Tewari, Raj Deo (Petronas Carigali Sdn Bhd) | Bui, Thang (Schlumberger) | Sedaralit, Mohd Faizal (PETRONAS) | Kittrell, Chuck M (Schlumberger IPM-RMG) | Riyadi, Slamet (Petronas Carigali Sdn Bhd) | Rahman, Hibatur (Petronas Carigali Sdn Bhd)
This paper discusses about the optimization study of applying the enhanced oil recovery technique in a multilayered mature offshore oilfield. This field is located at water depth 65-70 m. There is significant variation in rock and fluid properties from top to bottom in the field. Upper sands are highly porous and permeable, poorly consolidated and hold viscous oil.Whereas lower formations are fully consolidated and contain lighter oil with a high GOR. Oil in most of these reservoirs are under- saturated. The field is under primary production for the last 30 years with appropriate sand control and artificial lift measures.
Production performance indicates that current development strategy and practices will yield a moderate recovery lower than average recovery in Malay basin fields. A comprehensive reservoir characterization has been carried out to capture the reservoir heterogeneity and multiple realizations of reservoir properties distribution have been used to understand the major uncertainties of the field. Performance analysis combined with simulation modeling identified a suitable EOR application with appropriate well spacing to maximize the drainage of undrained oil while improving the sweep from partially drained portions of the reservoirs. Since the field is in mature stage of the producing life, delaying the enhanced oil recovery application may not be a sound strategy for maximizing the recovery. Improving the well density and applying EOR should be part of a redevelopment strategy. Exhausting the option of primary production and then embarking on enhanced oil recovery application may be detrimental in maximizing the value of the asset. Water alternating gas injection (WAG) in immiscible mode has been firmed up for improving the oil recovery from this offshore field. The improvement in recovery due to WAG injection is attributed to contact of the upswept zones and modification of residual oil saturations and targeting the attic oil. The combination of water and gas injection in WAG improves the microscopic displacement efficiency and increases the mobile oil saturation. Hysteretic effects which change saturation paths, due to sequential injection of water and gas, additionally improve the recovery. Thus the combined effect of water and gas injection in improving the recovery in WAG is better as compared to separate gas or water injection. Three phase flow (oil, water and gas) is better in displacing the residual oil compared to two phase flow water and oil or gas and oil.
One of the major challenges envisaged in the application of EOR in a multilayered reservoir with very large thickness is poor conformance of injectants. This is critical for the success of the process. Parameters which are critical for impacting the WAG enhanced oil recovery process are studied thoroughly. The study suggests that improving the well spacing and proper injection volume with good conformance control and timely initiation of the process would result into an improvement of recovery factor on the order of 8-10%. The paper also discusses the laboratory results of mechanism of formation damage with water injection and rock-fluid interaction.
Wan Daud, Wan Ata (Exploration and Production Technology Centre, PETRONAS) | Sedaralit, Mohd Faizal (PETRONAS) | Wong, Fadhli (PETRONAS) | Affendi, Amierul Redza (Exploration & Production Technology Centre. PETRONAS)
With declining oil production, the Exploration & Production companies are in search of applying innovative methodologies to improve recovery factors from existing fields. Immiscible Water Alternating Gas (IWAG) has been identified as one of the enhanced-oil recovery techniques for offshore Dulang oil field in Malaysia. The field redevelopment FDP study was initiated in 2007 to evaluate the optimum recovery scheme to increase oil production from all reservoirs in Dulang field. Results from the simulation study indicated that the major reservoirs will benefit from IWAG injection, with ultimate recovery as high as 50% in some reservoirs. Phase 1 of IWAG injection was started in April 2012
Prior to IWAG field implementation, extensive surveillance program was developed to ensure requires data is captured for monitoring the success of the project and provide a feedback for improvement.
This paper explores the selection of tools and testing programs adopted in surveillance program which include Integrated Operation (IO) for IWAG injection in the Dulang field. The new proposed surveillance program is expected to improve water flood and IWAG monitoring;
The new IWAG surveillance program with the IO system will enable the surveillance team to move from reactive to a proactive asset management system. Real time data will enable engineers to know the status of injection facilities, well status and rate and the performance of IWAG EOR in Dulang.
Mohd Shafian, Siti Rohaida (PETRONAS Research Sdn Bhd) | Kamarul Bahrim, Ridhwan Zhafri (PETRONAS Research Sdn Bhd) | Abdul Hamid, Pauziyah (Petronas Research Sdn Bhd) | Abdul Manap, Arif Azhan (PETRONAS Research Sdn Bhd) | Darman, Nasir B. (PETRONAS) | Sedaralit, Mohd Faizal (PETRONAS) | Tewari, Raj Deo (Petronas Carigali Sdn Bhd)
This paper discusses laboratory results of enhancing the performance of water alternating gas (WAG) injection process. Currently, field is under primary and secondary phases. It is light oil with moderate to good reservoir characteristics and relatively higher in reservoir temperature between 92 - 101oC and higher CO2 percentage in produced gas. Field is in decline phase and rise in water cut and GOR values. Redevelopment strategy of the field includes optimization of well spacing and WAG application to maximizing the oil recovery. One of the key challenges faced on WAG injection is gas overriding. Therefore, it becomes important to control the gas flood front during gas injection cycle of WAG and allowing the reservoir to reach to Sorg level.
The study will focus on measuring the variation of petrophysical parameters for surfactants that has bulk foam stabilization properties. In addition to classical foam Mobility Reduction Factor (MRF) determination, effect of foam on gas saturation has also been monitored along the core using in-situ X-ray monitoring tool. Propagation of foam in porous media is less understood and application of X-ray monitoring for gas saturation in dynamic condition helps to understand this to great extent.
Experiments have been carried out on Berea and reservoir cores mounted on dedicated X-Ray-equipped core flood bench. The core, initially at Swi, is flooded up to Sorw with water followed by gas injection to Sorg level to establish the reference condition for WAG. A slug of surfactant solution is then injected followed by gas prior to co-injection of surfactant and gas (83 % quality foam). Fluid propagation in core is correctly monitored for every 0.1 PV injection of fluids. The results suggest efficient mobility control by achieving required MRF in presence of ROS. High MRF is an essential ingredient for the success of the process. These results are also correlated with a homogenization of the gas front in presence of foam.