Deep-water Environments Research Articles

Turbidity Currents Carrying Shallow Heat Invading Stable Deep-Water Areas May Be an Unrecognized Source of “Pollution” in the Ocean

When turbidity currents carrying shallow heat enter stable stratified lakes or oceans, they can trigger changes in temperature, dissolved chemicals, oxygen concentrations, and nutrient mixing through the stable stratified environmental water. Although it is common for warm turbidity currents to invade stable regions, the impact of turbidity current characteristics on environmental entrainment and the impact of temperature changes caused by the mixing of warm turbidity currents with the environment remains poorly understood. In this study, systematic experiments on warm turbidity currents were conducted to understand how sediment-driven turbidity currents lead to mixing in stable stratification using existing environmental entrainment numbers. The experimental results show that the dimensionless numbers Rs (the ratio of the change in environmental water concentration caused by salinity to sediment load), RT (the ratio of the change in environmental water concentration caused by temperature difference to sediment load), and R0 (non-dimensional density ratio) control the flow process of warm turbid plumes, and corresponding functional relationships are summarized. The frequent occurrence of warm turbidity currents events caused by increasingly prominent environmental problems cannot be ignored, as it directly affects the deep-water environment of lakes or coastal oceans, which may be an important contribution to heat transfer that has not been evaluated in previous ocean events.

Microfacies of the Silurian/Devonian boundary interval in the Gorna Vrabcha 2 section (Morava Unit, SW Bulgaria) – preliminary results

This study is focused on the sedimentary strata of the Silurian/Devonian boundary interval in the Gorna Vrabcha section 2 from the Morava Unit (SW Bulgaria). Four microfacies types have been distinguished and described: Bioclastic wackestone/packstone (MFT 1), Bioclastic packstone with clayey mudstone laminae (MFT 2), Bioclastic mudstone (MFT 3) and Homogeneous mudstone (MFT 4). They are respectively interpreted as formed in various high- and low-energy open-marine environments. Thus, during the Přídolí and at the begging of the Lochkovian sedimentation occurred in an open-marine setting located between the fair-weather wave base and the storm wave base (MFT 1 and MFT 2), that was often affected by storms and storm-related currents. Later, during the Lochkovian, a calm and relatively deep-water environment predominated (MFT 3 and MFT 4) and was most probably located below the storm wave base. Based on the obtained microfacies data and depositional setting interpretations a deepening trend of sedimentary basin during the Přídoli–early Lochkovian time have been suggested.

A Review on the Recent Process of Lazy Wave Risers

Lazy wave risers (LWRs) are designed with equidistant buoyancy blocks attached in the lower half of the riser, allowing the riser to take on an arch shape under the buoyancy forces provided by buoyancy blocks. This arch configuration can provide flexibility to the LWR arrangement and effectively isolate the dynamic responses between the offshore floating structure and the riser’s touchdown zone (TDZ). Its design and application aim to address the issues of dynamic response and fatigue damage that traditional steel catenary risers (SCRs) face in deep water and complex marine environments. Given that research on the LWRs in the field of ocean engineering is not sufficiently abundant, the structural characteristics, hydrodynamic loads, global responses, fatigue damage assessment, and structural optimization progress of LWRs are systematically reviewed in this paper to provide references for researchers in related fields. Among these topics, the global response of LWRs is the main point of this review. This section details the theoretical analysis and numerical modeling methods employed in the study of LWRs’ global response, explores the research advancements in the vortex-induced vibration (VIV) related to LWRs, and discusses corresponding experimental studies. Finally, the installation, transfer, and repair processes of LWRs are investigated. Additionally, the importance of leveraging advanced technologies from other fields and combining them with current advanced algorithms is emphasized in efforts to assess fatigue damage and optimize the structures of LWRs, ultimately achieving complementary advantages.

