ABSTRACT

A correlation of permeability thickness from wireline derived petrophysical data to well productivity before and after fracture stimulation is established for South Texas Vicksburg sands. Data from McAllen Ranch Field are used. McAllen Ranch Field is located approximately 30 miles north of the Mexican border in Hidalgo County, Texas. The field has gas productivity from low permeability geopressured massive sand intervals in the Frio-Vicksburg. Commercial production is usually contingent on successful fracture stimulation. Permeability is related to porosity, median grain size, and the standard deviation of the grain size distribution exclusive of interstitial clays. Shell's LOGPAK computer program is used for reevaluation of candidate wells and to calculate a permeability profile. Fracture heights are estimated and an appropriate permeability thickness ("kh") is calculated. Flow rates are normalized for variations in bottom-hole pressure conditions by dividing the flow rate by the difference of the average static reservoir pressure squared and the flowing bottom-hole pressure squared. Well productivity before and after fracture stimulation is significantly correlative with wireline derived petrophysical data. An average of less than 40% of the total reservoir permeability thickness is estimated to have been effectively stimulated by fracture treatment. Given current economic conditions and typical reservoir pressures, a minimum of 10 millidarcy-feet is required for a commercial completion.

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