Offshore Section Research Articles

Characteristics of the Fault Damage Zone From High‐Resolution Seismic Imaging Along the Palos Verdes Fault, California

AbstractThe distribution and intensity of fault damage zones provides insight into fault activity and its relationship to fluid flow in the crust. Presently, measures of the in‐situ distribution of fault damage remain limited and along‐strike studies are rare. This study focuses on an offshore section Palos Verdes Fault damage zone that spans 28 km, near Los Angeles, California. To investigate the previously unresolved shallow (∼400 m below the seafloor) fault damage zone we use densely spaced (∼500 m line separation) newly collected sparker multichannel seismic lines and sub‐bottom profiles. The combination of high‐resolution acquisition methods and specialized seismic processing workflows provide improved imaging of shallow faulting. We apply a multi‐trace similarity technique to identify discontinuities in the seismic data that may be attributed to faults and fractures. This fault detection approach reveals diverse fault damage patterns on adjacent seismic profiles. However, a discernible damage zone pattern emerges by stacking multiple damage detection profiles along strike. We find that peak damage identified in this way corresponds to the active main fault strand, confirmed in this study, and thus the technique may be useful for identifying active fault strands elsewhere. Additionally, we observe that the variable width of the damage zone along strike is controlled by fault obliquity. Furthermore, our observations reveal a correlation between fault damage and seafloor fluid seeps visible in the water column, suggesting that damage plays a role in controlling fluid flow around the fault.

Adiabatic gas transport in the long flow channels

The paper present the determination of the state parameters of natural gas at the pipeline inlet based on knowledge of the pressure and temperature at the receiving point. Natural gas transport will be carried out through an offshore section of a transmission pipeline. The equations of the Fanno flow model will be used to describe the thermodynamic parameters of the gas in the flow lines. The mathematical equations of the flow mentioned above models have been derived from an analysis of the mass, energy and momentum balance equations. They also take into account the viscous friction forces in the transported gas. Based on the carried out calculations, changes in the Mach number, pressure and velocity of methane transported along the analysed pipeline were determined. In addition, the total entropy gain in the analysed methane flow was determined. The novelty of the calculations presented is the use of the Fanno flow model, which considers a realistic adiabatic gas flow. This is in contrast to the isothermal flow model, which assumes an unchanging temperature of the transported gas. In the case under consideration, the adopting model was possible because of the similar temperature values of the gas flowing in the pipeline and the corresponding temperature values of the surrounding seawater. The fundamental advantage of the Fanno flow model is that it satisfies the mass balance of the flowing gas in each cross-section. Thus, the product of the velocity and density of the gas in a pipeline of constant diameter assumes a constant value.

Field observations of surface ruptures accompanying a tsunami and supershear earthquake along a plate boundary strike-slip fault

AbstractStrike-slip earthquakes near major subduction zones have received less attention than thrust or reverse earthquakes in subduction zone areas. The occurrence of the 2018 Palu Mw 7.5 earthquake in eastern Indonesia provides an unprecedented opportunity to investigate the characteristics of one of these events. The Palu earthquake occurred on the left-lateral, north–south-striking Palu–Koro fault, which is the main plate boundary structure accommodating the convergence between blocks in a triple junction area. It excited a significant tsunami, which unusually is associated with strike-slip earthquakes, and also ruptured at a supershear speed, which is mostly observed on strike-slip faults in continents. Based on our fieldwork, we speculate that the normal slip component of the offshore rupture section in Palu bay on the middle segment probably favours tsunami genesis. Our field investigation has revealed evidence of a simple geometry as well as slip partitioning of dip-slip and strike-slip motion on two subparallel strands on the main segment, both of which may have contributed to the supershear of the rupture propagation. Instead of only a transtensive behaviour of the middle segment, our results also illustrate the transpressional property of the northern and southern rupture segments, which shows more complex behaviour than that of a common continental strike-slip fault.

