Use of Attributes on 3D Seismic Data for Studying Mishrif Formation in East Abu-Amoud Field, South-Eastern Iraq

The seismic method depends on the nature of the reflected waves from the interfaces between layers, which in turn depends on the density and velocity of the layer, and this is called acoustic impedance. The seismic sections of the East Abu-Amoud field that is located in Missan Province, south-eastern Iraq, were studied and interpreted for updating the structural picture of the major Mishrif Formation for the reservoir in the field. The Mishrif Formation is rich in petroleum in this area, with an area covering about 820 km2. The horizon was calibrated and defined on the seismic section with well logs data (well tops, check shot, sonic logs, and density logs) in the interpretation process to identify the upper and lower boundaries of the Formation. Seismic attributes were used to study the formation, including instantaneous phase attributes and relative acoustic impedance on time slice of 3D seismic data . Also, relative acoustic impedance was utilized to study the top of the Mishrif Formation. Based on these seismic attributes, karst features of the formation were identified. In addition, the nature of the lithology in the study area and the change in porosity were determined through the relative acoustic impedance The overlap of the top of the Mishrif Formation with the bottom of the Khasib Formation was determined because the Mishrif Formation is considered as an unconformity surface.

STUDI IDENTIFIKASI PERANGKAP HIDROKARBON PALEOGEN - NEOGEN DI PERAIRAN WOKAM ARU UTARA, PAPUA BARAT: DATA UTAMA HASIL SURVEI GEOMARIN III

ABSTRAKPerairan Wokam Aru Utara, Papua Barat merupakan bagian tepi utara passive margin Mesozoik Arafura – Australia. Hasil survei dengan KR. Geomarin III di perairan Wokam 2014 diperoleh lintasan seismik Multi Kanal 1.182 km, dan pemeruman batimetri/sub bottom profiles (SBP) 1.510 km. Metode dilakukan interpretasi penampang seismik hasil survei, pengikatan sumur pemboran dan seismik, analisis petrofisika dan pemetaaan geologi bawah permukaan. Pada penampang seismik telah dilakukan interpretasi aspek struktur geologi dan perlapisan sedimen yang sebelumnya telah diikat dengan data sumur ASA-1X, ASM-1X dan ASB-1X untuk tiga horizon yaitu Top Neogen, Top Paleogen dan Base PaleogenPeta bawah permukaan Paleogen – Neogen menunjukan beberapa klosur yang berpotensi di bagian batas paparan dengan palung Aru serta bagian barat. Pada bagian Tenggara terdapat kenampakan onlapping sedimentasi Tipe struktural yang berkembang sebagai perangkap secara dominan berupa graben – half graben dan tilted faul. Onlaping sedimentasi yang mebaji juga dapat berpotensi.Struktur geologi pada area penelitian secara umum dikontrol oleh sesar utama Zona Sesar Palung Aru Utara di tepian paparan sampai lereng, mengarah utara - timur laut ke selatan - barat daya. Struktur ikutan yaitu sesar-sesar normal mengarah utara - timur laut ke selatan - barat daya di paparan sebelah timur zonar sesar utama.Studi awal potensi migas ini teridentifikasi empat lokasi potensi perangkap hidrokarbon dari umur Paleogen - Neogen, yaitu satu lokasi dari Peta Base Paleogen, dua lokasi Top Paleogen dan satu lokasi Top Neogen. kata kunci: Wokam, Aru, migas, seismik, struktur, interpretasi, jebakan, Geomarin III ABSTRACTThe waters of Wokam North Aru, West Papua are part of the northern edge of the Mesozoic passive margin of Arafura - Australia. Survey results with KR. Geomarin III in the waters of Wokam 2014 obtained a multi-channel seismic trajectory of 1,182 km, and bathymarism/sub bottom profiles (SBP) 1,510 km. The method is to interpret the seismic cross-section of the survey results, tie drilling and seismic wells, petrophysical analysis and mapping the subsurface geology. In the seismic section, an interpretation of the structural aspects of the geology and sediment layers has been carried out previously tied to data from the ASA-1X, ASM-1X and ASB-1X wells for three horizons, namely Top Neogen, Top Paleogene and Base Paleogene.The subsurface map of the Paleogene - Neogeneous surface shows several potential closures in the exposure boundary with the Aru Trench as well as the western part. In the Southeast, there is the appearance of sedimentation onlapping. Structural types that develop as traps are predominantly graben - half graben and tilted fault. The onlaping sedimentation also has potential. The geological structure in the study area is generally controlled by the main fault of the North Aru Trench Zone on the edge of the exposure to the slope, heading north - northeast to south - southwest. Follow-up structures are normal faults pointing north - northeast to south - southwest on the eastern exposure of the main fault zone.This preliminary study of oil and gas potential identified four potential locations for hydrocarbon traps from the Paleogene - Neogene age, namely one location from the Paleogene Base Map, two Top Paleogene locations and one Top Neogen location.Keyword: Wokam, Aru, oil and gas, seismic, structure, interpretation, traps, Geomarin III

