3D Seismic Survey Research Articles

On new prospects for petroleum and gas capability of Paleozoic sediments of the Karpovski projection

The article presents the geological data of recent years – the results of seismic exploration and deep drilling, which allow us to make new constructions of the model of the structure of the Paleozoic sedimentary complex of the northern side zone of the Caspian basin. In the historical development of the Caspian sedimentary basin, multiple geotectonic collisions have been observed, leading to transgressions and regressions of the Paleocean, as well as erosion of accumulated sedimentary strata, as well as interruptions in sedimentation. In the northern side zone, the determining influence of the structural sedimentation factor affected the age-varying carbonate ledges of the Karachaganak carbonate platform of the Aksaiblock, the Teplov-Tokarev zone of the Karpovsky tectonic ledge. Most of the oil, oil and gascondensate and gas condensate fields identified in the subsalt complex of the north of the Caspian Basin are associated with these zones. A comparative comparison of the deposits of the instrument zones of the Caspian basin has shown a fundamental difference in the conditions of accumulation of productive horizons, which lies in the nature of the location and in the significant variability of the filtration and capacitance properties of formations in natural reservoirs. The presence of deep-submerged carbonate structures is predicted in the deep part of the depression, on the slopes of carbonate platforms. Prospects for the detection of organogenic structures in the inner part of the paleobasin are assumed on the eastern extension of the Karpovsky ledge of the foundation and inside the Pogodaevo-Ostafyevsky trough, where, according to the results of 2D and 3D seismic surveys, promising structures Cretaceous, Orlovskaya and a number of others have been identified.

Quantitative seismic fracture characterization of a sandstone reservoir — Decatur, Illinois Basin

The Illinois Basin Decatur Project, a carbon capture and sequestration task, was undertaken to sequester 1 million tonnes of CO2 into a sandstone reservoir. A 3D seismic survey was conducted to characterize the reservoir. A geomodel was developed from seismic data, inversion results, and well data to geostatistically map the storage potential of the reservoir. However, no fracture model was created or utilized in this exercise. Fractures inherently influence the porosity and permeability of a reservoir. Ignoring them in reservoir characterization is not an optimal reservoir management practice. The image-log interpretation from a few vertical wells drilled in the area shows the bedding plane dips, but no fracture has been identified. However, the lack of fracture crossings in a few vertical wells does not imply that a formation is devoid of fractures altogether. Hence, seismic fracture characterization (leveraging the dense 3D seismic data) is necessary for a reservoir characterization exercise. We utilized the publicly available Decatur 3D seismic data set to run a seismic fracture characterization workflow to delineate potential fracture corridors present in the reservoir. We calculated three edge detection attributes (structural tensor, structure-oriented semblance, and structural dip) in combination to delineate the fracture lineaments. Our workflow extracts several quantitative measures of the seismic lineaments such as dip, azimuth, area, and length, which can be analyzed statistically. The principal focus of this work is to find a way forward to integrate the fractures from seismic data in a geologic model that can be utilized in simulations. Based on our interpretation of seismic fractures, we created a discrete fracture network that can be a building block for creating a finer-resolution fracture model. We also explored the fractal characteristics of seismic-derived fracture lineaments as a way forward for generating discrete fracture networks.

