Use of Exclusion Zones in Mapping and Modeling Fracture Corridors

Abstract

Abstract Fracture corridors are sub-vertical tabular fracture clusters which are associated with faults, or originate as incipient faults. Fluid conductive fracture corridors may have significant permeability and profoundly affect reservoir flow dynamics. Mapping fracture corridors requires (i) locating fracture corridors and assigning to them (ii) length, (iii) orientation and (iv) fluid conductivity. Estimation of orientation and especially length is a major challenge in fracture corridor modelling. Exclusion zones may aid both in locating fracture corridors and assigning orientation and length. An exclusion zone is an area which can not have a conductive fault or fracture corridor passing through. Exclusion zones around vertical wells are defined mainly by well tests and remaining oil column thickness. Borehole image logs, wells tests, lost circulation and openhole logs define exclusion zones in horizontal wells. A vertical well test with homogeneous matrix can not have a fluid conductive fault / fracture corridors within the circle of investigation. Oil column thickness can be estimated from a combination production logs, water cut history or from recent openhole or surveillance logs. Wells with thick remaining oil column and no water sweep can not have a nearby fluid conductive fault or fracture corridor. Horizontal wells with image logs or openhole logs showing no conductive fault/fracture corridor indicate an exclusion zone around the well where no faults or fracture corridors can pass through.