EP0339825A1 — Apparatus for data transmission in a borehole

Claim 1

Independent Claim 247 words

Boring apparatus including a boring tool (12, 50) designed to bore a hole (18) through the ground, a drill string (14, 53) connected at one end with said boring tool (12, 50) and extending from there to ground level through the hole being formed, means (16) for urging the boring tool (12, 50) and drill string (14, 53) forward as the hole is being made, information providing means (26, 58) carried by said boring tool (12, 50) for generating an AC signal containing certain inground information between a pair of output terminals (28, 30; 56, 60), and transmitting means for transmitting said information containing signal to an above-ground location (38) wherin said information can be extracted from the signal, characterised in that said transmitting means includes the ground surrounding the boring tool as the latter moves through the hole being formed, at least a section of said drill string (14, 53) which is sufficiently electrically conductive to carry said signal, means for electrically connecting one (28, 56) of said pair of output terminals of said information providing means (26, 58) to said section of said drill string (14, 53), and means (32, 42, 44, 52) electrically insulated from said drill string section (14, 53) for connecting the other (30, 60) of said output terminals to said ground surrounding said boring tool (12, 50), whereby said drill string section (14, 53) serves to carry said AC signal and said surrounding ground is used as a signal return path.

Claim 2

Dependent Claim 247 words

Boring apparatus including a boring tool (12, 50) designed to bore a hole (18) through the ground, a drill string (14, 53) connected at one end with said boring tool (12, 50) and extending from there to ground level through the hole being formed, means (16) for urging the boring tool (12, 50) and drill string (14, 53) forward as the hole is being made, information providing means (26, 58) carried by said boring tool (12, 50) for generating an AC signal containing certain inground information between a pair of output terminals (28, 30; 56, 60), and transmitting means for transmitting said information containing signal to an above-ground location (38) wherin said information can be extracted from the signal, characterised in that said transmitting means includes the ground surrounding the boring tool as the latter moves through the hole being formed, at least a section of said drill string (14, 53) which is sufficiently electrically conductive to carry said signal, means for electrically connecting one (28, 56) of said pair of output terminals of said information providing means (26, 58) to said section of said drill string (14, 53), and means (32, 42, 44, 52) electrically insulated from said drill string section (14, 53) for connecting the other (30, 60) of said output terminals to said ground surrounding said boring tool (12, 50), whereby said drill string section (14, 53) serves to carry said AC signal and said surrounding ground is used as a signal return path.

Claim 3

Dependent Claim 76 words

Apparatus according to Claim 1, characterised in that said boring tool (12) utilises a drilling fluid (22) during formation of said hole (18) such that the drilling fluid (22) surrounds the tool (12) within the hole (18), said electrically insulated means (32) being connected to said other output terminal (30) and positioned to contact directly the drilling fluid (22) surrounding the boring tool (12) thereby to connect said other output terminal (30) to the surrounding ground.

Claim 4

Dependent Claim 57 words

Apparatus according to Claim 1, characterised in that said boring tool (12′) includes an outer body section electrically insulated from said drill string section (14), said other output terminal (30) being electrically connected with said outer body section (12′) which serves as said electrically insulated means for connecting said other output terminal (30) to the surrounding ground.

Claim 5

Dependent Claim 38 words

Apparatus according to Claim 3, characterised in that said drill string (14) includes a second section electrically insulated from said first-mentioned section (14A), said other output terminal (34) being electrically connected directly to said second drill string section.

Claim 6

Dependent Claim 49 words

Apparatus according to Claim 3, characterised in that said outer body section (52˝) of said tool (50) includes a sufficiently large outer surface so as to capacitively couple said other output terminal to the surrounding ground in the event the ground is very dry or very low in conductivity.

Claim 7

Dependent Claim 29 words

Apparatus according to Claim 1, characterised in that said electrically insulated means (44) includes means connected to said other output terminal (30) and engaging the wall defining said hole.

Claim 8

Dependent Claim 19 words

Apparatus according to any preceding claim, characterised in that said information providing means (26, 58) comprises a rotation transducer.

Claim 9

Dependent Claim 29 words

Apparatus according to any preceding claim, characterised by processing means (36, 38) located at said above ground location for acting on said AC signal and extracting said information therefrom.

Claim 10

Dependent Claim 27 words

Apparatus according to Claim 8, characterised in that said processing means includes inductive coupling means (36) located around said drill string (14) at said above ground location.

Apparatus for data transmission in a borehole

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