Drainhole well completion

In a method for completing a curved drainhole wellbore defined by a wall formed by drilling into at least one subsurface geologic formation, the improvement comprising inserting into said drainhole wellbore a casing string composed of alternating casing subs and external casing packer subs, each of said casing subs being solid and not perforated when said casing string is inserted into said wellbore, each of said external casing packer subs carrying an elastic member adapted to expand away from said casing packer sub toward and into contact with the adjacent wall of said drainhole wellbore, whereby, except for the end most casing sub, each said closing sub carries first and second external casing packer subs on either end thereof so that upon expansion of said elastic members carried by said first and second external casing packer subs the intermediate casing sub is isolated in the annulus outside said casing string assembly and inside said drainhole wellbore, and activating said external casing packer subs by pumping an activating fluid into said casing string to expand essentially all elastic members on said casing string at essentially the same time by expanding the elastic member into contact with said drainhole wellbore wall thereby to form isolated zones along said casing string, said isolated zones extending from outside said casing string to said drainhole wellbore wall, and thereafter perforating at least one of said solid casing subs to establish fluid flow contact between the interior of said casing string and said geologic formation.