Seismic Sections Research Articles

The late Cenozoic expansion of the northeastern Pamir: Insights from the stratigraphic architecture of the Wupoer Piggyback Basin

• Onset time of the basin was the late Miocene to early Pliocene (∼5.8–4.6 Ma). • Multiple depocenters existed in the basin and intergraded to one in the Quaternary. • Eastward migration of the depocenter records the collision between the Pamir and South Tian Shan. The Pamir salient is the preeminent example of an intracontinental collision and defines the western end of the Himalayan-Tibetan orogen. Previous work has paid much attention to reveal the internal evolution of the Plateau. However, the structural growth and expansion of the Northern Pamir still have several unknowns. To address this process of the indentation, we describe the architecture of the Wupoer Piggyback Basin (WPB), the westernmost tip of the Tarim Basin, in between the northeastern Main Pamir Thrust (MPT), and the Pamir Frontal Thrust (PFT). The geometry of the WPB growth strata and its relationship with the compressive structures were explored through six seismic sections, five cutting the WPB along dip and one along strike. According to the sense prevailing in the literature, we define the onset of a piggyback basin with the first evidence of tectonic deformation within the basin fill. Interpreted from the seismic sections and field work, an unconformity between the Atushi Fm. and the underlying strata marks the base of the WPB, dated the onset of the basin at the latest Miocene to early Pliocene (∼5.8–4.5 Ma). The growth strata were separated into 6 units above the unconformity (G1-G6). The relative isopach maps reveal the existence of three main depocenters, evolving to a single one in the Quaternary. The structural interpretation documents the PFT is significantly segmented by transfer faults and lateral ramps. The eastward migration of the depocenter since the Quaternary points to the oblique collision between the Pamir and the South Tian Shan and gradual encroachment of deformation towards the east.

How do tectonics influence the initiation and evolution of submarine canyons? A case study from the Otway Basin, SE Australia

The architecture of canyon-fills can provide a valuable record of the link between tectonics, sedimentation and depositional processes in submarine settings. We investigated the role of plate tectonics in the initiation and evolution of submarine canyons. We demonstrate that events at the plate tectonic scale (i.e. continental break-up and shortening) have a first-order influence on the initiation and development of submarine canyons. The Late Cretaceous ( c. 65 Ma) separation of Australia and Antarctica initially resulted in extensional fault systems, which then formed a steep stair-shaped palaeoseabed. Subsequently, the Late Miocene ( c. 5 Ma) collision of Australia and Eurasia resulted in substantial uplift and exhumation on the SE Australian continental margin. These tectonic events led to elevated seismicity, which ultimately gave rise to gravity-driven processes (i.e. turbidity currents and mass wasting processes) and formed the base of the canyon. The inherited stair-shaped topography then facilitated further gravity-driven processes that established a mature sediment conduit extending from the shallow marine shelf to the abyssal plain. We suggest that the stratigraphic architecture of canyons can be used as an archive to record tectonic movements. Moreover, the factors that precondition and trigger gravity-driven processes can induce canyon initiation and facilitate canyon development. Supplementary material: A PDF file containing all the clean, uninterpreted seismic sections is available at https://doi.org/10.6084/m9.figshare.c.5937760

Pore pressure prediction using seismic acoustic impedance in an overpressure carbonate reservoir

