IN THIS PAPER, WE PERFORM DYNAMIC IMBIBITION SIMULATIONS ON A LARGE SCALE HETEROGENEOUS FRACTURED BLOCK. THE PURPOSE IS TO SEEK OPTIMUM CONDITIONS UNDER WHICH MAXIMUM OIL CAN BE RECOVERED IN LARGE-SCALE EXTREMELY-HETEROGENEOUS RESERVOIRS. IN THIS PAPER, WE ONLY CONSIDER HORIZONTAL WELLS. HOWEVER, WE SIMULATE BOTH CONTINUOUS AND SLUG INJECTION SCENARIOS. VARIOUS CHEMICAL SOLUTIONS ARE INJECTED. THESE INCLUDE: WATER, POLYMER, SURFACTANT, ALKALI, AND DIFFERENT COMBINATIONS OF THEM. FOR CONVENIENCE OF SIMULATION, ALTHOUGH THIS IS NOT PHYSICALLY CORRECT, ALKALI REPRESENTS THE WETTABILITY MODIFYING AGENT, WHILE THE SURFACTANT IS THE AGENT THAT LOWERS THE IFT TO ULTRA-LOW VALUES. THEREFORE, A SIMULATION LABELED AS INDICATES THAT THE INJECTED CHEMICAL SOLUTION LOWERS THE IFT TO ULTRA LOW VALUES AS WELL AS ALTERS THE WETTABILITY FROM MIXED-WET TO WATER-WET. ON THE OTHER HAND, A SIMULATION LABELED ASP DOES THE ABOVE TASK AS WELL AS MAKING THE CHEMICAL SOLUTION VISCOUS (POLYMER). THE RECOVERY CURVES ARE COMPARED AND APPROPRIATE PROFILES ARE DEMONSTRATED IN ORDER TO UNDERSTAND THE RESULTS.