The goal of this research is to investigate the effect of surfactant and polymer found in the market and developed in the laboratory such as Sodium Ligno Sulfonat, Poly Vynil Alcohol (PVA) and Partially Hydrolyzed Polyacrylamide (HPAM) polymer on the oil recovery which can be used to optimize recovery and minimize residual oil in the reservoir by: lowering the oil / water interfacial tension and improving mobility ratio. The effectiveness of chemicals was tested through micro displacement using artificial reservoir as porous medium. The procedure of operation is as follows: initially the reservoir model was filled with brine until it was 100 % saturated. Then to represent oil migration, oil was injected into the medium until minimum water saturation (Swc) of about 30 % is reached. After this, the medium was flooded by the same brine until minimum oil saturation, Sor, was reached, which was about 10 %. The oil remaining in the reservoir model after this water flood was then subjected to the injection of various chemicals for additional oil recovery. A set of mathematical model of oil displacement from porous media using water and polymer flooding has also been developed, based on fundamental theories of two phase flow. Since the model includes the material balance of the water, surfactant and polymer, the concentration of the surfactant and polymer at any position and time can be predicted. The oil displacement experiments show that as much as 20 % to 60 % of remaining oil can be recovered by flooding it with the chemical developed in the laboratory. The results also show the oil recovery depends on chemical, chemical concentration, pressure and temperature in the model reservoir, and crude oil. It turns that the mathematical models proposed were in a good agreement with the experimental data.

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The energy needs in Indonesia are mainly fulfilled by fossil fuels based energy. Since there is the rise of fuel price, Indonesia government considers seeking alternative energies from renewable resources. Biogas becomes one of the alternative energy that supplies energy needs and manages cow manure waste in Indonesia. To increase adoption of biogas technology, biogas production through methane enrichment is required. The experiment was conducted with return sludge system. These instruments consist of a series portable bio-digester, gas holder and return sludge unit. There were three treatments on biogas production without and with sludge addition or re-use bio-digester sludge that produced after biogas production as raw material for next biogas production. Biogas that produced was observed every two days during 40 days. The results showed that the addition of bio-digester sludge increased biogas production and methane concentration. The optimum retention time of biogas production with sludge addition was 20 days with accumulation biogas volume of 156.38 liters or increased of 38.75 from biogas production without bio-digester sludge). The optimum retention time to increase methane level was 15 days with methane enrichment from 0.8% to 29.41%.