Highly paraffinic (or waxy) crude oil can cause significant problems in the pipelines due to wax–oil gel blockage resulting from the precipitation of the wax components. Once blockage of the pipeline occurs and flow ceases, the pipeline flow cannot be restarted with the original steady state operating pressure but instead requires significantly higher pressures to restart the flow. Due to this, it is important to maintain the oil at a temperature above its natural pour point. The incorporation of chemical products known as wax inhibitors and pour point depressant (PPD) reduce the pour point and viscosity of oil. This paper introduces an indigenously synthesized wax inhibitor from the hydrophobically modified polybetaines (zwitterionic) family for treating waxy crude A located in Peninsular Malaysia. The synthesized wax inhibitor had been evaluated as flow improver, crystal modifier and pour point depressant. The wax inhibitor coded CRODDA-AA, works efficiently since it can reduce the pour point of waxy crude A by 12°C and the viscosity about half of the original value at 1000 ppm concentration, as well as lowering the yield stress by 8 Pa at 51°C. In order to assess the use of the CRODDA-AA wax inhibitor for squeeze applications, a core flood study was conducted to determine its adsorption capability onto formation. A formation damage study was also conducted to ensure that there is no formation damage coupled with the injection of wax inhibitor. It was found that wax inhibitor CRODDA-AA can be retained in the formation up to 88.5% without significant formation damage. As a next step, it is planned to run the core flood and wax inhibitor release tests to refine the design of squeeze treatment.

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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.

A number of Malaysian mature oil fields have been and are still under investigation for Enhanced oil Recovery (EOR). This includes Water Alternating Gas (WAG), chemical flooding and Foam assisted WAG. This field is one of the most fields under extensive EOR studies for WAG & FAWAG. Despite the promising recovery factor from EOR application there are always the side effects that accompany these processes which are formation damage and injectivity issues. A lot experiments studies shown, when a large number of pore volumes of polymer is injected with medium permeability beyond a critical shear rate, a plugging tendency is observed. This plugging is attributed to a damage mechanism called "bridging adsorption" in which stretched polymer macromolecules form numerous bridges across pore throats. At the same time, causes fine migration issue. In this study, the effects of fines migration, clay swelling and injectivity were investigated in separate core floods studies (one test for fines migration, one test for clays swelling and three for chemical injectivity). For the fines migration study, the core flood test to investigate the critical flow rate of the seawater injection shows fines migration problem as observed from sea water injection of intermediate critical flow rate for fines migration in the core. For clays swelling the permeability reduction test and pH measurement with decreasing salinity indicates a critical salinity much less than the sea water salinity and sea water is the proposed medium for the EOR chemical in this field. Moreover, SEM investigation analysis result shows that most of the damage is due to fine migration caused by the velocity flow rate of the injection sea water. For injectivity study, core flood tests were conducted with injecting surfactant polymer (SP) solution and with surfactant and polymer individually. The results show that while minimum damage of less than 30% is typically expected in this type of test with permeability resistance factor of less than 3, what was actually obtained in this test is about 95% damage and permeability resistance factor (PRF) is 23 compared to KPI of 3. The results also indicate that incompatibility between the surfactant and polymer could be one of the reasons for permeability decline. This is because while injecting the chemicals separately no serious injectivity issue is observed. Introduction EOR studies prior to field application have recently enjoyed global attention due to several reasons including declining oil production below par primary and secondary recovery, high crude oil price and increasing energy demand which is growing at approximately 1.5% per year (Du, K., et al, 2011). Laboratory testing in support of field application is critical to minimize field application failures. This paper addresses possible risk of formation damage due to fine migration, clay swelling and polymer absorption during Foam Assisted Water Alternating Gas (FAWAG) process proposed for the field. The offshore field is located 170 km away from West- Malaysia land. Currently this field is being considered for enhanced WAG process called Foam assisted Water Alternating Gas (FAWAG). In this process it is proposed to alternate polymer surfactant with gas instead of water. Surfactant is proposed to precede the gas injection, which will generate foam in-situ. Foam so generated along with the polymer is expected to improve the displacement efficiency by virtue of better mobility control, once implemented, This field will be the first such application in Malaysia.

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