Ichnological record in gateways and other high-energy deepwater environments: a palaeo- and neoichnological approach

The evolution of gateways determines variations in palaeoenvironmental (ecological and depositional) conditions affecting tracemaker communities, and hence biogenic structures. With respect to palaeogateways, bottom currents and associated deposits (i.e. contourites) may be approached through trace-fossil studies. Ichnological analysis – individual ichnotaxa and changes in ichnofacies – of Late Miocene contourites and associated facies from the Rifian Corridor palaeogateway (Morocco) reveals a major impact of food supply, flow velocity, seafloor heterogeneity and hydrodynamic energy. The fact that Eocene to middle Miocene deep-marine deposits, mainly contourites, from the nearby Indian palaeogateway (Cyprus) show ichnofacies replacement is evidence of increased bottom-current flow velocity associated with sea-level variations. Moreover, ichnofabric changes reflect pelagic, gravitational and bottom-current processes that simultaneously influence sedimentation. Changes in the trace-fossil composition of both areas, and in the shape of burrows, reflect intermittent bottom-current processes that governed contourite deposition. Neoichnological studies complement and validate the trace-fossil record of high-energy deep-sea environments that can occur in palaeogateways. Modern traces ( lebensspuren ) observed on the seafloor show variable features (e.g. diversity, density, morphology) depending on the type of disturbance that high-energy conditions exert on the trace-making benthic fauna. Parameters such as substrate consistency, nutrient availability/distribution and the duration and intensity of energetic events play a major role in determining lebensspuren features. We conclude that an integrative palaeo- and neoichnological approach is a powerful tool when used to improve our knowledge of benthic ecosystems in high-energy deep-sea environments such as gateways.

Lotus rhizome-inspired superhydrophobic capillarity mesh surface for long-term plastron stability

Superhydrophobic surfaces have the ability to trap gases underwater. The entrapped gas, known as plastron, has demonstrated potential for many non-wetting-related applications. However, the plastron is fragile and inevitably vanishes due to challenging real-world environmental factors. Current methods for plastron regeneration require continuous matter or energy input, such as gas injection, chemical reaction, electrolysis, boiling, and control of solubility, which are difficult to fabricate at scale and require constant monitoring of the plastron. Here, we demonstrate a novel capillarity method to replenish the plastron. Inspired by the Lotus rhizomes that survive underwater, a superhydrophobic capillarity mesh surface (SCMS) that can act as capillaries to absorb gas spontaneously is presented. The SCMS enables rapid plastron self-recovery within 0.6 s and extends the plastron lifespan to at least 60 days without intervention or energy input. Furthermore, we extend this method to deep-water environments by adding a diving bell. The plastron of SCMS with capillary effect can withstand at least a pressure of 4 bar. Experimental results indicate that SCMS can recover its drag reduction effect after plastron loss. This capillarity strategy may enable previously unattainable underwater applications.

Observing the deepwater environment using an underwater vehicle

Observing the deepwater environment using an underwater vehicle

Effects of Typical Supplementary Cementitious Materials (SCMs) on the Bonding Property of Cement with Casing under Shallow Formation of Deep-Water Environment

Due to low temperature environments and other factors, the performance of cement slurry is affected by deep-water shallow formation cementing, which makes it difficult to ensure the interface bonding quality. The objective of this study is to investigate the effect of fly ash (FA), metakaolin (MK), and microsilica (MS) as supplementary cementitious materials (SCMs) by replacing 5–20% of the cement on the bonding property of cement with casing in the shallow formations of deep-water environments. This is based on the cementing conditions for the 20″ surface casing in the deep-water shallow formation of the LS18-1 well area. Under the 30 °C experimental conditions, the results showed that the compressive and bonding strength of cement with FA and MS decreased gradually as their dosage increased. In contrast, compared with the control group (BG0), the compressive strength of the MK group increased by 25.6%, 32.1%, and 24.2% under the optimal dosages (MK15, MK15, MK20) at 3, 7, and 14 days (d), and the bonding strength increased by 73.6% at 3 d (MK15) and 34.9% at 7 d (MK15). The test analysis showed that MK can promote cement hydration and generate more hydration products, which are conducive to cement-casing interface cementation. Additionally, it can improve the pore structure, reduce the fractal dimension of the pore volume, and ensure a more reasonable distribution of cement stone crack openings.

Study on shock wave load characteristics from condensed phase explosive detonations in deep-water explosions

This study investigates shock wave load characteristics from condensed phase explosive detonations in deep-water environments using a high-order compressible multiphase solver. Spatial terms of the solver are discretized by fifth-order weighted essentially non-oscillatory reconstruction in characteristic space, while a third-order total variation diminishing Runge–Kutta method is adopted to deal with the temporal terms. The level-set method captures multiphase interfaces, while a programed burn model describes detonation wave generation. Numerical and experimental validations focus on shock waves in explosives interacting with water. Validations across shallow and deep-water conditions align numerical results with theoretical and experimental values. The solver examines shock wave characteristics across varied charge masses and water depths, revealing peak pressure deviations under identical conditions. The numerical simulation results indicate that the similarity of shock wave loads in underwater explosions is evident not only in peak pressures but also in the pressure–time history curves. Through extensive comparative analysis of results, it has been found that existing formulas for calculating shock wave positive pressure durations are not applicable to deep-water explosions. The research findings and analytical methods presented in this paper can serve as crucial references for further studies on the characteristics of shock wave loads in deep-water explosions.

