The LRLC reservoir zone has been identified in SN-3 well, at the DAP-1 interval on Gumai Formatio... more The LRLC reservoir zone has been identified in SN-3 well, at the DAP-1 interval on Gumai Formation. This interval has a low resistivity value from 3-5 ohm.m and the drill stem test (DST) results show oil with gas without water. This study is objected to identify the causes of LRLC reservoir in gumai formation and finding a suitable sw calculation method. Some data such as well logs, reports, cores, and XRD are used to calculate petrophysical parameters such as Vsh, Phie, and Sw, and would be validated by DST data. Water saturation (Sw) calculations from Archie and the CEC method (Waxman Smits, Dual Water, Juhasz) were performed and the results were compared. The results showed that the main cause of the DAP-1 interval LRLC zone was the presence of clay minerals consisting of mixed layers (Illite/smectite). These clay minerals will be associated with high cation exchange capacity (CEC) values, with the value 70 (meq/100g), which can increase conductivity and reduce resistivity values. Based on lumping the more optimistic results of sw calculation from Waxman Smits Sw method (Sw based on CEC method). The DST data on the SN-3 well does not have water test data, so the calculation of the Sw value that is close to the Swirr value is considered the most suitable Sw for the low resistivity reservoir conditions of the Gumai Formation in the study area. The best practice for low resistivity reservoir for suitable petrophysical calculation is necessary to pay attention to the rock lithology conditions, the presence of mineral clay, and determining suitable Sw appropriate to the reservoir conditions.
Pada suatu pemboran eksplorasi, tahapan yang sangat penting adalah menganalisa kejenuhan fluida p... more Pada suatu pemboran eksplorasi, tahapan yang sangat penting adalah menganalisa kejenuhan fluida pada reservoar. Sistem fluida yang ada pada suatu reservoar biasanya multi fasa (air dan hidrokarbon). Saturasi hidrokarbon (minyak atau gas bumi) dapat diketahui dengan terlebih dahulu menghitung saturasi airnya, dengan demikian penentuan nilai saturasi air (Sw = water saturation) menjadi kunci untuk mengetahui suatu interval reservoar apakah dominan mengandung air atau hidrokarbon. Perkembangan teknologi eksplorasi khususnya teknologi logging serta kondisi reservoar yang beragam mempengaruhi konsep penentuan saturasi air dari waktu ke waktu. Tulisan ini berusaha mengkompilasi jenis-jenis metode penentuan saturasi air khususnya pada reservoar clean sandstone dan shaly sandstone serta kelebihan/kelemahan dari masing-masing metode. Kompilasi ini mendasarkan pada publikasi ilmiah dari para penulis yang dicoba diurutkan berdasarkan kesamaan konsep ataupun tahun dari publikasi tersebut. Manfaat dari kompilasi ini adalah mempermudah ahli petrofisika didalam melakukan evaluasi formasi untuk memilih metode yang sesuai dengan kondisi reservoar di masing-masing lapangan. Untuk menentukan saturasi air pada clean sand formation terdapat 4 metode yang umum digunakan yaitu : Archie (1942), Resistivity Ratio atau Rocky Mountain (1949), Crossplots (1960-an) dan F Overlay (1962). Metode penentuan saturasi air pada shaly-sand formation dapat dikelomokkan menjadi dua group berdasarkan pendekatan dan konsep yang digunakan yaitu : Vsh group dan CEC group. Group Vsh melakukan pendekatan dan konsep berdasarkan volume shale yang berada pada suatu formasi, yang termasuk dalam group ini antara lain adalah Laminated shale, Dispersed shale, Structural shale, Automatic Compensation (1950), Simandoux (1963), Indonesia (1971) dan Worthington (1985). Group CEC melakukan pendekatan dan konsep berdasarkan Cation Exchange Capacity yaitu pertukaran ion yang dapat terjadi pada formasi yang mengandung shale, yang termasuk dalam group ini antara lain adalah Waxman-Smith (1968), Dual-Water (1977) dan LSU model (1989).