The drilling engineers favor a quantifiable understanding of the subsurface overpressure zones to avoid drilling hazards. The conventional pore pressure estimation techniques in carbonate reservoirs are prone to uncertainties that affect the calculated pore pressure model resolution and are still far from satisfactory. Basically, in carbonate reservoirs, the effect of chemical process and cementation on porosity is more important than the mechanical compaction, so the conventional pore pressure prediction methods based on the normal compaction trend mostly do not provide acceptable results. Using the conventional methods for carbonate reservoirs can yield large errors, even suggesting a reduction in abnormal pressure in overpressure zones where considerable attention must be paid. Conventional methods need to model density and velocity to calculate the effective and overburden pressures. Converting acoustic impedance to density and velocity is always associated with errors and generally provides low resolution, which adds substantial uncertainties to the pressure prediction. Although pore pressure measurements are usually associated with low resolution, additional error-prone steps can be dropped if used directly. This research outlines the pore pressure estimation of a famous Iranian carbonate reservoir using direct acoustic impedance without inverting it to density and velocity. Finally, this method gives acceptable results in carbonate formations compared to the results of the Repeat Formation Test (RFT) in this region. The results show a zone of overpressure between the two low-pressure intervals of the carbonate reservoir. This result can be of great help in determining reservoir boundaries as well as in planning for drilling trajectory for new wells. Furthermore, the pore pressure estimation results also show pressure reduction in the central part of the seismic section. The proposed approach is a viable alternative to the conventional method and is in line with the geological field report, where the ratio of hydrocarbon potential of total rock on the reservoir sides is higher than its middle part. In this study, we want to emphasize that the calibrated function obtained in our area can be used in similar basins with carbonate reservoirs.

Semisupervised fuzzy clustering for facies analysis using extended elastic impedance seismic attributes

A novel method in seismic facies analysis is proposed to resolve the discrepancy between well and seismic facies concepts. Extended elastic impedance (EEI) attributes are ideally suited for facies analysis because they are representative of different elastic parameters of rocks. A semisupervised method aims to accept or reject seismic clustering based on the well facies interpretation. First, specific EEI logs/attributes are calculated after a feasibility study and EEI analysis of the well data set are used for facies analysis. Using EEI logs as input attributes prevents data deficiency as a result of upscaling of well-log data to the seismic scale in the learning process. Then, the seismic EEI attributes are calculated from prestack seismic data and used for seismic facies analysis considering a fuzzy clustering algorithm with parameters estimated from the well facies analysis stage. The fuzzy clustering methods using membership degrees in their algorithms are valuable tools to reduce uncertainties. To evaluate the method’s performance, 3D seismic data of an oil sand reservoir were selected as a case study. The comparison with previous crossplot methods in facies modeling confirmed the advantages of the presented results in seismic facies analysis. The seismic facies sections are sufficiently interpretable according to the geologic setting and correlate more with the well facies codes.

Three-stage extension in the Cenozoic Pearl River Mouth Basin triggering onset of the South China Sea spreading

In the Cenozoic, the East Asian Continental Margin developed intense rifting, producing massive rift basins and marginal seas. Among these, the South China Sea (SCS) and adjacent continental margin have attracted attention due to the obscure opening mechanism and strong lithospheric thinning. Based on the seismic sections and fault architecture data in this paper, we perform a delicate study of fault geometry, kinematics, and dynamics in the Pearl River Mouth Basin (PRMB). Three-stage Cenozoic extension is identified in the PRMB. The earliest NNW-SSE-directed extension occurred as early as the Paleocene, resulting in the NE- and ENE-trending faulting with dextral oblique extension to continue until the Middle Eocene. The second extension in the N-S direction resulted in NE-trending dextral transtension in the Late Eocene to Early Oligocene. Subsequently, the latest extension with the NNW-SSE direction occurred during the Late Oligocene, resulting in the sinistral strike-slip of a large number of WNW-trending faults. This second-third extension produced a NE-striking transtensional fault system with dextral right-stepping characteristics. In the Oligocene, this fault system resulted in the N-S directed scissor-type opening of the SCS with a progressively westward younging oceanic crust. During the Early Miocene, the dextral transtensional fault system disappeared due to the Pacific Plate subduction eastward retreat and the cease of the RRF sinistral strike-slipping. At this time, the SCS ridge spreading was controlled only by the NW-SE-oriented slab-pull linked to the proto-SCS.

