Abstract
The Mississippian limestone is a prolific hydrocarbon play in the northern region of Oklahoma and the southern part of Kansas. The Mississippian reservoirs feature variations in produced fluid chemistry usually explained by different possible source rocks. Such chemical variations are regularly obtained from bulk, molecular, and isotopic characteristics. In this study, we present a new geochemical investigation of gasoline range hydrocarbons, biomarkers, phenols, and diamondoids in crude oils produced from Mississippian carbonate and Woodford Shale formations. A set of oil samples was examined for composition using high-performance gas-chromatography and mass-spectrometry techniques. The result shows a distinct geochemical fingerprint reflected in biomarkers such as the abundance of extended tricyclic terpanes, together with heptane star diagrams, and diamantane isomeric distributions. Such compounds are indicative of the organic matter sources and stages of thermal maturity. Phenolic compounds varied dramatically based on geographic location, with some oil samples being depleted of phenols, while others are intact. Based on crude oil compositions, two possible source rocks were identified including the Woodford Shale and Mississippian mudrocks, with a variable degree of mixing reported. Variations in phenol concentrations reflect reservoir fluid dynamic and water interactions, in which oils with intact phenols are least affected by water-washing conversely and crude oils depleted in phenols attributed to reservoir water-washing. These geochemical parameters shed light into petroleum migration within Devonian-Mississippian petroleum systems and mitigate geological risk in exploring and developing petroleum reservoirs.
Highlights
Petroleum production in Oklahoma from Mississippian aged reservoirs was first discovered in 1897 near oil seeps at Bartlesville, Oklahoma [1]
Crude oils exhibit slight differences in bulk parameters that are consistent with the type of fluid, in which the majority of the samples are classified as medium oil
Such enrichment in saturated hydrocarbons is usually observed in naturally produced crude oil, as well as in immiscible oil generated under hydrous pyrolysis experimental conditions [18]
Summary
Petroleum production in Oklahoma from Mississippian aged reservoirs was first discovered in 1897 near oil seeps at Bartlesville, Oklahoma [1]. An important factor affecting hydrocarbon richness in Mississippian reservoir is due to source rock heterogeneity. Identifying petroleum sourcing is achieved using a collection of geochemical tools such as molecular and isotopic characteristics. Those include biomarkers together with stable carbon isotopes of saturate and aromatic hydrocarbons [5, 6]. We present new geochemical data of light hydrocarbons produced from Mississippian reservoirs across the Anadarko Basin in Oklahoma. Data suggest different sources of hydrocarbons, with various thermal maturity stages. These data shed light into factors affecting petroleum accumulation in Mississippian reservoirs such as water-washing and petroleum mixing
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