|
End of the road Rutter & Wilbanks finally gives up on its attempt to find new gas resource at its Glennallen gas exploration well Alan Bailey Petroleum News
Nearly five years after starting its gas exploration drilling project near Glennallen in Alaska’s Copper River basin, with something in excess of $20 million now expended, and having made multiple attempts to prove out what appeared to be a promising natural gas resource, Texas-based Rutter & Wilbanks has finally thrown in the towel on its Ahtna 1-19 wildcat well.
The company is plugging and abandoning the well, Bill Rutter Jr., Rutter & Wilbanks vice president, told Petroleum News Sept. 23.
After a two-year pause in drilling activity, while Rutter & Wilbanks tried to secure the use of a suitable drilling rig for continued testing at the well, a Schlumberger coiled tubing unit has been drilling a sidetrack well, the Ahtna 1-19B, into Nelchina sands, to test what Rutter believes to be a gas resource in the range of 50 billion to 150 billion cubic feet. An earlier sidetrack, the Ahtna 1-19A, had found the gas in 2007, but excessive water flow from the well had raised questions over the viability of the find. One purpose of drilling the second sidetrack was to determine whether the water came from the gas reservoir or from somewhere higher in the well, perhaps at a location in the well that could be sealed off.
Gas in the Nelchina When Rutter & Wilbanks drilled the Ahtna 1-19 well in 2005, it failed to find gas at the target depth of 7,500 feet but suspected the existence of a gas resource in the Nelchina at around 4,300 feet. Unfortunately, however, the use of heavy drilling mud as a consequence of exceptionally high formation pressures at a depth of about 1,200 feet had damaged the Nelchina reservoir around the well.
After an unsuccessful attempt in 2006 to penetrate the damaged section of reservoir rock using a Cad Pressure Central snubbing unit, Rutter & Wilbanks returned in 2007 to drill the Ahtna 1-19A sidetrack with the same coiled tubing unit that it has been using this year.
But this year’s attempt to prove the viability of the 2007 gas find has come to naught.
After auguring down through the cement that had been used to plug the well in 2007 and then using fresh cement to “squeeze” the subterranean channel, thought to be the source of the pesky water inflow, the drillers ran out the new sidetrack about 40 to 50 feet from the old well.
But testing of the well, rendered difficult by the narrow diameter of the coiled tubing and requiring a special perforating gun to be brought up from Texas, resulted in the production of more water from a high-pressure, underground source.
“Once I saw that pressure I knew we were tied,” Rutter said. “… There’s no rework you can do inside of 2-inch tubing, so I gave up.”
It is unclear at this point whether Rutter & Wilbanks will do any further exploration in the Glennallen region.
The Copper River Record contributed to this story.
| 