High voltage x-ray generator and related oil well formation analysis apparatus and method

• US 7,991,111 B2
• Filed: 09/14/2010
• Issued: 08/02/2011
• Est. Priority Date: 12/15/2006
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Wraight, Peter, Groves, Joel L., Becker, Arthur J., Stoller, Christian
• Primary Examiner(s): Kiknadze; Irakli
• Application Number:
  US12/882,005
• Publication Number:
  US 20110002443A1
• Time in Patent Office: 322 Days
• Field of Search: 378/89, 378/140, 378/101, 378/54, 378/119
• US Class Current: 378/54
• CPC Class Codes: H01J 2235/0233 High tension
• CPC Class Codes: H01J 2235/06 Cathode assembly
• CPC Class Codes: H01J 2235/163 shaped for a particular application
• CPC Class Codes: H01J 35/06 Cathodes
• CPC Class Codes: H05G 1/02 Constructional details
• CPC Class Codes: H05G 1/10 Power supply arrangements for feeding the X-ray tube supply circuits with converters in general H02M; supply circuits for emitters and amplifiers H04B1/16 - H04B1/1623

Abstract

An apparatus and method for determining the density and other properties of a formation surrounding a borehole using a high voltage x-ray generator. One embodiment comprises a stable compact x-ray generator capable of providing radiation with energy of 250 keV and higher while operating at temperatures equal to or greater than 125° C. In another embodiment, radiation is passed from an x-ray generator into the formation; reflected radiation is detected by a short spaced radiation detector and a long spaced radiation detector. The output of these detectors is then used to determine the density of the formation. In one embodiment, a reference radiation detector monitors a filtered radiation signal. The output of this detector is used to control at least one of the acceleration voltage and beam current of the x-ray generator.

Claims

1. A compact x-ray generator comprising:

an electron emitter;

a target;

a high voltage power supply operably coupled to one of the electron emitter and the target;

wherein said x-ray generator provides radiation with energy greater than or equal to 250keV; and

said x-ray generator operates at temperatures greater than or equal to 125°

C.; and

a filter to attenuate radiation from the target below 250 keV;

wherein at least one of the electron emitter and the target are grounded, such that a voltage differential of at least 250kV exists between the electron emitter and the target.

2. The compact x-ray generator as defined in claim 1 wherein the high voltage power supply is operably coupled to the electron emitter and the target is grounded, such that a voltage differential of at least 250kV exists between the electron emitter and the target.

3. The compact x-ray generator as defined in claim 1 wherein the high voltage power supply is operably coupled to the target and the electron emitter is grounded, such that a voltage differential of at least 250kV exists between the electron emitter and the target.

4. The compact x-ray generator as defined in claim 1 wherein the filter comprises a thickness of the target selected to attenuate emission of radiation below 250 keV.

5. The compact x-ray generator as defined in claim 1 wherein the filter comprises a copper window disposed in a radiation path from the target in a tube enclosing the electron emitter and the target.

6. The compact x-ray generator as defined in claim 1, wherein the high voltage power supply comprises a Cockcroft-Walton type voltage generator.

7. The compact x-ray generator as defined in claim 1, said compact x-ray generator being conveyed on a wireline.

8. The compact x-ray generator as defined in claim 1, said compact x-ray generator being conveyed on a drillstring, coiled tubing, wired drill pipe, or any other logging-while-drilling method of conveyance.

9. The compact x-ray generator as defined in claim 1, said compact x-ray generator being configured for permanent installation in a monitoring well.