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Provides an overview of research conducted on well cement behavior and gas migration during early hydration.
KIER and NETL will collaborate to study hydrate-based technologies to enhance desalination, gas separation, and hydrocarbon flow through pipelines and wellbores. With optimized selections of hydrate formers and reactors, gas hydrates can be effective and economic mechanisms of separation for solid-water and gas mixtures, and gas hydrate formation or dissociation can be significantly delayed or expedited with suitably selected additives. Comprehensive laboratory studies, including identifying novel hydrate formers or inhibitors to control temperature and pressure requirements and understanding their working mechanism or developing reactor systems for production of large quantities of hydrates, will be performed at both KIER and NETL either parallelly or serially.
KIER and NETL will collaborate to study hydrate-based technologies to enhance desalination, gas separation, and hydrocarbon flow through pipelines and wellbores. With optimized selections of hydrate formers and reactors, gas hydrates can be effective and economic mechanisms of separation for solid-water and gas mixtures, and gas hydrate formation or dissociation can be significantly delayed or expedited with suitably selected additives. Comprehensive laboratory studies, including identifying novel hydrate formers or inhibitors to control temperature and pressure requirements and understanding their working mechanism or developing reactor systems for production of large quantities of hydrates, will be performed at both KIER and NETL either parallelly or serially.
The water-gas relative permeability is an important parameter to characterize multiphase flow in sediments. To study the water-gas relative permeability of hydrate-bearing porous media, multiphase flow simulations were carried out at the pore scale using the lattice Boltzmann method. In this work, the effects of hydrate saturation and hydrate-growth habits on the water-gas relative permeability, which is scaled by the relative permeability considering the hydrate only, were evaluated in a two-dimensional porous medium. Results show that the increase of hydrate saturation causes the decrease of water-gas effective permeability as expected. However, the effect of hydrate saturation on the water-gas relative permeability is different from that of hydrate saturation on the water-gas effective permeability. The water-gas relative permeability increases with the increase of hydrate saturation in the pore-filling case. The water-gas relative permeability decreases with the increase of hydrate saturation in the grain-coating case. The wettability of solid phase has a different effect on the relative permeability of wetting phase and nonwetting phase. The Jamin effect (phase blocking) was observed and may exist in the production of gas from natural gas hydrate reservoirs. This seriously affects the multiphase flow characteristics. The changes of microscale fluid distribution effect the changes of water-gas relative permeability. The relationship between the water-gas relative permeability and the characterization parameters of microscale fluid distribution was analyzed.
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This paper was prepared for the National Petroleum Council's Study on Natural Gas GHG Emissions. Natural gas is the largest primary energy produced in the United States and its use is growing. Yet getting this gas to homes and businesses creates greenhouse gas emissions. That’s why reducing emissions from America’s natural gas is an urgent priority that requires collaborative solutions. The National Petroleum Council brought together a diverse group of stakeholders with the expertise to analyze this complex issue and identify ways to reduce natural gas GHG emissions for all future supply and demand scenarios. The result: actionable consensus on ensuring a lower-emission natural gas system. The study’s research charts a course forward to meaningfully reduce emissions from the natural gas system, contributing significantly to the United States’ ability to achieve its climate goals. The report concludes that through the implementation of existing policies, voluntary commitments, technologies, and market mechanisms, a 63% reduction in methane emissions can be achieved by 2030. The report went further to identify an additional pathway that methane emissions decrease by 70% and carbon dioxide emissions reduce by 33% through 2050.
Here, we present a systematic model that links the generation, migration, phase partitioning, and accumulation of methane into a closed loop as the sediment is deposited from the seafloor and buried through the base of hydrate stability zone (BHSZ). In our model, methane is generated by biodegradation of organic carbon in muds. Hydrate does not form and methane is not trapped until a coarse-grained layer is deposited, because the small pores prevent hydrate formation in muds. Instead, methane diffuses into sands/silts where methane solidifies into hydrate. As hydrate-bearing sands/silts pass through the BHSZ during sediment burial, methane hydrate dissociates, and releases free gas. The released and the newly generated free gas below the BHSZ concentrates into a vertical/dipping zone with low capillary entry pressure and high permeability and flows upward driven its buoyancy. When free gas reaches the hydrate stability zone (HSZ), capillary forces drive free gas to flow laterally, preferentially enter sands/silts, feed hydrate growth, and elevate hydrate saturation. With three-dimensional focused free gas flow, microbial methane that is generated from a much larger fetch area of the entire basin, both above and below the BHSZ, is concentrated into coarse-grained layers at structural closures for hydrate formation. Our model illustrates how geological evolution, microbial methane generation, and gas flow by buoyancy couple to generate concentrated hydrate deposits in geological system. These insights can be used to explore for high-concentration methane hydrate and are important for understanding the methane budget and carbon cycle under the seafloor.