Thermal Analysis and Debottlenecking of HVAC Export Cables for Offshore Windfarms

The substantial costs of HV export cables connecting offshore windfarms to the grid combined with their influence on energy availability requires extensive thermal evaluation of these cables. The analysis in this paper reveals that the offshore windfarm cables can be divided into onshore (underground), landfall, offshore (subsea) and J-tube sections based on their unique thermal behaviour. The utilization of long-term Distributed Temperature Sensing (DTS) data from a specific windfarm export cable in UK reveals that the J-tube and landfall sections are the major thermal bottlenecks, along with the cable joints/transition-points at onshore and offshore. Landfall is found to comprise of the most thermally strenuous environment due to large burial depths. While J-tube is influenced significantly by the ambient conditions in its air-section, thereby making it most prone to be affected by the local weather. Whereas, the thermal instability of the lengthy offshore section comes from the diffusion of thermal properties of surrounding material due to seabed geology and variation of cable burial depth over time due to seabed movement and sedimentation. Onshore cable section is found to be thermally stable and free from hotspots not only because of the difference in cable design and utilization of ducts for installation but also because the fibre optic cable for DTS is not embedded inside the cable. The temperature offset therefore needs to be established for the land and submarine cables respectively in order to obtain a more accurate account of the conductor temperature. In conclusion, employment of modern techniques combined with thermal analysis of each section can improve the existing design and operation practices.

Sedimentary evidence for a period of rapid environmental change in the Yangtze River Delta, China around 150 years ago

The mechanism of channel bifurcation in tide-dominated deltas is poorly understood. Here, we evaluate the function of extreme events on the channel bifurcation by examining the lithology, grain size, and organic carbon stable isotope (δ13C) composition, as well as the AMS 14C and OSL ages in two sediment cores (KZ01-A and KZ02) collected close to a site of a shipwreck of a known age at the offshore section of the North Channel in the Yangtze River mouth, China. The sedimentary sequence in both cores is mostly typical of deltaic succession, changing vertically from a prodelta to a subtidal mouth shoal, and finally to a subaqueous distributary channel. In KZ01-A, a shipwreck layer underlies the succession of the subaqueous distributary channel, and the porcelain collected from the sunken ship constrains the formation of the North Channel to post-1862, which is consistent with historical literature and marine charts though not with the OSL ages of the shipwreck layer, which are overestimated, likely owing to the rapid deposition during the event. After the formation of the North Channel, the consistently more negative δ13C values in the facies of subaqueous distributary channel in KZ01-A evidence the prevalence of fluvial input. Based on the shipwreck's location in the flood-dominated tidal channel of the outer delta front platform, the ship likely sank due to a large typhoon rather than a river flood. In core KZ02, significant fluctuations in both grain size and δ13C values, such as shifting from less negative to more negative δ13C in the mouth shoal facies, indicate periods of frequent river floods and typhoon events before formation of the channel. We therefore suggest that the frequent extreme events including both typhoons and river floods in the late 19th century played an important role in the geomorphological evolution of the North Channel in the tide-dominated Yangtze River Delta.

Sentinel optical and SAR data highlights multi-segment faulting during the 2018 Palu-Sulawesi earthquake (Mw 7.5)

The main active tectonic structure in the western part of Central Sulawesi (Indonesia) is the left-lateral Palu-Koro strike-slip fault. Its offshore section was thought not to have broken during the Mw 7.5 Palu Earthquake on 28 September 2018, challenging the established knowledge of the tectonic setting at this location. Here, we use Sentinel-1 SAR interferometry to produce a map of the ground velocities in the area of the Mw 7.5 earthquake for the seven months following the 2018 earthquake. We show evidence of surface deformation along the western coast of the Palu bay, indicating that the Palu Koro offshore fault section might have contribute to or been affected by the earthquake. As the possibility of multi-segment ruptures is a high concern in the area because of the high seismic and tsunami hazard, we present here, a fault model that includes the offshore section of the Palu-Koro fault. Thanks to four independents space-based geodetics measurements of the co-seismic displacement (Sentinel-1 and Sentinel-2 correlograms) we constrain the 3D co-seismic ground displacements. The modeling of these displacements allows us to estimate the co-seismic fault slip amplitude and geometry at depth. At the end, we consider the multi-segment faulting scenario, including the offshore section of the Palu-Koro fault, as a plausible model to explain the submarine landslides and the tsunamis. This study also gives the opportunity to observe a super-shear earthquake in the context of a complex fault network and implies an increase in the probability of submarine landslides within the bay in the forthcoming years.

