Method of detecting a lateral boundary of a reservoir

Abstract

A method of detecting a lateral boundary of a compacting or expanding region in a subsurface formation, which method comprises determining non-vertical deformation of the earth' s surface above the subsurface formation over a period of time; identifying at least on contraction area and at least one adjacent dilatation area of the earth' s surface from the non-vertical deformation over the period of time; and using the contraction area and the adjacent dilatation area as an indication of a lateral boundary of the compacting or expanding region; and a method for producing hydrocarbons.

1 . A method of detecting a lateral boundary of a compacting or expanding region in a subsurface formation, the method comprising:
 determining non-vertical deformation of the earth's surface above the subsurface formation over a period of time;   identifying at least one contraction area and at least one adjacent dilatation area of the earth's surface from the non-vertical deformation over the period of time; and   using the at least one contraction area and the at least one adjacent dilatation area as an indication of a lateral boundary of the compacting or expanding region.   
   
   
       2 . The method according to  claim 1  wherein a near-horizontal component of the deformation of the earth's surface is determined. 
   
   
       3 . The method according to  claim 1 , wherein the at least one contraction area and the at least one adjacent dilatation area at the earth's surface are separated by a non-deforming intermediate area, and wherein it is inferred that the lateral boundary is located underneath the non-deforming intermediate area. 
   
   
       4 . The method according to  claim 1 , wherein an area of maximum strain gradient is identified at the earth's surface, and wherein it is inferred that the lateral boundary is located underneath the area of maximum strain gradient. 
   
   
       5 . The method according to  claim 1 , wherein a number of contraction areas and adjacent dilatation areas in a predetermined zone on the earth's surface is determined, and wherein it is inferred using the number whether there is more than one expanding or compacting region in the subsurface formation. 
   
   
       6 . The method according to  claim 5 , wherein the method further comprises
 distinguishing a plurality of regions in the subsurface formation, at least one of which changes its volume due to production of a fluid from or injection of a fluid into that region;   inferring from the number of contraction areas or adjacent dilatation areas whether there is fluid connectivity between the regions.   
   
   
       7 . The method according to  claim 1 , wherein the expanding or contracting region of which the lateral boundary is identified forms part of a larger reservoir region, and wherein a flow barrier in the larger reservoir region is identified at the lateral boundary. 
   
   
       8 . The method according to  claim 1 , wherein the non-vertical deformation at the earth's surface is interpreted using a geomechanical model of the subsurface formation. 
   
   
       9 . A method for producing hydrocarbons from a subsurface formation, wherein a lateral boundary of a compacting or expanding region in the subsurface formation is detected according to the method of  claim 1 .