Methane hydrates, widely found in permafrost and deep marine sediments, have great potential as a future energy 6 source. Conventional production schemes perform poorly for challenging hydrate reservoirs with low permeability. We propose an 7 efficient production scheme by combining hydraulic fracturing from horizontal wells and hot water circulation through fractures. A 8 fully coupled thermo-hydro-chemical (THC) model is developed to simulate the key physical processes during gas production from 9 a hydrate reservoir representative of typical geological settings in Shenhu, South China Sea. We found that the gas production 10 process has two distinct stages divided by thermal breakthrough: a relatively short prebreakthrough stage and a postbreakthrough 11 stage yielding stable gas production. Heat advection along and near the hydraulic fracture dominates the prebreakthrough stage, 12 whereas conduction-driven thermal recovery in the volume around fractures dominates the postbreakthrough stage. We identified 13 that the steady-state injection temperature has a strong effect on the performance of the proposed scheme while the fluid mass 14 circulation rate has a moderate impact beyond a threshold. The proposed scheme proves to be efficient and robust over a range of 15 reservoir conditions with respect to initial hydrate saturation and intrinsic permeability, including their spatial heterogeneities, 16 thereby offering a promising solution for challenging reservoir conditions.
Hydrate-bearing sediments constitute complex hydrological systems, within which the pore habit of hydrate significantly affects all physical properties. However, there is scarce pore-scale evidence of the evolution of hydrate growth in porous media and the influence of water salinity in the micro-morphology of hydrate. In this paper, we used X-ray computed micro-tomography (CT) to monitor three experiments of methane hydrate growth in sand partially saturated with either NaBr or KI brine under excess-gas conditions. Gas, brine and hydrate are observed to co-exist at the pore-scale during the evolution of hydrate pore-habit towards three-phase equilibrium. The experiments and data analysis reveal that (1) hydrate forms as a porous medium mixed with inclusions of brine and gas, where hydrate and brine evolve gradually into separate phases as hydrate cages exclude salt ions, (2) hydrate growth mobilizes water over fairly long distances resulting in heterogeneous hydrate distribution, and (3) hydrate can exhibit interconnecting pore-habit at local hydrate saturations higher than ~50%, even if grown under excess-gas conditions. The results imply that hydrate micro-morphology and pore habit evolve during hydrate formation and, we suggest, so do the physical properties of hydrate-bearing sediments. Furthermore, our findings provide new insights into the micro-morphology of hydrate and evolution of the properties of hydrate-bearing sediments synthesized in the laboratory and in natural systems.
This is the Phase 4 Report for the ‘Deepwater Methane Hydrate Characterization and Scientific Assessment or Genesis of Methane Hydrates in the Gulf of Mexico (GOM2)’ research project (DOE Award No. DE-FE0023919). The report summarizes activities from October 1, 2019 to September 30, 2020. The project is led by the University of Texas at Austin (UT). The project objective is to gain insight into the nature, formation, occurrence and physical properties of methane hydrate-bearing sediments for the purpose of methane hydrate resource appraisal through the planning and execution of drilling, coring, logging, testing and analytical activities that assess the geologic occurrence, regional context, and characteristics of marine methane hydrate deposits in the Gulf of Mexico outer continental shelf (OCS). We published a dedicated American Association of Petroleum Geologists Bulletin volume describing initial results from the UT-GOM2-1 expedition in Sept. 2020. This is part 1 of a multi-volume commitment by AAPG to this project. We further confirmed that the natural gas in hydrate at GC-955 was formed by primary microbial processes (>76.1 %). The in-situ effective permeability hydrate-bearing sandy silts at the GC-955 reservoir ranges from 0.1 md (1.0×10-16 m2) to 2.4 md (2.4×10-15m2) in cores with 83% to 93% hydrate saturation. The intrinsic permeability (the single phase permeability) is estimated from reconstituted samples to be ~12 md (1.2×10-14 m2) to ~41 md (4.1×10-14 m2). We used observation and models to interpret that the core degradation that is found in pressure cores is due to dissociation of the methane hydrate in the outer circumference of the core and dissolution of that methane into the fresh pore water that the core is stored with. We are designing approaches to minimize this core loss in the future. We spent an enormous amount of effort to further improve the ability of the pressure coring tool (the PCTB) to pressure seal correctly. We completed upgrading the upper section of the PCTB to address poor pressure. We successful tested the modifications at Geotek’s test facility in Salt Lake City (Bench Test II). We completed a Land Test of the PCTB at the Schlumberger Cameron Test and Training Facility (CTTF). The tool did not seal in 6 out of 7 tests and we clearly demonstrated that cuttings were wedging in the ball valve assembly, keeping the ball valve from sealing. We reproduced the failure mechanism observed during the land test at Salt Lake City and confirmed the sensitivity of the ball valve assembly to grit. Geotek designed and tested 9 modifications to address this issue and the PCTB is now 100% successfully sealing in the presence of grit. Our science expedition is scheduled for spring 2022 and we are fully focused on preparing for this. UT and Ohio State completed a Shallow Hazard Assessment report for each proposed UT-GOM2-2 drilling location, pursuant to 30 CFR 250.214(f) and 250.244 (f). The Shallow Hazard Reports will accompany the UT-GOM2-2 Exploration Plan that is submitted to BOEM, and completes the geological and geophysical analysis for UT-GOM2-2 permitting efforts. We updated the UT-GOM2-2 Operations Plan (Version 1). We completed the UT-GOM2-2 Science and Sample Distribution Plan (Version 1). We evaluated the scope, budget, and schedule that would result from using a commercial vessel. We developed detailed drilling schedule, mud volume, and resource estimates. We developed a vessel specification document and a well plan, and sent these documents to prospective vessel contractors.