A semi-analytical approach for simulating oblique kinematic distress of offshore pipelines due to submarine landslides

Deep water offshore pipelines are usually directly laid on the seabed, a fact that makes them vulnerable to geohazards, such as submarine landslides and debris flows. The intersection angle between the pipeline and the moving sediments can vary taking into account the pipeline route and the unstable nature of deep seabed. The aim of the current study is to examine the distress of a seabed-laid offshore natural gas pipeline subjected to combined lateral and axial kinematic distress due to an oblique submarine landslide or a debris flow. For this purpose, a new semi-analytical model is developed combining the finite-difference method and the elastic-beam theory. Firstly, the proposed model is compared with a finite-element model for various intersection angles, as well as with previous analytical models considering exclusively lateral loading. Subsequently, various combinations of soil resistance forces and loading conditions that affect the examined problem are investigated. Realistic input data were taken from the offshore section of the high-pressure natural gas pipeline TAP (Trans Adriatic Pipeline). Finally, useful conclusions are drawn regarding the applicability and efficiency of the proposed approach to accurately represent the pipeline response under these loading conditions.

Geology and petroleum prospectivity of the Larne and Portpatrick basins, North Channel, offshore SW Scotland and Northern Ireland

The Larne and Portpatrick basins, located in the North Channel between SW Scotland and Northern Ireland, have been the target of a small programme of petroleum exploration activities since 1971. A total of five hydrocarbon exploration wells have been drilled within the two basins, although as of yet no commercial discoveries have been made. The presence of hydrocarbon shows alongside the discovery of two good-quality reservoir–seal couplets within Triassic and underlying Permian strata has encouraged exploration within the region. The focus of this study is to evaluate the geology and hydrocarbon prospectivity of the Portpatrick Basin and the offshore section of the Larne Basin. This is achieved through the use of seismic reflection data, and gravity and aeromagnetic data, alongside sedimentological, petrophysical and additional available datasets from both onshore and offshore wells, boreholes and previously published studies. The primary reservoir interval, the Lower–Middle Triassic Sherwood Sandstone Group ( c . 600–900 m gross thickness), is distributed across both basins and shows good to excellent porosity (10–25%) and permeability (10–1000 mD) within the Larne Basin. The Middle–Late Triassic Mercia Mudstone Group should provide an excellent top seal where present due to the presence of thick regionally extensive halite deposits, although differential erosion has removed this seal from the margins of the Larne and Portpatrick basins. The Carboniferous, which has been postulated to contain organic-rich source-rock horizons, as inferred from their presence in adjacent basins, has not yet been penetrated within the depocentre of either basin. There is, therefore, some degree of uncertainty regarding the quality and distribution of a potential source rock. The interpretation of seismic reflection profiles presented here, alongside the occurrence of hydrocarbon shows, indicates the presence of organic-rich pre-Permian sedimentary rocks within both basins. 1D petroleum system modelling of the Larne-2 borehole shows that the timing of hydrocarbon generation and migration within the basins is a significant risk, with many traps post-dating the primary hydrocarbon charge. Well-failure analysis has revealed that trap breach associated with kilometre-scale uplift events, and the drilling of wells off-structure due to a lack of good-quality subsurface data, have contributed to the lack of discoveries. While the Larne and Portpatrick basins have many elements required for a working petroleum system, along with supporting hydrocarbon shows, the high risks coupled with the small scale of potential discoveries makes the Portpatrick Basin and offshore section of the Larne Basin poorly prospective for oil and gas discovery. Thematic collection: This article is part of the Under-explored plays and frontier basins of the UK continental shelf collection available at: http://www.lyellcollection.org/cc/under-explored-plays-and-frontier-basins-of-the-uk-continental-shelf

Intergranular aragonite cement as evidence for widespread cryogenic brine formation during Quaternary glaciation in the McMurdo Sound region, Antarctica

Briny groundwater is present below the extremely cold and dry surface of the McMurdo Dry Valleys and below the seafloor of the adjacent McMurdo Sound in Antarctica. The lack of reliable groundwater samples in the region, however, has long limited understanding of its origin, nature, and spatial distribution. In this regard, intergranular carbonate cements, widespread in subsurface Cenozoic strata and recently recognized as brine precipitates, provide an indirect means of solving these issues. This study examines the petrography and isotope geochemistry of intergranular aragonite cement phases that occur in subsurface Pliocene-Quaternary sedimentary sections that formed in the lower Taylor Valley (cores DVDP-10, -11) and in offshore McMurdo Sound (core AND-1B). Aragonite cement in the coastal Taylor Valley sections is characterized by very low δ18O values (−26.9 to −19.4‰ VPDB) compared to values in the offshore section (−12.5 to −2.7‰ VPDB). These differences are interpreted to reflect two settings for cryogenic brine formation, which produced isotopically distinct brines during Quaternary glaciation. In the coastal region, seawater-meltwater mixtures were isolated and cryogenically concentrated in an ice-dammed lake setting that formed in response to the expansion of the East and West Antarctic Ice Sheets into the lower Taylor Valley. In McMurdo Sound, cryogenic concentration of seawater occurred in a semi-isolated flexural trough that was deepened by lithospheric depression of volcanic edifices and the expanded West Antarctic Ice Sheet. Aragonite cement phases serve as excellent proxies for tracing the extents of subsurface brine bodies along the continental margin of Antarctica. Given the propensity for cryogenic brine formation in glaciomarine settings, the likelihood of brine cements in rock records from other analogous high-latitude, cold settings must not be overlooked.

