A NOVEL OPTIMIZATION STUDY OF OIL RECOVERY IN CARBONATE “X” FIELD BY SIMULTANEOUS GAS ALTERNATING GAS (SGAG) INJECTION USING COMPOSITIONAL RESEVOIR SIMULATION
Field X is a tight reservoir, this field started with a good production rate. unfortunately, that was short-lived as not only sharp declination in oil production rate, but coincided with rising water cut too. The field is under-saturated with 36 API and average viscosity of 1.72 cp, with a high gas-oil ratio (GOR). Enhanced Oil Recovery (EOR) applications then are highly recommended especially if possible, using gas that is highly produced from the same field. The first indications to use the Gas-Assisted Gravity Drainage (GAGD) method reveal that will not be the suitable as many horizontal wells with shallow vertical depth. Simultaneous Gas Alternating Gas, (SGAG) is a new technique. To proceed, a reservoir compositional model is made to determine the tight oil reservoir's properties and composition, then this method is implemented using two lateral wells under each other with suitable vertical depth. Both of these injection wells are located lower than the production well with zero horizontal displacement. some scenarios for 20 years in this study, start by using the gas produced from the same well (ProdG) direct from the gas separator, and second with using enhanced gas (ProdG30)after the separation of 50% process of methane gas that is available in this produced gas. Then using CO2. The first two scenarios were tried by using the ProdG and ProdG30 alternated with CO2. The best result using SGAG method during using ProdG alternated with CO2 and Prodg30 was 33 and 44.2% respectively. While during using ProdG30 it was better without alternating with CO2 slug it reached 54.2%. A comparison was made between SGAG and four conventional methods. results reflect a preference for using this new technique. The conventional methods that their performance checked here were GAG, normal one vertical in- between injection well, WAG- W/ProdG30, SWAG-W/ProdG, SWAG-W/ProdG30. The best results have gotten: 16.9, 31.22, 31.6, 27.4 and 34 respectively. SGAG is sensitive to vertical space between production and injection wells so that, for tight reservoir formations, it is recommended in high thickness reservoirs.