Enhancing Characterization of Reservoirs Within the Niger Delta Basin Using Integration of Seismic and Well Logs

This research utilized well logs and seismic to unravel the reservoir architecture of a field within the offshore depolbelt of Niger Delta. Gamma ray and resistivity log responses were used for lithology and hydrocarbon reservoirs identifications. The principle of similarity in log signatures was used for correlation across the three studied wells. Pertinent reservoir parameters such as shale volume, effective porosity, permeability, hydrocarbon saturation and water saturation were calculated using well-established equations consistent with the geology. Seismic structural interpretation that will give insight to deformation of the field involves the identification and mapping of faults and horizons from seismic sections. By integrating information from seismic and wells, 3D geological modelling was done using geostatistical methods of Sequential Gaussian Simulation and Indicator. The general stratigraphy of the studied field comprises of intercalation of sands and shales which is typical of Agbada formation. Three reservoirs designated as AA, BB and CC were identified and mapped. Only reservoir CC was laterally continuous across the three wells. Reservoir AA has average shale volume of 13%, effective porosity 26%, hydrocarbon saturation 46% and permeability 1328 mD. Reservoir BB has shale volume of 10%, effective porosity 28%, hydrocarbon saturation 43% and permeability 1616 mD. Reservoir CC has shale volume of 21%, effective porosity 20%, hydrocarbon saturation 89% and permeability 580 mD. Twenty faults comprising of both major and minor faults were mapped. The faults mapped were majorly normal faults. The result of the seismic structural interpretation shows that the probable structures harboring oil and gas are a combination of four-way closure and fault assisted anticlinal structures. The modelling of facies and petrophysical parameters into maps aided the understanding of parameter’s influence on oil and gas production. Reservoir CC has oil and gas in commercial quantities with 2520 MMcf and 622Mbbls respectively. The result shows the reservoir has high performance system and is therefore recommended for development and production. The resulting models will aid placement of production wells and monitoring of future performance of the reservoirs.

Horizontal/vertical motion and wedge geometry of the Sinú Fold Belt, South-Caribbean accretionary prism, NW Colombia: Implications for a morphostructural zoning

The Sinú Fold Belt, located in the southwestern part of the South Caribbean Deformed Belt, northwest Colombia, has been interpreted as the outer portion of an accretionary wedge resulting from the subduction of the Caribbean Plate under the South American Plate. Several geological sections, across and along the offshore portion of the Sinú Fold Belt, have been constructed through geological interpretation of 2D seismic sections constrained by a few exploration wells. Their analysis has allowed us to quantify the amount of horizontal motion (shortening responsible for the structures and basal detachment displacement) and vertical motion (tectonic subsidence/uplift and wedge vertical thickening) undergone by the belt over time; unravel its recent evolution consisting of almost no active structures in the south edge and a large amount of active structures northwards; quantify its pore pressure, coefficient of friction and strength using its wedge geometry consisting of high taper angles in the lower continental slope near the deformation front and lower taper angles in the upper continental slope away from it; and understand the aseismic and trench-lacking character of the belt. These observations have been crucial to identify the main features of the morphostructural zones across the belt (Colombian Basin, lower continental slope, upper continental slope and continental shelf) and establish a new along-strike zoning (north region influenced by the Magdalena Fan/Canoas Oblique Ramp, Sinú Fold Belt s.s., and south salient influenced by the Uramita Fault).

Опасные газонасыщенные объекты на акваториях Мирового океана: Восточно-Сибирское море

For the first time, the researchers performed the interpretation of the upper part of the common depth point (CDP) seismic sections in the northwestern part of the East Siberian Sea (ESS) along the 44 lines of JSC MAGE in the amount of 8200 km. They revealed 129 anomalous objects in near-bottom sediments, potentially associated with gas accumulations and channels of its subvertical migration. The average distance between these objects along the lines was 63.6 km — 5.2—6.2 times less than in the Chukchi, Laptev and Bering seas. The authors substantiate that the ESS is characterized by a significantly smaller number of gas migration channels — active faults reaching the near-bottom sediments, compared to the seas mentioned above. This is consistent with the lower neotectonic activity of the ESS and the absence of significant seismic events. In the study area, the researchers revealed a large number of depressions in the bottom relief, which are associated with the furrows of ice gouging during the transgressions-regressions of the sea and at the present stage. Significant errors in the GEBCO bathymetry database were also revealed.

