Southwestern Energy marks progress in Arkoma basin shale gas play

Southwestern Energy Co., Houston, now pursuing a shale gas play in and adjacent to the Arkoma basin gas producing fairway, has estimated dry gas in place at 58-65 bcf/sq mile in the formation in a new field in northwestern Conway County, Ark.

The Arkansas Oil and Gas Commission approved Southwestern's application for field rules covering Griffin Mountain field, one of the company's pilot areas in the Mississippian Fayetteville shale play.

Southwestern is drilling its 14th well in the play and has placed 4 wells on production. The wells are in Franklin, Conway, Van Buren, and Faulkner counties.

Two of the producing wells are in the basin's traditional producing fairway. Sales are 125-160 Mcfd of gas from a thinner section of the shale. Sales are 250-450 Mcfd from the two producing wells in Griffin Mountain field.

Six wells are in various stages of testing or completion, and three are shut-in pending pipeline connection.

Southwestern has acquired leases on 500,000 net undeveloped acres and controls 125,000 net developed acres held by conventional production in the basin fairway.

The company boosted its budget to $28.2 million to drill 23 wells and acquire more acreage in the play in 2004 (OGJ Online, Aug. 18, 2004).

Fayetteville formation

Modeling data for two of Southwestern's wells indicated an expected drainage area of 30 acres/well or less and estimated ultimate recovery of 580-600 MMcf/well in Griffin Mountain field, in 9n-17w on the north flank of the old Jerusalem gas field.

The commission approved minimum spacing of 560 ft between wells. Southwestern said the estimates in the application are based on preliminary data and will revise models as more data become available.

Griffin Mountain field, to cover 9 sq miles, represents a small initial area of testing relative to the company's acreage position in the play, Southwestern said.

"The company expects variability throughout the play area; therefore, the drainage area per well, gas-in-place, and ultimate recovery estimates included in the company's filing for the Griffin Mountain Field are not necessarily indicative of the expected drainage area, estimated gas-in-place, or estimated ultimate recovery for the other pilot areas or the entire play area," Southwestern said.

Southwestern has completed 10 wells using nitrogen foam fracture stimulation treatments of various sizes and has completed one well with a larger slick-water fracture treatment. The wells are in various stages of flowing back frac fluids, and well performance has varied significantly. No certainty exists as to the most effective stimulation.

"Further testing will be required to understand the optimum fracture techniques, reservoir continuity, fault and fracture patterns, and their relationship to well performance, and additional production history will be necessary to determine production profiles and project ultimate well recoveries. We continue to be encouraged by our early operational results in this play," Southwestern said.