Judul: Production and formulation of methyl ester sulfonate-based surfactant from palm olein for enhanced oil recovery application
Abstrak: The remaining oil in a reservoir that cannot be produced using the natural driving force (primary recovery) is about 50 to 80% of the initial oil volumes (IOIP). A secondary recovery technique such as waterflooding can only increase the recovery as much as 5 to 20% of the IOIP. Therefore, a method known as Enhanced Oil Recovery (EOR) has to be implemented in the reservoir in the effort to recover much more oil. One of the EOR methods is surfactant injection. The injection of surfactant solution is aimed to significantly reduce the capillary forces in the reservoir by lowering the oil-water interfacial tension within the pore spaces. Once the capillary force is diminished, the reservoir oil is much easier to be displaced and moved toward the production wells. This is an excellent opportunity to develop a type of vegetable oil-based surfactants. One of potential surfactant types to develop is methyl ester sulphonate surfactant (MES). This study was aimed at producing MES surfactant and formula-based methyl ester sulfonate surfactant from palm olein to be applied for in the process of improving oil recovery using carbonate formation fluids. Results of the study showed that the best condition was achieved in a sulphonation process done in 3-4 hours with the flowrate of dry air of 1.8 kg/hour and a purification performed without the addition of methanol in a pH of 8. The best MES surfactant-based formula for EOR applications on the formation of carbonate was the one with the composition of 0.3% MES surfactant, 0.3% Na2CO3, and 15,000 ppm salinity. MES surfactant produced from this formula had more heat resistance, higher salinity, and higher hardness than the commercial surfactants did. Results of the performance test of surfactant-based formula showed that the MES surfactant formula was compatible with formation water and injection water. The formed phase was a lower phase which was relatively stable on a heating up to day 77 (reservoir temperature of 70 and 112 °C) with a range of interfacial tension of 10-2 dynes/cm. The adsorption reached 152.86 μg active matter/g core and the incremental oil recovery using synthetic core of 8-19% and using native core of 9.1%. Surfactant solution coreflooding test with bottom-up flow direction resulted in a greater oil recovery (16%) than that with top-down flow direction. This was caused by the influence of gravity.
Keyword: Palm Olein

Judul: Uji Kinerja Surfaktan MES (Metil Ester Sulfonat) dari Stearin Sawit untuk Enhanced Water Flooding
Abstrak: Surfactant has been widely used for the application of Enhanced Oil Recovery (EOR) by decreasing the interfacial tension. Recently, most of the surfactants that are still used are petrochemical surfactants. MES surfactant is a surfactant derived from renewable resources that can replace petrochemical surfactant and has many advantages. The study was conducted by formulating the surfactant solution, testing performance of the surfactant formula, and testing the core flooding. The results of the study showed that palm stearin MES surfactant was compatible to the water injection of Ty field. The formulation generated average number of interfacial tension formula up to 7.88E-03 dyne/cm, so the formulation met the expected number of IFT for EOR. The thermal stability test showed that palm stearin MES surfactant is heat resistant. It was proven by the low of IFT number increasing and the decreasing of both viscosity and density. Phase behavior showed that the phase between oil and surfactant were in the type II (-) or low phase. Core flooding test was done by differentiation of surfactant solution injection of 0.1PV, 0.2PV, 0.3PV and soaking for 12 hours. The Incremental recovery that is obtained after the surfactant solution injection was between 12-14% OOIP. Statistical analysis showed that the variation of pore volume that was injected has no significant effect to the oil recovery, but it increased with increasing of surfactant volume that was injected. Therefore, stearin MES surfactant has good performance to be applicated for enhanced waterflooding in the Ty field.
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Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf