METHOD FOR PRODUCING RETORTING CHANNELS IN SHALE DEPOSITS

• US 3,696,866 A
• Filed: 01/27/1971
• Issued: 10/10/1972
• Est. Priority Date: 01/27/1971
• Status: Expired due to Term

• Current Assignee: Julian R. Dryden
• Original Assignee: Julian R. Dryden
• Inventors: Dryden, Julian R.
• Application Number:
  US05/110,090
• Time in Patent Office: 622 Days
• US Class Current: 166/248
• CPC Class Codes: E21B 43/2401 by means of electricity

Abstract

A method for producing in situ retorting channels in subterranean shale deposits. Electro-pneumatic treatment is used for lean shale. Additional electro-chemical treatment is required for rich shale.

Claims

1. A method for producing an in situ retorting channel in a subterranean shale deposit comprising the steps of:

drilling two spaced wellbores into a shale bed, electrically forming a charred conducting path through an impermeable portion of the shale between the wellbores, removing a substantial percentage of the material along the charred conducting path to form a permeable retortIng channel.

2. A method for producing an in situ retorting channel in a subterranean shale deposit as claimed in claim 1, in which the step of removing includes:

electrically forming a molten, fluid core along the conducting path, and forcing the fluid core to flow along the path and out of the surrounding shale, leaving an open retorting channel between the wellbores.

3. A method for producing an in situ retorting channel in a subterranean shale deposit as claimed in claim 1, in which the step of removing includes:

electrolyzing an oxygen bearing electrolyte in one of the spaced wellbores so that free oxygen forms at the intersection of the electrolyte and the conducting path, and applying a sufficiently high voltage across the conducting path to cause a combustion front to advance between the wellbores, forming a burned out, permeable retorting channel.

4. A method for producing an in situ retorting channel in a subterranean shale deposit as claimed in claim 3, including the additional steps of:

electrically forming a molten, fluid core along the burned out, permeable channel, and forcing the fluid core to flow along the channel and out of the surrounding shale, leaving an open retorting channel between the wellbores.

5. A method for producing an in situ retorting channel in a subterranean shale deposit as claimed in claim 2 in which the step of electrically forming a charred conducting path further includes:

positioning first and second conducting electrodes, respectively, in each wellbore in electrical contact with the shale deposit, and applying a high electrical voltage across the first and second electrodes to cause electrical current flow through the shale deposit on a conducting path between the first and second electrodes, the voltage and resulting current flow having sufficient intensity to ultimately melt the shale along the conducting path and form a viscous, molten, fluid core, and the step of forcing further includes;

Establishing a pressure differential between the spaced wellbores to cause the molten fluid core to flow out of the surrounding shale and into one of the wellbores.

6. A method for producing an in situ retorting channel in a subterranean shale deposit as claimed in claim 1 in which the step of electrically forming a charred conducting path further includes:

positioning first and second conducting electrodes, respectively, in each wellbore in electrical contact with the shale deposit, applying a high electrical voltage across the first and second electrodes to cause electrical current flow through the shale deposit on a conducting path between the first and second electrodes, and removing the applied voltage after increased current flow shows that a conducting path has been established between the first and second electrodes, and the step of removing further includes;

removing one electrode from one of the wellbores, filling the one wellbore to a level above the conducting path with an oxygen bearing electrolyte, immersing a third electrode in the electrolyte, applying a high d.c. electrical voltage between the third electrode and the other electrode to cause electrolysis of the oxygen bearing electrolyte, with the polarity of the electrodes such that free oxygen forms at the intersection area of the conducting path and the electrolyte, whereby continued application of the high d.c. voltage causes a combustion front to advance along the conducting path toward the other electrode, and interrupting the high d.c. voltage after decreased electrical resistance of the core indicates that combustion has progressed a sufficient distance.

7. A method for producing an in situ retorting channel in a subterranean shale deposit as claimed in claim 6 including, following the step of interrupting, the additional steps of:

removing the third electrode and electrolyte from the one wellbore, re-positioning the one electrode in its approximate origiNal position within the one wellbore, applying a high electrical voltage across the first and second electrodes to cause electrical current flow through the shale deposit on the conducting path between the first and second electrodes, the voltage and resulting current flow having sufficient intensity to ultimately melt the shale along the conducting path and form a viscous, molten fluid core. electrically forming a molten, fluid core along the conducting path, and establishing a pressure differential between the spaced wellbores to cause the molten fluid core to flow out of the surrounding shale and into one of the wellbores.