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Love 'em or Hate 'em — They're There

GOM Gas Hydrate Opportunities Explored

There are two schools of scientific thought when it comes to gas hydrates —one views them as a nuisance, and one sees them as a potential resource.

Love them or hate them, there's no ignoring them. Gas hydrates are garnering much attention among geoscientists hoping to better understand their occurrence.

In fact, the U.S. Department of Energy and the petroleum industry have joined forces to study gas hydrate accumulations in the Gulf of Mexico. (See related story, November 2003 Explorer).

(Also involved in the project is the Minerals Management Service, which will have to approve the drilling plan, environment report and application for a permit to drill any deep stratigraphic hydrate test well.)

And while there is a major challenge facing the DOE Gulf of Mexico Joint Industry Project (JIP), dealing with the development of protocols and laboratory tests for acquisition, processing and interpretation of seismic data to image gas hydrate zones.

But that is only slowing, not stopping, the research.

Acquisition parameters and survey design of exploration 3-D seismic are not optimal for shallow sediments where gas hydrates are found and do not allow accurate characterization of naturally occurring hydrates, according to Michael A. Smith, operation geologist for the deepwater Gulf of Mexico with the Minerals Management Service.

Several years ago a Senate bill funding a $50 million, five-year research effort on gas hydrates was passed, and at that time the DOE sent out requests for proposals to study gas hydrates in the Gulf of Mexico and the arctic regions of Alaska, according to Smith.

"DOE had three main goals for the research—to develop technology, to characterize the gas hydrates and understand the hazards, particularly in regard to seafloor stability, and develop safe and efficient drilling and coring protocols," he said.

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There are two schools of scientific thought when it comes to gas hydrates —one views them as a nuisance, and one sees them as a potential resource.

Love them or hate them, there's no ignoring them. Gas hydrates are garnering much attention among geoscientists hoping to better understand their occurrence.

In fact, the U.S. Department of Energy and the petroleum industry have joined forces to study gas hydrate accumulations in the Gulf of Mexico. (See related story, November 2003 Explorer).

(Also involved in the project is the Minerals Management Service, which will have to approve the drilling plan, environment report and application for a permit to drill any deep stratigraphic hydrate test well.)

And while there is a major challenge facing the DOE Gulf of Mexico Joint Industry Project (JIP), dealing with the development of protocols and laboratory tests for acquisition, processing and interpretation of seismic data to image gas hydrate zones.

But that is only slowing, not stopping, the research.

Acquisition parameters and survey design of exploration 3-D seismic are not optimal for shallow sediments where gas hydrates are found and do not allow accurate characterization of naturally occurring hydrates, according to Michael A. Smith, operation geologist for the deepwater Gulf of Mexico with the Minerals Management Service.

Several years ago a Senate bill funding a $50 million, five-year research effort on gas hydrates was passed, and at that time the DOE sent out requests for proposals to study gas hydrates in the Gulf of Mexico and the arctic regions of Alaska, according to Smith.

"DOE had three main goals for the research—to develop technology, to characterize the gas hydrates and understand the hazards, particularly in regard to seafloor stability, and develop safe and efficient drilling and coring protocols," he said.

ChevronTexaco put together a proposal that was accepted by DOE—a 42-month, $13.2 million investigation funded 80 percent by the DOE.

The company held a workshop in 2000 to determine industry interest in the research venture, and seven other companies have joined them to date: ConocoPhillips, Halliburton, Japan National Oil Co., MMS, Reliance Industries, Schlumberger and TotalFinaElf.

Defining the Goals

The JIP is a multi-phase, multi-year project, and its goals include:

  • Developing and implementing a research and technology plan to assist characterization of sediments containing naturally occurring hydrates in deepwater in the Gulf of Mexico.
  • Assessing and understanding potential safety hazards associated with drilling wells and running pipelines through sediments containing gas hydrates.
  • Developing a database of existing seismic, core, log, thermo physical and biogeochemical data to identify current hydrate containing sites in deepwater Gulf of Mexico.
  • Using existing knowledge to choose several sites in the deepwater Gulf of Mexico for field tests.
  • Planning and executing a drilling and sample collection field testing program to collect data and obtain cores to characterize the hydrate containing sediments in the Gulf of Mexico.
  • Using existing data and data collected during the project to develop wellbore and seafloor stability models pertinent to hydrate containing sediments in the Gulf of Mexico.

