| Abstrakt: |
Significant unconventional shale resource potential has been discovered in the Barremian–Albian succession outcrop of Jebel Sidi Salem (SS section) in northeastern Tunisia. In-place and expelled hydrocarbon measurements in shale resource systems were performed using Hawk, liquid chromatography, and X-ray diffraction techniques. The biostratigraphic analysis identified a geological sequence spanning the Upper Barremian–Albian interval. There is a mixture of type II (marine planktic) and type III (continental) with low, medium, and relatively high organic matter content. Calculated transformation ratio (TR) and expelled hydrocarbons (EHC) are based on estimated initial hydrocarbon generation potential and initial organic carbon content. Due to the high TR ratio with an average value of 78%, the EHC content increases compared to RHC (retained hydrocarbons) (EHC/RHC = 3/4). This may be sufficient to elicit the highest level of organic maturity. The fractionated composition of the extracted oil is mainly high NSO and low-saturated, unsaturated, and aromatic compounds. This is not consistent with high maturity, but may be due to increased hydrocarbon emissions and migration from the source rock. The Tmax values recorded the late oil and early wet gas window. However, the shale resource system has reached its maximum potential for hydrocarbon generation, production, and expulsion because a significant portion of its original HGP is expelled (EHC = 3/4), and only 1/4 still exists as “in-place” hydrocarbons. The geological sequence of the Barremian–Albian interval can be viewed as a shale oil and et gas resource system. To predict the brittleness capacity for hydraulic fracturing of shale reservoirs, the main proxy that has been considered is mineral composition. The brittle minerals are silicates and carbonates. Together, they account for more than 65%. The clay fraction accounts for less than 35%. The brittle mineral content is higher than that of the Barnett and Marcellus shales, but close to that of the Three Forks shales. The shale classification diagram displays the Barremian Albian Shale and the Three Forks Shale in the same domain (mudstone shale). XRD analysis of the illite–smectite mixed layers revealed an illite composition ranging from 25 to 50%. This corresponds to the burial stage that coincides with the end of the oil window and the early gas window. |
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