Realizing the Energy Potential of Methane Hydrate for the United States (2010) / Chapter Skim
Currently Skimming:
2 State of the Science: Recent Advances and Current Challenges in Methane Hydrate Research
2 State of the Science: Recent Advances and Current Challenges in Methane Hydrate Research
Pages 31-82
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 31... ...
This chapter reviews recent, critical, international, and domestic advances in methane hydrate research and identifies some of the remaining challenges to realizing the goal of commercial methane hydrate production. These challenges form a basis for Chapter 3, which discusses the research 1
|
From page 32... ...
METHANE HyDRATE RESoURCE ASSESSMENT The "goal" in methane hydrate research and development is the identification and quantification of technically and economically recoverable natural gas from methane hydrate occurrences. Because of the paucity of reliable field data, past research focused on the basic documentation of the existence and regional locations of global methane hydrate occurrences.
|
From page 33... ...
of natural gas, the global estimates of volumes of methane in methane hydrate are significant. Although the global methane hydrate resource inventories illustrate the importance of methane hydrate as a component of the global carbon cycle, their utility to address the energy potential of methane hydrate is limited.
|
From page 34... ...
. Recent Methane Hydrate Resource Assessments Considerable effort has been devoted recently to carrying out more focused methane hydrate resource appraisals in specific regions by applying, with some modifications, quantitative methods commonly used for appraising conventional oil and natural gas deposits.
|
From page 35... ...
Methane Hydrate Resource Assessments Gulf of Mexico Using the extensive industry database of exploratory wells and twodimensional (2D) and three-dimensional (3D)
|
From page 36... ...
Although these data were not collected with methane hydrate targets in mind, the data nonetheless provided a substantial basis for model inputs such as geologic setting with respect to the methane hydrate stability field, percentage of sand, as well as considerations of the gas sources, migration pathways, and trapping mechanisms. The assessment also considers possible seafloor indicators such as chemosynthetic communities and carbonates that may be associated with areas of higher probability for methane hydrate occurrences at depth.
|
From page 37... ...
Alaska North Slope A methane hydrate resource assessment was released in November 2008 by the U.S. Geological Survey (USGS)
|
From page 38... ...
Figure 2.2.eps landscape
|
From page 39... ...
These areas often coincide with very shallow salt features that occupy the bulk of, and sometimes the entire, methane hydrate stability zone. Also, areas that offered a thick sedimentary section, such as the deep minibasins and much of the abyssal plain, provide an abundant supply of microbial methane from the generation model.
|
From page 41... ...
Geological Survey (USGS) assessment predicts the total mean undiscovered technically recoverable methane from methane hydrate to be approximately 85 TCF based on the cumulative mean estimates from three assessment units, the Sagavanirkok Formation, the Tuluvak–Schrader Bluff–Prince Creek Formation, and the Nanushuk Formation.
|
From page 42... ...
However, estimating the recoverability of this resource has been undertaken with the reasonable expectation that conventional oil and gas recovery methods can be employed for sand-dominated methane hydrate reservoirs. Eastern Nankai Trough, Japan Japan has been pursuing an ambitious national methane hydrate research and development program to evaluate the energy potential of methane hydrate accumulations in the Nankai Trough (ohno, 2009)
|
From page 43... ...
LWD wells LWD and Coring wells FIGURE 2.4 Map showing the location of 2D/3D seismic surveys and Ministry of International Trade and Industry of Japan exploratory test wells from Tokai-oki to Kumano-nada in the eastern Nankai Trough. SOURCE: Fujii et al.
|
From page 44... ...
Mapping the Methane Hydrate Stability Field (Pressure and Temperature) Defining the pressure-temperature stability field of methane hydrate (Box 1.1)
|
From page 45... ...
Finally, the geochemistry of the pore fluids and natural gas species is also important in determining the in situ stability of methane hydrate occurrences (e.g., Ruppel et al., 2005)
|
From page 46... ...
. Use of BSRs as an Estimate of the Base of the Methane Hydrate Stability Zone Since the 1970s, methane hydrate in the marine environment has traditionally been inferred by mapping of BSRs in seismic reflection profiles (e.g., Shipley et al., 1979)
|
From page 47... ...