Seismic Reprocessing Overcomes Uncertainty in Offshore Egyptian Field

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 214066, “Seismic Reprocessing Leads to New Breakthroughs—A Successful Case in the ASH Field, AG Basin in Egypt,” by Mohamed Elokr and Ahmed Lotfy, Kuwait Energy Egypt, and Wei Xing, United Energy Group, et al. The paper has not been peer reviewed. _ The ASH oil field is in the eastern portion of the AG Basin in Egypt. The Lower Cretaceous Alam El Bueib is the main oil-producing formation. Because of the high heterogeneity of the Abu Roash succession, in addition to the influence of thick limestone of the Upper Cretaceous and the influence of multiple complex faults, the quality of seismic data is very poor, requiring seismic reprocessing. Two key techniques were used to achieve the goal: New vertical seismic profile (VSP) well data were acquired to adjust the velocity model, and common reflection angle migration (CRAM) prestack depth migration (PSDM) was used for reprocessing. Introduction The ASH field produces oil from the Aptian Lower Cretaceous reservoir. The ASH structure is interpreted as an elongated east-northeast/west-southwest anticline with intensive breaching on the downthrown side of northwest/southeast to west-northwest/east-southeast-oriented normal faults with obvious signature of synsedimentary activities. The entire area was subject to a series of tectonic events affecting the Western Desert, which led to a complex fault regime clearly recognized in the ASH structure by a series of horizontal displacement across the northwest/southeast faults. Strike/slip to oblique-slip faults also are observed from thicknesses of the cretaceous formations, creating significant difficulty in fault definition. The 3D seismic data acquired in 2007 suffered from losing amplitude of the Lower Cretaceous and deep Jurassic reflectors because of the complex structure. The strong carbonate markers disappear north of the field, where high, dense fault intersection is present closing from the main bounding fault. Loss of seismic amplitude could have severe effects on of the future economics of the field. The seismic survey was reprocessed two times without significant enhancement of the fault imaging. PSDM was run without velocity control, resulting in an uncertain velocity model with inaccurate fault imaging and a mismatching between actual and prognosed depths of the drilled wells of greater than 50 m. This contradiction in reservoir mapping meant that the northern portion of the field remained unexplored. Acquiring VSP in the recently drilled well encouraged reprocessing of the 3D seismic survey using well velocity as a control point in adjusting the seismic velocity model, and application of CRAM technology to improve fault imaging and appraise the uncertain area of the ASH field. CRAM Methodology CRAM was developed as a type of beam migration. Asymptotic ray tracing is performed, assuming that one-way diffraction rays from the subsurface image point to the surface sources and receivers. The takeoff angles from the image point are measured around a given local normal to a background reflection surface for each source ray and receiver ray. A system of source and receiver ray pairs is formed, and the recorded seismic data can be mapped into a local angle domain based on the reflection angles at the subsurface image points.​​​​

Seismic survey of steeply inclined coal seams using the vertical data acquisition system

Prior to the establishment of a coal mine, a high-resolution three-dimensional (3D) seismic survey was carried out. For seismic exploration of steep coal seams with an inclination angle more than 45°, the selection of the data gathering system is essential. The time disparity that remains when the traditional acquisition technology acquires 3D seismic data will be rather significant. The relationship between coal seam inclination, remaining time difference, and reflection coefficient is investigated in light of the presence of steeply inclined coal seams. When the direction of the generation surveying line is parallel to the coal seam, it is suggested as a vertical data acquisition system. To create a vertical data gathering system, the point is situated on the down-dipping side of the coal seam and a predetermined distance is kept between shooting points and detection points. A vertical data collection system was used to implement 3D seismic data acquisition in the Muli Coalfield in northern Qinghai. As a solid foundation for the future processing and analysis of 3D seismic data, valuable observation data with high resolution were successfully obtained. The study came to the conclusion that a vertical data collecting system is helpful in promoting effective coal mine output.

Generalization of Snell's Law for the propagation of acoustic waves in elliptically anisotropic media

<abstract> <p>In seismic data processing, both in inversion (Inverse Processing) and modeling (Direct Processing), it is essential to consider anisotropy to unravel the geological structure of the subsoil. Besides, in most cases, the macroscopic model of anisotropy in 2D seismic surveys is elliptical and weak, with ratios of anisotropy close to one. Therefore, it is crucial to have at disposal the analytical formulas for acoustic wave propagation in elliptical anisotropic media. We presented the generalization of the Snell's Law for the case of acoustic wave propagation in elliptically anisotropic media. The generalization of the Snell's Law for acoustic anisotropic media had different applications in digital processing, raytracing, and acoustic inversion to properly consider elliptical anisotropy.</p> </abstract>

Reflection seismic imaging of subsurface geologic structures in the Bayan Obo mining area, China

