Judul: Relative Plugging Index Larutan Surfaktan Berbasis Metil Ester Sulfonat Menggunakan Media Pembawa Air Injeksi Lapangan Minyak T
Abstrak: The high demand of oil has become the main reason of oil exploration optimization. There were 60-70% oil stock that still unexplored and below the primary recovery stage. Enhanced oil recovery (EOR) as an advanced draining method is fluid injection method to drain the remained oil in reservoir rocks. One of EOR mechanism is surfactant injection to decrease interface tense between oil and water. Surfactant injection could optimize the oil act of ousting. This research studied about the effect of surfactant formula to the relative plugging index (RPI). RPI is a value that show the plugging rate of surfactant flow. RPI obtained by lessen total suspended (TSS) value with milipore test slope number (MTSN). This research used some materials, such as T oil field ijection water, NaCl 0.5%, MES 0.3%, and Na2CO3. Each formulation used different Na2CO3 concentration, which was 0, 1, 2, and 3%. Na2CO3 addition increased surfactant solution’s pH, density and viscosity. Na2CO3 contents in the solution also increased the TSS value therefore the flowrate became slower. The solution of surfactant with the minimal TSS value about 0.03 mg/L was the solution A (water injection A + NaCl 0,5% + MES 0,3% ) with the minimal 5 μ filtration. The solution of surfactant with the maximum MTSN value about -0,79 was the solution A (water injection A + NaCl 0,5% + MES 0,3% ) with the minimal 5 μ filtration. The filtration of 37,25 and 5 μ had the was excellent RPI value. But the filtration just of the step 37 and 25 μ and it’s in the good ranges for application.
Keyword: relative plugging index, methyl ester sulfonat, enhanced oil recovery, surfactant

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: 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