Injection Fall-off Interpretation from Fractured Injectors

We performed numerical simulations of injection fall-off (IFO) testing for both water and (non-Newtonian) polymer in which the gradual closure of the induced fracture is explicitly included. A large variety of induced fracture sizes and shapes was included in this study. Results show that half-slope and quarter-slope ranges will only occur very exceptionally in the early-time pressure derivative curves. On the other hand, the unit slope (storage flow dominated) occurs very often at early time. In principle, both half-slope / quarter-slope and unit slope can be used for IFO test analysis to estimate the dimensions (length, height) of the induced fractures. However, based on the above, we conclude that fracture dimensions in IFO tests can only be reliably interpreted from the unit slope part. This point is further illustrated by a two IFO test examples from the field, where it is shown that interpretation of half-slope or quarter-slope can often result in unrealistically large fractures.