The effects of temporarily shutting in steam injection wells on oil recovery by steamflooding were studied using a steam injection simulator. Both heavy and light oil steamflood situations were considered. One-eighth of a five-spot models representing the two types of reservoirs were employed to study the effects of shutting in the injector for up to eight months on the oil production performance during the shut-in period as well as following the resumption of steam injection.
The simulation results show that temporarily shutting in injectors is not detrimental to overall oil recovery. For each type of reservoir (heavy or light oil) the cumulative oil production at a limiting instantaneous steam-oil ratio of 10 was essentially the same regardless of the length of injector shut-in. The cumulative steam-oil ratio at the end of the project life also remains the same regardless of the length of shut-in. Shutting in the injector, however, prolongs the project life, increasing it by about the length of shut-in for the heavy oil and by more than the length of shut-in for the light oil case.
This paper compares oil production performances for steamflood projects operating under different shut-in scenarios, and recommends strategies to cope with changing economic environment.
Once a steamflood project is initiated, steam injection is continued at a more or less constant rate until the project matures or becomes ready for conversion to hot water injection. In some situations, however, temporary shut-ins or curtailment of steam injection is unavoidable and is usually necessitated by steam generator problems, well and production equipment problems, or changes in project operation for a variety of reasons, either economic or strategic. Recently the sharp drop in oil prices has forced the operators to consider selectively shutting in uneconomical or marginal steamflood projects for extended periods of time. For this, many operators are asking how temporarily shutting in the injectors would affect oil production performance during the shut-in period as well as after the resumption of steam injection at a later time. They are, in essence, seeking assurances that the shut-ins would not harm the steamflood.