Accessing Residual Reserves in the Giant Hugoton-Panoma Field, Midcontinent United States
Kansas portions of the Giant Hugoton and Panoma fields have produced 29 tcf gas since 1922 from a differentially-depleted, layered Wolcampian reservoir system (depth 2600 ft [800 m]). More permeable of the 13 main pay zones, are currently depleted with bottom hole pressures as low as 10 psig, while less permeable zones are higher pressured (200-300 psig) and contain most of the remaining reserves. Initial reservoir pressure was 450 psig. An existing production infrastructure coupled with large volumes of remaining gas in this giant field, the largest onshore in North America, makes this an attractive target for operators who are interested in making the best use of field rules which allow three wells per 640-acre unit and a fourth well if it is demonstrated that new gas reserves can be accessed by it.
The focus of this study was to better understand how to economically produce residual gas reserves in tighter zones in the differentially depleted multi-layered reservoir system. Reservoir characterization and simulations studies were carried out on a 9-section area around the Flower A1 (science well) to match production and pressure histories at existing wells over 75 years including limited layer-pressure data. A fracture simulator was calibrated with measured rock properties to model fracture propagation and characteristics using prevalent hydraulic fracturing treatment plans and by history matching early production data from newly completed (hydraulically fractured) wells.
Reservoir simulation results show minimal interference at existing wells due to completion of (4th) infill wells and that hydraulically fractured vertical wells are nearly as effective as longitudinally-fractured horizontal wells. Also, a horizontal well with 3 equidistant transverse fractures produces at similar rates as it would were it just longitudinally fractured. These studies show that the majority of the produced gas is incremental and is mobilized from less-drained tighter zones, supporting the observed lack of interference from recent new drills. Simulations suggest three wells per unit are insufficient to effectively drain low permeability zones across the entire unit and that a fourth well adds 0.4 to 0.7 bcf recoverable per unit. Adding a fourth well in a unit could increase the ultimate gas recovery from the Hugoton-Panoma field in Kansas by 5%, or approximately 2 tcf.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009