Open/Closed Natural Fractures

If a reservoir is suspected of being fractured but the fracture pattern and distribution is not well known, the more productive or ‘open’ fractures will tend to align with SHD. Therefore a horizontal producer drilled parallel with ShD will deliver maximum production when fracced parallel with SHD.


If the fracture pattern is known from imaging logs to be simple regular conjugate shears (left top) and, as shown, SHD = 005° bisects them when the fractures formed and still does today, each fracture set should produce at approximately equal, but moderate, rates if the horizontally fracced well direction is approximately 095°. However, a horizontal well drilled at 107° within 10-12° of ShD = 095° will produce fracs that should attempt to open sub-parallel with SHD = 017° but the energy would be concentrated on the 027° set of conjugate shears and that set would preferentially open. Production could therefore be maximised and the productive area will be relatively large due to interconnectivity provided by the less fracced partly closed 163° conjugates.