Nearshore natural convection induced by a periodic thermal forcing at the water surface

Field observations reveal that under calm weather conditions, natural convection resulting from spatial variations in the temperature field plays a significant role in promoting exchanges and mixings in lakes and reservoirs. The present investigation is concerned with natural convection generated by a periodically varying surface temperature within a reservoir model consisting of a sloping nearshore section and a flat offshore section. Three approaches, including derivation of analytical solution, numerical simulation, and scaling analysis, are integrated to reveal the variation of flow response with the intensity of the thermal forcing. The analytical solution reveals that for a sinusoidally varying surface temperature, a cosinusoidally varying surface heat flux is imposed if the duration of the period is sufficiently long. Numerical results show dramatic differences in flow response between conduction-dominated and convection-dominated thermal flow. The former is in phase with the cosinusoidal variation of surface heat flux, whereas the latter is in phase with the sinusoidal variation of surface temperature. The thermal forcing for conduction-dominated and convection-dominated flow is prescribed by surface heat flux and surface temperature, respectively. An evident phase lag is observed shortly after the thermal forcing switches sign. For convection-dominated flow with a Rayleigh number of 2 × 107, the maximum velocity during the cooling phase is significantly larger than that during the heating phase owing to the occurrence of flow instability during the cooling phase, which agrees with field observations. The scales for flow velocity and phase lag are derived by scaling analysis and verified by the results of numerical simulations.

An improved analytical approach for simulating the lateral kinematic distress of deepwater offshore pipelines

Offshore pipelines are critical infrastructures and any possible damage may have devastating financial and environmental consequences. Earthquake-related geohazards (such as strong ground motion, active seismic faults, submarine landslides and debris flows) consist crucial threats that an offshore pipeline has to overcome. The main aim of the current study is to examine analytically a seabed-laid offshore pipeline subjected to a lateral kinematic distress due to a submarine landslide or a debris flow. Extra emphasis is given on the impact of pipe-soil interaction on the pipe response, by the realistic representation of the soil resistance via a tri-linear model. Firstly, the proposed analytical model is validated with a numerical model utilizing the finite-element method. Subsequently, various combinations of soil parameters and loading conditions that affect the examined problem are investigated with realistic input data taken from the offshore section of the high-pressure natural-gas pipeline TAP (Trans Adriatic Pipeline) in the Adriatic Sea. Finally, useful conclusions are drawn regarding the applicability and the efficiency of the proposed approach.