Groundwater exploration is an alternative to meet raw water needs because of the increasing water... more Groundwater exploration is an alternative to meet raw water needs because of the increasing water demand and the dwindling surface water availability. Water use continues to increase along with the rate of population growth in the Rote Ndao Regency. Therefore, an initial assessment of the presence of groundwater can be carried out by identifying the groundwater basin area. Batutua is one of the groundwater basin areas occupied by the most population because it is the capital of Rote Ndao Regency. This study aims to identify aquifer systems and flow patterns as the basis for groundwater exploration in the Batutua groundwater basin area. The method used in this groundwater aquifer system study is the Vertical Electrical Sounding (VES) method. The VES method is a geoelectrical method used to investigate the layers of an aquifer by interpreting the current that penetrates the soil using two electrodes and the potential response. Geoelectrical investigations were carried out at 8 points in the Batutua groundwater basin area. The aquifer is found in water-containing coral limestone areas where water flows through fractures as secondary permeability. The groundwater flow direction was obtained by measuring the groundwater levels in 14 dug wells and 24 springs. The research’s area aquifer system is formed by upper shallow aquifer as an unconfined aquifer with a thickness less than 20 m and lower shallow aquifer as a semi-confined aquifer that has clay or marls on upper layer and limestone in below with the flow direction from the East to the West and the North part of the study area.
Welcome to the 3oth IAS Meeting of Sedimentology, held at the University of Manchester in the Uni... more Welcome to the 3oth IAS Meeting of Sedimentology, held at the University of Manchester in the United Kingdom, under the auspices of the International Association of Sedimentologists. The organisers hope you find these proceedings informative and wish you a very successful conference.
Welcome to the 3oth IAS Meeting of Sedimentology, held at the University of Manchester in the Uni... more Welcome to the 3oth IAS Meeting of Sedimentology, held at the University of Manchester in the United Kingdom, under the auspices of the International Association of Sedimentologists.
IOP Conference Series: Earth and Environmental Science, 2021
Rock typing is a technique of grouping rocks that have similar properties, which properties can b... more Rock typing is a technique of grouping rocks that have similar properties, which properties can be in the form of sedimentary, petrophysical, and reservoir parameters. Classification based on sedimentary parameters is called sedimentary rock type (SRT), while grouping based on petrophysical parameters is called petrophysical rock type (PRT). The purpose of this study is to determine the relationship between SRT and PRT in the research area. The method used to determine sedimentary rock type is to use the facies concept approach, while the method used to determine petrophysical rock type is the Hydraulic Flow Unit Method, Global Hydraulic Element, Winland R35, and Pore Geometry Structure. In this study, determined the relationship between sedimentary rock type with petrophysical rock type, where some facies that have certain characteristics will have a certain type of petrophysical rock type pattern. Thoroughly bioturbated mudstone facies which have low porosity and permeability have...
An integrated subsurface study has been performed for a large and mature field at the Bekasap For... more An integrated subsurface study has been performed for a large and mature field at the Bekasap Formation in Central Sumatra Basin. The Bekasap Formation sand represents an undeveloped reservoir because of its heterogeneity. There are five sand reservoirs (BK1, BK2, BK3, BK4, and BK5) from Bekasap Formation, which each zone or layer bounded by a flooding surface. Each sand reservoir has particular characterization based on petrophysical properties that represent geological process. The petrophysical properties consist of shale volume, porosity, and water saturation obtained by wireline log calculation. This study uses conventional core data to validate the log calculation to achieve an accurate interpretation. Bekasap reservoir is a sandstone reservoir deposited in an estuarine with tide-dominated. Formation evaluation was done to determine the interest zone by petrophysical properties. The result well-log calculation and reservoir cut-offs showed the thickest reservoir in the BK 3 wi...
IOP Conference Series: Earth and Environmental Science
Groundwater exploration is an alternative to meet raw water needs because of the increasing water... more Groundwater exploration is an alternative to meet raw water needs because of the increasing water demand and the dwindling surface water availability. Water use continues to increase along with the rate of population growth in the Rote Ndao Regency. Therefore, an initial assessment of the presence of groundwater can be carried out by identifying the groundwater basin area. Batutua is one of the groundwater basin areas occupied by the most population because it is the capital of Rote Ndao Regency. This study aims to identify aquifer systems and flow patterns as the basis for groundwater exploration in the Batutua groundwater basin area. The method used in this groundwater aquifer system study is the Vertical Electrical Sounding (VES) method. The VES method is a geoelectrical method used to investigate the layers of an aquifer by interpreting the current that penetrates the soil using two electrodes and the potential response. Geoelectrical investigations were carried out at 8 points ...
IOP Conference Series: Earth and Environmental Science, 2021
The presence of pyrite in sandstone reservoirs will cause a problem known as low resistivity rese... more The presence of pyrite in sandstone reservoirs will cause a problem known as low resistivity reservoirs case. The impact of pyrite volume in sandstone reservoirs is very important to be determined, especially to conduct its resistivity correction factor (Rcf). This research was done in the laboratory used nine sandstone pseudo-cores with various pyrite contents. Some data parameters such as voltage (V) and current (I) are directly measured and others (resistance R and reservoirs resistivity Rt) are calculated. The resistivity of pseudo-core data is calculated using the combined method between Ohm Law and Wenner. The result of this research shows that pyrite will reduce sandstone reservoirs resistivity exponentially. Pyrite will significantly reduce reservoirs resistivity if its presence > 4% and the Rt needs to be corrected. Plotting data between Rt and pyrite volume number for every Sw line can guide us to build a resistivity correction factor (Rcf). This Rcf will drive us to ob...