Depositional sequence interpretation using seismic and well data of offshore Central Sumatra Basin

Offshore Central Sumatra Basin is an integral part of Central Sumatra Basin known for producing hydrocarbon basins. The derivation of stratigraphic study of seismic and well data is intended to improve accuracy of geological interpretation. Sequence stratigraphy studies have a significant role in exploratory studies to determine which depositional sequence can be inferred as hydrocarbon reservoir and its correlation in petroleum system. This study aims to identify biogenic gas sequential interpretation using seismic and well data of offshore Central Sumatra Basin. The procedure to analyze sequence stratigraphy is to identify stratigraphy surface markers using GR log, then map these markers to the seismic section that has been tied with good data to determine the distribution of each stratigraphy sequence. This study area has five depositional sequences, which are predominantly formed in marine depositional environments. Potential source rock in this area is at DS-1 which has a lacustrine depositional environment with euxinic conditions. The euxinic shale at the upper TST-1 deposit could be a source rock with hydrocarbon migration through faults. Biogenic gas reservoir potential is in Petani Formation (DS-5). Shale in MFS-5 and HST-5 could be a hydrocarbon trap, whereas LST-5 and TST-5 sandstone deposits can be a reservoir.

2D Seismic Reflection Study for Zubair Formation in East Nasiriya area, Southern Iraq

An interpretive (structural and stratigraphic) study of the two,-dimensional seismic, data of East Nasiriya area (30 km to the south east of Nasiriya oil field within Thi-Qar province, southeastern Iraq) was carried out using Petrel 2017 program. The study area has an importance due to its location between many oil fields, but still without exploration of oil wells. Twenty five seismic lines were used, date back to different types of seismic surveys conducted in the region at different time periods. Also, the seismic velocity surveys of the nearest wells to oil fields, such as Nasiriya-1 and Subba-8, in addition to their sonic and density logs were used. A synthetic seismogram with a good matching with the seismic section was achieved to ensure the identification of the reflectors and reflectivity type (peak or trough) and follow up each one through the whole area of interest. Top Zubair reflector was picked using the composite line to link the seismic sections with each other after enhancing the ties between seismic lines. Time and depth maps were made using velocity maps created from the velocity model. The seismic, interpretation, in the area showed the existence of certain stratigraphic, features, in the ,studied reflector. Some distribution mounds and sand lenses were observed in the study area, which are continuous in more than two-dimensional seismic line in the area. These activity elements provide a reasonable explanation for the distribution of hydrocarbons in the area of study.

Interactions between the prograding Giant Foresets Formation and a subsiding depocentre: Insights from the Parihaka 3D & ES89 2D seismic surveys

<p>This seismic interpretation project provides new insights into the interaction between the Pliocene-aged Giant Foresets Formation and the faults bounding the Northern Graben. A newly named fault-bounded depocentre within the North Taranaki Graben, the Arawa Sub-Basin, has subsided during the Pliocene, attracting volumes of sediment across the Parihaka Fault within large-scale channels. The study images kilometer-scale channels and explores the interplay between the progradation of the Giant Foresets Formation and normal faulting along the Cape Egmont Fault Zone. A focus is placed on imaging the provenance and depositional facies of sedimentary packages throughout the foresetting sequence of the Giant Foresets Formation. Mapping of the Waipipian-Nukumaruan-aged foresetting sequence within the offshore northern Taranaki Basin has previously shown the primary sediment transport direction is primarily NNW. This is contradicted by sediment-transport features mapped within the study area showing the sediment transport direction fluctuates between NE and SE. The primary mechanism of sediment redirection is faulting along the Cape Egmont Fault Zone and subsidence within the North Taranaki Graben, an elongate SW-NE graben within the northern Taranaki Basin. Smaller (˜10s m-scale) channels concentrate into much larger (˜100s m- to km-scale) mega-channels that travel E/NE into the subsiding Arawa Sub-Basin. Volcanic intrusions of the Mohakatino Volcanic Formation have also influenced the evolution of the mega-channels in the study area, via uplift and doming of the seafloor which provided a barrier to the transport of sediment. The Parihaka 3D and ES89 2D seismic surveys are interpreted using the IHS Kingdom software package to create a basic framework of horizons and faults over the Pliocene-Recent interval. Depth grid maps are produced from the grid of horizon picks. Isochore maps are produced which span key intervals between depth grids. A coherency cube of the Parihaka 3D is generated from the 3D seismic volume using OpendTect. Using the framework of faults and horizons within the coherency cube, imaging sediment transport and deposition features in the vicinity of normal faulting is made possible by flattening on a top foresets horizon and horizontally slicing the data at regular intervals. This recreates past conditions by removing the effects of fault-slip and differential compaction. These “time-slices” contain clear images of channels, canyons and fan-deposits allowing sediment provenance and transport direction to be mapped and interpreted. Finally, seismic section images from the Parihaka 3D and ES89 2D seismic surveys are generated along paths intersecting key geological features within the study area.</p>

