Method for 4D permeability analysis of geologic fluid reservoirs

A method for determining a plurality of maximum compressive stress directions of an ambient stress field within a fluid reservoir field comprising the steps of:

• establishing a network of earthquake recording devices for acquiring, resolving, analyzing and monitoring earthquake waves, said network being of a predetermined size and location in and around said reservoir field;
• causing a fluid pressure wave to be generated by operation of at least one fluid injection site within said reservoir field, said fluid pressure wave causing failure to occur on ambient fractures that comprise an ambient permeability field associated with said at least one injection site, with said failure enhancing permeability on said ambient fractures, and with said failure generating earthquake seismic waves being acquired by said network;
• using said network to image at least one conidial volume of ambient fractures generating said earthquake seismic waves for said at least one injection site, with said at least one conidial volume having an acute apical angle and a cone axis that passes through said at least one injection site, said conidial volume showing a temporal migration of earthquakes away from said at least one injection site;
• plotting an orientation of said cone axis in space, said cone axis being a maximum compressive stress direction of an ambient stress field in the vicinity of said at least one injection site;
• and
• repeating said establishing step, said causing step, said using step and said plotting at additional injection sites said reservoir field;
• whereby a plurality of maximum compressive stress directions are determined for said reservoir field.

A method for the multidimensional imaging of an ambient permeability field that is within a fluid reservoir having at least one well therein, comprising the steps of:

• establishing a network of earthquake recording devices for acquiring, resolving, analyzing and monitoring earthquake data, said network being of a predetermined size and location in and around said fluid reservoir;
• causing a fluid pressure wave to be generated by operation of a fluid injection site within said fluid reservoir, said fluid pressure wave causing failure to occur on ambient fractures within an ambient permeability field that is associated with at least one injection site, with said failure enhancing permeability on said ambient fractures, and with earthquake data generated by said failure being acquired by said network;
• using said network to image at least one conoidal volume of ambient fractures generating said earthquake data for said at least one injection site, with said at least one conidial volume having an acute apical angle and a cone axis that passes through said at least one injection site, said conidial volume showing a temporal migration of earthquakes away from said at least one injection site;
• using said at least one conidial volume and said showing of a temporal migration of said earthquakes away from said at least one injection site to identify said ambient fractures as those that comprise an ambient permeability field to which said at least one injection site is connected;
• and
• plotting data acquired by said network in n-dimensional space to locate wells within said reservoir that are hydraulically linked to said at least one injection site.