Taking advantage of injectivity damage to improve reservoir sweep on horizontal wells.
Ab Wahab, Muhammad A.
Engineering Honours Degree 2008
University of Adelaide
Injectivity formation damage with waterflooding using sea/produced water has been widely reported for North Sea, Gulf of Mexico and Campos Basin. It happens due to capture of solid/liquid particles by rock with consequent permeability decline, and also due to formation of external filter cake.
Yet, moderate injectivity decline does not make much damage in case of long horizontal injectors with high initial injectivity. In this case, injection of raw or poorly treated water would save cost on water treatment, which is critical problem on sea platform or sea-bottom-placed filters.
In this paper we investigate effect of injected water quality on waterflood using horizontal wells. It was found out that induced injectivity damage results in increase of sweep efficiency. The explanation of the phenomenon is as follows: injectivity rate is distributed along horizontal well non-uniformly; water advances faster from higher rate intervals resulting in early breakthrough; the injectivity damage plugs mostly permeable channels that appear during flooding and homogenises the injectivity profile along the well. This cause a better sweep efficiency compared to a treated water injection.
Analytical model for injectivity decline accounting for particle capture and cake formation have been implemented into reservoir simulator Eclipse 100.
Several injection and production well configurations have been modelled in reservoirs with different heterogeneity. It was shown that sweep efficiency can increase up to 10% if compared with “clean” water injection.