Interactions between the prograding Giant Foresets Formation and a subsiding depocentre: Insights from the Parihaka 3D & ES89 2D seismic surveys

<p>This seismic interpretation project provides new insights into the interaction between the Pliocene-aged Giant Foresets Formation and the faults bounding the Northern Graben. A newly named fault-bounded depocentre within the North Taranaki Graben, the Arawa Sub-Basin, has subsided during the Pliocene, attracting volumes of sediment across the Parihaka Fault within large-scale channels. The study images kilometer-scale channels and explores the interplay between the progradation of the Giant Foresets Formation and normal faulting along the Cape Egmont Fault Zone. A focus is placed on imaging the provenance and depositional facies of sedimentary packages throughout the foresetting sequence of the Giant Foresets Formation. Mapping of the Waipipian-Nukumaruan-aged foresetting sequence within the offshore northern Taranaki Basin has previously shown the primary sediment transport direction is primarily NNW. This is contradicted by sediment-transport features mapped within the study area showing the sediment transport direction fluctuates between NE and SE. The primary mechanism of sediment redirection is faulting along the Cape Egmont Fault Zone and subsidence within the North Taranaki Graben, an elongate SW-NE graben within the northern Taranaki Basin. Smaller (˜10s m-scale) channels concentrate into much larger (˜100s m- to km-scale) mega-channels that travel E/NE into the subsiding Arawa Sub-Basin. Volcanic intrusions of the Mohakatino Volcanic Formation have also influenced the evolution of the mega-channels in the study area, via uplift and doming of the seafloor which provided a barrier to the transport of sediment. The Parihaka 3D and ES89 2D seismic surveys are interpreted using the IHS Kingdom software package to create a basic framework of horizons and faults over the Pliocene-Recent interval. Depth grid maps are produced from the grid of horizon picks. Isochore maps are produced which span key intervals between depth grids. A coherency cube of the Parihaka 3D is generated from the 3D seismic volume using OpendTect. Using the framework of faults and horizons within the coherency cube, imaging sediment transport and deposition features in the vicinity of normal faulting is made possible by flattening on a top foresets horizon and horizontally slicing the data at regular intervals. This recreates past conditions by removing the effects of fault-slip and differential compaction. These “time-slices” contain clear images of channels, canyons and fan-deposits allowing sediment provenance and transport direction to be mapped and interpreted. Finally, seismic section images from the Parihaka 3D and ES89 2D seismic surveys are generated along paths intersecting key geological features within the study area.</p>

Structural Interpretation of Seismic Data of Mishrif Formation in East Abu-Amoud Field, South-eastern Iraq

The seismic method depends on the nature of the reflected waves from the interfaces between layers, which in turn depends on the density and velocity of the layer, and this is called acoustic impedance. The seismic sections of the East Abu-Amoud field that is located in Missan Province, south-eastern Iraq, were studied and interpreted for updating the structural picture of the major Mishrif Formation for the reservoir in the Abu-amoud field. The Mishrif Formation is rich in petroleum in this area, with an area covering about 820 km2. The seismic interpretation of this study was carried out utilizing the software of Petrel-2017. The horizon was calibrated and defined on the seismic section with well-logs data (well tops, check shot, sonic logs, and density logs) in the interpretations process for identifying the upper and lower boundaries of Mishrif Formation. As well, mapping of two-way time and depth structural maps was carried out, to aid in understanding the lateral and vertical variations and to show the formation of the structural surfaces. The study found that Mishrif thickness increases toward the east, which means that it increases from the Abu-Amoud field in Nasiriyah towards the East Abu-Amoud field in Missan province. The aim of the study is to draw a high-resolution structural image of the East Abu Amoud field in southeast Iraq and to show the types of the existing faults and structures in the study area.

