Streamline based compositional reservoir simulation

The streamline-based simulations are generally orders of magnitude faster than the simulation based on the conventional methods. The advantages of the streamline method have boosted its wide application and fast commercialization. Commercial streamline simulators like 3DSL and Frontsim are available but neither of them has included compositional effects and capillary effects. Compositional effects are indispensable for simulations like gas injection or water-alternating-gas (WAG) injection where components exchange between phases is active. And capillary effects are of key importance to waterflooding simulations in low permeable reservoir typical of the Danish sector of North Sea. This is the background for the three-year project 'Compositional Streamline Simulation'. In this project, IVC-SEP has aimed at extending streamline simulation methods to more applicable situations by introducing more physics into the 3DSL simulator provided by SUPRI-C group at Stanford University, whom we are in cooperation with. Two main objectives in the project are to introduce capillary effects, which are of key importance to water flooding in low permeable reservoir, and to develop two-phase/three-phase compositional streamline simulators. Corresponding to the above two objectives, two versions of 3DSL streamline simulator have been developed: 1) 3DSL black oil version which can be used for simulating incompressible, immiscible two component displacement, e.g. water flooding. Capillary and gravity effects have been fully introduced into the 3DSL simulator by using an operator splitting method. The simulation results obtained by the modified 3DSL simulator support our physical intuition for a variety of capillary and/or gravity dominant water displacements on permeability fields of different complexity and are also in satisfactory agreement with Eclipse 100. By application of a new criterion on time step selection, the number of pressure solves in 3DSL can be much fewer than Eclipse 100. 2) 3DSL compositional version which can be used for simulating two-phase/three-phase compositional displacement. This version has been developed by integrating an efficient 1-D compositional solver into the original 3DSL simulator. An optimized flash algorithm with stability analysis has been adopted in the new simulator to make the most time consuming flash calculation step more efficient and more reliable. For three-phase simulations, different equilibrium descriptions of hydrocarbon-water equilibrium are available to provide flexible choices. The developed compositional 3DSL simulator is capable of simulating both two-phase and three-phase gas injections, including WAG process. It has been proven that the compositional streamline simulator is orders of magnitude faster than its finite difference counterpart Eclipse 300. And the speedup factor increases with the size of simulation. The gravity effect has also been included in the simulator