Temporal-Feature-Based Classification of Active Sonar Targets in a Deep-Water Environment

Temporal-Feature-Based Classification of Active Sonar Targets in a Deep-Water Environment

A Study on the Paleoclimate and Sedimentary Environment of the Upper Kuli Formation in the Hailar Basin

Abstract The Kuli Formation in the Hailar Basin has a wide distribution range, complex and variable lithology, and oil and gas indications during field investigations, which has great research significance and value. In order to better understand the paleoclimate and sedimentary environment of the Upper Kuli Formation, this article uses three methods for the first time: heavy mineral analysis, sporopollen fossils identification, and inorganic element analysis. Based on the characteristics of heavy mineral assemblages, sporopollen fossils identification, and element analysis correspond to the five bottom layer combinations of heavy mineral analysis, analyzing their respective combination characteristics and change patterns. With a more comprehensive perspective and higher time resolution, Cross validation improves the accuracy and credibility of its inference. The results indicate that the Upper Kuli Formation can be divided into five combinations from bottom to top. The paleoclimate underwent a transition from a humid environment to a drier environment. The sedimentary environment has undergone a transition from a deep-water environment to a shallow water environment, transitioning from dynamic, rapid sedimentation, and strong terrestrial influences to a sedimentary environment dominated by more static water, chemical precipitation, and diagenesis. This study combines different geological and geochemical analysis methods to provide strong basis for inferring the paleoclimate and sedimentary environment of the Upper Kuli Formation. The research results are of great significance for interpreting geological changes such as paleoclimate change and ecosystem evolution.

Numerical Modeling of Scholte Wave in Acoustic-Elastic Coupled TTI Anisotropic Media

Numerical modeling of acoustic-elastic media is helpful for seismic exploration in the deepwater environment. We propose an algorithm based on the staggered grid finite difference to simulate wave propagation in the interface between fluid and transversely isotropic media, where the interface does not need to consider the boundary condition. We also derive the stability conditions of the proposed method. Scholte waves, which are generated at the seafloor, exhibit distinctly different propagation behaviors than body waves in ocean-bottom seismograms. Numerical examples are used to characterize the wavefield of Scholte waves and discuss the relationship between travel time and the Thomsen parameters. Thomsen parameters are assigned clear physical meanings, and the magnitude of their values directly indicates the strength of the anisotropy in the media. Numerical results show that the velocity of the Scholte wave is positively correlated with ε and negatively correlated with δ. And the curve of the arrival time of the Scholte wave as a whole is sinusoidal and has no symmetry in inclination. The velocity of the Scholte wave in azimuth is positively related to the polar angle. The energy of the Scholte wave is negatively correlated with the distance from the source to the fluid-solid interface. The above results provide a basis for studying oceanic Scholte waves and are beneficial for utilizing the information provided by Scholte waves.

Seismic sedimentology analysis of meter-scale thin sand bodies in the Jurassic Qigu Formation, Yongjin area, Junggar Basin

Seismic sedimentology is an interdisciplinary field that integrates sedimentary geology and geophysics to accurately characterize the spatial and temporal distributions of sedimentary systems. This paper focuses on the Qigu Formation in the Yongjin area of the Junggar Basin, China. The objectives are to establish a high-resolution sequence stratigraphic framework and to clarify the types of sedimentary systems present. Various technical methods, including 90° phase adjustment, attribute clustering, red-green-blue attribute fusion, stratal slicing, and seismic phase-controlled waveform indication inversion, are employed to restore the vertical evolution history of the sedimentary system and quantitatively characterize the spatial-temporal distribution of the thin sand bodies in the Qigu Formation. The results revealed that the Qigu Formation is divided into a third-order sequence, consisting of a lowstand systems tract and a lacustrine transgressive systems tract. During the lowstand systems tract, a thick channel sand body developed in the delta front, exhibiting a non-muddy, intermittent normal grading structure. The lacustrine transgressive systems tract features thin, discontinuous channel sand bodies with mud layers, also forming an intermittent normal grading structure. Two distinct types of delta fronts are identified: the first, formed during the lowstand systems tract, is characterized by branching subaqueous distributary channels in a shallow-water environment. The second, associated with the lacustrine transgressive systems tract, displays a network-like distribution of subaqueous distributary channels in a relatively deeper-water environment.

