A novel prestack sparse azimuthal AVO inversion

In this paper we demonstrate a new algorithm for sparse prestack azimuthal AVO inversion. A novel Euclidean prior model is developed to at once respect sparseness in the layered earth and smoothness in the model of reflectivity. Recognizing that methods of artificial intelligence and Bayesian computation are finding an every increasing role in augmenting the process of interpretation and analysis of geophysical data, we derive a generalized matrix-variate model of reflectivity in terms of orthogonal basis functions, subject to sparse constraints. This supports a direct application of machine learning methods, in a way that can be mapped back onto the physical principles known to govern reflection seismology. As a demonstration we present an application of these methods to the Marcellus shale. Attributes extracted using the azimuthal inversion are clustered using an unsupervised learning algorithm. Interpretation of the clusters is performed in the context of the Ruger model of azimuthal AVO

An integrated approach to study the impact of fractures distribution on the Ilam-Sarvak carbonate reservoirs: a case study from the Strait of Hormuz, the Persian Gulf

Most of the Iranian hydrocarbon reservoirs in the Persian Gulf Basin and the Zagros Fold-Thrust Belt are composed of fractured carbonate rocks. In this regard, determining the spatial distribution of fractures has been a challenging issue. In this study, an integrated approach was applied for understanding the impact of fractures spatial distribution on the Ilam-Sarvak (Cenomanian to Santonian) carbonate reservoir rocks. For this purpose, seismic interpretation techniques along with geomechanical and geostatistical modeling were employed to characterize fractures at different scales. Initially, the relationship between fractures origin and the normal faults was investigated by conducting an in-situ stress analysis. Afterwards, the velocity deviation log (VDL) and fracture intensity log (FIL) were derived as fracture attributes from the interpretation of Formation Micro Imager (FMI) and conventional well logs. A 3D model of VDL and FIL was achieved by using a sequential Gaussian simulation (SGS) method. In order to achieve a more realistic and accurate model of the factures distribution, variations of the shear-wave velocity and geomechanical properties (Young's modulus and Poisson's ratio) were estimated by applying the advanced seismic interpretation techniques in the normal faults domain. The results show that the intensity of fractures increases once they are introduced to the normal faults, especially in the central part of the study area around well#2. Such a fractured zone is verified by fracture density log derived from FMI logs of the mentioned well. Obviously, there is a close-knit relationship between the fracture system and the normal faults. Eventually, secondary porosity caused by features was determined though identification of Hydraulic Flow Units (HFUs). Based on the porosity and permeability data, seven HFUs were determined for the Ilam-Sarvak reservoirs. The very high values of Log FZI indicate the possible presence of fractures. Overall, the fractures contributed to enhance the secondary porosity of the reservoir rocks though increasing matrix permeability. To sum up, the fractures system plays a critical role in controlling reservoir properties especially in the hanging-wall of normal faults where the majority of the macro and micro fractures are distributed

Seismic Expressions of Paleokarst

Paleokarst are characterized by epigene and/or hypogene processes in their formation and hold significant numbers of hydrocarbons and other natural resources. This dissertation examines worldwide seismic expression of paleokarst; and specifically, the characterization of paleokarst reservoirs developed across the Cherokee Platform, and in the Arkoma Basin, Oklahoma. Worldwide subsurface paleokarst formations are of Precambrian to Miocene age and found at depths less than 200 m to as great as 8000 m. Karst can be are expressed on seismic records as sinkholes, paleocave collapse, and tower morphologies. Seismic modeling indicates that karst can be modeled and imaged to better understand its subsurface architecture. High variance, negative curvature, bright amplitudes/localized bright spots characterize karst. As part of this dissertation, a worldwide map of paleokarst locations was generated, and geophysical measurements for some of these locations were taken for further analysis. In the Arkoma Basin, the Ordovician Viola Limestone, Mississippian Caney Shale, Pennsylvanian Jefferson Sandstone and Wapanucka Limestone were mapped on seismic data, and paleokarst sinkhole and pipe features were identified. Viola sinkholes can be recognized as structural depressions, characterized by higher seismic variance, and lower positive amplitude, and most-negative curvature. Wapanucka sinkhole features are subtle, show lower variance and higher positive amplitude, and no structural relief. The Ordovician sinkholes are coincident with the Pennsylvanian Wapanucka Limestone which are 610 m apart, with some of these sinkhole features occurring over vertical pipe features. The Viola sinkholes and pipe features are inferred to be a mature epigene karst system. The Wapanucka sinkholes are interpreted as an immature karst system with epigene and hypogene elements. This study indicates for the first-time evidence of pipe features that extend from the Ordovician into the Mississippian, and the presence of Wapanucka sinkhole features in the Arkoma Basin of Oklahoma. In the Cherokee Platform, the term Chat designates residual chert which is either in place or transported, formed by an epigene process, and found above the Miss Lime. The tripolite is internal to the Mississippi Lime formed by in place alteration of the limestone by epigene and/or hypogene processes. I have classified and mapped Chat and tripolitic chert (tripolite) zones by seismic evaluation calibrated by well control with full-wave sonic log data. Chat and tripolite show clear separation on total acoustic impedance from Miss Lime, but no separation with VP /VS, and both exhibit total porosities greater than 20 % with an indication of fracture porosity. Sonic-based normal incidence wedge models for Chat bounded above by Pennsylvanian Shale and below by Miss Lime indicate two seismic expressions are probable: a strong negative amplitude when Chat thickness is above tuning and a weak or non-existent amplitude associated with small impedance contrast between Chat and overlying Pennsylvanian shale. This analysis suggests both the traditional Chat ‘strong response’ and a new ‘dim-out’ exploration approach. Tripolite response is consistently a negative amplitude event that strengthens with increasing tripolite thickness. This study provides an interpretive framework for characterizing Chat and tripolite zones associated with the Mississippian Lime in the US Midcontinent, which may be applicable to areas around the world