A dense 2D seismic reflection survey was conducted at the Bayan Obo rare-earth-elements-Nb-Fe deposit in China to explore its geologic features and mineral endowment. A composite processing workflow was established for prestack depth imaging of this data set, which involved static correction to compensate for shifts caused by lateral inhomogeneities in near-surface layers and rugged topography. Standard methods were used to attenuate different types of noise and improve the signal-to-noise ratio of the data. A velocity model in the depth domain was obtained from refraction tomography and velocity analysis, and then used in migration. The preliminary interpretation of the final image revealed the mapping of mineralization at its true position in depth, indicating a relatively deep extension (approximately1.5 km). The results demonstrate the potential of seismic imaging as a complementary exploration tool to gravity and electromagnetic methods for mineral exploration purposes in the Bayan Obo mining area, providing a high-resolution seismic image and allowing for depth characterization of the mineral deposits. In addition, the images provide important information for guiding the selection of drilling borehole locations for deep exploration.

3D modeling of salt domes according to detailed drilling data in the Precaspian region

To create three-dimensional models of arcomorph structures based on detailed data of drilling without involving genetic considerations and indirect information, the potential fields method is effective, which consists of finding an approximating three-dimensional function, the set of isolevel surfaces of which are identified with stratigraphic boundaries, using the coordinates of the formation intersection points. For approximation, mainly three-dimensional splines expressed in terms of Green’s functions were used. The main difficulties are associated with the presence of structural unconformities, to take into account which the initial data, and the models built on their basis, are subjected to special spatial transformations. To avoid the influence of high-amplitude arcomorphs on the geometry of the layers of the pre-salt complex, the modeling of the latter was carried out separately from the intensely deformed evaporates and overlying layers. Assaying of the method was carried out at one of the sites in the Caspian Sea. On the study area, according to the interpretation of logging data from 249 wells, a three-dimensional model was created, including several arcomorph structures, and covering the stratigraphic interval from the Emsian stage of the Lower Devonian to Quaternary deposits. The results confirmed the presence of arcomorphs with overturned beds. Such structural forms are poorly fixed by 2D–3D seismic survey methods. The proposed method can be applied in geological studies in the search and exploration of hydrocarbons in salt dome areas.

A 3D Seismic Survey Designing to Visualize the Oil Reservoir in West Kifl and Al-Marjan Fields, Central Iraq

Marjan fields west of Kifl, represent the underground geological structures that contain oil-producing reservoirs in central Iraq. The objective of this study is to identify the most important acquisition criteria that can design an optimal 3D reflection seismic survey to obtain high-resolution seismic images of four major reservoirs. Hartha, Zubair, Najma, and Churra chine in Marjan fields, west of Kifl as oil reservoirs within the study area, for which a three-dimensional design is required. Generally, it is found that a specific container size of 25×25 m is suitable for sampling the field of the reflected waves in the study area. The group interval and the survey resource interval determined this size of 50 m was adopted for the time interval of the source and receiver. A dip of 30, and a maximum frequency of 70 H, were used to create the survey design. The migration aperture is calculated using the variation of velocity with depth and is 2450 m. All these computational and statistical parameters were performed using MESA Expert v11.02 software.

Achieving Robust Compressive Sensing Seismic Acquisition with a Two-Step Sampling Approach

The compressive sensing (CS) framework offers a cost-effective alternative to dense alias-free sampling. Designing seismic layouts based on the CS technique imposes the use of specific sampling patterns in addition to the logistical and geophysical requirements. We propose a two-step design process for generating CS-based schemes suitable for seismic applications. During the first step, uniform random sampling is used to generate a random scheme, which is supported theoretically by the restricted isometry property. Following that, designated samples are added to the random scheme to control the maximum distance between adjacent sources (or receivers). The null space property theoretically justifies the additional samples of the second step. Our sampling method generates sampling patterns with a CS theoretical background, controlled distance between adjacent samples, and a flexible number of active and omitted samples. The robustness of two-step sampling schemes for reallocated samples is investigated and CS reconstruction tests are performed. In addition, using this approach, a CS-based 3D seismic survey is designed, and the distributions of traces in fold maps and rose diagrams are analyzed. It is shown that the two-step scheme is suitable for CS-based seismic surveys and field applications.