Petroleum exploration and production in Brazil: From onshore to ultra-deepwaters

The Santos Basin in Brazil has witnessed significant oil and gas discoveries in deepwater pre-salt since the 21st century. Currently, the waters in eastern Brazil stand out as a hot area of deepwater exploration and production worldwide. Based on a review of the petroleum exploration and production history in Brazil, the challenges, researches and practices, strategic transformation, significant breakthroughs, and key theories and technologies for exploration from onshore to offshore and from shallow waters to deep–ultra-deep waters and then to pre-salt strata are systematically elaborated. Within 15 years since its establishment in 1953, Petrobras explored onshore Paleozoic cratonic and marginal rift basins, and obtained some small to medium petroleum discoveries in fault-block traps. In the 1970s, Petrobras developed seismic exploration technologies and several hydrocarbon accumulation models, for example, turbidite sandstones, allowing important discoveries in shallow waters, e.g. the Namorado Field and Enchova fields. Guided by these models/technologies, significant discoveries, e.g. the Marlim and Roncador fields, were made in deepwater post-salt in the Campos Basin. In the early 21st century, the advancements in theories and technologies for pre-salt petroleum system, carbonate reservoirs, hydrocarbon accumulation and nuclear magnetic resonance (NMR) logging stimulated a succession of valuable discoveries in the Lower Cretaceous lacustrine carbonates in the Santos Basin, including the world-class ultra-deepwater super giant fields such as Tupi (Lula), Mero and Buzios. Petroleum development in complex deep water environments is extremely challenging. By establishing the Technological Capacitation Program in Deep Waters (PROCAP), Petrobras developed and implemented key technologies including managed pressure drilling (MPD) with narrow pressure window, pressurized mud cap drilling (PMCD), multi-stage intelligent completion, development with Floating Production Storage and Offloading units (FPSO), and flow assurance, which remarkably improved the drilling, completion, field development and transportation efficiency and safety. Additionally, under the limited FPSO capacity, Petrobras promoted the world-largest CCUS-EOR project, which contributed effectively to the reduction of greenhouse gas emissions and the enhancement of oil recovery. Development and application of these technologies provide valuable reference for deep and ultra-deepwater petroleum exploration and production worldwide. The petroleum exploration in Brazil will consistently focus on ultra-deep water pre-salt carbonates and post-salt turbidites, and seek new opportunities in Paleozoic gas. Technical innovation and strategic cooperation will be held to promote the sustainable development of Brazil's oil and gas industry.

Combination effects of laser heating and water cooling on the repair performance of Hastelloy C-276 by underwater laser direct metal deposition

The Ni-based Hastelloy C-276 was repaired by in-air and underwater laser direct metal deposition (in-air DMD and UDMD) with four gradient cooling rates (in-air DMD, in-air DMD with interlayer cooling, UDMD and UDMD with each layer re-covered by water). The microstructure and mechanical properties of repaired samples were systematically characterized with respect to the cooling rates. All samples presented good metallurgical bonding and columnar dendrites with epitaxial growth. The underwater environment had a more pronounced acceleration effect on the cooling rate compared to interlayer cooling. The rapid cooling induced intense thermal cycling, resulting in increased dislocation density and grain refinement with primary dendrite arm spacing (PDAS) diminishing from 5.30 to 3.21 μm. Accelerated cooling rate contributed to precipitation of massive M6C carbides. Carbides coarsened (sizes from 257 to 354 nm) and exhibited a reduced content as cooling rate slowed down due to intrinsic heat treatment (IHT). The residual water film in UDMD repair promoted oxide formation. Samples with increased cooling rates exhibited superior mechanical performance. The improved microhardness, tensile and impact properties were primarily attributed to the enhanced fine grain strengthening and Orowan strengthening facilitated via reduced grain size, increased dislocation density and carbide content. Quantities of large-size carbides were detrimental to tensile and impact properties as displayed in the in-air DMD sample with interlayer cooling (carbide size of 341 μm). The study could serve as a reference for in-situ restoration in deep-water environments.

