receiving said mixed signals with a single pressure transducer located at a single location;
• producing control signals representing said characteristic shape;
• and
• converting said mixed signals and said control signals into resultant signals representative of said useful information.

For use in conducting measurement operations in drill holes, the method of obtaining useful information by selectively filtering data signals carrying said information from mixed signals representing a mixture of said data signals and of interfering signals which tend to obscure said information, said data signals being arranged in a coded sequence of individual signals, said sequence being arranged in accordance with a code representing said useful information and wherein said individual signals and said interfering signals have characteristic shapes respectively, one of said characteristic shapes being distinguishable from the other characteristic shape, said method comprising:

• receiving said mixed signals;
• producing two control signals representing said characteristic shapes;
• and
• converting said mixed signals and said two control signals into resultant signals representative of said useful information.

An apparatus for obtaining useful information from a relatively inaccessible location in an earth borehole, said apparatus comprising:

• generating means at said relatively inaccessible location for generating data signals carrying said useful information, said data signals being transmitted to a relatively accessible location near the earth's surface as a succession of individual signals having a characteristic shape, said data signals transmitted to said relatively accessible location being obscured by interfering signals;
• receiving means at said relatively accessible location for receiving said data signals and said interfering signals and for producing mixed signals representing a mixture of said received signals;
• controlling means for producing control signals representative of said characteristic shape;
• and
• information producing means for receiving at its input said mixed signals and said control signals and for translating said received signals into output signals representing said useful information.

An apparatus for obtaining useful information from a relatively inaccessible location in an earth borehole, said apparatus comprising:

• generating means at said relatively inaccessible location for generating data signals carrying said useful information, said data signals being transmitted to a relatively accessible location and wherein they are obscured by interfering signals, said interfering signals being characterized by a distinguishable shape;
• receiving means at said relatively accessible location for receiving said data signals and said interfering signals and for producing mixed signals representing a mixture of said received signals, said receiving means comprising a single transducer located at a single location;
• controlling means for producing control signals representative of said distinguishable shape;
• and
• information producing means for receiving at its input said mixed signals and said control signals and for translating said received signals into output signals representing said useful information.

For use in conducting measurement operations in drill holes, the method of obtaining useful downhole information by selectively filtering data signals carrying said information from mixed signals resulting from a mixture of said data signals and of interfering signals, said data signals being arranged in a coded sequence of individual signals, said sequence being arranged in accordance with a code representing said useful information and wherein said individual signals have a characteristic shape, said method comprising:

• a) introducing said mixed signals into an input of a digital filter;
• b) selecting the memory function of said digital filter so that using said input and said memory function the output of said digital filter produces output signals representative of an approximation of said individual signals;
• and
• c) producing an indication of said useful information from said individual signals.