Polymer flooding is emerging as a high-potential enhanced oil recovery technique and is expected to become the most widely applied chemical EOR-technique in Europe. The objective of this project is to quantify enhanced oil recovery by:
1. Describing the in-situ rheology of a polymer solution in a porous medium; 2. Establishing the maximum permissible reservoir temperature for injection of (cold) polymer solution;
3. Quantifying the reduction of oil trapped in high permeability regions by polymer flooding
4. Better understanding the impact of micro heterogeneities on oil recovery by polymer flooding.
The results from the project succeeded in improving the basic scientific knowledge on the behaviour of Xanthan. The results included flow experiments of Xanthan solution in porous media and in tubes. These compiled details of the interactions of the polymer molecules with the pore wall and the effective permeability of the polymer solution. The thermal stability of Xanthan material used was found to be limited to about 70(C. Thermal degradation of Xanthan was accelerated in the presence of sand, whilst additives such as thiourea and sodium pyruvate were effective as thermal stabilisers. The results provided more information on the flow behaviour of the macromolecules in the pore space, especially at the oil/aqueous phase interface and displacement from behind the oil/aqueous phase.
The project investigates new elements of this technique as applied to light and medium gravity oil reservoirs. In view of the North Sea and Central Europe reservoir conditions (high salinities and temperatures of up to 90(C), i biopolysaccharide Xanthan. For this polymer a rheological/mathematical model will be formulated for Darcy's Law to be included in available simulators. This will require basic flow experiments in specially packed sand packs and sandstone cores.
Moreover the displacement in heterogeneous media will be investigated with the help of a novel mathematical model technique. The heterogeneity will be described by geostatistical methods currently in use for reservoir characterization.
An attempt will be made to describe the capillary flow mechanism as completely as possible including wall effects and polymer concentration gradients across the pore.
To investigate the upper temperature limit of the reservoir for Xanthan solutions, survival (life) times of the polymer will be determined for a range of temperatures in relation to reservoir cooling down due to cold fluid injection and in relation to recovery efficiency.
The deliverables are:
- A more general formulation of the polymer rheology in the porous medium including relative mobilities;
- Understanding of the effect of micro heterogeneities on polymer flooding efficiency;
- New polymer flooding simulators which incorporate the findings of the two previous deliverables.
The project will lead to an improved understanding of the polymer flooding process and thus form the basis for its more widespread application.
Funding SchemeCSC - Cost-sharing contracts
2600 GA Delft