Geological risk calculation through probability of success (PoS), applied to radioactive waste disposal in deep wells: a conceptual study in the pre-neogene basement in the Northern Croatia

https://v2.sherpa.ac.uk/id/publication/24819The basic principles of geological risk calculation through probability of success (PoS) are mostly applied to numerical estimation of additional hydrocarbon existence in proven reservoirs or potential hydrocarbon discoveries in selected geological regional subsurface volumes. It can be adapted and validated for a comprehensive input dataset collected in the selected petroleum province, by dividing up geological events into several probability categories and classes. Such methodology has been widely developed in the last decades in the Croatian subsurface—mostly in the Croatian Pannonian Basin System (CPBS). Through the adaptation of geological categories, it was also applied in hybrid, i.e., stochastic, models developed in the CPBS (Drava Depression), mostly for inclusion of porosity values. As the robustness of this methodology is very high, it was also modified to estimate the influence of water-flooding in increasing oil recovery in some proven Neogene sandstone reservoirs in the CPBS (Sava Depression). This new modification is presented to be applied to geological risk calculation, intending to assess the safety of geological environment storage in deep wells, where spent nuclear fuel (SPN) would be disposed, a subject of great importance. The conceptual study encompassed the magmatic and metamorphic rocks in the pre-Neogene basement of the CPBS, intended to be used for such purpose. Regionally distributed lithologies are considered for nuclear waste disposal purpose, in order to detect the safest ones, considering petrophysical values, water saturation, recent weathering and tectonic activity.info:eu-repo/semantics/publishedVersio

Advances in Methane Production from Coal, Shale and Other Tight Rocks

This collection reports on the state of the art in fundamental discipline application in hydrocarbon production and associated challenges in geoengineering activities. Zheng et al. (2022) report an NMR-based method for multiphase methane characterization in coals. Wang et al. (2022) studied the genesis of bedding fractures in Ordovician to Silurian marine shale in the Sichuan basin. Kang et al. (2022) proposed research focusing on the prediction of shale gas production from horizontal wells. Liang et al. (2022) studied the pore structure of marine shale by adsorption method in terms of molecular interaction. Zhang et al. (2022) focus on the coal measures sandstones in the Xishanyao Formation, southern Junggar Basin, and the sandstone diagenetic characteristics are fully revealed. Yao et al. (2022) report the source-to-sink system in the Ledong submarine channel and the Dongfang submarine fan in the Yinggehai Basin, South China Sea. There are four papers focusing on the technologies associated with hydrocarbon productions. Wang et al. (2022) reported the analysis of pre-stack inversion in a carbonate karst reservoir. Chen et al. (2022) conducted an inversion study on the parameters of cascade coexisting gas-bearing reservoirs in coal measures in Huainan. To ensure the safety CCS, Zhang et al (2022) report their analysis of available conditions for InSAR surface deformation monitoring. Additionally, to ensure production safety in coal mines, Zhang et al. (2022) report the properties and application of gel materials for coal gangue control

Structure and in Situ Stress Analysis of the Tazhong Uplift, NW China: Implications for Fault Reactivation

The Tarim Basin in northwest China is an intracratonic, poly-phase basin with a subsurface structure that records a protracted tectonic history associated with crustal accretion and amalgamation. Currently, the basin is bounded by actively deforming mountain belts but displays little evidence of active deformation within the basin. Here, detailed interpretation of 3D seismic reflection data and analysis of drilling-induced deformation in deep boreholes (e.g. borehole breakouts) are used to resolve uncertainties about the timing and distribution of past deformation, the effect of pre-existing structures on subsequent deformation, and the current in situ stress state in the Tazhong Uplift of the Central Tarim Basin. The geometry and kinematics of Ordovician thrust faults and folds, Silurian-Permian strike-slip faults, and Triassic igneous bodies and normal faults, along with stratigraphic relationships, suggest that creation of new faults, and reactivation of pre-existing faults occurred during tectonic events in the Paleozoic and Early Mesozoic; however, no evidence of faulting is observed in Late Mesozoic or Cenozoic strata in the Tazhong Uplift. The current in situ stress should favor extensional and strike-slip tectonics with maximum horizontal compression directed NE, which contrasts with past stress states in the basin inferred from Paleozoic and Mesozoic structures. In situ differential stress magnitude in the Tazhong Uplift (ranging from 94 to 170 MPa) is insufficient to reactivate the most optimally-oriented faults in the Central Tarim Basin, even though the basin is bounded by the active Tian Shan and Kunlun Shan thrust belts to the north- and south-west, and the left-lateral strike-slip Altyn Tagh fault to the south, all associated with the ongoing Himalayan-Tibetan orogeny. The low differential stress may be understood if the basin-bounding faults (particularly the Altyn Tagh fault) operate at low absolute shear stress, similar to continental transform faults such as the San Andreas fault, CA