An Investigation of Micro-emulsion and Fine Foams Induced by EOR Application in Malaysian Fields

Abstract

Implementation of Enhanced Oil Recovery (EOR) methods to augment additional oil recovery is gaining momentum in Malaysia. A study completed in May 2010 revealed huge potential benefit in Malaysian fields by application of various EOR schemes. It was recommended to implement Alkaline Surfactant (AS) Flooding in Terengganu A, Alkaline Surfactant Polymer (ASP) Flooding in Sabah A, Foam Assisted CO2 WAG (FACO2WAG) for Terengganu B and, Foam Assisted Natural Gas WAG (FAWAG) for Sarawak A and B. EOR offer various top side challenges in terms of formation of tight emulsion, foam and poor effluent quality discharge (EQD) water. EOR fluids breakthrough for a particular field has a lot of behaviour on type and measure of the flow assurance challenges. The studies were conducted to identify potential problems and to find out right tailored chemicals to mitigate them. This paper illustrates the method of investigation and possible resolution of the problems. It was endeavoured to find a single chemical blend to alleviate the problem to ease the logistics of operation and procurement. Background: EOR Processes: Enhance Oil Recovery relates to the methods to obtain additional recovery from oil reservoirs by way of flooding some fluid to generate efficient sweep towards producers. Water Alternating Gas (WAG) and Chemical Flooding also called Chemical EOR (CEOR) are commonly employed. Some methods which improve the recovery of WAG by addition of chemicals like surfactants and polymers in the water phase are termed as Enhanced WAG (EWAG). Among EWAG schemes foam assisted WAG (FAWAG) has gained acceptance where a surfactant is added in the water phase which helps generate foam as soon the gas cycle is started. Movement of this foam at the interface provide added mobility control in the WAG process. It will be pertinent to add that usual WAG process entails natural gas as the gas phase. But use of CO2 (CO2WAG) and N2 (N2WAG) have been reported 1, 2. The EOR study completed in May 2010 revealed huge potential of additional recovery in Malaysian fields by application of various EOR schemes. It was recommended to implement Alkaline Surfactant (AS) Flooding in Terengganu A, Alkaline Surfactant Polymer (ASP) Flooding in Sabah A, Foam Assisted CO2 WAG (FACO2WAG) for Terengganu B and, Foam Assisted Natural Gas WAG (FAWAG) for Sarawak A and B fields. Implementation of EOR process poses some or other challenges on top side at producers' end. Formation of tough emulsion and foams and difficulty in removal residual oil from effluent water has been well recognised by the industry. Formation of tight emulsion and fine foam during EOR production process is recognised as major flow assurance challenge which occurs due to nature of crude oil, produced water and phase separation of solids like scales, asphaltenes and naphthenates. Implementation of EOR schemes may aggravate these problems at the producers' end because of use of surfactants and polymers. Increase in pH by use of alkali in ASP Floods may also cast its shadow on the process control4, 5.