Constraining 3D geometric gravity inversion with a 2D reflection seismic profile using a generalized level set approach: application to the eastern Yilgarn Craton

One of the main tasks in 3D geological modeling is the boundary parametrization of the subsurface from geological observations and geophysical inversions. Several approaches have been developed for geometric inversion and joint inversion of geophysical datasets. However, the robust, quantitative integration of models and datasets with different spatial coverage, resolution, and levels of sparsity remains challenging. One promising approach for recovering the boundary of the geological units is the utilization of a level set inversion method with potential field data. We focus on constraining 3D geometric gravity inversion with sparse lower-uncertainty information from a 2D seismic section. We use a level set approach to recover the geometry of geological bodies using two synthetic examples and data from the geologically complex Yamarna Terrane (Yilgarn Craton, Western Australia). In this study, a 2D seismic section has been used for constraining the location of rock unit boundaries being solved during the 3D gravity geometric inversion. The proposed work is the first we know of that automates the process of adding spatially distributed constraints to the 3D level set inversion. In many hard-rock geoscientific investigations, seismic data are sparse, and our results indicate that unit boundaries from gravity inversion can be much better constrained with seismic information even though they are sparsely distributed within the model. Thus, we conclude that it has the potential to bring the state of the art a step further towards building a 3D geological model incorporating several sources of information in similar regions of investigation.

Imaging of shallow structures around Küçükçekmece Lake in Istanbul land area with high resolution geophysical data.

Küçükçekmece Lake and surrounding land area play an important role to understand the active tectonism of the southern land area of Istanbul. This study gives the results of a geophysical survey to understand the structural features of the study area. We collected geo-electrical data on the surrounding Küçükçekmece Lake. Totally 14 different VES values were inverted and evaluated variation of resistivity with depth. Additionally, the obtained apparent resistivity cross-sections for 3 profiles of VES points. All of them are interpreted considering geological well data from the study area and previous geophysical studies, which included especially high resolution shallow seismic data and chirp seismic data from the lake and shelf area in the Sea of Marmara close to the lake. The resistivity sections and inverted VES data show that faults cut the recent units and also cause resistivity changes in these units in the land area. These faults are consistent with the orientation of active faults observed from the seismic section on the lake and deforming the lake floor. This data set can be given as geophysical evidence for the existence of faults in the Istanbul land area.

Seismic imaging of dolerite sills and volcanic vents in the Central Karoo, South Africa: implications for shale gas potential

The Karoo Basin of South Africa covers an area of 700 000 km2 and has been identified as a possible shale gas reserve. Any evaluation of the shale gas potential of the basin must consider the widespread dolerite dykes and sills. These intrusions were emplaced into the Karoo Supergroup and are well dated at around 183 Ma. Their intrusion triggered the explosive releases of gas in the basin, marked on surface by breccia pipes and hydrothermal vents. This outpouring of gas has been proposed as a significant contributor to global climate change. Research into the three-dimensional interconnected structure of these dolerite sills and dykes and their interaction with the hydrocarbon rich layers in the lower part of the Karoo Supergroup has been limited to localized observations of outcrop, magnetic data, legacy seismic data (from the 1970s) and well core. Here we present an interpreted 65 km long higher-resolution 2D seismic reflection profile across the Karoo Basin, approximately 100 km southeast of Trompsburg. These data were collected in the 1990s and at the time deeper structures along the line interpreted. In this study we focus on the top 0.6 to 2 seconds TWT of the data. The seismic line images the interconnected and cross cutting nature of the dolerite dykes and sills along the profile. We also report possible evidence of a gas escape structure (approximately 2.5 km in diameter at surface) emerging near the edge of a dolerite sill in close proximity to the Whitehill Formation, which is the main target for shale gas exploration. This suggests that gas vents in the eastern Karoo Basin close to Lesotho are due to the release of gas from the carbonaceous shales of the Ecca Group. This is similar to breccia pipes mapped on surface in the western part of the Karoo Basin. This seismic section highlights why dolerite sills and dykes must be considered when evaluating the shale gas potential of the Karoo Basin. We propose that better characterization of the Karoo Basin subsurface by seismic and magnetic studies is necessary prior to any efforts to calculate shale gas reserves.