Proc. Indon. Petrol. Assoc., 39th Ann. Conv., 2015
Hydrocarbon reservoirs are usually indicated by high resistivity on well log measurements based o... more Hydrocarbon reservoirs are usually indicated by high resistivity on well log measurements based on the response to fluids in the sediment pore space. However, there are some cases where a productive reservoir has a low resistivity―known as Low Resistivity Pay Zone. A Low resistivity pay zone has a log response based on the nature of the constituent minerals and fluid contained in the reservoir. One of the causes of a low resistivity reservoir is the presence of conductive minerals. This study delves into understanding this phenomenon by making simulations through pseudo-cores that contain magnetite minerals with a volume of 2%, 4%, 6%, 8%, 10%, 15%, 20%, and 25% in total of 17 pseudo-cores and conditionally, formation water saturations of 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%. The main parameters are measured and counted against the total resistivity and resistivity of the fluid and each pseudo-core while the porosity is known from petrographic analysis. In addition, these experiments attempt to make corrections to the formation water saturation in each pseudo-core to obtain the true resistivity pseudo-core value. Based on measurement results and data analyses, it can be concluded that the presence of magnetite influences resistivity by decreasing, on average, by 42% the resistivity of a clean sandstone reservoir with porosity of 25% -37%. Resistivity decreases with increasing volume of conductive minerals in the rocks. Additionally, this study concluded that if a rock contains magnetite at 2%, a correction needs to be applied using a regression equation obtained in this study whereby the total value of the resistivity and water saturation decreased gradually.
Pada tahun 2004 PT. Pertamina DOH JBB melakukan pemboran di sumur Explo#1 yang berhasil menembus ... more Pada tahun 2004 PT. Pertamina DOH JBB melakukan pemboran di sumur Explo#1 yang berhasil menembus reservoar karbonat setebal 79 meter pada kedalaman 1444-1523 meter yang dikenal sebagai interval MMC (Mid Mean Carbonate). Evaluasi petrofisika yang dilakukan pada pada sumur Explo#1 saat itu menggunakan asumsi bahwa MMC adalah 1 interval reservoar & nilai parameter petrofisika dianggap sama sepanjang interval tersebut. Hasil perhitungan petrofisika awal menunjukkan adanya 4 interval yang cukup berpotensi mengandung hidrokarbon (Sw berkisar antara 67% - 81%), sementara hasil UKL (Uji Kandung Lapisan dengan RFT/Repeat Formation Tester) menunjukkan sampel fluida yang mengalir dari 4 interval tersebut adalah air. Hal tersebut mendasari untuk dilakukan penelitian, meliputi karakterisasi reservoar pada MMC secara terperinci untuk mengetahui heterogenitasnya, penyesuaian nilai parameter petrofisika (porositas, m dan Rw) dan perhitungan ulang nilai saturasi fluida (Sw) dengan menggunakan parameter petrofisika yang sudah disesuaikan. Karakterisasi reservoar diperlukan untuk membagi zona reservoar berdasarkan kondisi geologi reservoar. Data FMI dijadikan data utama karena dapat memberikan gambaran tentang struktur geologi, struktur sedimen, litofasies dan tipe porositas sepanjang interval. Sementara itu penentuan nilai eksponen sementasi (m) didasarkan pada perhitungan dengan mempertimbangkan tipe porositasnya. Rw dihitung dari data log SP, sedangkan Sw dihitung menggunakan rumusan Archie karena formasi yang ada adalah clean formation. Karakterisasi reservoar yang dilakukan menunjukkan bahwa MMC bukan merupakan 1 reservoar yang homogen tetapi terdiri dari 19 zona, 11 zona merupakan zona reservoar dan 8 zona non-resevoar. Struktur sedimen dan struktur geologi tidak dijumpai secara signifikan. MMC tersusun oleh litofasies wackestone, packstone dan serpih. Lingkungan pengendapan bervariasi dari low energy shelf edge sampai dengan low energy outer shelf. Terdapat 12 stage pengendapan dan yang ditembus oleh sumur Explo#1 adalah stage 1, 6, 10 dan 12. Dijumpai 4 subaerial exposure yaitu pada kedalaman 1471,3 m, 1486 m, 1495 m,dan 1507,8 m. Secara umum porositas yang berkembang adalah porositas primer jenis intergranular dan porositas sekunder jenis porositas vugular (isolated vugs, interconnected vugs, channeling vugs) dan fracture/rekahan (open fracture, partially mineral filled/healed fracuture). Geometri eksternal MMC adalah berbentuk carbonate build up yang diperkirakan sebagai skeletal