Cadmium isotope evidence for near-modern bio-productivity in the early Cambrian ocean

The Ediacaran–Cambrian transition was one of the major transitions in Earth's history, with mass extinctions and radiation of animals. This event has been linked with perturbations in ocean geochemistry, including redox conditions and the oxygenation of Earth's surface environments. Here we present a highly resolved cadmium isotope record (δ114Cd) from shales deposited in a deep-water environment covering the Late Ediacaran to Cambrian Stage 4. Our δ114Cd data vary from −0.70 to +0.35 ‰ and demonstrate the importance of local redox-dependent burial phases on bulk sediment Cd isotope compositions, which are superimposed on global-scale changes in the Cd cycle. The heaviest Cd isotope composition recorded in the early Cambrian Liuchapo Formation is similar to the modern deep ocean, implying a broad similarity in global Cd cycling, perhaps involving similar organic-Cd burial rates. The provision of bio-limiting nutrients by continental weathering with rising oxygen concentrations in Earth's surface environments could have expanded the habitable area of the ocean and contributed to animal diversification.

Geochemistry of BIF in the Quadrilátero ferrífero, Brazil, as a proxy to neoarchean paleoenvironmental and depositional conditions

Precambrian Algoma-type banded iron formations (BIFs) are biochemical metasedimentary rocks formed in the deep water environment relatively close to centers of volcanic expansion and can be characterized on the basis of their paleodepositional environment and the associated rock types. These rocks may contain geochemical signatures indicative of changes in the redox conditions of the Archean ocean. Such variations in the Meso- and Neoarchean are crucial in understanding the processes that led to the gradual increase of oxygen in the early atmosphere, culminating in the Great Oxidation Event (2.4–2.3 Ga). Oxide- and carbonate-facies BIFs were intercepted by drill cores in the Pilar gold deposit in the NE sector of the Quadrilátero Ferrífero (QF), Brazil, located in the Neoarchean Rio das Velhas greenstone belt. These rocks are interbedded with mafic and ultramafic metavolcanic rocks and carbonaceous phyllites. In light of the potential to reconstruct paleodepositional evidence indicative of the Earth's atmospheric redox history based on this stratigraphy, we have considered specific proxies from geological and geochemical observations. Pilar BIFs geochemistry exhibits positive anomalies of La, Eu, and Y, indicating characteristics inherited from seawater and high-temperature hydrothermal fluids. In addition, a superchondritic Y/Ho ratio further supports the influence of seawater. The signatures of the major elements Al2O3 and other immobile elements typical of detrital sediments corroborate the interpretation that these rocks were deposited in a deep marine environment with low clastic influence. Furthermore, negative Ce/Ce*SN anomalies in some sections of the Pilar BIF indicate limited oxygen availability which, together with Mo, U, V, and Zn trace-element enrichment factors, indicate deposition under suboxic/euxinic conditions. This research, together with other similar BIF data from the NW QF provide new insights into the paleoenvironmental conditions prevailing during the formation of the Archean volcano sedimentary basins that compose the southern São Francisco craton (SFC).

An efficient approach to detect and segment underwater images using Swin Transformer

In managing the fish environment and underwater ecosystem, there's been a big shift from old-generational schoolings, hands-on methods to high-technologies, automatic ways of doing things, because of some clever computer technology, using a type of Artificial Intelligence smartness known as Convolutional Neural Networks, or CNNs in short. These smart systems help deal with the tricky task of keeping tabs on where fish stay out in deeper underwater, particularly when it's hard to see underwater and when the fish are all over the place. There are some pretty good tools and techniques already out there, like DPANet and a few others with names like PIFS-Net, EFS-Net, and MFAS-Net, which have been helping a bunch of researches and developments for underwater ecosystem. But Deeper water environment still needs a newer and better way to get the tasks done. So, to answer this major question, this hybrid architecture rolls out a new combination that takes the best bits of transformer architecture known as Swin Transformer and another mechanism known as ConvMixer, making it in a form of SwinUNet Architecture. This Swin Transformer is well defined at picking up on the spatial information from underwater deeper images in our case, which is a key point to be highlighted in really getting the fish's niche turf and enquiring their ecosystem. And when the underwater turns misty, the specialized implementation of ConvMixer modules incorporated with Swin Transformer increases its ability to sort out the fish from the rest of the underwater world. And this makes it to perform even more better compared with the existing state of arts model, even under Modern Underwater Machine Vision System conditions. This model even over takes to utilization of Few-Shot Learning model for training it in this lesser Underwater Images, with its capability of identifying the patterns and differentiations in both larger and smaller class objects in the given ground truth image. In this new approach, the paper combines the smart focusing methods with a way to blend different signals to better mIoU score, making it super useful for having a deeper understanding on fish-ecosystem and also their underwater ecosystem. While comparing it with the pre-existing state of arts model and the booming Image Segmentation models (YOLO v8, Pix 2 Pix GAN model, Auto Encoders, UNet), the hybrid approach outperformed the existing model results on this Semantic Segmentation for Underwater Imagery (SUIM) dataset, which is been disclosed in the further sections below.

