Dukhan Field CO2 Injection EOR Pilot: Reservoir Modeling & Planning

Abstract A reservoir study was conducted to plan a near-miscible CO2 gas injection pilot in the Dukhan Field with the following study guidelines:Determine overall objectives and timeframe for the pilotDesign the pilot to meet the objectives and timeframePlan the pilot in a portion of the field with representative reservoir descriptionPropose a surveillance and monitoring plan to ensure high quality information is obtained for interpreting the pilot performanceDesign the pilot so the recovery processes are scalable to larger well spacing for reservoir-wide application Using these guidelines, the following pilot objectives were developed:Provide data on well injectivity and productivityReduce uncertainty in the estimation of incremental oil recovery from CO2 gas injection relative to waterfloodProvide data to allow commercial scale well and facility CO2 gas injection designMinimize the impact on current operations outside the pilot area The results of the reservoir modeling study provided the detail for well orientation and placement to satisfy the pilot objectives at a reasonable cost and within appropriate timeframe for information gathering, analysis, and commercialization decisions. The reservoir model pilot area selected is one kilometer square segment in a crestal structural location that does not contain active wells and is near existing surface facilities. The reservoir description data used for the segment models were extracted from history matched full-field reservoir models. The proposed pilot wells are located within close proximity of each other to achieve gas breakthrough and oil bank arrival within the proposed pilot evaluation period of two years. The pilot design ensures that the pilot would allow for data gathering of key project design information; such as injectivity, gas breakthrough timing, oil displacement, and reservoir sweep. Introduction The large, mature Dukhan Field is located onshore Qatar, approximately 80km west of Doha. It is a north-south plunging anticline approximately 70km long by 8km wide. The field was discovered in 1939 and first production occurred in 1949. The field has more than 750 well penetrations. The major oil reservoirs are the Upper Jurassic Arab C and Arab D. There are lesser amounts of oil and gas in the Middle Jurassic and non-associated gas in the Permo-Triassic Khuff formation. The Arab C reservoir was initially filled with over 1400ft of oil between the structural crest and the oil-water contact. The Arab D reservoir was initially filled with over 700ft of oil rim in equilibrium with 700ft of gas-cap.