mound carbonate dengan platform berbentuk shelf, tetapi geometri masing-masing stage pengendapan bervariasi yaitu mound dan sheet draped. Penyebaran MMC yang membentuk closure (tutupan) build up sejumlah 3 tempat yaitu di tengah, utara dan timur laut daerah penelitian. Interval reservoar yang mempunyai porositas paling tinggi adalah zona 6 pada kedalaman 1495-1495,6 m dengan porositas efektif rata-rata 19 %, sedangkan interval reservoar yang mempunyai porositas terkecil adalah zona 9 (1509-1510,5 m) dan zona 10 (1510,5-1511 m dengan porositas efektif rata-rata sebesar 5 %. Nilai m terendah adalah 1,31 pada fasies wackestone zona 10, sedangkan nilai tertinggi adalah 2,59 pada fasies packstone zona 6. Hasil perhitungan Rw menunjukkan variasi dari nilai 0,04 ohmm sampai dengan 0,07 ohmm. Secara keseluruhan nilai Sw hasil perhitungan ulang menunjukkan nilai yang sangat besar, berkisar 93 % sampai dengan 99 %. Hasil perhitungan Sw ini sesuai dengan hasil UKL (tes atau Uji Kandung Lapisan) yang dilakukan yaitu semua interval yang dites berisi air. Dengan demikian ketidaksesuaian perhitungan Sw sebelumnya dikarenakan menggunakan harga m dan Rw yang kurang sesuai. Explo#1 well was drilled by PT. Pertamina DOH JBB in 2004 and reached carbonate reservoir at 1444-1523 m. The reservoir has 79 m thickness and known as MMC interval (Mid Main Carbonate). Previous petrophyisic analysis was done in assumption that MMC Âis a hornogen carbonate reservoir so the analysis use same value for along interval. Then calculation result of Sw is about 67%-8 1 % but the test result (RFT) showed 1 00% water. Based on that problem, this research was conducted to analyze the heterogenity of reservoir. identify vertical facies changes. recognize porosity types which is develope along interval, calculate cementation exponent (m), re-calculate resistivity of formationwater (Rw) and re-calculate Sw. Reservoir characterization is needed as the base of reservoir zonation. i.e. devide the reservoir based on its geological condition. FMi is used as the main data because it can give information about geological structures, sedimentary strucutres, lithofacies dan porosity types along interval. Otherwise, cementation exponent (m) could be define by calculation using certain equation which suitable with the porosity types. Rw is calculated from SP data. while SW comes from Archie equation due to its clean formation. The result of characterization shows that MMC is not a homogen…
The 27 th May 2006 earthquake of 5.9 Richter scale has created hundreds of landslides along the f... more The 27 th May 2006 earthquake of 5.9 Richter scale has created hundreds of landslides along the flanks of the Baturagung Range which bordered the Yogyakarta Lowland to the west and the Wonosari Plateau to the east. One of the landslide events occurred at Dusun Buyutan, Desa Ngalang, Kecamatan Gedangsari, Kabupaten Gunungkidul of the Yogyakarta Province, which involved a series of tuffaceous sandstones and carbonaceous siltstones with coal flags of the Semilir Formation. There appeared an interesting natural phenomenon of subsurface heat anomalies and gas escapes from a slided debris, raising an issue of a birth of a new volcano to the alarming local people, although it also created a new local tourism draw, as sulphur smells was dominant. Gas composition dominated by CO and CO 2 , which were presents in a hazardous level for the people. The landslide was controlled by two boundary faults which aligned SW-NE and NNE-SSW and the slided mass involved a 5 m thick of the uppermost rock succession. Systematic surface mapping indicates two main hot spots occurred and was aligned NE-SW, with their peak temperatures exceeding 60 o C. A shallow boring conducted at one of the hot spot and vertical temperature gradients were measured from the borehole and the cutting samples. The results indicate a temperature peak of >65 o C existed at 2 m depth before considerably decreased to below 55 o C. These evidences confirm that the heat anomalies and gas escapes were local and only associated with the slided debris. Possible mechanisms that initiated the heat are interpreted as self combustion processes of the carbonaceous sediments and coal flags due to landslide frictions and increasing oxygen level within the slided debris. Abundant carbonaceous material contributes the persistent heat for months, although further observation suggests that the heat anomalies decreased onward.
