ExxonMobil in Alaska: XTO enters Cook Inlet, Exxon buys XTO

In 1998, Cross Timbers Oil (later renamed XTO Energy) purchased producing properties in the Middle Ground Shoal field from Shell in exchange for $40 million in stock, including two platforms set in 70 feet of water with 39 active wells (as of 2006). The Cook Inlet field was in decline, producing about 3,600 barrels of oil a day,

Since that time XTO has done sterling work in maintaining oil production at the field, and in increasing the field reserves — from 12 million barrels to 24 million barrels.

XTO has developed new reserves by, among other things, directional drilling in the west flank, where the strata are essentially tipped on end. The company has also maintained production through coiled drilling work on production wells, injection well workovers and artificial lift optimization. (Reservoir pressure is maintained by injecting filtered water from Cook Inlet.)

In 2008, Middle Ground Shoal was producing at a rate in the range of 3,000 to 4,500 barrels per day.

In 2009, ExxonMobil acquired XTO in an all-stock deal, making XTO a subsidiary.

At the end of 2010, Middle Ground Shoal was still producing from 28 wells with a total daily average of 2,585 barrels a day.