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.
Abdul Manap, Arif Azhan (Petronas Research Sdn Bhd) | Chong, Mizan Omar (Petronas Carigali Sdn Bhd) | Sai, Rithauddin M. (Petronas) | Zainal, Suzalina (Petronas Research Sdn Bhd) | Yahaya, Abdul Wafi (Petronas Carigali Sdn Bhd) | Othman, Mohamad (Petronas Carigali Sdn Bhd)
Angsi field is located offshore Terengganu, Malaysia. It was identified as the candidate for a pilot project to evaluate the effectiveness of chemical enhanced oil recovery (CEOR). Injection of alkali-surfactant (AS) slug was used to improve recovery factor through the reduction of residual oil saturation (Sor). The pilot project utilized single well chemical tracer test technique (SWCTT) to measure Sor change near well bore due to reactions of CEOR process. The pilot results were later used to update the reservoir dynamic model and to support decision making for potential expanded field application.
The pilot project faced many challenging technical and operational obstacles: offshore location, high reservoir temperature, sea water as injection water, water softening facilities requirement, and unmanned satellite platform with limited space. In addition, compliance to all Health, Safety, and Environment (HSE) requirements is a must, to ensure the pilot operation is carried out in a safe manner.
This paper will focus on the overall pilot design, planning and some results. Operational, HSE and quality control will also be discussed as background to the pilot project.
As part of the initiatives to increase reserve and extend field life, PETRONAS embarked on various technology projects, including application of Enhanced Oil Recovery (EOR) studies for Malaysian oil fields. Chemical flooding was identified as one of the potential EOR processes for field implementation. A research feasibility study was conducted to evaluate the potential of this EOR process and to identify a candidate reservoir for possible field implementation. The result was a suitable chemical flooding process utilizing alkali-surfactant (AS) cocktail tailored to suit the candidate reservoir condition. Laboratory coreflood results yielded an average incremental recovery of 14.6% OOIP for this process showed that there is potential to explore further chemical flooding field application in Malaysian oil fields, despite having high temperature reservoir and sea water as injection water1.
In the beginning of the project, the project team has to decide the type of pilot test required to gauge the effectiveness of chemical EOR by field trial. The options were a producing pilot, an observation pilot, or a single well test. Since the candidate reservoir is located offshore, the critical factors for the pilot which need to be considered were test objectives, test complexities, operational constraints, pilot duration and overall cost. The main objective was to test the chemical cocktail EOR performance by measuring residual oil saturation (Sor) change - before and after chemical slug injection. Considering PETRONAS have no previous experience in conducting any chemical flood field trial, it was decided to proceed with single well test; a more conservative and lower risk options among the pilot types considered.