Carbonate Facies and Sedimentation of the Klapanunggal Formation in Cibinong, West Java

DOI:10.17014/ijog.v1i3.196The limestone of Klapanunggal Formation is well exposed in the area of Cibinong and its surrounding,West Java. Detailed Observation of carbonate rock has been conducted in this area and aims to studythe carbonate facies and its growth environment. The method used in the field is the detailedinvestigation, while mikropaleontology and petrogaphic analysis conducted in the laboratory. Theresult of this study indicate that the carbonate rocks in the study area consists of four facies. namely:(1) boundstone facies, (2) packstone facies, (3) rudstone facies, and (4) limestone breccia facies. Basedon these data be interpreted that the boundstone facies was deposited in the reef front to reef crestenvironment, packstone facies developed on the lower slope, upper slope, and back-reef lagoonenvironment. Rudstone facies formed on the reef front, and breccia limestone facies were formed inthe lower slope. Geographically, the position of the carbonate body environment that is at the reeffront, upper slope and lower slope is expected to be in the North – North East while the reef crest andback reef lagoon is on the South – Southwest

Turbidite Facies of the Halang Formation in Ajibarang Area, Central Java

DOI: 10.17014/ijog.v6i1.112An understanding of deepwater turbidite sediments is very important mainly dealing with the determination of a reservoir geometry. The problem arising in the turbidite sediment geometry is very complex and varied, and its existence depends on how, when, and type of its environment. In Central Java, the broad turbidite sediment distribution of the Halang Formation is needed to be observed its facies association. This paper will discuss the turbidite facies of Halang Formation in the Ajibarang area. The method used to analyze the turbidite facies is by measuring stratigraphic sections and observing the lithofacies characteristics to reconstruct its depositional environment. The Halang Formation outcrop in the Ajibarang area is dominantly composed of alternating sandstone and claystone or marl. Based on the observation, the turbidite facies of Halang Formation, in the Ajibarang area, was deposited on a submarine fan system at the middle fan of suprafan lobes. Compiling with the previous studies, the source of the Halang Formation is indicated to be derived from the south southwest

Nose Structure Delineation of Bouguer Anomaly as the Interpretation Basis of Probable Hydrocarbon Traps: a Case Study on the Mainland Area of Northwest Java Basin

DOI: 10.17014/ijog.v7i3.144Two important aspects in the exploration of oil and gas are technology and exploration concepts, but the use of technology is not always suitable for areas with geological conditions covered by young volcanic sediments or limestone. The land of the Northwest Java Basin is mostly covered by young volcanic products, so exploration using seismic methods will produce less clear image resolution. To identify and interpret the subsurface structure and the possibility of hydrocarbon trap, gravity measurements have been carried out. Delineation of nose structures of a Bouguer anomaly map was used to interpret the probability of hydrocarbon traps. The result of the study shows that the gravity anomalies could be categorized into three groups : low anomaly (< 34 mgal), middle anomaly (34 - 50 mgal), and high anomaly (> 50 mgal). The analysis of Bouguer anomaly indicates that the low anomaly is concentrated in Cibarusa area as a southern part of Ciputat Subbasin, and in Cikampek area. The result of delineation of the Bouguer anomaly map shows the nose structures existing on Cibinong-Cileungsi and Pangkalan-Bekasi Highs, while delineation of residual anomaly map shows the nose structures occurs on Cilamaya-Karawang high. Locally, the gas fields of Jatirangon and Cicauh areas exist on the flank of the nose structure of Pangkalan-Bekasi High, while the oil/gas field of Northern Cilamaya is situated on the flank of the nose structure of Cilamaya-Karawang High. The concept of fluid/gas migration concentrated on nose structures which are delineated from gravity data can be applied in the studied area. This concept needs to be tested in other oil and gas field areas

