Geosteering difficulty index

Abstract

Systems and methods for determining a geosteering difficulty index are disclosed. The methods may include obtaining, using a well logging tool, a typelog recorded in a first borehole penetrating a subterranean region of interest and, using a well log interpretation system, identifying at least one geological layer of interest from the typelog, determining a plurality of typelog indices based on typelog values within and adjacent to the at least one geological layer and determining a geosteering difficulty index (“GDI”) based on the plurality of typelog indices. The methods further include determining, using a borehole planning system, a borehole plan for a second borehole based, at least in part, on the GDI.

What is claimed is: 
     
         1 . A method, comprising:
 obtaining, using a well logging tool, a typelog recorded in a first borehole penetrating a subterranean region of interest;   using a well log interpretation system:
 identifying at least one geological layer of interest from the typelog, 
 determining a plurality of typelog indices based on typelog values within and adjacent to the at least one geological layer, and 
 determining a geosteering difficulty index (“GDI”) based on the plurality of typelog indices; and 
   determining, using a borehole planning system, a borehole plan for a second borehole based, at least in part, on the GDI.   
     
     
         2 . The method of  claim 1 , wherein the plurality of typelog indices comprise an edge index, a symmetry index, and a slope index. 
     
     
         3 . The method of  claim 2 , wherein each of the plurality of typelog indices is based, at least in part, on variations of the typelog with depth. 
     
     
         4 . The method of  claim 1 , wherein the at least one geological layer comprises a hydrocarbon reservoir. 
     
     
         5 . The method of  claim 1 , further comprising drilling, using a drilling system, the second borehole guided by the borehole plan. 
     
     
         6 . The method of  claim 5 , wherein drilling comprises using a geosteering system, based, at least in part, on a second typelog recorded in the second borehole during drilling. 
     
     
         7 . The method of  claim 1 , wherein the typelog is a gamma ray log. 
     
     
         8 . The method of  claim 2 , wherein the edge index comprises a quadratic dependence on depth. 
     
     
         9 . The method of  claim 2 , wherein the symmetry index comprises a normalized Pearson correlation coefficient. 
     
     
         10 . A system, comprising:
 a well logging tool configured to obtain a typelog recorded in a first borehole penetrating a subterranean region of interest;   a well log interpretation system configured to:
 identify at least one geological layer of interest from the typelog, 
 determine a plurality of typelog indices based on typelog values within and adjacent to the at least one geological layer, and 
 determine a geosteering difficulty index (“GDI”) based on the plurality of typelog indices; and 
   a borehole planning system configured to:
 determine a borehole plan for a second borehole based, at least in part, on the GDI. 
   
     
     
         11 . The system of  claim 10 , wherein the plurality of typelog indices comprise an edge index, a symmetry index, and a slope index. 
     
     
         12 . The system of  claim 11 , wherein each of the plurality of typelog indices is based, at least in part, on variations of the typelog with depth. 
     
     
         13 . The system of  claim 10 , wherein the at least one geological layer comprises a hydrocarbon reservoir. 
     
     
         14 . The system of  claim 10 , further comprising drilling, using a drilling system, the second borehole guided by the borehole plan. 
     
     
         15 . The system of  claim 14 , wherein drilling comprises using a geosteering system, based, at least in part, on a second typelog recorded in the second borehole during drilling. 
     
     
         16 . The system of  claim 11 , wherein the typelog is a gamma ray log. 
     
     
         17 . The system of  claim 12 , wherein the edge index comprises a quadratic dependence on depth. 
     
     
         18 . The system of  claim 12 , wherein the symmetry index comprises a normalized Pearson correlation coefficient.