Seismic Interpretation and Petrophysical Analysis for Evaluation of Ataga Field, Onshore Niger Delta, Nigeria

The majority of geophysical survey in hydrocarbon exploration and production sector is driven by the ability to describe reservoirs. This research is aimed at describing the interpretation and petrophysical analysis of the reservoirs in Ataga field Niger Delta using a combination of seismic and well-log data. The Ataga Field in the Niger Delta was subjected to 3-D seismic interpretation and petrophysical study to perform comprehensive structural interpretation, prospect evaluation, and volumetric calculation. Two reservoir windows “1” and “2” were identified and correlated from four wells ATA 10, ATA 11, ATA 5 and ATA 7. Detailed evaluation was done on well ATA 11 since it is the only well that has sufficient data for both qualitative and quantitative interpretation. Structural interpretation for inline 5731 revealed fifteen faults on the seismic vertical section through ATA 11, most of which are antithetic faults while the rest are synthetic faults. Top and base of each reservoir window was delineated from the well. Result of the petrophysical assessment of reservoir A, B and C for ATA 11 revealed that the porosity values range from (24 -29) % which are indicative of very good to excellent porosity value according to Rider (1996). While the permeability values range from (1887-2582) mD were obtained from the three reservioir A, B and C of ATA 11 which depict very good to excellent reservoir units. Since, .all of the wells were discovered to have hydrocarbon-bearing reservoir formations (sandstones), the integration of structural interpretation and well logs have successfully revealed that the reservoirs are mostly oil-bearing zones.

Study of Subsurface Structural Image and Model Using 2D Seismic Reflection Method of Injana Field Area, Northeastern Iraq

The Injana field area is located to the north of Baquba city within Diyala. which was studied and interpreted by using 2D seismic data from the Oil Exploration Company. The study was concerned with the Jeribe Formation which is located within the Injana field area and belongs to the Tertiary Age. Two reflectors were detected based on synthetic seismograms and well logs of the Khashim Al-Ahmer-2 well. The structural maps were derived from seismic reflection interpretations to determine the location and direction of the basin. The depth maps were conducted depending upon the structural interpretation of the picked reflectors to show several structural features. Structurally, seismic sections show that the Injana area is affected by two types of reverse fault systems trending in a NW-SE direction, the first represents thrust faults affected on the lower Fars (Red Beds & Seepage) and the layers above it, the salt bed within Lower Fars Formation being as a detachment surface of this fault, the second represents two reverse faults affected on the bottom part of the Lower Fars (Transition beds) and the layers beneath. In addition, the reverse faults become dense in the north part. The structural maps reveal an elongated asymmetrical narrow anticline affected by one major thrust fault at Lower Fars Formation, and an elongated asymmetrical narrow anticline surrounded by two major reverse faults and consisting of three domes separated, Injana, Khashim Al-Ahmer and Khashab domes at the Jeribe Formation.

Structural Characteristics and Tectonic Evolution of the Wunansha Uplift in the South Yellow Sea Basin, China

By selecting typical seismic sections to carry out detailed structural interpretation, the structural style features of the Wunansha Uplift in the South Yellow Sea basin were systematically combined, and the compressional structures (imbricate, opposite/back thrust, and Y-shaped structures), strike-slip faults (positive flower-shaped faults), and extensional normal faults (listric-shaped normal faults) were identified. On this basis, combined with the characteristics of the regional stress field and the background of deep geodynamics, the genetic mechanism and structural evolution of the structural style in the Wunansha Uplift were defined. The stress mechanism of the compressional structures originated from the initial high-speed and low-angle NW subduction of the paleo-Pacific plate during the early Yanshanian movement in the Early Jurassic. The regional strike-slip fault was mainly a positive flower structure with compression and torsion characteristics, and its stress mechanism originated from sinistral shear caused by the Early Cretaceous low-angle NNW subduction of the paleo-Pacific plate. The Tan-Lu fault in eastern China also had sinistral shear characteristics in this period. The extensional normal fault was characterized by a listric shape, which developed along the northern boundary of the Wunansha Uplift, that is, the connection between the Wunansha Uplift and the Southern Depression of the South Yellow Sea basin. The stress mechanism was derived from the transition of the paleo-Pacific plate from low-angle to high-angle subduction during the late Yanshanian movement in the Late Cretaceous. Simultaneously, the tectonic stress system in eastern China also changed from compressional to tensional.

