Develop models to help determine the potential for sea floor and wellbore instability during drilling.

Clarkson University – Project Management and Research Products

Location

Potsdam, NY 13699

There currently are no models that can address all of the characteristics of natural gas hydrates in sediments. The proposed effort was to develop a method to utilize the unique characteristics of hydrates for future offshore development. Specifically the project will develop computational techniques that can describe the behavior of gas hydrates, predict possible safety problems and provide a fundamental understanding of the conditions that cause the natural gas to disassociate within sediments. It will also visualize and measure the way hydrates disassociate under controlled conditions in a multiphase flow laboratory setup and develop computational models to predict the way gas and water flow in a reservoir as hydrates release gas, and the rate of natural gas pressure buildup during drilling.

The effort to create new models for describing the changes to naturally occurring gas accumulations has historically been a gradual development from a basic one dimensional model to 3-D visualization as characterization data is acquired from the reservoirs. This effort is a basic beginning to the understanding of gas hydrate behavior in sediments. If the development of past reservoir models holds true, the results of this effort will be used to develop more complex model algorithms. As gas hydrate research efforts continue to accumulate, more detailed reservoir analysis with each new coring, logging and well testing demonstration, better parameters will be provided for modeling gas hydrate accumulations.

Results

• Developed semi-analytical computational models for natural gas flow in a hydrate reservoir and evaluated the impact of variations in porosity and permeability on pressure and temperature profiles and the movement of a dissociation front,
• Developed an experimental setup for hydrate formation and dissociation that allows for the visual observation of the processes being modeled,
• Measured variations in gas pressure and temperature during hydrate formation and dissociation for various mixtures of crushed ice and glass beads,
• Fabricated a shear flow device and performed preliminary experiments on liquid phase shearing,
• A thermodynamically consistent model for multiphase liquid-gas flows through porous media was developed, and
• Numerical model for hydrate dissociation in an axis-symmetric reservoir is developed.

A computational model for hydrate dissociation in a reservoir was developed and used to perform a set of sensitivity analyses on the effect of variations in reservoir permeability and porosity on the hydrate dissociation process. Progress was also made in studying dense two-phase solid-liquid mixture flows.  Model predictions compared well with experimental data.  A series of experimentations for propane hydrate formation and dissociation under laboratory conditions was performed. Propane is used in place of methane for safety reasons. Pressure and temperature data during formation and dissociation were obtained.  A thermodynamically consistent model for multiphase flows in porous media was developed.

The task to develop a full numerical version of an axis-symmetric computational model for evaluating reservoir conditions during hydrate formation and dissociation has been completed. All of the remaining effort required to complete the model for multiphase flows at higher shear rates and speeds has also been completed.

$268,183

$103,795

NETL – Thomas Mroz (Thomas.Mroz@netl.doe.gov or 304-285-4071)
Clarkson University – Dr. Goodarz Ahmadi (ahmadi@clarkson.edu or 315-268-2322)

Fundamentals of Natural Gas and Species Flow from Hydrate Dissociation [PDF-1201KB]

Peer-Reviewed Publications
Ahmadi, G., C. Ji, and D. Smith, 2000, A Simple Model for Natural Gas Production from Hydrate Decomposition, in Holder, G., and P. Bishnoi, eds., Gas Hydrates: Challenges for the Future, Annals of the New York Academy of Sciences, Volume 912, p. 420-27.

Ahmadi, G., C. Ji, and D. Smith, 2004, Numerical Simulation of Natural Gas Production from Methane Hydrate Dissociation, Journal of Petroleum Science and Engineering, Volume 41, p. 269-285.

Ji, C., G. Ahmadi, and D. Smith, 2003, Constant Rate Natural Gas Production from a Well in a Hydrate Reservoir, Energy Conversion and Management, Volume 44, p. 2403-2423.

Ji, C., G. Ahmadi, and D. Smith, 2001, Natural Gas Production from Hydrate Decomposition by Depressurization, Chemical Engineering Science, Volume 56, p. 5801-5814.

Presentations
Ji, C., G. Ahmadi, W. Zhang, and D. Smith, 2002, Natural Gas Production from Hydrate Dissociation: A Comparison of Axisymmetric Models, Yokohama, Japan, Fourth International Conference on Gas Hydrates, May 19-23.

Ji, C., G. Ahmadi, and D. Smith, 2000, Computational Simulation for Natural Gas Production from Hydrate Decomposition, Lake Placid, NY, Annual Technical Meeting of the Center for Advanced Material Processing, May 23-25.

Nazridoust, K., T. White, C. Ji, G. Ahmadi, D. Smith, and M. Dean, 2002, Natural Gas Production from Hydrate Dissociation, Saratoga Springs, NY, Annual Technical Meeting of the Center for Advanced Material Processing, May 13-15.