STRUKTUR TINGGIAN DI SUB CEKUNGAN MAJALENGKA BERDASARKAN METODE GAYABERAT

Majalengka sub-basin in the eastern part of the Bogor Basin is mostly covered by thick volcanic deposits. However, oil and gas seepage appeared in the volcanic area. Due to seismic technology has not been able to penetrate the thick layers of volcanic rock, gravity is an alternative method to describe subsurface conditions in this area. Gravity method can determine the configuration of the basin based on different rock density. Identification of the structure and determination of structural high area is analyzed based on interpretation of gravity anomaly, residual anomaly, gradient analysis and 3D modeling of the gravity. Vertical gradient technique was used to determine the position of fault structure, while the Second Vertical Derivative (SVD) to determine the type of fault. A 3-dimensionals model was made to determine the distribution and geometry of the basin. The results showed that the structures control the formation of the basin is in the form of northwest-southeast reverse fault, east-west and southwest-northeast shear fault. The depth of the basement in the study area is between 2700-5000 m. These gravity analysis provide the information of structural highs that allow the presence of hydrocarbon trap: Kadipaten- Majalengka and Ujungjaya-Babakan Gebang High.Sub-cekungan Majalengka termasuk dalam Cekungan Bogor bagian timur yang   sebagian besar tertutup oleh endapan vulkanik yang cukup tebal.  Namun demikian cekungan ini mempunyai rembesan minyak dan gas yang banyak muncul di area vulkanik. Hingga saat ini, teknologi seismik belum mampu menembus lapisan vulkanik tebal untuk mengungkap konfigurasi lapisan batuan di bawahnya. Oleh karena itu digunakan metode gayaberat sebagai metode alternatif dalam menggambarkan kondisi bawah permukaan yang tertutup batuan vulkanik. Gayaberat adalah salah satu metoda geofisika yang dapat digunakan untuk mengetahui konfigurasi cekungan berdasarkan perbedaan parameter fisis densitas batuan. Identifikasi struktur dan penentuan area tinggian dilakukan berdasarkan interpretasi dari peta anomali gayaberat dan anomali residual, analisis teknik gradien dan pemodelan 3D gayaberat. Teknik gradien vertikal digunakan untuk menentukan posisi struktur sesar sedangkan Second Vertical Derivative (SVD) untuk menentukan jenis sesar. Model 3-dimensi dibuat untuk menentukan sebaran dan geometri cekungan. Hasil penelitian menunjukkan bahwa struktur yang mengontrol pembentukan cekungan adalah berupa sesar naik arah baratlaut-tenggara, sesar geser arah barat-timur dan baratdaya-timurlaut. Kedalaman basement pada daerah penelitian antara 2700-5000 m. Peta anomali Bouguer, anomali residual dan model 3D gayaberat memberikan informasi terdapat tinggian yang memungkinkan terdapatnya perangkap hidrokarbon, yaitu Tinggian Kadipaten–Majalengka dan Ujungjaya-Babakan Gebang

POTENSI DAN KARAKTERISTIK BATUAN SUMBER HIDROKARBON DARI CONTO PERMUKAAN DI DAERAH KARAWANG, JAWA BARAT

ABSTRAK Penelitian batuan sumber hidrokarbon yang dilakukan di daerah Karawang bertujuan untuk memperoleh data permukaan endapan klastik berbutir halus serta karakteristik litofasies yang diduga sebagai batuan induk hidrokarbon. Metode yang dipakai adalah penelitian lapangan dan laboratorium. Penelitian lapangan meliputi pengamatan stratigrafi detil dan pengambilan conto batuan. Analisa laboratorium terdiri dari analisa kandungan TOC dan pirolisis Rock Eval. Hasil analisa TOC terhadap 17 conto batulempung yang diambil dari Formasi Jatiluhur menunjukkan nilai berkisar antara sebesar 0,53-2,02%. Tmax delapan  conto sebesar 422o-432oC menunjukkan tingkat kematangan thermal yang belum matang. Delapan conto lainnya masuk dalam kategori matang dengan nilai Tmax sebesar 436o-462oC, sedang satu conto dengan nilai Tmax 467oC menunjukkan kategori pasca matang. Nilai HI berkisar antara 33-143 mg HC/TOC, dan termasuk dalam Fasies D, CD dan C. Berdasarkan nilai tersebut, batuan sumber di daerah penelitian dapat menghasilkan gas dengan kuantitas kecil. Potensi hidrokarbon di daerah penelitian menunjukkan kategori kekayaan material organik rendah hingga menengah, dengan kerogen yang termasuk type II dan III. Kualitas batuan sumber berdasarkan nilai HI termasuk dalam kategori gas prone