Salt Eruptions and Their Role in the Shaping of the Oil Trapping for Selected Fields in Eastern Iraq

This research had been achieved using 2D seismic sections to study the presence of subsurface salty bodies in the Khashim Al-Ahmer, Galabat, Injana fields as a case study. The selected oil fields is located to the northeast of Baquba city within Diyala Governorate. The study aims to determine the salt accumulations of the selected fields and their role in the formation of oil traps. The interpretation of seismic data was focused on two reflectors Fatha and Jeribe Formations which belong to the lower and Middle Miocene. Structurally, Two systems of reversal faults are affecting the fields, according to seismic sections, the first represents thrust faults affected on the top part of Fatha (Red Beds & Seepage) and the layers above with large displacements and trending in an NW-SE orientation; The separation surface of these faults is the salt bed in the Fatha Formation. the second represents reversal faults affected on the lower section of Fatha (Transition beds) and the layers beneath with high displacements. The research concludes Petroleum flow from the source was directed by the faults created by the broad Zagros tectonism to Miocene and younger traps, also seal fracturing exceeds vertical petroleum flow. The differences in fault types are caused by the presence of a salt bed within the Fatha Formation and the high variation in its thickness at the crest and flanks. So, the main recommendation of research is to implement a 3D seismic survey covering these fields to determine salt body areas.

A prospect analysis of the Upper Oligocene sandstone reservoirs of the Wenchang 9 block, Pearl River Mouth Basin, northern South China Sea margin

Faults can act as a migration pathway and/or a lateral seal in structural traps in the Wenchang 9 block (WC9B) oil field, affecting the potential for enhanced hydrocarbon recovery in the field. In this study, three-dimensional (3D) seismic survey and well data are used to characterize Upper Oligocene fan delta - tidal flat heterogeneous reservoirs and investigate fault seal potential in two new structural traps interpreted in the WC9B oil field. Five lithofacies are identified in the Upper Oligocene Zhuhai Formation based on the well log analysis and core description. The fan delta front and sand-rich tidal flat sandstone of facies F1 in reservoir unit A of the middle Zhuhai member is characterized by the best porosity and permeability. The RMS amplitude attribute analysis and facies modeling help to predict gradual upward progression of the F1 fan delta deposits from the proximity of the Shenhu Uplift to the NW into the basin for ∼ 7–8 km during accumulation of the middle member. The NE-dipping conjugate normal faults of lower throw in the hanging wall of the NW-dipping main normal basement faults contributed to the formation of hydrocarbon-bearing structural traps and side seals. Two new structural traps in the middle member of Zhuhai Formation interpreted in the WC9B oil field. The traps are 3-way dip closure bounded by the NE-dipping normal faults of the conjugate set that are characterized by good sealing potential in the interval of the middle member. The results of this study contribute to the optimization of the enhanced hydrocarbon recovery of the WC9B oil field.

CO2 geological storage prospects of Lithuania – update

The CO2 geological storage assessment in the Cambrian saline aquifers in west Lithuania is considerably improved by 3D seismic survey of the Gargždai Elevation and Syderiai Uplift. The CO2 storage capacity of the Syderiai site is assessed as large as 56.7 Mt (area 62 km2) owing to the high reservoir properties (average porosity 17 % and permeability 400 mD) of the Middle Cambrian saline aquifer of 50 m thick and 1458-1508 m deep. The tectonic uplift is controlled by the large-scale Telšiai strike-slip fault. The Syderiai site was initially considered as the potential UGS site. The acreage of the Gargždai Elevation, comprising six depleting oil fields, is assessed 133 km2 and the storage volume is evaluated 31.3 Mt. The main challenging parameter is a poor average porosity (7 %) and fractured type of reservoir (permeability about 10 mD) about 70 m thick and 2200 m deep. A residual oil zone (ROZ) assessment suggests are very high protentional for CO2 combination in west Lithuania which is the only prospective site known in the Baltic region of this kind.

