The Devonian–Mississippian (D–M) black shales of the Bakken Formation are of interest as a hydrocarbon source due to their high total organic carbon (TOC; 2.2–17.4%) content. The Upper and Lower Members of the Bakken Fm. are shallow marine (100–150 m) sequences. Thirty samples were selected for maceral identification, kerogen typing, and solid bitumen reflectance (SBR_o) based on TOC content and down-core spacing. The shales contain alginite, bituminite, abundant solid bitumen (SB), and minor amounts of inertinite. Solid bitumen increases in quantity with increasing thermal maturity. Pyrolysis (85 samples) provided S1 (avg. 8.0 mg HC/g rock), S2 (avg. 24.3 mg HC/g rock), hydrogen index (HI; avg. 201 mg HC/g TOC), oxygen index (OI; avg. 7 mg CO₂/g TOC), and R_o (0.60–1.03%) calculated from T_max. Plots of HI vs. OI and HI vs. T_max (°C) were used to assess kerogen type but are not consistently in agreement with the petrographic assessment. Some samples from more thermally mature cores plot as Type III (vitrinite) kerogen instead of Type II (alginite and bituminite) kerogen, the latter confirmed through petrographic observations of lower maturation samples. This is largely due to increased SB in more thermally mature samples (R_o = 0.83–1.03%), as SB is known to have a lower HI content than Type II kerogen. Petrographic data show more alginite and bituminite (19–55%) in the thermally less mature samples (R_o = 0.60–0.83%) compared to more dispersed SB (67–86%) and less alginite and bituminite (<1%) in the more thermally mature samples (R_o = 0.89–1.01%).

Early research on the Bakken Fm. reported lower than expected vitrinite reflectance values and attributed them to vitrinite “suppression”. The scarcity of vitrinite and abundance of SB suggest that early work likely reported reflectance on SB. Recent attempts to assess the thermal maturity of the Bakken black shales have converted SBR_o to vitrinite reflectance equivalence (V_RE). However, there are multiple SB populations present in these shales and it is not always clear which SB populations were included, possibly contributing to error. In the current study, only smooth, homogenous SB was measured (0.68–1.14% SBR_o) and V_RE values calculated (0.54–1.49%) to assess thermal maturity from the basin margin to the depocenter; inclusion of measurements on granular, heterogeneous SB (14–21 vol%), which are ∼53% lower than those for smooth, homogenous SB (3–12 vol%), results in lower mean reflectances, especially in more mature samples. Vitrinite reflectance equivalent data calculated using the D–M New Albany Shale equation of Liu et al. (2019) agrees with liptinite fluorescence and Rock-Eval R_o, whereas V_RE based on the D–M Woodford Shale equation of Cardott and Comer (2021) does not. This suggests the importance of applying V_RE equations from similar formations both in terms of thermal history, as well as kerogen type and age. Results from SBR_o, Rock-Eval R_o, V_RE, and observations of alginite fluorescence indicate that samples from the current study range from the early oil window into the condensate, wet gas zone.

巴肯组泥盆系-密西西比系 (D-M) 黑色页岩因其总有机碳含量高而成为碳氢化合物来源。（TOC；2.2–17.4%）含量。巴肯组的上段和下段。是浅海（100–150 m）序列。根据 TOC 含量和下岩心间距，选取 30 个样品进行显微组分鉴定、干酪根分型和固体沥青反射率（SBR_o）。页岩含有褐藻土、烟煤、丰富的固体沥青(SB) 和少量惰质岩。固体沥青的数量随着热成熟度的增加而增加。热解（85 个样品）提供 S1（平均 8.0 mg HC/g 岩石）、S2（平均 24.3 mg HC/g 岩石）、氢指数（HI；平均 201 mg HC/g TOC）、氧指数（OI；平均 201 mg HC/g TOC）。平均 7 mg CO₂/g TOC) 和 R_o (0.60–1.03%) 根据 T_max 计算。 HI 与 OI 和 HI 与 T_max (°C) 图用于评估干酪根类型，但与岩相评估不一致。来自较热成熟岩心的一些样品绘制为 III 型（镜质体）干酪根，而不是 II 型（褐藻岩和烟煤）干酪根，后者通过较低成熟度样品的岩相观察得到证实。这主要是由于更热成熟的样品中 SB 增加 (R_o = 0.83–1.03%)，因为已知 SB 的 HI 含量较低高于 II 型干酪根。岩相数据显示，与分散程度较高的样品相比，热不太成熟的样品 (R_o = 0.60–0.83%) 中有更多的褐藻岩和烟煤 (19–55%)热成熟度较高的样品中，SB (67–86%) 和较少的褐藻矿和烟煤 (<1%) (R_o = 0.89–1.01% ）。

巴肯组的早期研究。报告低于预期的镜质体反射率值，并将其归因于镜质体“抑制”。镜质体的稀缺和 SB 的丰富表明，早期的工作可能报告了 SB 的反射率。最近评估巴肯黑色页岩热成熟度的尝试已将 SBR_o 转换为镜质体反射率当量 (V_RE ）。然而，这些页岩中存在多个 SB 种群，并且并不总是清楚包含哪些 SB 种群，这可能会导致错误。在当前的研究中，仅测量了光滑、均质的 SB (0.68–1.14% SBR_o) 和 V_RE 计算值（0.54–1.49%），用于评估从盆地边缘到沉积中心的热成熟度；包含颗粒状、异质 SB (14–21 vol%) 的测量值，比光滑、均质 SB (3–12 vol%) 的测量值低约 53%，导致平均反射率较低，尤其是在更成熟的样品中。使用 Liu 等人的 D-M New Albany 页岩方程计算的镜质体反射率当量数据。 (2019) 与 liptinite 荧光和 Rock-Eval R_o 一致，而 V_RE 基于 Cardott 和 Comer (2021) 的 D–M Woodford 页岩方程则不然。这表明在热史以及干酪根类型和年龄方面应用类似地层的 V_RE 方程的重要性。 SBR 结果_o、Rock-Eval R_o、V，以及藻酸盐荧光的观察表明，当前研究的样品范围从早期石油窗口到凝析油、湿气区。_RE