Development of a Through-Tubing (Microhole) Artificial Lift System
The project goal was to develop an economical artificial lift system that would allow operators in the Gulf of Mexico to reactivate wells that can no longer flow naturally due to fluids in the wellbore.
Gas Production Specialists, LLC
The Gulf of Mexico and mature onshore fields contain many gas wells rendered uneconomic because the depleted reservoir pressure cannot overcome the weight of fluid in the wellbore. In many cases these gas reservoirs have considerable remaining gas-in-place but lack cost-effective methods to produce them. The artificial lift system being developed in this project is expected to provide a low-cost way to dewater wells and increase gas production. Development of this technology will allow operators to extract more reserves out of depletion-drive reservoirs in the Gulf of Mexico and the continental U.S.
This technology was expected (if successful) to improve gas recovery by removing bottomhole water from gas wells so that the reservoir energy has only to lift the gas column. This lift also could be used for oil wells under depletion drive. The technology allows operators to produce more oil and gas out of known reservoirs in areas that already have an existing infrastructure, as with many of the mature fields in the United States.
The through-tubing artificial lift system has the potential to allow operators to reactivate wells that can no longer flow by natural reservoir pressure. By reactivating these wells, more production and thus more reserves recovery could be realized from currently idle assets. The technology focuses on extracting more oil and gas out of known reservoirs in areas that already have an existing infrastructure.
Of the estimated 17,402 active wells in the Gulf of Mexico, over two thirds are currently shut-in. (OCS Report MMS 2003050). Assuming that a very conservative 5% of the 17,402 are candidates for the through-tubing artificial lift technology, 870 wells potentially could benefit from the technology. Further assuming 1-2 billion cubic feet of gas per installation is being produced, a potential incremental reserves addition of ~1.3 trillion cubic feet (TCF) of gas is possible.
Another way to demonstrate the potential market of this technology is to look at the total reserves for the Gulf of Mexico. Proved reserves are estimated to be 14.93 billion barrels of oil and 167.3 TCF of gas. Assuming a conservative 1% incremental reserve increase resulting from the technology, an incremental reserve addition of ~1.6 TCF of gas and 30 million barrels of oil is possible.
This research and development project was aimed at developing a new through-tubing artificial lift pump system capable of removing small liquid volumes from gas wells. The advantage of this system approach is that it could be completely deployed and retrieved in a "rigless" fashion. In operating environments where costs are relatively high, such as offshore fields, this rigless deployment method could save the operating company hundreds of thousands of dollars.
The system was to be made small enough to pass through the existing tubing string. The system would pump liquids up a small inner string and allows gas to flow in the newly formed annulus areas. The pump system was to consist of a small-diameter (2 1/8-inch) electric submersible motor, gear reducer, thrust section, intake screen section, and a small-diameter liquid pump. Because it is a pumping system, all liquids were to be pumped to the surface, allowing a gas well to be produced to its lowest abandonment pressure. Virtually no reservoir energy would be consumed moving liquids to the surface because the hydrostatic and friction pressure losses would be overcome by the pump.
To accomplish the primary objective, the project plan was to 1) finalize the design and development of the various components, 2) acquire all of these components, 3) perform surface testing of the completed components, and 4) test the entire system in a well.
Current Status (October 2008)
This project has been closed out. Complications during the performance of the award prevented achievement of the goals and objectives as defined above. Although the system could not be developed by GPS using the same basic technology that already exists within the oil & gas industry, it is still believed that the idea/concept to pump small volumes of liquids from wells to eliminate well loading problems still holds potential value and that value is increased in a higher oil / gas price environment.
The major hurdles during attempts to carry out this project centered around the electrical system and how to get power downhole to the motor in such a slimhole environment. It is considered that perhaps a better approach would have been to use either gas or hydraulic power to supply a downhole pump that could then pump fluids to the surface. A slimhole system would need to be developed but the system could be accomplished by running two strings of small diameter coil (example Dyna-Coil) and allowing the gas to flow up the annular space between the two strings of coil and the production tubing. In retrospect, this type of system now seems less complicated when compared to the electrically powered system that GPS attempted to develop under this project. Project personnel indicated that additional project complications were encountered due to attempts to develop this system solely on their own and that development at a larger scale with more groups involved would have increased the likelihood of success.
Project Start: June 15, 2004
Project End: September 30, 2006
Anticipated DOE Contribution: $80,000
Performer Contribution: $130,000 (62% of total)
NETL - Richard Baker (email@example.com or 304-285-4714)
Gas Production Specialists - Steven Bodden (firstname.lastname@example.org or 337-839-0816)
Final Project Report [PDF-69KB]
Slimhole electric submersible motor.
Motor to gear coupling.