Pseudo-3D cubes from densely spaced subbottom profiles via projection onto convex sets interpolation: An open-source workflow applied to a pockmark field

High-resolution subbottom profiler (SBP) data are commonly recorded during academic or industrial surveys and analyzed as 2D profiles. However, there is growing interest in 3D imaging of the shallow seafloor subsurface, e.g., site surveys prior to the installation of offshore wind farms. Despite ongoing advancements in 3D systems, SBPs continue to be used mainly for 2D profiling. In other seismic imaging applications, “pseudo-3D” seismic cubes have been successfully generated from dense 2D seismic surveys. We developed a novel open-source Python-based workflow to interpolate densely spaced 2D SBP profiles acquired with a hull-mounted parametric SBP into pseudo-3D cubes. This workflow is applied to a study area on the Chatham Rise east of New Zealand’s South Island, comprising numerous seafloor pockmarks and subsurface paleo-pockmarks. Our workflow consists of two stages: (1) processing of individual 2D profiles to compensate for existing vertical offsets and (2) sparse data interpolation by applying the iterative projection onto convex sets algorithm. We correct the residual static effect caused by the sea state during acquisition, compensate for the varying tidal elevations, and apply vertical time shifts to individual profiles to correct misties at profile intersections. The interpolation of the binned sparse 3D cube is performed in the frequency domain using the fast Fourier transform and executed in parallel processes, which significantly increases the computational efficiency. We validate our workflow by testing different bin sizes, sparse transforms, thresholding approaches, and varying total iterations, which noticeably impact the resulting interpolation quality. Our developed workflow generates pseudo-3D subsurface images from densely spaced SBP profiles, with numerous potential applications for academic and industrial surveys.

Geometry and kinematics of the Middle to Late Miocene salt tectonics, central Egyptian Red Sea margin

The Red Sea basin includes a thick Middle to Late Miocene evaporitic succession that underwent halokinesis and caused intensive reshaping of the seafloor and the development of salt-tectonic structures. However, the geometry and kinematics of these structures are still poorly understood. This study uses 2D and 3D seismic surveys and well data of the northern Egyptian Red Sea to systematically describe the distribution and morphology of salt structures, discuss their initiation, and construct a kinematic model for their origin. Our results indicate that the massive salt layer developed into five major NW-SE to NNE-SSW trending salt walls, characterized by relatively irregular crests and moderately dipping flanks. In addition, several symmetrical and asymmetrical folds and two categories of normal faults (subsalt and suprasalt) have been recognized. Based on our observations, salt mobilization in the study area started in the Late Miocene, during the precipitation of layered evaporites, and continued until the present day. In the northern Egyptian Red Sea, seismic interpretation indicates that halokinesis was triggered by a combination of thin- and thick-skinned systems, where the latter played a major role. The salt layer was welded during the Quaternary as several sags and grabens developed above the salt diapirs. Thick-skinned physical models are compatible with our observations, supporting the impact of basement faulting on Red Sea diapirism.

The application of graph theory to optimize the design of onshore 2D seismic surveys

Despite ongoing innovations in the design of 3D seismic surveys, the design of 2D seismic surveys has changed relatively little since their introduction. Two-dimensional and 3D surveys face similar challenges. One challenge is how to plan survey lines to minimize health, safety, and environmental (HSE) exposure and cost. In this paper, I show how graph theory can be used to automatically design optimized 2D survey lines. The paper includes examples that address minimizing the impact of new line clearing, maximizing the use of existing clearing, and reducing HSE risk.

An integrated approach to the study of Achimov deposits within the South Tambey field (Western Siberia)

In order to clarify the structure of promising oil and gas objects in the South Tambey field (Western Siberia), an integrated approach to the study of Achimov deposits has been developed. The oil and gas potential level includes layers from PK1 to Yu9 at depths from 1000 to 4000 meters. Despite the fifty-year history of drilling wells in the area, the Achimov objects are currently poorly explored in the study area and may have significant potential for development. The purpose of this work was to clarify the geological structure of the Achimov deposits, which became possible thanks to the acquisition of new geological exploration data during the study of the underlying Jurassic complex. CDP 3D seismic exploration work was completed using a modern full-azimuth observation system, and active drilling of exploration wells for Jurassic deposits in the slope parts of the main structures began. The objectives of the study were the interpretation of a 3D seismic cube covering most of the area of the site, seismic geological linking of data from the Achimov interval of the field with neighboring areas, including using the sequence stratigraphy method, accounting for the results of drilling wells for the pilot development of the Jurassic complex and the transit fund of prospecting and exploration wells, as well as the inclusion of the results of a petrophysical model in a first approximation for the Achimov reservoir interval of the South Tambey field. The results of full-azimuth CDP 3D seismic surveys made it possible to obtain reliable correlations between well data and seismic data, including analysis of AVO attributes (Amplitude Variation with Offset). Based on sequence stratigraphic analysis, the stratification of the section was clarified, correlation with neighboring territories was made, and a conceptual model of the clinoform complex was created. For each layer, system tracts within the sequences were determined. There is strong relationship existing between the formation conditions, geometry of objects and reservoir properties.

