Date of Award
Master of Science (MS)
The purpose of studying the hydrocarbon producing Bluell zone (upper Mission Canyon Formation), Flaxton Field, northern Burke County, North Dakota was to understand and explain its deposition, diagenesis, and hydrocarbon occurrence. The rocks of the Bluell zone were deposited mainly in shallow, sublittoral settings. Seven distinct lithofacies can be recognized in the Flaxton Field area: A) coated grain, intraclastic packstone and grainstone; B) skeletal, peloidal, intraclastic wackestone and packstone; C) fenestral, green algal mudstone and wackestone; D) skeletal, slightly intraclastic wackestone and packstone; E) patterned dolomitic mudstone; F) intraclastic, peloidal wackestone; and G) dolomudstone.
The history of Bluell deposition at Flaxton Field can be subdivided into four depositional time units (T1-T4). Deposition of the lower Bluell occurred during T1 (early Bluell time), in a shallow sublittoral environment in which topographic highs were subaerially exposed during occasional drops in local water levels. Sub-environments during T1 include: broad, gently sloping, topographic highs; shallow sublittoral environments that contained lagoon-like conditions; and topographic lows which experienced near-normal marine conditions. Deposition during T2 (middle Bluell time) was in a supralittoral environment during which significant amounts of silt-sized quartz grains were transported into the study area by eolian processes. During T3 (middle to late Bluell time), shallow sublittoral and littoral deposition occurred across the study area. Throughout most of T4 (late Bluell time), across the study area and possibly along the northeastern margin of the Williston Basin, deposition was primarily through the subaqueous precipitation of primary dolomite and the deposition of quartz grains by eolian processes.
The diagenetic history of the Bluell rocks at Flaxton Field is very complex. The major diagenetic processes that occurred in the study area include: cementation, pressure solution, dolomitization, the creation of porosity, the development of structure, and the migration of hydrocarbons. In addition, several minor diagenetic processes have been recognized to have been active in the Bluell rocks at Flaxton Field. These minor processes include: micritization, pyritization, compaction, neomorphism, and silicification.
This study has also found that the majority of present day structure in the Bluell zone at Flaxton Field is not a result of the differential compaction of sediments, but instead, is probably a result of tectonic movement. The trapping of hydrocarbons in Bluell rocks in the Flaxton Field study area is controlled both by structure and stratigraphy with the majority of hydrocarbons being produced from mud-supported rocks that contain a system of interconnected micro-vuggy pores.
Schwartz, Dirk Anson, "The deposition and diagenesis of the Bluell Zone, Upper Mission Canyon Formation (Mississippian), Flaxton Field, Burke County, North Dakota" (1987). Theses and Dissertations. 269.