Indicators for identification of lacustrine sandstones of sandy debris‐flow origin: A case study of Es1 Member, Palaeogene Shahejie Formation, Nanpu Sag, Bohai Bay Basin, China

The first member of Shahejie Formation of Eocene–Early Oligocene (Es1, Nanpu Sag) consists of fluvio-deltaic to deep lacustrine shale-sandstone accumulations, and the deep lacustrine deposits include sandy debris flow (SDF), turbiditic and mudrock facies. In the process of hydrocarbon exploration, it was found that that SDF sandstones in the deep lacustrine deposits can constitute excellent hydrocarbon reservoirs. Therefore, the identification of these lithofacies, especially SDF sandstones, is crucial for hydrocarbon exploration. We document here parameters that discriminate lacustrine SDF sandstones from turbiditic and mudrock deposits. Data from cores, wireline logs, and seismic sections are integrated and interpreted. Core-based identification indicators of the SDF sandstones include massive structures with upper and lower sharp contacts with interbedded mudrocks, lateral pinch-outs, locally imbricated to floating pebble-size grains, and elongated (teared) mudrock clasts within the middle and upper parts of normally- or inversely-grading sandstone and poor to high matrix content. These properties are attributed to deposition of non-Newtonian flows with sediment-support mechanism of dispersive pressure, matrix strength and buoyancy, sediment-transportation mechanism, and sediment-settling properties (hindered settling and freezing of the SDF). Log-facies identification indicators of the SDF sandstones are characterized by higher RLLD/RLLS values (40–80 Ω m), higher SP values (35–70 mV), lower Gamma ray (GR) values (70–120 API), and strongly serrated curve motifs. Seismic facies identification indicators of the SDF sandstones have mound-like, lenticular, or wedge-shaped external geometries, and interior worm-like and fusiform chaotic reflections with medium to strong amplitude, medium to high frequency, and medium to low continuity. The results and interpretation of the integrated core-log-seismic data as identification indicators are useful tools for identifying SDF sandstones and effectively distinguishing them from other deep lacustrine deposits.

Deep seismic structure of the Sikhote-Alin folded system according to the GSZ (in the alignment of the reference profile 8-DV)

The results of deep seismic studies on the Sikhote-Alin fragment of the reference geophysical profile 8-DV are presented. A deep seismic section of the Earth's crust and upper mantle with the velocity distribution of longitudinal waves is constructed. The complex dislocated structure of a powerful Paleozoic sedimentary complex within the Middle Amur Depression has been established. Crystalline rocks with longitudinal wave velocities of 6.0-6.2 km/s lie at depths from 8 to 13 km in different parts of the Middle Amur Depression and 4-6 km within the Sikhote-Alin orogenic complex. In the entire thickness of the Earth's crust of the Sikhote-Alin fragment of the 8-DV profile, the velocities of longitudinal waves are 6.3-6.35 km/s. The thickness of the Earth's crust varies from 32 to 35 km. Along the Mohorovichich boundary, the velocity of longitudinal waves in general is 7.8-8.3 km/s. The correlation of the identified anomalies according to P-wave data with structural-tectonic zones was carried out.

