Method and apparatus for monitoring the position and movement progress of the flame front in an underground combustion

In a system for underground combustion of a combustible material in a selected subsurface geological formation F at a selected depth D below the surface, said system including a first input well drilled to a depth D to said formation F and adapted to receive air at a selected pressure P for combustion of said combustible material, and at least one second output well drilled to depth D to said formation F, through which products of said combustion can be brought to the surface;

• apparatus for monitoring the outward progress of the flame front from said first well, comprising;
• (a) a plurality of tilt meters to be positioned at or near the surface of the earth, arranged in at least one selected array between said first well and said second well;
• (b) means to supply air under pressure to said input well, and to ignite said combustible material in said formation F at said first well;
• whereby a flame front will be started, which will travel outwardly between said first well and said second well, and a portion of the overburden inside of said flame front will slump;
• (c) means amplifying the output signals of said tilt meters to form amplified output signals;
• (d) means for recording said amplified output signals as a function of time;
• and
• (e) means for determining the angle of tilt of the surface of the earth in the direction of down toward said first well.

In a system for monitoring the progress of the flame front in an underground combustion operation, wherein the combustion takes place in a selected subsurface geological formation F, in which the overburden above said formation F is supported in part by combustible material within said formation F, the method of monitoring the position and progress of said flame front, comprising;

• (a) providing at least a first well drilled to the depth of said formation F, in which said combustion is to be initiated;
• (b) providing at least a second well, spaced from said first well, to said formation F, through which products of said combustion can be brought to the surface;
• (c) providing a source of combustion air to said first well at a selected super atmospheric pressure;
• (d) positioning a plurality of tilt meters, at or near the surface of the earth, in at least one selected spaced array, between said first and second wells;
• (e) igniting said combustible material in said formation F, at said first well, to provide a flame front;
• whereby, as said combustible material is burned, under the pressure of said combustion air, said flame will progress outwardly from said first to said second well;
• (f) recording the output of said tilt meters as a function of time during the progress of said flame front past the position of at least one of said tilt meters;
• and
• (g) said tilt meters are designed to indicate tilt in 2 orthogonal directions, and positioning said tilt meters by aligning one of said directions along the line to said first well.

In a system for underground combustion of a combustible material in a selected subsurface geological formation F at a selected depth D below the surface, said system including a first input well drilled to a depth D to said formation F and adapted to receive air at a selected pressure P for combustion of said combustible material, at least one second output well drilled to depth D to said formation F, through which products of said combustion can be brought to the surface;

• apparatus for monitoring the outward progress of the flame front from said first well, comprising;
• (a) a plurality of tilt meters to be positioned at or near the surface of the earth, arranged in at least one array between said first well and said second well;
• (b) means to supply air under pressure to said input well, and to ignite said combustible material in said formation F at said first well;
• whereby a flame front will be started, which will travel outwardly as a function of the integrated flow of air supplied to said first well;
• (c) means for recording the output signals from said tilt meters as a function of time;
• and
• in which at least one of said tilt meters is positioned in the earth in a positioning system, comprising;
• (1) a drilled shallow borehole in the earth;
• (2) a support casing comprising a piece of pipe closed at the bottom, of selected length and diameter, positioned in said borehole, surrounded by tamped sand in the annulus between said pipe and the earth;
• (3) a plurality of angularly-spaced radial positioning screws through said pipe near its top end;
• (4) said tilt meter attached to a tubular support means and positioned vertically inside said pipe;
• sand poured around said tubular support means at its bottom end;
• the upper end of said tubular support means locked by said positioning screws to hold said support means vertical.
• (5) a streamlined cover means over said borehole at the surface;
• and
• (6) the void space under said streamlined cover means filled with thermal insulation means.

In a system for underground combustion of a combustible material in a selected subsurface geological formation F at a selected depth D below the surface, said system including a first input well drilled to a depth D to said formation F and adapted to receive air at a selected pressure P for combustion of said combustible material, and at least one second output well drilled to depth D to said formation F, through which products of said combustion can be brought to the surface;

• apparatus for monitoring the outward progress of the flame front from said first well, comprising;
• (a) a plurality of tilt meters to be positioned at or near the surface of the earth, arranged in at least one array between said first well and said second well;
• (b) means to supply air under pressure to said input well, and to ignite said combustible material in said formation F at said first well;
• whereby a flame front will be started, which will travel outwardly as a function of the integrated flow of air supplied to said first well;
• (c) means for recording the output signals from said tilt meters as a function of time;
• and
• (d) said tilt meters indicate the tilt in two orthogonal directions, and including means to position and tilt meters such that one of said orthogonal direction lies in the line to said first well.

In a system for underground combustion of a combustible material in a selected subsurface geological formation F at a selected depth D below the surface, said system including a first input well drilled to a depth D to said formation F at a selected depth D below the surface, said system including a first input well drilled to a depth D to said formation F and adapted to receive air at a selected pressure P for combustion of said combustible material, and at least one second output well drilled to depth D to said formation F, through which products of said combustion can be brought to the surface;

• apparatus for monitoring the outward progress of the flame front from said first well, comprising;
• (a) a plurality of tilt meters to be positioned at or near the surface of the earth, arranged in at least one array between said first well and said second well;
• (b) means to supply air under pressure to said input well, and to ignite said combustible material in said formation F at said first well;
• whereby a flame front will be started, which will travel outwardly as a function of the integrated flow of air supplied to said first well;
• (c) means for recording the output signals from said tilt meters as a function of time;
• and
• (d) in which said plurality of tilt meters are divided into at least two groups, each group positioned in a radially spaced array, angularly spaced from each other.