Studi Potensi Batuan Induk pada Sub Cekungan Banyumas dan Serayu Utara

Kajian yang dilakukan di daerah Banjarnegara, Wonosobo dan Kebumen bertujuan  untuk memperoleh data permukaan endapan klastik berbutir halus serta karakteristik litofasiesnya yang diduga berpotensi sebagai batuan induk. Sebanyak 9 conto dianalisa kandungan material organik karbonnya (TOC). Hasil analisa tersebut memperlihatkan bahwa nilai TOCnya berkisar antara   0,08 % dan 1,42 %. Berdasarkan hasil tersebut, didapatkan 2 conto berpotensi baik dan 3 conto berpotensi sedang  untuk dapat membentuk hidrokarbon, sedangkan  4 conto lainnya tidak berpotensi untuk membentuk hidrokarbon. Pyrolisis rock-eval dilakukan terhadap 5 conto yang berpotensi membentuk hidrokarbon, dan mempunyai nilai HI berkisar antara 26 dan 95 mgHC/gTOC. Berdasarkan nilai parameter evaluasi batuan induk HI (Waples, 1985), conto tersebut  berada dalam fasies organik CD dan D. Batuan induk tersebut dapat menghasilkan gas dalam kuantitas kecil. Hasil sementara dari pengamatan singkapan menunjukkan bahwa batuan klastik berbutir halus di daerah Banjarnegara diduga diendapkan dalam lingkungan dysaero

Audio-Magnetotelluric Modeling of Cimandiri Fault Zone at Cibeber, Cianjur

DOI: 10.17014/ijog.4.1.39-47The characteristic of Cimandiri Fault Zone has not been completely defined despite plenty of studies had already been accomplished. Therefore, an audio-magnetotelluric modeling was carried out. An audiomagnetotelluric survey was conducted at two parallel lines (N166oE) that intersected Cimandiri Fault Zone in Cibeber area, Cianjur. The distance between those two lines was 4.5 km and each line consisted of twenty-one stations with the distance between stations was 500 m. From the acquired forty-two apparent resistivity curves, inversion was executed to obtain two models. The models indicate layers with resistivity value of > 1000 ohm.m at about 500 m depth at both lines, which are associated to the basement layer. Columns of low resistivity zones in about the middle of each model represent fault zones as the weak zones of the area, and both models displayed them slightly dip southward as thrust faults

FASIES DAN LINGKUNGAN PENGENDAPAN BATUAN KARBONAT FORMASI PARIGI DI DAERAH PALIMANAN, CIREBON

ABSTRAK Batuan karbonat Formasi Parigi tersingkap baik di Komplek Kromong daerah Palimanan, Cirebon dimana studi fasies karbonat ini dilakukan.  Berdasarkan karakter fisik dan biota yang dikandungnya, batuan karbonat Komplek Kromong dapat dikelompokkan menjadi  7 fasies, yakni : (1) fasies boundstone, (2) fasies rudstone, (3) fasies cross bedded grainstone, (4) fasies foraminiferal packstone, (5) fasies algal-foram packstone,  (6) fasies floatstone, dan (7) fasies thin bedded wackestone-packstone. Fasies boundstone dapat dibagi menjadi 2 subfasies yaitu subfasies bafflestone dan subfasies framestone. Lingkungan pengendapan Formasi Parigi diperkirakan  diendapkan pada lingkungan reef front, reef crest, back reef, lagoon-surge chanel dan tidal flat-tidal chanel. Hasil analisis  fosil foraminifera besar menunjukkan  umur Formasi Parigi adalah Miosen Awal. Berdasarkan pada  pola lingkungan pengendapan Formasi Parigi diinterpretasikan terumbu bagian depan berada di sebelah timur laut, sedangkan terumbu bagian belakang di bagian baratdaya