Excavating deposits from an underground formation layer

Abstract

Deposits, such as coal, tar sand, heavy crude oil and/or minerals are excavated from an underground formation layer ( 4 ) by:—inserting a chain cutter string ( 11 ) into a 1st section ( 8, 9 ) and a control cable ( 12 ) into a 2nd section ( 10 ) of a T-, V-, U-, or L-shaped channel assembly ( 8, 9, 10 ) traversing the layer (4);—connecting the control cable ( 12 ) to the chain cutter string ( 11 ) at a branchpoint ( 13 ) of said 1st & 2nd sections ( 8, 9 & 10 ); and—pulling the chain cutter string ( 11 ) in a continuous or oscillating manner through the first section ( 8,9 ) while continuously pulling the control cable ( 12 ), such that the chain cutter string ( 11 ) carves deposits from the layer ( 4 ) and the control cable ( 12 ) optimizes the performance and reduces the risk of breakage of the chain cutter string ( 11 ).

1 . A method of excavating deposits from an underground formation layer, comprising:
 drilling a well assembly, which penetrates the underground formation layer at a first, a second and a third location, which locations are triangularly spaced;   drilling from these locations a channel assembly that traverses the formation layer and interconnects the locations;   inserting a chain cutter string into a first section of the channel assembly that is located between the first and second locations;   inserting a chain cutter control cable from the third location into a second section of the channel assembly;   connecting the chain cutter control cable to the chain cutter string at a branchpoint of the first and second sections of the channel assembly;   pulling the chain cutter string through the first section of the channel assembly while exerting a lateral force to the chain cutter string by the chain cutter control cable such that the chain cutter string is pressed against the wall of the first section of the channel assembly and is thereby induced to carve deposits from the underground formation layer; and   flushing carved out deposits through the channel assembly and the well assembly.   
     
     
         2 . The method of  claim 1 , wherein during an initial or subsequent moment of execution of the method:
 the first section of the channel assembly extends as a substantially straight line between the first and the second locations;   the second section of the channel assembly extends from the third location to the branchpoint, which is formed by a midpoint of the first section of the channel assembly, so that the channel assembly substantially has a T-shape; and   the chain cutter string is pulled through the first section while the chain cutter string is pressed against the sidewall of the first section by the chain cutter control cable and is pulled by the chain cutter control cable towards the third location.   
     
     
         3 . The method of  claim 1 , wherein during an initial or subsequent moment of execution of the method:
 the first section of the channel assembly has a V-shape and has a first leg, which extends from the first location towards the third location and a second leg, which extends from the third location towards the second location and the chain cutter string extends through the first and second legs of the V-shaped first section of the channel assembly;   the chain cutter control cable is connected to the chain cutter string at the third location, which location forms the branchpoint of the first and second sections of the channel assembly; and   the chain cutter string is pulled through the first section.   
     
     
         4 . The method of  claim 3 , wherein the chain cutter control cable is gradually slackened while the chain cutter string is pulled through the first section of the channel assembly, thereby controlling the pressure between the chain cutter string and the sidewall of the first section. 
     
     
         5 . The method of  claim 1 , wherein the chain cutter string is pulled sequentially from the first to the second location and from the second to the first location to mine deposits from the underground formation layer. 
     
     
         6 . The method of  claim 1 , wherein the chain cutter string is an endless chain, which carries a series of cutting elements and is moved in a continuous motion through the first section of the channel assembly to mine deposits from the underground formation layer. 
     
     
         7 . The method of  claim 6 , wherein the cutting elements are selected from the group of mechanical cutters and/or hydraulic jets. 
     
     
         8 . The method of  claim 1 , wherein the method is used to create at least one high permeability plane in a viscous crude oil or tight gas containing formation and/or in a formation comprising a flow barrier, such as a shale layer with a low permeability. 
     
     
         9 . The method of  claim 1 , wherein the method is used to mine hydrocarbon deposits selected from the group of coal, oil shale, tar sand and heavy crude from the subsurface formation layer. 
     
     
         10 . The method of  claim 9 , wherein after mining a deposit from a first triangular section of the subsurface formation layer between the first, second and third locations an additional wellbore or well section is drilled such that it penetrates the underground formation layer at a triangularly spaced fourth location relative to a pair of the first, second and third locations, and deposits are mined from a second triangular section between the fourth location and said pair of the first, second and third locations. 
     
     
         11 . The method of  claim 10 , wherein after mining a deposit from the second triangular section of the subsurface formation layer a fifth wellbore or section is drilled such that it penetrates the underground formation layer at a fifth triangularly spaced location relative to the third and fourth locations, and deposits are mined from a third triangular section between the third, fourth and fifth locations. 
     
     
         12 . The method of  claim 11 , wherein after mining a deposit from an n-th triangular section of the subsurface formation layer, wherein n is a number that is larger than five, a further wellbore or section is drilled such that it penetrates the underground formation layer at another triangularly spaced location relative to a pair of locations located at the outer periphery of the array of n existing triangular sections, and deposits are mined from said another triangular section between the n-th and said pair of locations located at the outer periphery of the array of n existing triangular sections.