Stratigraphy, sedimentology, geochemical analysis and hydrocarbon potential of the Woodford Shale, Central Basin Platform, West Texas

The Permian Basin is a prolific and emerging unconventional basin that is known for its oil and gas production. Located in New Mexico and Texas, it consists of the Delaware Basin, Midland Basin, Val Verde Basin, Central Basin Platform and the Ozona Arch. This thesis focuses on the stratigraphy, sedimentology, geochemical characteristics and the hydrocarbon potential of the Woodford Shale in the Central Basin Platform (CBP). The Woodford Shale is an Upper Devonian organic-rich source and reservoir rock that generated vast quantities of hydrocarbon into the Permian Basin and is still currently generating hydrocarbons. On the CBP, the Woodford Shale primarily thickens from east to west from 100 feet to over 500 feet thick. There are areas within the CBP where the Woodford Shale is absent due to post depositional erosion. Woodford depth in the CBP ranges from ~5000 feet subsea on the eastern side of the platform to ~13,000 feet subsea on the westernmost side of the platform. The Woodford Shale has been subdivided into three members: upper, middle and lower Woodford due to differences in geochemical and log characteristics. Thirty nine wells were studied for this thesis within the Central Basin Platform. Analyses such as Rock Eval 6 and TOC, X-ray diffraction (XRD), Argon Ion Milling (AIM), Mercury Injection Capillary Pressure (MICP) and X-ray fluorescence (XRF) identified the Middle Woodford Shale member in the western most part of the CBP as the most prospective area for commercial hydrocarbons.;Geochemical analyses for the study area indicate the western most part of the basin is organic-rich and thermally mature. TOC content for the three Woodford Shale members range from 3 to 9.4 wt. % on the western part of the basin and range from 1.5 to 3.8 wt. % on the central and eastern part of the basin. Rock Eval 6(RE6) analysis indicates all members of the Woodford Shale are within the oil generation window, with maturity increasing to the west. The Woodford Shale consists of clay-rich mudstones, silty and siliceous mudrocks and calcareous/dolomitic mudrocks. The dominant clay content in all three members of the Woodford Shale is illite. This type of clay content is acceptable for drilling since illite does not swell and therefore will not cause problems while drilling a well through the formation. The silt and clay are predominantly terrigenous grains and detrital clay. The terrigenous grains are dominated by quartz and the carbonate component of the rocks consists predominantly of dolomite. High quartz and carbonate content aid in brittleness of the rock. Total porosity from AIM analyses indicates porosity is restricted to micro-scale and nano-scale pores, which is common for an unconventional play. The analyses also indicate most of the porosity is filled with oil/bitumen, indicating a mature rock. XRF results coincide with the RE6 data and indicate the Woodford Shale was deposited in a euxinic environment, thereby such high total organic content (TOC) values would be expected in the western part of the basin.