The first phase, concluded last year, was devoted to data collection, analysis, model development and generating protocols to detect and characterize the hydrate containing sediments. The results will be used to plan and execute phase II's drilling, sampling and data collection field program.

The goal of the recently begun phase II is to drill and core up to a dozen or more 1,000- to 2,000-foot test wells through bedded hydrate deposits, probably starting in April.

The JIP comprises three technical teams—a gas hydrates characterization team, a seafloor stability team led by Smith and a drilling and coring team.

"Each team has hosted a workshop to identify the critical issues in each area, and several contracts have been awarded to fill the knowledge gaps identified in those meetings," Smith said.

The characterization team awarded Georgia Tech a contract to study the effects of the thermal history and gas hydrate properties. A wellbore stability project was awarded to a division of Schlumberger and a critical research contract was awarded to WesternGeco to study the potential of seismic for gas hydrates detection.

The WesternGeco study is particularly important, because a successful detection method is critical to any meaningful research on gas hydrates. The firm is currently completing its project at several prospective drill sites.

Nader Dutta, chief geoscientist with WesternGeco's seismic reservoir division, is heading the team studying seismic detection of gas hydrates. He said he first became interested in gas hydrates after conducting a literature survey a couple of years ago.

Dutta said there are two camps in the United States concerning gas hydrates:

  • One camp is interested in identifying gas hydrates because they feel there is a great deal of natural gas trapped in the hydrates that can be exploited to meet our energy demands.
  • The other camp is interested in avoiding gas hydrates when establishing infrastructure because of presumed seafloor instability associated with hydrates.

    "However, I view both camps as an opportunity," Dutta said, "because either way it is important to identify the gas hydrates, and seismic is the key detection technology. The deepwater Gulf of Mexico is the ideal location to test how useful seismic can be in detecting , quantifying and mapping gas hydrates, since the entire area is covered by 3-D seismic data."

Both Dutta and Smith presented papers on seismic prediction of gas hydrates at the AAPG international conference in Barcelona, and both will be speaking at the upcoming AAPG annual meeting in Dallas.

Dutta said that the first key challenge for the research team was to find if there were, in fact, subsurface gas hydrates in the Gulf of Mexico.

"With the exception of one or two anecdotal incidences of bottom simulating reflectors, there have been no direct seismic signatures of gas hydrates like in other parts of the world, even though the deepwater Gulf is the right environment for gas hydrates," he said.

"The second critical element for the study was, if seismic or some other technology could prove the existence of gas hydrates, then could we quantify the resource?"

The team focused on the extensive seismic data covering zones where people believed gas hydrates might exist. To make seismic data a useful remote sensing tool for gas hydrates, Dutta and his group had to determine which models needed to be developed and how the seismic data should be conditioned.

"Processing techniques typical for oil and gas detection focus on deeper targets and, therefore, were not useful in detecting gas hydrates that are found at relatively shallow depths," he said. "So the first step was to develop a new processing technique that keyed on the shallow depths completely ignored in the original processing phase."

As a result, the team "began to see hints of bottom simulating reflectors that were never identified in the past."

For instance, at the Keathley Canyon and Atwater Valley locations was evidence of a bottom simulating reflector.

Gas hydrate mounds are known at the seabed near both sites, and gas is percolating up through those mounds, creating a good environment for gas hydrates to form.

"Our seismic interpretation picked up deeply steeping events in the deepwater environment, and we see gas hydrates cross-cutting the sedimentary strata," he said. "The rock physics models seem to be working well at Keathley Canyon, so we are getting some concentration estimates."

Something else they "think we found" this summer is a second layer of gas hydrates that was not visible on conventional seismic—it became visible following the seismic inversion.

If this turns out to be definitive, it will be the first paleo bottom simulating reflector in our seismic data.

According to Smith the first drilling leg of the JIP will get under way this spring. The plan calls for at least 12 holes about 10 inches in diameter at six sites. The log data and additional wireline logs will give scientists a better picture of where to collect core samples in a twin hole.

"The MMS would like to include an estimate of total gas hydrate resources on all four coasts in the next national oil and gas assessment in 2005," Smith said. "To reach that goal this JIP research is critical."

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