The LRLC reservoir zone has been identified in SN-3 well, at the DAP-1 interval on Gumai Formatio... more The LRLC reservoir zone has been identified in SN-3 well, at the DAP-1 interval on Gumai Formation. This interval has a low resistivity value from 3-5 ohm.m and the drill stem test (DST) results show oil with gas without water. This study is objected to identify the causes of LRLC reservoir in gumai formation and finding a suitable sw calculation method. Some data such as well logs, reports, cores, and XRD are used to calculate petrophysical parameters such as Vsh, Phie, and Sw, and would be validated by DST data. Water saturation (Sw) calculations from Archie and the CEC method (Waxman Smits, Dual Water, Juhasz) were performed and the results were compared. The results showed that the main cause of the DAP-1 interval LRLC zone was the presence of clay minerals consisting of mixed layers (Illite/smectite). These clay minerals will be associated with high cation exchange capacity (CEC) values, with the value 70 (meq/100g), which can increase conductivity and reduce resistivity values. Based on lumping the more optimistic results of sw calculation from Waxman Smits Sw method (Sw based on CEC method). The DST data on the SN-3 well does not have water test data, so the calculation of the Sw value that is close to the Swirr value is considered the most suitable Sw for the low resistivity reservoir conditions of the Gumai Formation in the study area. The best practice for low resistivity reservoir for suitable petrophysical calculation is necessary to pay attention to the rock lithology conditions, the presence of mineral clay, and determining suitable Sw appropriate to the reservoir conditions.
Pada suatu pemboran eksplorasi, tahapan yang sangat penting adalah menganalisa kejenuhan fluida p... more Pada suatu pemboran eksplorasi, tahapan yang sangat penting adalah menganalisa kejenuhan fluida pada reservoar. Sistem fluida yang ada pada suatu reservoar biasanya multi fasa (air dan hidrokarbon). Saturasi hidrokarbon (minyak atau gas bumi) dapat diketahui dengan terlebih dahulu menghitung saturasi airnya, dengan demikian penentuan nilai saturasi air (Sw = water saturation) menjadi kunci untuk mengetahui suatu interval reservoar apakah dominan mengandung air atau hidrokarbon. Perkembangan teknologi eksplorasi khususnya teknologi logging serta kondisi reservoar yang beragam mempengaruhi konsep penentuan saturasi air dari waktu ke waktu. Tulisan ini berusaha mengkompilasi jenis-jenis metode penentuan saturasi air khususnya pada reservoar clean sandstone dan shaly sandstone serta kelebihan/kelemahan dari masing-masing metode. Kompilasi ini mendasarkan pada publikasi ilmiah dari para penulis yang dicoba diurutkan berdasarkan kesamaan konsep ataupun tahun dari publikasi tersebut. Manfaat dari kompilasi ini adalah mempermudah ahli petrofisika didalam melakukan evaluasi formasi untuk memilih metode yang sesuai dengan kondisi reservoar di masing-masing lapangan. Untuk menentukan saturasi air pada clean sand formation terdapat 4 metode yang umum digunakan yaitu : Archie (1942), Resistivity Ratio atau Rocky Mountain (1949), Crossplots (1960-an) dan F Overlay (1962). Metode penentuan saturasi air pada shaly-sand formation dapat dikelomokkan menjadi dua group berdasarkan pendekatan dan konsep yang digunakan yaitu : Vsh group dan CEC group. Group Vsh melakukan pendekatan dan konsep berdasarkan volume shale yang berada pada suatu formasi, yang termasuk dalam group ini antara lain adalah Laminated shale, Dispersed shale, Structural shale, Automatic Compensation (1950), Simandoux (1963), Indonesia (1971) dan Worthington (1985). Group CEC melakukan pendekatan dan konsep berdasarkan Cation Exchange Capacity yaitu pertukaran ion yang dapat terjadi pada formasi yang mengandung shale, yang termasuk dalam group ini antara lain adalah Waxman-Smith (1968), Dual-Water (1977) dan LSU model (1989).
