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: Kajian kinerja Surfaktan Mes (Metil Ester Sulfonat) dari Jarak Pagar (Jatropha Curcas L.) untuk enhanced waterflooding
Abstrak: Year by year, the production of petroleum decreases but its demand increases. The world will get the energy crisis if that condition happens continously. The main cause of low production of petroleum in Indonesia is the majority Indonesia’s oil wells being mature field/brown field and the discovery of new oil field in small scale. Indonesia focuses on maximize oil recovery in brown field because its oil production decreases naturally up 15% in total production. In recent years, the field of enhanced oil recovery has grown became more popular due to a combination of stagnant oil production and low recoveries by conventional methods. Many fields use unconventional method like enhanced oil recovery (EOR) which is tertiary oil recovery phase. One way of EOR is chemical flooding which uses surfactant for injection. Surfactant is injected to water and it is known as enhanced waterflooding. Generally, surfactant of petroleum sulfonates is used for oil recovery. This surfactant has many weaknesses such as resistance to water hardness, susceptible detergency to high salinity and being imported with expensive price. Due to these weaknesses, therefore it trigger to get surfactant substitute like MES (methyl ester sulfonates) that is synthesized by biooil. One of biooil is Jatropha oil. The study was aimed to know experimental of surfactant formula for enhanced waterflooding in fluida sample of oil field and synthetic core sandstone. The result showed that injection of surfactant 0,2 PV gave the influence differently to oil recovery. The best condition was surfactant 0,2 PV with the soaking time of 12 hours. This formula gave the highest of incremental total oil recovery 61,07%. The number were resulted from 47,73% waterflooding and 13,34% surfactant injection. Surfactant formula gave the good performance of compatibility, thermal stability, phase behavior and filtration test.
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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