Enhanced-Gel-Strength Concept Optimizes Chemical Use in Pipeline for Waxy Crude

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 186295, “Application of Enhanced-Gel-Strength Concept for PPD Chemical Optimization in Banyu Urip Export Pipeline,” by Alinda Dwitawidi, ExxonMobil, prepared for the 2017 SPE/IATMI Asia Pacific Oil and Gas Conference and Exhibition, Bali, Indonesia, 17–19 October. The paper has not been peer reviewed. Banyu Urip crude contains 26% wax, which can lead to flow-assurance challenges in a crude pipeline exposed to lower temperatures. Injection of pour-point-depressant (PPD) chemicals has been considered an effective method to ensure flow of moderate waxy crude. For the Banyu Urip field, PPD injection was compared with other methods and found to be the best option. Nevertheless, it still contributes to approximately 20% of the operating costs. Optimization of this chemical use can bring benefits through lowering operating costs. Introduction The Banyu Urip Field is in East Java, Indonesia. The facilities process a stabilized crude, which is then transported through a 20-in. export pipeline to a floating storage and offloading vessel. The export pipeline is divided into two sections, a 72-km onshore section and a 23-km off-shore section. High wax content is a key characteristic of Banyu Urip crude. The stabilized crude’s wax appearance temperature is 46°C, and its pour point is 33°C (±3°C). With a lowest ambient temperature of 27°C for the onshore section and 24°C for the offshore section, a risk exists of the crude temperature dropping below the pour-point temperature during a no-flow condition, which may cause gelling in the pipeline (Fig. 1). Several options were considered for a flow-assurance strategy, including continuous PPD injection, pipeline displacement, and electrical heating along the pipeline. Continuous PPD injection was seen as the best option from cost and operability perspectives. Consequently, chemical-injection facilities were installed in all the well pads for continuous PPD injection. To maintain pour point at 24°C, initial calculations required approximately 500-ppm PPD injection. At current production rates, this equates to approximately 20% of the Banyu Urip operational expenditures. Description of Processes Continuous PPD injection with a 24°C pour-point target is an inherently conservative approach to keeping the crude pour point lower than the lowest expected ambient temperature. Furthermore, the PPD is not required in normal flowing conditions; rather, it is only required when the pipeline is shut in for a long period, which can cause the crude to cool to ambient temperatures. In normal operation at design rates, crude enters the export pipeline at approximately 75°C and reaches the storage vessel at approximately 70°C. The export pipeline is insulated, which helps maintain heat in the crude for several days before reaching its pour point, even in no-flow conditions. When the crude has reached pour point and starts forming a gel, the weak gel (within a certain gel strength threshold) is still breakable by application of export pump pressure within the pipeline maximum allowable working pressure (MAWP). With a 20-in. pipeline, a radial temperature profile exists in which the center of the pipeline usually will have a higher temperature, making it easier to break the center with pressure.

Protective coatings for offshore wind energy devices (OWEAs): a review

Coating specifications for offshore wind energy devices (OWEAs) are still based on specifications for the offshore oil and gas industry. Recently, two standards, developed for OWEA in the German offshore section (North Sea and Baltic Sea), were issued. This article reviews current offshore standards and commercial specifications used in the German OWEA industry. Stresses are defined for different zones of the structures. Specified coating systems for different stresses, including testing methods, are discussed. A review of 34 commercial coating specifications for OWEA in the North Sea and the Baltic Sea is provided. Evaluation parameters include number of layers, dry film thickness, and binder types for different coats. Special coating requirements are discussed, namely impact resistance, abrasion resistance, icing/deicing performance, low friction, color and gloss stability, and low-temperature performance. Finally, trends for the utilization of thermal spray metals are reviewed.

Discussion on ‘A 2.3 million year lacustrine record of orbital forcing from the Devonian of northern Scotland’, Journal of the Geological Society, London 173, 474 – 488

The standard approach to the application of spectral analysis in the search for orbitally forced cycles in stratigraphic data series involves comparing the power spectrum of the data with that of a statistical model representing (random) background noise. The discrimination of a (candidate) periodic cycle from random noise requires estimation of the statistical confidence that power at a given frequency in the spectrum is unlikely to be part of the noise. Andrews et al. (2016) made spectral analyses of natural gamma-ray (GR) data from onshore and offshore sections through the lacustrine Caithness Flags (Middle Devonian, Scotland), the offshore section comprising 807 m of strata in the UK Continental Shelf (UKCS) well 11/25-2 ST1. They generated periodograms using Thomson's multi-taper method (MTM), followed by the Matlab function Redconf (Husson et al. 2014) to model the noise in the data and to derive their statistical confidence levels. As is the convention in cyclostratigraphic analysis, Redconf uses a first-order autocorrelation (AR(1)) process to model the random noise inherent in the data. The resulting periodograms for the total dataset and for subgroup-level subsets (fig. 9a–e of Andrews et al. 2016) appear to show the presence of substantial numbers of cycles significant at the statistical 90% confidence level (CL).

