The goal is to develop fundamental baseline thermodynamic and hydrodynamic data to support optimal operation conditions that prevent gas hydrate blockage formation in gas storage fields during high gas demand withdrawal and gas cycling periods.
Colorado Engineering Experiment Station, Inc. (CEESI), Nunn, Colorado 80648
Hydrate formation can severely restrict the flow of gas from storage wells during periods of peak demand and rapid withdrawal, limiting the availability of the gas when it is needed most. The lack of carefully measured storage field data coupled with detailed control data from a high quality flow facility hinders reliable engineering assessment of the technology opportunities to control gas hydrates for storage field operators. This research will provide key data and analysis that is required to mitigate flow blockages that restrict gas storage field operational flexibility and deliverability during critical peak demand periods.
This project will design and configure a high pressure, multiphase Hydrate Test Facility (HTF) to simulate storage field operations under conditions of hydrate formation. Thermodynamic and hydrodynamic data from the HTF will be obtained in a real-time manner under a wide variety of storage well fluids and field operating scenarios consistent with actual storage field operating practices. The HTF test results will be compared to actual field site results and used to establish consistency between the field sites and the test facility, and for validation of the test facility results.
The storage field data and corresponding HTF data from this project will provide a foundation to develop and support technologies to identify, minimize, and mitigate flow line blockages caused by gas hydrate formation during periods of peak natural gas withdrawal.
Data has been collected from a moderate pressure gas well at the El Paso Latigo field in Colorado and from a high pressure gas well at the Dominion Greenlick field in Pennsylvania during operating conditions when flow line hydrate blockages are formed. Inhibitor analyses were made based on field conditions at these sites. Results show that at non-isothermal surface conditions during shut-ins, the quantity of inhibitor required can exceed 40 wt% of the amount of water in the flow line. Sub-surface isothermal conditions require a minimum of 20 wt% inhibitor. Based on the field work, a design basis for flow tests at the HTF was configured to investigate hydrate control chemicals for different applications.
A new hydrate well-bore test section is being developed to provide the capabilities to obtain hydrate flow and hydrate blockage data in a simulated well-bore; in particular at subsurface safety valves in vertical flow lines. The test section is being installed into an existing 50 foot vertical shaft adjacent to the HTF. The design includes a subsurface safety valve, multiple viewing ports, and temperature, pressure and flow monitoring equipment. Subsurface flow lines will provide conditioned gas, liquids and inhibitors to the test section.
CEESI has completed a study of in-line rotary compact separator technology. The technology offers many advantages over conventional field separation systems however; it is currently too expensive and has some perceived maintenance issues that must be overcome before widespread commercial application occurs. The report recommends careful testing of the separation technology under controlled conditions so that performance and maintenance issues can be investigated prior to conducting gas storage field testing of such units. This testing would provide manufacturers with the necessary data to develop the best options for improving the design of the compact in-line separators for storage field applications.
Gas storage well-bore fluid flow calculations for gas and liquid are being analyzed. The results are expected to permit hydrate flow analysis over a wide range of gas/liquid/particulate flow rates and loadings common in gas storage field operations. Preliminary analysis has produced a large matrix of physical and flow property data which will be coded and incorporated into the initial two-fluid phase flow work and used to support the shake down tests of the new well-bore test section at the CEESI HTF in 2008.
The new well-bore test section is currently in the construction and installation phase. The piping from the main hydrate flow test section to the new well-bore test section as well as the return piping has been installed. The pipe remains to be welded to the existing hydrate loop and the new well-bore section. The well-bore test section is expected to be installed during the second quarter of 2008 with shakedown testing commencing shortly thereafter.