,8 and offshore India (National Gas Hydrate Program Expedition 01) 9 have all shown an apparent disconnect between the occurrence of methane hydrate and the presence of a BSR.
|
From page 48... ...
Several approaches use seismic data for methane hydrate saturation mapping including impedance inversion and analysis of prestack seismic data; shear-wave or multicomponent seismic data may also be employed to map methane hydrate occurrences (Box 2.2 provides more technical detail regarding these techniques)
|
From page 49... ...
S-wave or multicomponent seismic data may offer an additional approach to help identify methane hydrate occurrences and to distinguish among methane hydrate formation models. However, acquisition of S-wave data is typically more challenging than P-wave data (on land as well in the marine realm)
|
From page 50... ...
but are not commonly used in the Arctic because of operational challenges in permafrost regions. However, the typically broad-scale geophysical anomalies detected with these techniques are not optimal for the purpose of methane hydrate resource appraisals.
|
From page 51... ...
has been a long-standing goal of the methane hydrate research community. The first attempts to apply pressure coring methods for methane hydrate drilling investigations in the 1980s, including later modifications to these systems through the 1990s, identified various technical problems and the significant time required to extract a sample from the core barrel.
|
From page 52... ...
During the past decade a number of laboratories around the world have strived to build devices styled upon apparatuses used commonly in soil mechanics. These devices hold the potential to apply 3D confining pressure and to introduce methane dissolved in pore water rather then as free gas.
|
From page 53... ...
Makogon (1981) has proposed that the Messoyakha natural gas field in northern Siberia may have been capped by methane hydrate and that the production response of this field can be explained in part by dissociation of methane hydrate as the pressure of the free-gas reservoir declined with time.
|
From page 54... ...
, thereby po tentially affecting the structural and physical properties of the hydrated sample. Methane hydrate–bearing sediment samples synthesized with dissolved gas can exhibit a formation mechanism and morphology more closely replicating nature (particularly hydrate formed within the hydrate stability zone and in coarse-grained sediment; Dallimore et al., 1999; Winters et al., 1999; Waite et al., 2009)
|
From page 55... ...
mostly free of hydrate. Grain cementing Figure Box 2.4.eps tends to occur when hydrate samples are formed from free gas plus liquid water (sediment bitmaps, 2 fixed images Waite et al., 2009)
|
From page 56... ...
, and a simpler operational sequence. A downhole heater was also used to prevent methane hydrate formation within the production tubing.
|
From page 57... ...
The 2007-2008 production testing at Mallik demonstrated sustained methane production from methane hydrate by depressurization from a clastic, sand-dominated methane hydrate reservoir. Continuous and significant gas flow rates were observed and water production rates were judged to be manageable.
|
From page 58... ...
, and the 2007 drilling program in northern Alaska as part of the BPXA-managed Alaska North Slope project (Hunter et al., 2008; see also Chapter 3)
|
From page 59... ...
Chemical Stimulation The original production concept for the chemical stimulation of methane hydrate was to modify the in situ methane hydrate equilibrium conditions by injecting hydrate inhibitors such as salts and alcohols; these inhibitors act to decrease methane hydrate stability and induce dissociation. This technique has been used for decades to deal with methane hydrate blockages in pipelines, but it has not been seriously considered as an option for long-term production.
|
From page 60... ...
The possibility of seafloor strip mining has also been discussed as a potential approach to recover methane from near-seafloor methane hydrate deposits.11 With all novel production methods, where practical experience is limited and new techniques are being evaluated, the environmental impacts of development will require careful consideration. Reservoir Simulation Modeling Reservoir simulation models are computer models routinely used by engineers to simulate production from a hydrocarbon field over long timescales.
|
From page 61... ...
Acceptance of a verified methane hydrate simulation model would enable prediction of methane production rates and formation responses from different production strategies (e.g., depressurization, thermal stimulation, chemical inhibitor injection) for either Arctic or marine hydrate reservoirs.
|
From page 62... ...