The role of aeromagnetic data analysis (using 3D Euler deconvolution) in delineating active subsurface structures in the west central Arabian shield and the central Red Sea, Saudi Arabia

In this paper, we present a case study of structural mapping by applying the 3D Euler method to the high-resolution aeromagnetic data that was collected in the west central Arabian Shield region and the coastal region of the central Red Sea in Saudi Arabia. We show the 3D Euler deconvolution algorithm and apply it to magnetic potential field data from the west Central Arabian Shield and the Central Red Sea. The solution obtained with 3D Euler deconvolution gives better-focused depth estimates, which are closer to the real position of sources; the results presented here can be used to constrain depth to active crustal structures (volcanisms) for the study area. The results indicated that the area was affected by sets of fault systems, which primarily trended in the NNW–SSE, NW–SE, EW, and NE–SW directions. Moreover, estimated Euler solution map from aeromagnetic data delineated also the boundaries of shallow, small, and confined magnetic bodies on the offshore section of the study area. These nearly exposed basement intrusions are most likely related to the Red Sea Rift and may be associated with structures higher up in the sedimentary section. These volcanic bodies are extended to the continental part (onshore) of the west central Arabian Shield, particularly beneath both sides of the Ad Damm fault zone. This extension verifies that the fault was largely contemporaneous with a major period during the extension of the Red Sea Basin. Moreover, according to the distribution of circular magmatic-source bodies (circular-shaped ring dikes) that resulted from this study, we can state that the clustering of most earthquakes along this fault may most likely be attributed to the active mantle upwelling (volcanic earthquakes), which are ultimately related to volcanic processes. Furthermore, the oceanic crustal structures near and in the Red Sea offshore regions were also estimated and discussed according to the ophiolite occurrences and further opening of the Red Sea. Our results are largely comparable with studies of previous crustal sections, which were performed along the Red Sea Rift and the Arabian Shield. As a result, the areas above these anomalies are highly recommended for further geothermal study. This example illustrates that high-resolution aeromagnetic surveys can greatly help delineating the subsurface active structures in the west central Arabian Shield and the middle coastal region of the Red Sea of Saudi Arabia.

A liquefied energy chain for transport and utilization of natural gas for power production with CO 2 capture and storage – Part 4: Sensitivity analysis of transport pressures and benchmarking with conventional technology for gas transport

A novel energy and cost effective transport chain for stranded natural gas utilized for power production with CO 2 capture and storage is developed. It includes an offshore section, a combined gas carrier and an integrated receiving terminal. In the offshore section, natural gas (NG) is liquefied to LNG by liquid carbon dioxide (LCO 2) and liquid inert nitrogen (LIN), which are used as cold carriers. In the onshore process, the cryogenic exergy in the LNG is utilized to cool and liquefy the cold carriers, LCO 2 and LIN. The transport pressures for LNG, LIN and LCO 2 will influence the thermodynamic efficiency as well as the ship utilization; hence sensitivity analyses are performed, showing that the ship utilization for the payload will vary between 58% and 80%, and the transport chain exergy efficiency between 48% and 52%. A thermodynamically optimized process requires 319 kWh/tonne LNG. The NG lost due to power generation needed to operate the LEC processes is roughly one third of the requirement in a conventional transport chain for stranded NG gas with CO 2 capture and sequestration (CCS).

A liquefied energy chain for transport and utilization of natural gas for power production with CO 2 capture and storage – Part 2: The offshore and the onshore processes

A novel energy and cost effective transport chain for stranded natural gas utilized for power production with CO 2 capture and storage is developed. It includes an offshore section, a combined gas carrier, and an integrated receiving terminal. In the offshore process, natural gas (NG) is liquefied to LNG by liquid carbon dioxide (LCO 2) and liquid inert nitrogen (LIN), which are used as cold carriers. The offshore process is self-supported with power, hot and cold utilities and can operate with little rotating equipment and without flammable refrigerants. In the onshore process, the cryogenic exergy in LNG is used to cool and liquefy the cold carriers, which reduces the power requirement to 319 kWh/tonne LNG. Pinch and exergy analyses are used to determine thermodynamically optimized offshore and onshore processes with exergy efficiencies of 87% and 71%, respectively. There are very low emissions from the processes. The estimated specific costs for the offshore and onshore process are 8.0 and 14.6 EUR per tonne LNG, respectively, excluding energy costs. With an electricity price of 100 EUR per MWh, the specific cost of energy in the onshore process is 31.9 EUR per tonne LNG.

