Trapped Fluid Analysis of 58 Wells from the SCOOP and STACK Plays, Oklahoma

Archived cuttings samples (n = 6713) from 58 wells located in the SCOOP and STACK plays of the Anadarko Basin in Oklahoma (Figure 1; Table 1) were analyzed for their bulk trapped fluid content (fluid inclusions and other tightly held volatiles) via the fluid inclusion stratigraphy (FIS) technique. Fluid inclusion petrography (n = 300) and microthermometry (n = 58) analyses were also performed on selected intervals, based on FIS results. Data were used to evaluate the vertical and lateral distribution of hydrocarbons and non-hydrocarbon volatiles, oil gravities, phase state, salinity, and burial temperatures. The most prominent gas and liquid hydrocarbon FIS responses are recorded in the Caney to Viola sections. Both migrated and locally generated components are distinguished, and several episodes of migration may be documented within a given well. Overall, FIS oil/condensate responses and petrographic observations suggest a liquids-enhanced interval at 8,000–12,000 ft, although in some instances liquid petroleum zones extend to 15,000 ft. Gas-enrichment occurs to the west in response to increased thermal maturity, and sulfur species related to thermochemical sulfate reduction at high temperature occur towards the west and at depths >13,000 ft. Measured petroleum inclusions show mostly values of 38° to 45° API gravity. Most petroleum inclusions homogenize via bubble-point transition, and bubble-point temperatures suggest that they occur as undersaturated liquids at current reservoir conditions. Aqueous inclusion homogenization temperatures (T_h) imply maximum burial temperatures that are generally higher than current temperatures, and probably reflect 3000–4000 ft of uplift since inclusion formation. Inclusion salinities are generally in the 1–5 weight percent NaCl-equivalent range suggesting brackish to evolved basin fluids. Independent measures of thermal maturity, including pyrolysis, T_h of aqueous inclusions, and biomarkers, are in general agreement, and suggest that much of the recorded petroleum was proximally sourced. This historically productive region is attractive for unconventional reservoir development due to liquids potential and favorable economics. However, fluid characteristics can vary greatly over a relatively small area, resulting in significant differences in recovery from nearby wells. By analyzing fluid inclusions, it is possible to establish regional hydrocarbon potential with a small amount of unpreserved, archived drill cuttings and evaluate the likely production characteristics of fluids within a given area.