Seismic clues into the origin of polygonal faulting and pockmarks in the Great South Basin, New Zealand

Description Geologic feature: Polygonal faulting and pockmarks in the Great South Basin New Zealand Appearance: Dense faulting among horizons in cross section and reflector concave features in seismic sections Map view appearance: Dense faulting and multiple circular features Features with a similar appearance: Tectonic faulting, mounds, syneresis, carbonate mounds, and dissolution features Formation: Rakiura Group, offshore, Great South Basin, southern New Zealand Location: Great South Basin, southern side of the Southern Island in New Zealand Age: Eocene Data sets: A 3D seismic reflection data, from New Zealand Petroleum and Minerals (NZP&M), New Zealand Seismic attributes: Variance, curvature, dip magnitude, and color blending

Geometry and Kinematics Characteristics of Strike-Slip Fault Zone in Complex Structure Area: A Case Study From the South No. 15 Strike-Slip Fault Zone in the Eastern Sichuan Basin, China

The eastern Sichuan Basin has undergone multiple stages of tectonic evolution and shows complex structural characteristics. It is found that there are a series of NW-SE base-trending strike-slip faults in this area besides NE-SW strike-blocking structures. There are almost no previous studies on strike-slip faults in the eastern Sichuan Basin. This paper fills in the blank of geometry and kinematics research on the strike-slip fault zone in this area. Based on highly precise 3D seismic section, coherent attribute slice and time slice, the geometric and kinematic characteristics of the fault are analyzed. The dynamic characteristics are analysed based on the structural style of the superimposed development model and the nature and activity intensity of strike-slip faults in different periods. and it was found that No. 15 strike-slip fault was a large basement strike-slip fault. The research results show that the profile of the No. 15 strike-slip fault mainly shows a subvertical fracture, positive flower structure and negative flower structure and a composite flower structure with positive and negative flower structures superimposed on each other in the upper and lower planar sections with linearly outspread and zonal distribution characteristics; spatially, there is a “ribbon” effect and a “dolphin” effect. the left strike-slip distance of the TS interface is 0.462 km, and the right strike-slip distance of the TP2 interface is 0.782 km. The strike-slip fault experienced at least three active stages of superimposed deformation during its formation and reconstruction, among which episode II in the middle Caledonian movement was the main active stage of the No. 15 strike-slip fault zone. This study of the structural style and genetic mechanism of a strike-slip fault zone is of guiding significance to the exploration and development of strike-slip fault-controlled reservoirs in the study area.

Current Challenges in Seismic Drilling Operations: A New Perspective for Petroleum Industries

The location of the well is usually selected with the help of surface seismic images. It can be helpful to know the position of the drill relative to the seismic section when starting underground drilling. However, obtaining this information is based on the fact that the vertical axis of the seismic section is in terms of distance. Seismicity during drilling operations provides valuable solutions to overcome many limitations in conventional well seismography. Nevertheless, so far, it has not succeeded in gaining a significant share of the market. Recent advances have provided new opportunities for this technique. As we know, revising the prediction of the results or data of a well is only possible when the drilling work of the well has been completed. Indeed, the new information and conclusions obtained from the revision of the information will be considered too late, and there is no possibility of changing the drilling performance. In this study, techniques are discussed in which the information obtained during drilling can affect the performance and drilling path. The project also presents the principles of seismic drilling and its application potential and examines the progress made so far and how new research initiatives are reviving enthusiasm for the technique.

Geophysical investigation of hydrocarbon in the southern part of Douala Kribi Campo basin, Cameroon

Well logging analysis and 3D seismic method are combined to evaluate the nature of fluids and reservoir characteristics in the southern part of the Douala/Kribi-Campo basin (DKC). Scientifiques researches that exhibit the important geological and geophysical settings of this basin are lacked. The successful investigation of these areas is possible if the stratigraphical and petrophysical properties of reservoir are properly evaluated. Extracting facies types from 3D seismic sections is a rapidly evolving discipline that facilitates the development of reservoir prediction models. So, a 25m × 25m seismic grid associated with Gamma-Ray log (GR), Neutron (Nphi) log, resistivity log, sonic log and density (RHOB) log have been performed. The results highlight the sedimentary environment and facies, porous-permeable clay banks, clay content, the porosity, saturation and the nature of the fluids in the reservoir. The petrophysical evaluations indicates the presence of potential petroleum reservoirs, mainly sandy-clay with 3.81–29.47% volume, 17.37–27.85% porosity and 47.74–56.02% water saturation. The nature of fluids present in the reservoir is oil, gas and water. This research work will serve to encourage hydrocarbon (HC) exploration in the DKC Basin by adopting strategies where seismic stratigraphy combined with well datas will be the most likely means of providing drill targets to more independent operators. The results of this study will serve for the future prospector on the neighboring oil and gas fields of our study area. Significant advances has been made to ensure future exploration success.