A liquefied energy chain for transport and utilization of natural gas for power production with CO 2 capture and storage – Part 3: The combined carrier and onshore storage

A novel energy and cost effective transport chain for stranded natural gas utilized for power production with CO 2 capture and storage is developed. It includes an offshore section, a combined gas carrier and an integrated receiving terminal. The combined carrier will transport liquid carbon dioxide (LCO 2) and liquid nitrogen (LIN) outbound, where natural gas (NG) is cooled and liquefied to LNG by vaporization of LIN and LCO 2 onboard the carrier. The same carrier is used to transport the LNG onshore, where the NG can be used for power production with CO 2 capture. The combined carrier consists of 10 cylindrical tanks with a diameter of 9.2 m and varying lengths from 14 to 40 m. The total ship volume is 13,000 m 3. Assuming 85% capture rate of the CO 2, the maximum ship utilization factor (SUF) is 63.4%. Due to the combined use of the storage tanks, the SUF is decreased with 1.4% points to 62%. The ship is equipped with a bi-directional submerged turret loading for anchoring and loading of NG and unloading of CO 2. Two ships can deliver NG to and remove CO 2 from a 400 MW net power plant, and still obtain continuous production of LNG offshore without intermediate storage. The investment cost for each gas carrier is 40 million EUR giving total transport cost of 16.9 EUR/tonne LNG. The cost for the offshore transfer system is 6.6 million EUR per tonne LNG, whereas the cost for onshore storage and loading system is 3.1 and 0.8 million EUR per tonne LNG, respectively. The total specific costs for the ship transport, including onshore storage, loading shipping and offshore unloading are 27.5 EUR per tonne LNG for a roundtrip of 5 days, including voyage, production of LNG, unloading, connecting and berthing.

A liquefied energy chain for transport and utilization of natural gas for power production with CO 2 capture and storage – Part 1

A novel transport chain for stranded natural gas utilized for power production with CO 2 capture and storage is developed. It includes an offshore section, a combined gas carrier, and an onshore integrated receiving terminal. Due to utilization of the cold exergy both in the offshore and onshore processes, and combined use of the gas carrier, the transport chain is both energy and cost effective. In this paper, the liquefied energy chain (LEC) is explained, including novel processes for both the offshore field site and onshore market site. In the offshore section, natural gas (NG) is liquefied to LNG by liquid carbon dioxide (LCO 2) and liquid inert nitrogen (LIN), which are used as cold carriers. The LNG is transported in a combined gas carrier to the receiving terminal where it is used as a cooling agent to liquefy CO 2 and nitrogen. The LCO 2 and LIN are transported offshore using the same combined carrier. Pinch and Exergy Analyses are used to determine the optimal offshore and onshore processes and the best transport conditions. The exergy efficiency for a thermodynamically optimized process is 87% and 71% for the offshore and onshore processes, respectively, yielding a total efficiency of 52%. The offshore process is self-supported with power and can operate with few units of rotating equipment and without flammable refrigerants. The loss of natural gas due to power generation for the energy requirements in the LEC processes is roughly one third of the loss in a conventional transport chain for stranded natural gas with CO 2 sequestration. The LEC has several configurations and can be used for small scale (<0.25 MTPA LNG) to large-scale (>5 MTPA LNG) transport. In the example in this paper, the total costs for the simple LEC including transport of natural gas to a 400 MW net power plant and return of 85% of the corresponding carbon as CO 2 for a total sailing distance of 24 h are 58.1 EUR/tonne LNG excluding or including the cost of power. The total power requirements are 319 kWh/tonne, hence the energy costs are 31.9 EUR/tonne LNG adding up to 90.0 EUR/tonne LNG. The exergy efficiency for this energy chain including power production and CO 2 capture is 46.4% with a total cost of 20.4 EUR/MWh for the produced electricity. The total emissions (in CO 2 equivalents) in the chain are 1–1.5% of the transported CO 2.

Crustal structure in the Falcón Basin area, northwestern Venezuela, from seismic and gravimetric evidence

Abstract The Falcon Basin in northwestern Venezuela has a complex geological history driven by the interactions between the South American and Caribbean plates. Igneous intrusive bodies that outcrop along the axis of the basin have been associated with crustal thinning, and gravity modeling has shown evidence for a significantly thinned crust beneath the basin. In this study, crustal scale seismic refraction/wide-angle reflection data derived from onshore/offshore active seismic experiments are interpreted and forward-modeled to generate a P-wave velocity model for a ∼450 km long profile. The final model shows thinning of the crust beneath the Falcon Basin where depth to Moho decreases to 27 km from a value of 40 km about 100 km to the south. A deeper reflected phase on the offshore section is interpreted to be derived from the downgoing Caribbean slab. Velocity values were converted to density and the resulting gravimetric response was shown to be consistent with the regional gravity anomaly. The crustal thinning proposed here supports a rift origin for the Falcon Basin.