ABSTRACT

The South Sulphur Asphalt deposits are located on the northwest flank of the Arbuckle Mountains. The Reagan Fault, a major left wrench fault, lies 2.5 miles to the south. The Mill Creek Fault defines the northern limit of the study area. These two major faults delineate the Mill Creek Syncline.

In the study area all five formations of the Simpson Group are exposed at the surface. Of these five units, all but the Joins Formation is characterized by a basal sandstone unit. Other beds in the study area range from lower-middle Ordovician Arbuckle Limestone to upper Pennsylvanian conglomerates. The Oil Creek Sandstone contains the bulk of the bitumen in the south Sulphur area. The sand is loose to friable, well sorted, and clean.

The basic structure in the study area is a northeast-southwest trending anticline, possibly plunging southwest, broken by thrusts and extensive high-angle reverse faulting. Superimposed upon this, a thrust sheet from the northwest has left an erosional remnant or klippe, separated from the major part of the thrust sheet by a fenster.

The orientation of structural trends in the south Sulphur area apparently results from stress orientations characteristic of right wrenching. Regional faults and folds however, fit a left wrench system. This suggests that two distinct periods of different stress orientation have occurred in southern Oklahoma. These separate stress periods may result from varied convergence along the Paleozoic continental margin of the southern and southeastern United States. Geologic evidence suggests that dominant left wrenching occurred before right wrenching.

Calculation of the in-place resource of heavy oil within the confines of the study area indicates that the potential may be as large as 376,000,000 bbls. This is a significant portion of the total potential heavy oil in the state of Oklahoma. The heavy oil (or bitumen) in the study area has migrated updip from a source formation to the north or west. Geochemical analysis and correlation show that the heavy oil and conventional crude oil downdip are probably sourced from the same formation. The absence of any potential source rocks in the immediate area also seems to favor migration into the principal reservoir rock (Oil Creek Sandstone), rather than local generation and accumulation. The bitumen may have been emplaced early, and thrusting then moved the oil trap into a position susceptible to meteroic water influx. Extraction yields of bitumen from sand show that the deeper samples have less saturation, indicating this may have been a structural oil trap prior to thrusting.

Alteration processes associated with formation waters degraded conventional crude oil into the heavy oil present in the south Sulphur area. This degradation was apparently initiated when meteoric waters began percolating through the formations after thrusting. These alteration processes included: biodegradation, water washing, and inorganic oxidation.

* EDITOR'S NOTE

We present the major portion of this thesis, but have chosen to omit certain portions.

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