--> Abstract: Interaction of Burial History and Diagenesis of the Upper Cretaceous Frontier Formation, Moxa Arch, Green River Basin, Wyoming, by S. P. Dutton and H. S. Hamlin; #91017 (1992).

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ABSTRACT: Interaction of Burial History and Diagenesis of the Upper Cretaceous Frontier Formation, Moxa Arch, Green River Basin, Wyoming

DUTTON, SHIRLEY P., and H. SCOTT HAMLIN, Bureau of Economic Geology, University of Texas at Austin, Austin, TX

Low-permeability sandstones of the Frontier Formation produce gas from reservoirs along the south-plunging Moxa arch in the Green River basin, southwestern Wyoming. Petrographic examination of 247 Frontier thin sections indicates that the main causes of low porosity and permeability in these sublitharenites and litharenites are compaction and cementation by quartz, calcite, and clay minerals. Major differences in burial history between the northern and southern ends of the arch have resulted in an average of 5% quartz cement in Frontier sandstones at the northern end, compared with 13% quartz cement at the southern end.

Burial histories of four wells along the length of the Moxa arch and one well off the arch in the deep basin were reconstructed using stratigraphic data from well logs. Uplift and erosion incorporated into the burial-history curves occurred during the Late Cretaceous, at the end of the Cretaceous, and from the Oligocene to the present. Modern geothermal gradients of 3.1 to 3.7 degrees C/100 m were used to model thermal maturity. Second Frontier sandstone on the La Barge platform at the northern end of the arch (T28N, R113W) has a calculated time-temperature index (TTI) value of 30, compared with a TTI of 334 in Henry field at the southern end of the arch (T13N, R113W). Second Frontier sandstone in the deep basin well (T22N, R106W) has a TTI value of 3078.

In the five wells for which TTI was calculated, an excellent correlation (r = 0.95) exists between thermal maturity of the sandstone (log TTI) and average volume of quartz cement. Frontier sandstones at the southern end of the Moxa arch and in the basin were buried to greater depths and exposed to higher temperatures than those at the northern end, so the southern-end and basin sandstones underwent more stylolitization and intergranular pressure solution of chert, thereby liberating more silica for quartz cement. However, TTI is not a good predictor of reservoir quality because porosity and permeability in Frontier sandstones are controlled by more variables than quartz cement volume alone.

 

AAPG Search and Discovery Article #91017©1992 AAPG Rocky Mountain Section Meeting, Casper, Wyoming, September 13-16, 1992 (2009)