Groundwater exploration is an alternative to meet raw water needs because of the increasing water... more Groundwater exploration is an alternative to meet raw water needs because of the increasing water demand and the dwindling surface water availability. Water use continues to increase along with the rate of population growth in the Rote Ndao Regency. Therefore, an initial assessment of the presence of groundwater can be carried out by identifying the groundwater basin area. Batutua is one of the groundwater basin areas occupied by the most population because it is the capital of Rote Ndao Regency. This study aims to identify aquifer systems and flow patterns as the basis for groundwater exploration in the Batutua groundwater basin area. The method used in this groundwater aquifer system study is the Vertical Electrical Sounding (VES) method. The VES method is a geoelectrical method used to investigate the layers of an aquifer by interpreting the current that penetrates the soil using two electrodes and the potential response. Geoelectrical investigations were carried out at 8 points in the Batutua groundwater basin area. The aquifer is found in water-containing coral limestone areas where water flows through fractures as secondary permeability. The groundwater flow direction was obtained by measuring the groundwater levels in 14 dug wells and 24 springs. The research’s area aquifer system is formed by upper shallow aquifer as an unconfined aquifer with a thickness less than 20 m and lower shallow aquifer as a semi-confined aquifer that has clay or marls on upper layer and limestone in below with the flow direction from the East to the West and the North part of the study area.
Welcome to the 3oth IAS Meeting of Sedimentology, held at the University of Manchester in the Uni... more Welcome to the 3oth IAS Meeting of Sedimentology, held at the University of Manchester in the United Kingdom, under the auspices of the International Association of Sedimentologists. The organisers hope you find these proceedings informative and wish you a very successful conference.
Welcome to the 3oth IAS Meeting of Sedimentology, held at the University of Manchester in the Uni... more Welcome to the 3oth IAS Meeting of Sedimentology, held at the University of Manchester in the United Kingdom, under the auspices of the International Association of Sedimentologists.
IOP Conference Series: Earth and Environmental Science, 2021
Rock typing is a technique of grouping rocks that have similar properties, which properties can b... more Rock typing is a technique of grouping rocks that have similar properties, which properties can be in the form of sedimentary, petrophysical, and reservoir parameters. Classification based on sedimentary parameters is called sedimentary rock type (SRT), while grouping based on petrophysical parameters is called petrophysical rock type (PRT). The purpose of this study is to determine the relationship between SRT and PRT in the research area. The method used to determine sedimentary rock type is to use the facies concept approach, while the method used to determine petrophysical rock type is the Hydraulic Flow Unit Method, Global Hydraulic Element, Winland R35, and Pore Geometry Structure. In this study, determined the relationship between sedimentary rock type with petrophysical rock type, where some facies that have certain characteristics will have a certain type of petrophysical rock type pattern. Thoroughly bioturbated mudstone facies which have low porosity and permeability have...
An integrated subsurface study has been performed for a large and mature field at the Bekasap For... more An integrated subsurface study has been performed for a large and mature field at the Bekasap Formation in Central Sumatra Basin. The Bekasap Formation sand represents an undeveloped reservoir because of its heterogeneity. There are five sand reservoirs (BK1, BK2, BK3, BK4, and BK5) from Bekasap Formation, which each zone or layer bounded by a flooding surface. Each sand reservoir has particular characterization based on petrophysical properties that represent geological process. The petrophysical properties consist of shale volume, porosity, and water saturation obtained by wireline log calculation. This study uses conventional core data to validate the log calculation to achieve an accurate interpretation. Bekasap reservoir is a sandstone reservoir deposited in an estuarine with tide-dominated. Formation evaluation was done to determine the interest zone by petrophysical properties. The result well-log calculation and reservoir cut-offs showed the thickest reservoir in the BK 3 wi...
IOP Conference Series: Earth and Environmental Science
Groundwater exploration is an alternative to meet raw water needs because of the increasing water... more Groundwater exploration is an alternative to meet raw water needs because of the increasing water demand and the dwindling surface water availability. Water use continues to increase along with the rate of population growth in the Rote Ndao Regency. Therefore, an initial assessment of the presence of groundwater can be carried out by identifying the groundwater basin area. Batutua is one of the groundwater basin areas occupied by the most population because it is the capital of Rote Ndao Regency. This study aims to identify aquifer systems and flow patterns as the basis for groundwater exploration in the Batutua groundwater basin area. The method used in this groundwater aquifer system study is the Vertical Electrical Sounding (VES) method. The VES method is a geoelectrical method used to investigate the layers of an aquifer by interpreting the current that penetrates the soil using two electrodes and the potential response. Geoelectrical investigations were carried out at 8 points ...
IOP Conference Series: Earth and Environmental Science, 2021
The presence of pyrite in sandstone reservoirs will cause a problem known as low resistivity rese... more The presence of pyrite in sandstone reservoirs will cause a problem known as low resistivity reservoirs case. The impact of pyrite volume in sandstone reservoirs is very important to be determined, especially to conduct its resistivity correction factor (Rcf). This research was done in the laboratory used nine sandstone pseudo-cores with various pyrite contents. Some data parameters such as voltage (V) and current (I) are directly measured and others (resistance R and reservoirs resistivity Rt) are calculated. The resistivity of pseudo-core data is calculated using the combined method between Ohm Law and Wenner. The result of this research shows that pyrite will reduce sandstone reservoirs resistivity exponentially. Pyrite will significantly reduce reservoirs resistivity if its presence > 4% and the Rt needs to be corrected. Plotting data between Rt and pyrite volume number for every Sw line can guide us to build a resistivity correction factor (Rcf). This Rcf will drive us to ob...
