Mid-Continent Region

Whiting holds a total of approximately 125,000 net acres in the Mid-Continent region, primarily in Oklahoma. The Company drilled a total of 18.0 net wells in the region during 2005 with a success rate of 93% and plans to drill approximately 50 wells there in 2006. At year-end 2005, the Mid-Continent region contained 53.6 MMBOE of our estimated proved reserves, representing 20% of our total net proved reserves, and generated about 13% of our total production. The majority of the proved value within our Mid-Continent operations is related to properties in the Postle field.

Postle Field

The Postle Field, located in Texas County, Oklahoma, is one of Whiting’s most important assets. The field includes five producing units and one producing lease covering a total of approximately 25,600 gross acres (24,223 net) with working interests of 94% to 100%. Three of the units are currently under active CO2 enhanced recovery operations. As of December 31, 2006, there were 127 producing wells and 107 injection wells completed in the Morrow zone at 6,100 feet. The Postle properties produced at an estimated average net daily rate of 4,500 BOE per day during the month of December 2006. In the Postle field, the estimated proved reserves as of December 31, 2006 were 40% PDP, 26% PDNP and 34% PUD.

The Postle Field was initially developed in the early 1960s and unitized for waterflood in 1967. Enhanced recovery projects using CO2 were initiated in 1995 and continue in three of the five units. Operations are under way to expand CO2 injection into the remaining two units on the western side of the field. These expansion projects include the restoration of shut-in wells and the drilling of new producing and injection wells. This expansion work is under way with three drilling rigs and six workover rigs in the field. Whiting is the sole owner of the Dry Trail Gas Plant located in the Postle Field. This gas processing plant separates CO2 gas from the produced wellhead mixture of hydrocarbon and CO2 gas, so that the CO2 gas can be reinjected into the field’s producing Morrow sand reservoir. Whiting expanded the Dry Trail Gas Plant in 2006. The plant is injecting 108 MMcf of gas per day, up from approximately 60 MMcf per TERTIARY day at the time of its acquisition in August 2005. During the second quarter of 2006, new compressors were installed resulting in additional CO2 being injected. Subsequent to the delivery and installation of two new compressors in the second half of 2007, Whiting expects the plant’s injection capacity to increase to approximately 130 MMcf per day. As previously reported Whiting is now using produced natural gas from Postle Field to help fuel the Dry Trail Gas Plant, thus reducing third-party gas purchases and lowering lease operating costs at the field. In addition to the producing assets and processing plant, we have a 60% interest in the 120-mile TransPetco operated CO2 transportation pipeline serving the Postle Field, thereby assuring the delivery of CO2 at a fair tariff. Whiting has a long-term CO2 purchase agreement with a major supplier to provide the necessary CO2 for the planned expansion of the field.