Применение технологии объединения методов разведочных работ для достижения экологического эффекта на месторождениях Каспия

The method of performing exploration works allowing to obtain an environmental effect in the Caspian Sea fields is described in the article. The research area includes the Rakushechno-Latitudinal and Khvalynsko-Sarmatian zones. Deposits of these zones differ in a complex geological structure. When creating a model of deposits a set of data is used: high-precision 3D seismic surveys on the study area and the results of drilling wells. Such detail of seismic exploration works allows to obtain high-quality results that are due to the high density of reflection points over the area and to the maximum use of various dynamic parameters of reflected waves. The results of such surveys are used in the calculation of reserves, justification of work on additional exploration and subsequent operation. Based on the results of seismic surveys a quantitative forecast of reservoir properties was carried out due to the inversion. For implementation seismic data was processed while preserving the true amplitudes of the seismic signal. Drilling wells were also the main source of information when performing work on calculating reserves. The complex structure and heterogeneity conditions of reservoir properties in area and section, the presence of discontinuous violations led to the use of the described technology, which involves the assessment of reserves and their transfer to the industrial category without testing in the column and causing inflow to the surface. This is done by means of a comprehensive accelerated diagnostics of productive formations for the assessment of reserves of the industrial category. Such a diagnosis provides for the study of productive formations based on the analysis and generalization of accumulated material on core, GIS, GDIS, GDK-OPK and PVT studies, without conducting tests in wells. With the help of these studies the filtration-capacitance properties of rocks, the nature of fluid saturation, contact positions, static levels, reservoir and bottom-hole pressures and reservoir temperatures, as well as deep sampling are determined. The use of modern instruments such as MDT (reservoir Tester) makes it possible to obtain reliable deep samples of the reservoir fluid. The results of data interpretation are successfully approved when making reports on UVS reserves calculation.

Hydraulic fracturing-induced microseismicity controlled by rock brittleness and natural fractures in Tongren, Guizhou, China

Hydraulic fracturing-induced microseismicity has drawn public attention in recent years. However, understanding the behavior of hydraulic fracture is limited due to the complex relationship between microseismicity and various geologic conditions. To further understand this question, we conduct a study to detect and locate hydraulic fracturing-induced microseismicity at a shale gas production site in Tongren, Guizhou, China. We investigate the relationship between their distribution and two important geologic factors: the brittleness index (BI) of rocks and the distribution of natural fractures. With the aid of a 3D active seismic survey, we first calculate the BI of rocks in the hydraulic fracturing region using Young’s modulus and Poisson’s ratio, compared with the locating result of fracturing-induced microseismicity, which indicates that most of the events are distributed in the area with higher BI. We then delineate natural fractures using the ant-tracking method of the 3D seismic attribute. The microseismic location is consistent with the region of natural fractures. Based on our findings, we suggest that the spatial distribution of induced microseismicity is highly controlled by the brittleness of rocks and the distribution of natural fractures in this region. This research provides insights into the factors controlling hydraulic fracturing-induced microseismicity and enhances our understanding of the complex interplay between geologic conditions and the behavior of hydraulic fractures.

