--> Abstract: Diagenesis of the Sandflat and Mudflat Facies of the Upper Queen Formation, Midland Basin, Texas, by C. J. McKone, A. Malicse, and J. M. Mazzullo; #91004 (1991)

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Diagenesis of the Sandflat and Mudflat Facies of the Upper Queen Formation, Midland Basin, Texas

MCKONE, CHARLES J., ARIEL MALICSE, and JAMES M. MAZZULLO, Texas A&M University, College Station, TX

The upper Queen Formation (Permian, Guadalupian) of the Midland basin, Texas, consists of cyclically interbedded clastics and evaporites that were deposited in a fluvial-dominated continental sabkha environment. Fluvial sandflat deposits, consisting of thin units (0.2-5.0 m) of very fine grained arkosic sandstones constitute reservoir horizons, whereas 0.1-1.3 m thick units of coarse siltstones and evaporites of playa-mudflat deposits are nonproductive. This study addresses the diagenetic histories of the reservoir and nonreservoir clastics.

The primary porosity of the clastics was first reduced by pore-filling hematitic smectite clay, anhydrite, and dolomite during an early diagenetic phase. Subsequent dissolution of the anhydrite and dolomite by acidic pore-waters created high porosities (mean = 15%) and permeabilities (mean = 70 md) in the sandflat deposits, porosities which were only slightly occluded by later dissolution and reprecipitation of grain-lining smectite.

Pore-water movement and subsequent hydrocarbon migration were both controlled by the coarser grain size and lower clay-matrix and silt content of these sandflat deposits. In contrast, the finer grain size and higher clay-matrix and silt content prevented similar dissolution of cements within the mudflat facies, which have significantly lower porosities (mean < 10%) and permeabilities (mean < 0.1 md). Fluids and gases used in enhanced recovery techniques will follow pathways created by dissolution of anhydrite and dolomite cements within the sandflat facies. However, caution must be used with fluids that can cause swelling of the grain-lining smectite.

 

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)