Proc. Indon. Petrol. Assoc., 39th Ann. Conv., 2015
Hydrocarbon reservoirs are usually indicated by high resistivity on well log measurements based o... more Hydrocarbon reservoirs are usually indicated by high resistivity on well log measurements based on the response to fluids in the sediment pore space. However, there are some cases where a productive reservoir has a low resistivity―known as Low Resistivity Pay Zone. A Low resistivity pay zone has a log response based on the nature of the constituent minerals and fluid contained in the reservoir. One of the causes of a low resistivity reservoir is the presence of conductive minerals. This study delves into understanding this phenomenon by making simulations through pseudo-cores that contain magnetite minerals with a volume of 2%, 4%, 6%, 8%, 10%, 15%, 20%, and 25% in total of 17 pseudo-cores and conditionally, formation water saturations of 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%. The main parameters are measured and counted against the total resistivity and resistivity of the fluid and each pseudo-core while the porosity is known from petrographic analysis. In addition, these experiments attempt to make corrections to the formation water saturation in each pseudo-core to obtain the true resistivity pseudo-core value. Based on measurement results and data analyses, it can be concluded that the presence of magnetite influences resistivity by decreasing, on average, by 42% the resistivity of a clean sandstone reservoir with porosity of 25% -37%. Resistivity decreases with increasing volume of conductive minerals in the rocks. Additionally, this study concluded that if a rock contains magnetite at 2%, a correction needs to be applied using a regression equation obtained in this study whereby the total value of the resistivity and water saturation decreased gradually.
Pada tahun 2004 PT. Pertamina DOH JBB melakukan pemboran di sumur Explo#1 yang berhasil menembus ... more Pada tahun 2004 PT. Pertamina DOH JBB melakukan pemboran di sumur Explo#1 yang berhasil menembus reservoar karbonat setebal 79 meter pada kedalaman 1444-1523 meter yang dikenal sebagai interval MMC (Mid Mean Carbonate). Evaluasi petrofisika yang dilakukan pada pada sumur Explo#1 saat itu menggunakan asumsi bahwa MMC adalah 1 interval reservoar & nilai parameter petrofisika dianggap sama sepanjang interval tersebut. Hasil perhitungan petrofisika awal menunjukkan adanya 4 interval yang cukup berpotensi mengandung hidrokarbon (Sw berkisar antara 67% - 81%), sementara hasil UKL (Uji Kandung Lapisan dengan RFT/Repeat Formation Tester) menunjukkan sampel fluida yang mengalir dari 4 interval tersebut adalah air. Hal tersebut mendasari untuk dilakukan penelitian, meliputi karakterisasi reservoar pada MMC secara terperinci untuk mengetahui heterogenitasnya, penyesuaian nilai parameter petrofisika (porositas, m dan Rw) dan perhitungan ulang nilai saturasi fluida (Sw) dengan menggunakan parameter petrofisika yang sudah disesuaikan. Karakterisasi reservoar diperlukan untuk membagi zona reservoar berdasarkan kondisi geologi reservoar. Data FMI dijadikan data utama karena dapat memberikan gambaran tentang struktur geologi, struktur sedimen, litofasies dan tipe porositas sepanjang interval. Sementara itu penentuan nilai eksponen sementasi (m) didasarkan pada perhitungan dengan mempertimbangkan tipe porositasnya. Rw dihitung dari data log SP, sedangkan Sw dihitung menggunakan rumusan Archie karena formasi yang ada adalah clean formation. Karakterisasi reservoar yang dilakukan menunjukkan bahwa MMC bukan merupakan 1 reservoar yang homogen tetapi terdiri dari 19 zona, 11 zona merupakan zona reservoar dan 8 zona non-resevoar. Struktur sedimen dan struktur geologi tidak dijumpai secara signifikan. MMC tersusun oleh litofasies wackestone, packstone dan serpih. Lingkungan pengendapan bervariasi dari low energy shelf edge sampai dengan low energy outer shelf. Terdapat 12 stage pengendapan dan yang ditembus oleh sumur Explo#1 adalah stage 1, 6, 10 dan 12. Dijumpai 4 subaerial exposure yaitu pada kedalaman 1471,3 m, 1486 m, 1495 m,dan 1507,8 m. Secara umum porositas yang berkembang adalah porositas primer jenis intergranular dan porositas sekunder jenis porositas vugular (isolated vugs, interconnected vugs, channeling vugs) dan fracture/rekahan (open fracture, partially mineral filled/healed fracuture). Geometri eksternal MMC adalah berbentuk carbonate build up yang diperkirakan sebagai skeletal mound carbonate dengan