Visual duplicates search of fracture zones of seismic databasesbased on the method of solving the ICP variational problemin closed form and inverted index

In this paper fast methods are proposed for search the fracture zones in seismic databases on two types of data: seismic section (two-dimensional data) and seismic cube (three-dimensional data). These methods are an integral part of the mapping technology for filtering channels and large volumes of seismic data and useful for automating interpretation of heterogeneous seismic data. The proposed methods for searching the similarity of fracture zones were investigated using the Open Seismic Repository reference dataset, which contains information about geological rocks in the area of the North Sea and compared with other known methods for solving this problem, the results were discussed in the article.

Three-dimensional seismic analysis of a polygonal fault system (PFS) in the Northern Carnarvon Basin, Australia: Implications for fluid flow migration and gas hydrate system

Polygonal fault system (PFS) is confined to fine-grained strata and have significant potential for hydrocarbon plumbing systems in sedimentary basins from deeper structures to shallow-depth gas hydrate systems. Based on a three-dimensional (3D) seismic reflection dataset from the Exmouth Plateau, Northern Carnarvon Basin, NW Shelf Australia, two different tiers of PFS (PFS–I and PFS-II) are characterized in section as well as in the plan views. The PFS-I is consisted of Early Jurassic-Early Cretaceous shallow marine limestone and marl, while the PFS-II is composed of Late Cretaceous to Paleogene bathyal facies with mudstone, calcareous mudstone, marl and silty mudstone. The polygonal faults of PFS-I show relatively low amplitude reflections, which are difficult to identify in seismic amplitude sections. PFS-I can be effectively depicted via coherency sections and time slices, with a good relationship between the low coherent black anomalies and the polygonal faults. In contrast, the polygonal faults of PFS-II are characterized by high-medium amplitude and low continuity seismic reflections, which can be easily identified in the seismic profiles and coherency time slices. The polygonal faults are represented by small throws (5–15 m) and multidirectional strikes. In addition, a series of gas chimneys, pockmarks, and shallow-depth high-amplitude anomalies of the gas hydrate system have also been identified above the deeper Triassic tectonic faults and uplifts. The polygonal faults might increase the connectivity and permeability of the seal and fine-grained layers, resulting in a certain local reduction of seal integrity and an increase in the possibility of fluid leakage. The typical seismic characteristics of PFS and the shallow depth high-amplitude anomalies of the gas hydrate system indicate a significant relationship among the deep-depth Triassic thermogenic gas, the fluid flow migration, and the development of the generation of gas hydrate system.

2D Seismic Data Analysis of Judaida Structure, Northern Iraq

This research aims to study the structural analysis of the 2D reflection seismic data for the Judaida subsurface structure located in Kirkuk province, northern Iraq. It is located 60 Km southwest of Kirkuk oil field, and 35 Km southwest of Jambur oil field, the Daquq River passes through the study area. The reflectors in the seismic section were picked and identified by using the synthetic seismograms generated from the logs data of the Jd-1 well. Three main seismic reflectors, Fatha, Jeribe, and the Euphrates were chosen. These mentioned sedimentary formations were deposited during the Middle Miocene, Lower Miocene, and Early-Mid Miocene respectively. Time and depth maps were drawn for these three reflectors by processing average data from Jd-1well. The structural interpretation results showed a structural closure on both time and depth domains in the middle of the study area. Judaida structure represented an asymmetrical longitudinal anticline fold. The Northeast limb has a dipping angle of 6-8 degrees more dip than the Southwest limb that has a dipping angle of 1-6 degrees, and the direction of the axis of the general structure is towards the Northwest-Southeast. The general dipping of the fold is toward the north east.