Method of characterising a subsurface region using multiple point statistics

A computer program product comprising a non-transitory, computer readable storage medium storing instructions which, when run on a suitable computer apparatus, cause the computer apparatus to perform operations for detecting and extracting hydrocarbons from a hydrocarbon reservoir including a subsurface region by creating an image, the operations comprising:

• defining a plurality of pixels of the image for describing the subsurface region, each pixel comprising a cell representing at least one of a subsurface area or a subsurface volume forming part of the subsurface region, at least one of the plurality of pixels being initially unassigned, each of the plurality of pixels of the image having corresponding thereto:
• a domain set, the domain set comprising possible values assignable to its corresponding pixel;
• a neighborhood set, each neighborhood set comprising a subset of the plurality of pixels of the image which neighbor its corresponding pixel;
• and
• a conflict set;
• and
• sequentially performing the following steps a) to g):
• (a) determining whether all pixels of said plurality of pixels have been assigned, and, if so, proceeding directly to step g);
• (b) if at step a) it is determined that not all of said plurality of pixels have been assigned, selecting an unassigned pixel from the plurality of pixels of the image as a selected pixel;
• (c) assigning a value to the selected pixel from the selected pixel's corresponding domain set, provided it is not empty;
• (d) assessing whether a constraint is satisfied with the selected pixel assigned the assigned value, wherein the constraint is based on a training image describing a conceptual geological model of a subsurface region;
• (e) if it is determined that the constraint being assessed is satisfied at step d), designating said selected pixel as an assigned pixel and returning to step a);
• and
• (f) if it is determined that the constraint being assessed is not satisfied at step d) with the selected pixel assigned the assigned value, updating the selected pixel's corresponding conflict set to include one or more conflict pixels, the conflict pixels being one or more previously assigned pixels comprised within the selected pixel's corresponding neighborhood set;
• and
• (g) outputting the image when all pixels of said plurality of pixels have been assigned;
• wherein, when it is determined during performance of any of steps d) through f) that the selected pixel's corresponding domain set comprises no values which satisfy the constraint, thereby indicating that the selected pixel is a dead-end pixel, the instructions, when run on the computer apparatus, further cause the computer apparatus to perform operations comprising:
• (1) determining a most recent conflict pixel from the selected pixel's corresponding conflict set, the most recent conflict pixel comprising the pixel in the selected pixel's corresponding conflict set which has been most recently assigned a value;
• (2) unassigning the values previously assigned to the selected pixel, the most recent conflict pixel, and all intervening pixels which were assigned values between the selected pixel being assigned a value and the most recent conflict pixel being assigned a value;
• and
• (3) returning to step a) with the selected pixel being the most recent conflict pixel;
• and
• wherein the constraint is satisfied for at least a first pixel of the plurality of pixels, and the constraint is not satisfied for at least a second pixel of the plurality of pixels.