The heats of formation of carbonate, bicarbonate and bicarbonate/hydroxide metal complexes and hydrated versions these complexes of Mg 2+ , Ca 2+ , Fe 2+ , and Cd 2+ are predicted from atomization energies using correlated molecular orbital theory at the CCSD(T) level extrapolated to the complete basis set limit following the Feller-Peterson-Dixon (FPD) approach. Using the calculated gas phase values and the available experimental solid state values, the cohesive energies of selected minerals were calculated. The gas phase decomposition energies into MO, CO 2 and H 2 O follow the order Mg ~ Ca > Cd ~ Fe, and correlate with the hardness of the metal +2 ions. Gas phase hydration energies show that the order is Mg > Fe > Ca ~ Cd. There are a number of bulk hydrated Mg and Ca complexes that occur as minerals but there are few if any for Fe and Cd, suggesting that a number of factors are important in determining the stability of the bulk mineral hydrates. The FPD heats of formation were used to benchmark a range of density functional theory exchange-correlation functionals, including those commonly used in solid state mineral calculations. None of the functionals provided chemical accuracy agreement (± 1 kcal/mol) with the FPD results The best functionals are ωB97X and ωB97X-D with mean average unsigned errors of 10 kcal/mol.
An abundant source of CH 4 can be found in natural hydrate deposits. Recent demonstration of CH 4 recovery from hydrates via CO 2 exchange has revealed the potential as a fuel source that also provides a medium for carbon sequestration. It is vital to understand the structural and dynamic impacts of guest variation in CH 4 , CO 2 , and mixed hydrates and link the results to the stability of various deposits in nature, harvesting methane, and sequestering CO 2 . Molecular vibrations are examined in CH 4 , CO 2 , and mixed CH 4 -CO 2 hydrates at 5 and 190 K and Xe hydrates for comparison. Inelastic neutron scattering (INS) is an ideal spectroscopy technique to observe the dynamic modes in the hydrate structure and enclathrated CH 4 , as it is extremely sensitive to 1 H. The presence of CO 2 in hydrates tightens the lattice. It introduces more active librational modes to the host lattice, while hindering the motion of CH 4 in mixed CH 4 -CO 2 hydrate at 5 K. At 190 K, a large broadening of the CH 4 librational modes indicates disorder in the structure leading to dissociation.
The University of Texas (UT), Genesis of Methane Hydrate in Coarse-Grained Systems: Northern Gulf of Mexico Slope Project (GOM2), will perform the UT-GOM2-2 drilling and coring expedition in the Terrebonne Basin, Gulf of Mexico outer continental shelf. This is the scientific plan for the acquisition, storage, analysis, and distribution of core and other collected samples for UT-GOM2-2.
Methods used during the University of Texas (UT) Deepwater Hydrate Coring Expedition (UT-GOM2-2) include work done onboard the Helix Q4000 in the offshore Gulf of America (Gulf of Mexico), herein “the Gulf”, “dockside” in Salt Lake City, Utah, and some shore-based work in individual laboratories. The goal of this report is two-fold: to provide enough detail on the methods so they can be repeated by others; and to provide a reference document for the team to enhance cross-disciplinary understanding and knowledge. Methods include drilling operations, depth references and depth modification, downhole tool deployment, coring tool performance assessment, core processing, lithostratigraphy, biostratigraphy, as well as physical properties, including core logging and imaging, rock magnetism, dissolved methane concentration, hydrate saturation, microbiology, and geochemistry. An extensive amount of operational work and planning was required before mobilization of the expedition to permit, build mobile labs, and test downhole tools for deepwater drilling.
We performed 18 X-ray diffraction (XRD) measurements on sediment samples acquired at Holes H002 (6 samples) and H005 (12 samples) during the UT-GOM2-1 Expedition in Green Canyon Block 955, in the northern Gulf of Mexico. Results indicate a predominance of quartz, with significant proportions of alkali feldspar and carbonate, and minor amounts of amphibole, micas, and clays.