Characteristics and sedimentary evolution of late Ediacaran-early Cambrian microbial carbonates, chert, and phosphorite in South China

ABSTRACT The Ediacaran-Cambrian (E-C) transition period witnessed one of the most important environmental changes in Earth’s history. The western margin of the South China Block (SCB), a shallow-water environment, shows a complete sedimentary record of the E-C transition. Section surveys revealed that dolostone, microbial carbonate, chert, and phosphorite predominantly compose the lithologies of the western margin of the SCB during the E-C transition. Petrological analysis indicates that microbial carbonates in this region exhibit stromatolitic, thrombolytic, cavitated, and sporadic microbial structures. Microbial carbonates with stromatolitic, thrombolytic/cavitated, and sporadic structures correspond to strong, moderate, and weak hydrodynamic conditions, respectively. Microcrystalline dolomites crystallize during the syngenesis stage, while meso- to macrocrystalline and sparry dolomites develop during the burial diagenesis stage. Analysis of major elements and rare earth elements anomalies (δCe: 0.580 ~ 0.753; δEu: 1.234 ~ 1.433) suggests that the siliceous component originates from hot-water sources and is transported into shallow-water environments by upwelling. The absence of a δEu anomaly and the morphology of peloids indicate that the phosphatic component is primarily influenced by biological activity and upwelling. During the Tongwan Movement (545–535 Ma) in the E-C transition period, cyclical upwelling transported increased amounts of deep-source materials into shallow platform waters, leading to higher concentrations of siliceous components and widespread microbial mortality. Following the widespread microbial mortality, the phosphatic component became enriched in deep-water environments. Subsequently, the upwelling transported siliceous- and phosphatic-rich fluids back into the shallow-water environments. The phosphatic component was ultimately assimilated by small shelly fauna and deposited in the phosphatic-rich strata of the early Cambrian period. This study elucidates the origins of complex lithological compositions and the sedimentary evolution model in shallow water environments of the E-C transition period in western SCB, offering evidence for global environmental changes during this period.

North-south discrepancy in the contributors to CB153 accumulation in the deep water of the Sea of Japan

The deep-water environment and its ecosystem are becoming the ultimate sinks for Polychlorinated Biphenyls (PCBs). A three-dimensional hydrodynamic-ecosystem-PCB coupled model was applied to the Sea of Japan (SoJ), where deep water is isolated from the surrounding oceans, to elucidate the accumulation processes of CB153 and assess the contributions of physical and biological processes to the accumulation. We suggest that the dissolved CB153 concentration formed a three-layer vertical structure in the SoJ: the highest concentration is in the intermediate layer (100–600 m), followed by those in the deep (600 m to the bottom) and surface layers (0–100 m). Different accumulation mechanisms in the northern and southern SoJ were discovered. The oceanic biological pump enhances the accumulation in the northern SoJ by taking CB153 out of the thermocline in summer and contributes 70 % to the accumulation in the intermediate layer; while the vertical advection contributes 70 % to the accumulation in the intermediate and deep layer in the southern SoJ.

First Successful Wireline Stress Testing in a Gas Hydrate Reservoir in the Hyuganada Sea, Japan

This study presents a stress testing operation conducted using a wireline formation tester in a newly discovered gas hydrate prospect located offshore in Japan. The campaign, which spanned from December 2021 to January 2022, involved drilling a well using logging-while-drilling technology. Subsequently, wireline formation testing and stress testing were successfully conducted at three different depths within a gas hydrate-concentrated zone. The testing was accomplished in a single riserless descent, with the primary goal of obtaining crucial data such as mobility, formation pressure, and fracture gradient for one of the prospects. This operation marked the first stress testing job performed with dual packers in an open water and deepwater environment specifically for gas hydrate reservoirs. The study also provides a comprehensive interpretation of the data gathered during the operation. Moreover, it evaluates various properties such as formation mobility, formation pressure, initial breakdown pressure, closure pressure, fracture propagation pressure, and instantaneous shut-in pressure.