GEoLoGIC PRoCESSES AND FEATURES ASSoCIATED WITH METHANE HyDRATE oCCURRENCES As described previously, methane hydrate in certain marine and permafrost environments is thought to constitute a significant storehouse of natural gas. In addition to the energy potential of methane hydrate, considerable
|
From page 63... ...
A number of authors have also suggested that methane seepage may occur where natural processes have either warmed formation temperatures or reduced pressure, causing methane hydrate dissociation. Some of the most perturbed methane hydrate deposits in the world occur in the Arctic in terrestrial permafrost environments with very cold mean annual surface temperatures.
|
From page 64... ...
Dissociating methane hydrate has been implicated as a possible source of methane release observed in lakes on the North Slope of Alaska and Siberia (Walter et al., 2006) and as a source for thermogenic gas seeps observed beneath lakes and channels of the Mackenzie Delta (Bowen et al., 2008)
|
From page 65... ...
. Submarine Landslides Many authors have tentatively associated major submarine landslides on continental margins with methane hydrate occurrences (e.g., Paull et al., 2003b)
|
From page 66... ...
and the time lag of methane hydrate deposits to an imposed surface temperature change (Taylor et al., 2002)
|
From page 67... ...
methane hydrate decomposition while drilling with warm drilling fluids or drilling fluids containing methane hydrate inhibitors such as glycol or (2) encountering preexisting overpressured gas pockets within the methane hydrate stability zone (see Box 1.1)
|
From page 68... ...
. present in the seismic reflection profiles at potential well locations, because BSRs were related to the potential of entering overpressured gas zones beneath the base of methane hydrate stability (Figure 2.6; see also section The Challenge of Mapping and Quantifying Methane Hydrate)
|
From page 69... ...
. Targeted drilling activities through BSRs where methane hydrate is stable within the surface sediment have also been conducted in numerous global marine settings: drilling projects coordinated by national research programs in China, India, Korea, and Japan; at a research site off Norway; by Deep-Sea Drilling Project, ocean Drilling Program, and Integrated ocean Drilling Program expeditions;12 in the Gulf of Mexico JIP supported by the DoE Program (Ruppel et al., 2008)
|
From page 70... ...
. These concerns relate to the substantial changes in sediment strength and permeability experienced when methane hydrate deposits are dis sociated during production when the production well passes through a hydrate-bearing zone and when the production is from the hydrate-bearing zone.
|
From page 71... ...
Another largely understudied topic is the amount and chemistry of the produced water that may be released when methane hydrate deposits dissociate. Some reservoir simulation models suggest that the pore water liberated when methane hydrate dissociates will be highly mobile and will 1
|
From page 72... ...
. The relatively shallow depths of methane hydrate occurrences also may mean that secondary sealing by the overlying sediment may only be weakly developed.
|
From page 73... ...
field activities on- and offshore and from laboratory experiments and modeling have advanced the understanding of the behavior and properties of methane hydrate and the potential to produce methane from methane hydrate accumulations. Although these advances in knowledge testify to the great interest in the potential of methane hydrate to serve as a future energy source, they belie the need for considerably more information on methane hydrate including its behavior in nature, during drilling, and in production settings, and the approaches needed to identify and reliably produce methane from this type of occurrence.
|
From page 74... ...
2002. Energy resource potential of natural gas hydrates.
|
From page 75... ...
Pp. 211-233 in Natural Gas Hydrates, Occurrence, Distribution and Detection, C
|
From page 76... ...
Pp. 1-29 in Natural Gas Hydrates: Energy Resource Potential and Associated Geologic Hazards, T
|
From page 77... ...
In P roceedings of the Sixth International Conference on Gas Hydrates, Vancouver, BC, July 6-11. Available online at https://circle.ubc.
|
From page 78... ...
In Natural Gas Hydrates, Occurrence, Distribution and Detection, C
|
From page 79... ...
2009. Acoustic impedance inver sion and seismic reflection continuity analysis for delineating gas hydrate resources near the Mallik research sites, Mackenzie Delta, Northwest Territories, Canada.
|
From page 80... ...
2009. Preliminary report on the commercial viability of gas production from natural gas hydrates.
|
From page 81... ...
In Natural Gas Hydrates: Energy Resource Potential and As sociated Geologic Hazards, T Collett, A
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.