Effect of Formation Compaction on Steam Injection Response

Abstract

ABSTRACT Formation compaction, if present, can have an important influence on thermal recovery methods, as observed in Western Venezuela, and elsewhere. This paper discusses the effect of formation compaction on oil production by cyclic steam stimulation and steamflooding, using a fully implicit steam injection simulator. The simulator accounts for three-phase mass and heat transport occurring in steam injection processes, for a wide variety of operating conditions. It employs an implicit formulation together with a Newtonian, direct solution approach, and was shown to be stable for large time steps. It was found that oil recovery in a compacting reservoir increases with an increase in the uniaxial compaction coefficient. However, whereas cyclic steam stimulation yielded a favorable response in a compacting reservoir, the opposite was true for a continuous steamflood. A delay in implementing a steamflood in a non-compacting reservoir can lead to a considerable loss of recovery, in the range of 10 to 40% of oil-in-place, depending on the value of the uniaxial compaction coefficient. This finding has far-reaching implications for steamflooding subsequent to intensive depletion by cyclic steaming, or primary production. Although formation compaction can be beneficial from the standpoint of cyclic steam stimulation response, there is strong dependence on the compaction coefficient. Furthermore, it was found that if the oil in question exhibits non-Newtonian flow behavior – reported for some Venezuelan oils – it must be accounted for in numerical simulations, otherwise the oil production rates may be in error by as much as 100%.