**5. Conclusions**

Based on past experience in cuttings injection monitoring, it can be concluded that the quality of fracture closure after shut-in has a critical impact on the efficiency of a cuttings injection operation. Cuttings injection is inefficient when the fracture closure cannot be assured as a result of an insufficient shut-in period between batch injection operations. Conversely, cuttings injection becomes efficient when sufficient time is provided between batch injections to allow adequate fracture closure.

The quality of the cuttings injection can be evaluated by analyzing the trend of batch injections. The rising peak batch pressures during injection and slow declining of terminal batch pressures during shut-in are indications of poor pressure maintenance and thus poor cuttings injection management. Rising batch injection pressure usually reveals difficulties in maintaining needed injectivity while slow pressure decline can be the result of insufficient shut-in time in a low permeability disposal domain. The required solutions include but are not limited to: a) mitigating the injection pressure or pump power and ensuring the proper breakdown of the injected formation, b) extending the shut-in period to dissipate injection pressure, and c) adjusting the injected batch volume or injection rate to allow the relevant acceptance of the disposal formation for the injected cuttings.

The quality of fracture closure analysis also affects the quality of cuttings injection manage‐ ment. Among various methods, using GFSD in interpreting BHP responses to the cuttings injection operation appears to be an efficient way to identify the occurrence of fracture closure. Interpreting the shapes of GFSD over the P – G relationship may help identify the different responses from various formations such as injection in naturally fractured reservoirs, reflect various behaviors involved in the injection process such as the pressure/stress dependency in a poro-elastic formation, or reveal the outcome from the complex, coupled process of rock deformation and fluid flow under various reservoir boundary conditions.
