A brine well is a salt mine. A well, or sometimes more than one well, is drilled into a salt layer below the ground, fresh water is pumped down into the well, allowed to dissolve the salt and then pumped back to the surface where it is used for oilfield applications such as drilling mud and workover fluids.
For years this practice was an inexpensive and reliable means of getting salt saturated fluids for oil and gas operations. However last year, two of the fourteen recently active brine well operations in southeastern New Mexico collapsed into massive craters hundreds of feet across and a hundred or more feet deep.
The Oil Conservation Division examined and discovered that the two brine wells that collapsed had several features in common. They were both relatively shallow (approximately 500 feet deep), had produced large amounts of brine (between 6 and 8 million barrels), and had been used for relatively large periods of time.
The Carlsbad Brine Well
What alarmed division investigators most was that there was another well that fit this profile, and it was located near one of the busiest intersections in Carlsbad and adjacent to the main canal for the Carlsbad Irrigation District. Business operations were stopped at the location and a consulting engineering firm hired by the Oil Conservation Division began to monitor the site for any sign of an impending collapse.
Monitoring and Warning System
The division determined that the first thing to do was to acquire an early warning system that would warn persons near the site of an impending collapse. The consulting firm contacted the manufacturer of the needed equipment and found that it was not immediately available and that it would have to be built to order. An order was placed and a plan developed to monitor the site until the equipment could be acquired and installed.
While the detectors are being built, very accurate survey instruments were acquired and elevation points were established that were far enough away that they would not be affected by any possible collapse. Every morning, an Oil Conservation Division consultant checks the elevations at 24 points near the brine well against the points away from the site to make sure that there has not been subsidence or heaving (upward movement) that would be associated with geologic movement or an impending collapse. While Oil Conservation Division and its contractor are still analyzing the data, preliminary analysis indicates that no verifiable geologic subsidence has occurred at the site.
In addition, the Oil Conservation Division “borrowed” surface instruments that could detect minor changes in slope and installed 13 surface points around the location. The contractor checks them daily for changes. These instruments will be replaced by the automated borehole tiltmeters that are currently being installed.
Permanent Automated System
The Oil Conservation Division is now starting to take delivery of the permanent automated system and is installing it. Two out of the three below ground sensors are already on location, but the third did not pass its final factory testing. It is being rebuilt and will be shipped and installed as soon as possible. Oil Conservation Division will continue to do the manual monitoring until the automated system is functional and connected to the Eddy County Emergency Management office, who is responsible for notification and evacuation of parties who might be effected by a collapse at the location.
Geological Evaluation
Simultaneously, the Oil Conservation Division’s consultant is proceeding with a geological evaluation of the site and will be presenting a proposal for a geophysical program to determine the location and size of the cavern. With this information, the Oil Conservation Division will be able to determine the available courses of action to deal with the cavern and the costs associated with each option |
