Recent Developments at Wilburton Field, Latimer County, Oklahoma
Richard C. Hook
Recent deeper drilling in Wilburton field has resulted in new production from the Spiro, Cromwell, and Arbuckle formations in a structurally high fault block in situ beneath the old field pay in the overthrusted Spiro. ARCO Oil and Gas Company first found production from Spiro in situ beneath a low-angle thrust fault in Sec. 36, T5N, R17E. Nine wells now produce from this reservoir. Two wells have been completed below the Spiro in the in-situ Cromwell reservoir, and others are thought to be productive. Three wells are currently being drilled for in-situ Spiro and Cromwell.
Structural data generated by drilling the in-situ Spiro and Cromwell pays revealed a southwest-dipping, upthrown fault block with nearly 2,000 ft of vertical relief. ARCO tested this feature with their ARCO 2 Yourman well in Sec. 15, T5N, R18E, discovering prolific gas production from the Arbuckle. The Arbuckle reservoir consists largely of vugs and solution-enlarged fractures in a clean dolostone. Conventional neutron-density logs show very low porosity, but cores and formation microscanner images reveal the vugs, some of which are several inches across. Permeability is created by a pervasive system of younger fractures and microfaults. All current production is from the uppermost 700 ft of the Arbuckle, with a gas column of at least 1,100 ft. To date, six Arbuckle wells have been co pleted, two are in completion, and two are being drilled.
AAPG Search and Discovery Article #91025©1989 AAPG Midcontinent, Sept. 24-26, 1989, Oklahoma City, Oklahoma.