Segmentation and lateral growth of intracratonic strike-slip faults in the northern Tarim Basin, NW China: influences on Ordovician fault-controlled carbonate reservoirs

Intracratonic strike-slip faults have been recognized as a major factor controlling the formation of fracture-cave carbonate reservoirs in deep buried basins, yet which properties and how the strike-slip faults influence reservoir distribution and their connectivity are still ambiguous. This uncertainty significantly restricts hydrocarbon exploration and development, such as in the Fuman oilfield, northern Tarim Basin, NW China. Using a high-resolution 3D seismic reflection survey and borehole data, we investigated the geometry and kinematic evolution of the FI17 fault zone in the Fuman oilfield. This fault zone is characterized by a single fault zone, pop-up or pull-apart structures, right-stepping en echelon normal faults, and much smaller displacement (<30 m) normal fault arrays from bottom to top. The FI17 fault zone consists of four genetic segments, including the extensional strike-slip duplex, Riedel left-lateral shear, right-stepping horsetail splay, and horizontal slip segments in map view. In particular, the formation of the ∼18 km Riedel shear zone is characterized by the growth and linkage of segmented shear faults (synthetic and secondary synthetic shears). We observed that the large-scale fault-controlled fracture-cave reservoirs are distributed in positions with wider fault zones, which are characterized by overlapping of neighboring secondary shear faults. Furthermore, the reservoir width examined in this study is natural logarithmic correlated (positively) to the fault zone width. The reservoirs linked by the same shear faults show better internal connectivity. The spatial coherence between fault geometry and reservoir features indicates that segmentation and lateral growth of intracratonic strike-slip faults controls the occurrence of fracture-cave reservoirs, which may provide support for reservoir prediction in the Fuman oilfield and other deeply buried fault-controlled carbonate reservoirs in general.

Detailed study of geology of the lower parts of Pliocene in Kurovdagh area by use of 3D seismic survey

The article is devoted to the study of the geological structure of the lower parts of the Productive Series of the Lower Pliocene of the Kurovdagh field.
 It consists of an introduction, problem statement, research questions, research methodology, results, conclusion and list of references. The introduction provides basic information about the field under study, its geographical location, the history of geological and geophysical studies, the lithology of the section, the structure of the Kyurovdag fold and the oil and gas potential of the field.
 Oil and gas presence inthefield is related to the Absheron stage of Pleistocene, Akchagyl stage and Productive Series (horizons PS01—PS23) of Neogene. Despite the long-term production from the field, the lower parts of the Productive Series and underlying sediments have not been recovered and sufficiently studied by deep drilling due to the complicated surface and deepseismo-geological environment. It has been recommended to carry out a 3D seismic survey due to a high level of lateral one-fold reflections on seismic records.
 The major goals of the 3D seismic survey were studyingthe Kurovdagh field's geologic setting, obtaining characteristics previously unknown to geoscientists, and providing detailed research on velocity section to derive prognostic time-depth dependence.
 It was noted that thePetroalliance Services Company Limited geophysical company has performed a field seismic survey on request «The Caspian Energy Group» company. Processing of the acquired data used the FOCUS 5.4 software package manufactured by Paradigm Geophysical.
 For repeated interpretation of 3D seismic survey data, the 3D CDP data acquired from the field were used. The kinematic analysis by use of the 3 D cubes revealed the difference by the time shift, frequency spectrum, and amplitude range. The 3 D cubes were brought to a single formby time, phase, and amplitude. The further kinematic interpretation displayed the good quality of the data acquired from Kurovdagh area. The study applied PANGEYA® software for a multi-attribute geological and geophysical data analysis and the standard interpretation.
 For volumetric modeling of the productive layers of the Kurovdagh oil field, we used the PETREL.10.2 software package. The study targets included complex, lithologically, and tectonically sealed deposits of Productive Series PS01—PS09 and Akchagyl stage (AKCH). Productive layers are attributed to Neogene's Pliocene stage within the Caspian basin's limits.
 It is represented by a thick series of continental, coastal, and marine sediments (sand, clay, coarsely fragmented depositions) of 1600 m thickness and is unconformity laying over the Pontian stage and covered by the Akchagyl layers in a transgressive form. The Akchagyl stage is one of the stages of the Upper Pliocene which is made of clay, limestone, marl, sandstone, sand, and conglomerates.
 It became clear that the Kurovdagh field is characterized by a block type structure across the geological section. Block sizes are almost unchanged, evidencing conformance of structural stages and heritance of tectonic movements. Mud volcano and diapiric folding and their sizes are the major distinguishing features of the area.