platform berbentuk shelf, tetapi geometri masing-masing stage pengendapan bervariasi yaitu mound dan sheet draped. Penyebaran MMC yang membentuk closure (tutupan) build up sejumlah 3 tempat yaitu di tengah, utara dan timur laut daerah penelitian. Interval reservoar yang mempunyai porositas paling tinggi adalah zona 6 pada kedalaman 1495-1495,6 m dengan porositas efektif rata-rata 19 %, sedangkan interval reservoar yang mempunyai porositas terkecil adalah zona 9 (1509-1510,5 m) dan zona 10 (1510,5-1511 m dengan porositas efektif rata-rata sebesar 5 %. Nilai m terendah adalah 1,31 pada fasies wackestone zona 10, sedangkan nilai tertinggi adalah 2,59 pada fasies packstone zona 6. Hasil perhitungan Rw menunjukkan variasi dari nilai 0,04 ohmm sampai dengan 0,07 ohmm. Secara keseluruhan nilai Sw hasil perhitungan ulang menunjukkan nilai yang sangat besar, berkisar 93 % sampai dengan 99 %. Hasil perhitungan Sw ini sesuai dengan hasil UKL (tes atau Uji Kandung Lapisan) yang dilakukan yaitu semua interval yang dites berisi air. Dengan demikian ketidaksesuaian perhitungan Sw sebelumnya dikarenakan menggunakan harga m dan Rw yang kurang sesuai. Explo#1 well was drilled by PT. Pertamina DOH JBB in 2004 and reached carbonate reservoir at 1444-1523 m. The reservoir has 79 m thickness and known as MMC interval (Mid Main Carbonate). Previous petrophyisic analysis was done in assumption that MMC Âis a hornogen carbonate reservoir so the analysis use same value for along interval. Then calculation result of Sw is about 67%-8 1 % but the test result (RFT) showed 1 00% water. Based on that problem, this research was conducted to analyze the heterogenity of reservoir. identify vertical facies changes. recognize porosity types which is develope along interval, calculate cementation exponent (m), re-calculate resistivity of formationwater (Rw) and re-calculate Sw. Reservoir characterization is needed as the base of reservoir zonation. i.e. devide the reservoir based on its geological condition. FMi is used as the main data because it can give information about geological structures, sedimentary strucutres, lithofacies dan porosity types along interval. Otherwise, cementation exponent (m) could be define by calculation using certain equation which suitable with the porosity types. Rw is calculated from SP data. while SW comes from Archie equation due to its clean formation. The result of characterization shows that MMC is not a homogen…
The 27 th May 2006 earthquake of 5.9 Richter scale has created hundreds of landslides along the f... more The 27 th May 2006 earthquake of 5.9 Richter scale has created hundreds of landslides along the flanks of the Baturagung Range which bordered the Yogyakarta Lowland to the west and the Wonosari Plateau to the east. One of the landslide events occurred at Dusun Buyutan, Desa Ngalang, Kecamatan Gedangsari, Kabupaten Gunungkidul of the Yogyakarta Province, which involved a series of tuffaceous sandstones and carbonaceous siltstones with coal flags of the Semilir Formation. There appeared an interesting natural phenomenon of subsurface heat anomalies and gas escapes from a slided debris, raising an issue of a birth of a new volcano to the alarming local people, although it also created a new local tourism draw, as sulphur smells was dominant. Gas composition dominated by CO and CO 2 , which were presents in a hazardous level for the people. The landslide was controlled by two boundary faults which aligned SW-NE and NNE-SSW and the slided mass involved a 5 m thick of the uppermost rock succession. Systematic surface mapping indicates two main hot spots occurred and was aligned NE-SW, with their peak temperatures exceeding 60 o C. A shallow boring conducted at one of the hot spot and vertical temperature gradients were measured from the borehole and the cutting samples. The results indicate a temperature peak of >65 o C existed at 2 m depth before considerably decreased to below 55 o C. These evidences confirm that the heat anomalies and gas escapes were local and only associated with the slided debris. Possible mechanisms that initiated the heat are interpreted as self combustion processes of the carbonaceous sediments and coal flags due to landslide frictions and increasing oxygen level within the slided debris. Abundant carbonaceous material contributes the persistent heat for months, although further observation suggests that the heat anomalies decreased onward.
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