Abstract
In-depth profile modification, that is blocking the already swept high permeable zones in a reservoir with a gelling agent, would be one of the most effective sweep efficiency improvement (SEI) methods.
Firstly, in this paper, gelling agents developed for the in-depth profile modification are reviewed in order to understand their present situation and problems. Then, it is shown that TAP (thermally active polymer), PPG (preformed particle gel), CDG (colloidal dispersion gel) are suitable for the in-depth profile modification and overcome the difficulties of in-situ gelation, but they still have limitations in the applicable range of pH, temperature, pore throat diameter, and so on.
Secondly, a visualization experiment of the in-depth profile modification performed to a multilayered reservoir model, in which high permeable formations and low permeable formations are alternate, is shown to confirm the effect of indepth profile modification on SEI and oil recovery. Moreover, the problem that the injected water bypasses the blocked zones in high permeable formation from the low permeable formations and the 100% of sweep efficiency is quite difficult to be achieved is shown.
Finally, following results of the numerical simulations conducted to thirty-two heterogeneous reservoir models under the several blocking conditions are shown. The effect of in-depth profile modification on SEI increases with the increase in the volume of gelling agent and the decrease in the volume of chase water. But, in this case, the bottom-hole pressure increases and the risk to cause a severe formation damage or to make a fracture increases. Furthermore, the effect of in-depth profile modification on SEI increases with the increase in the vertical heterogeneity, and the horizontal heterogeneity is less correlated to the effect than the vertical heterogeneity when the heterogeneity indexes, Dykstra-Parsons coefficient and correlation length, are in the range set for this study.
