Variation in Pore Space and Structure of Organic‐rich Oil‐prone Shales from a Non‐marine Basin: Constraints from Organic Matter and Minerals

Heat carried by deep fluid might greatly affect hydrocarbon generation and pore space in shale. Dyke intrusion carrying high levels of heat may be a means by which to explore the influence of deep fluid on shale reservoirs. This study evaluates hydrocarbon generation and analyzed the evolution of shale storage space in the third member of the Xiamaling Formation in the Zhaojiashan section, Hebei Province, based on experimental data such as TOC, SEM, VRo, lowtemperature N 2 adsorption and high-pressure mercury injection. The results show that the dyke intrusion reduced the shale TOC content drastically-by up to 77%-and also induced instantaneous hydrocarbon generation over a range about 1.4 times the thickness of the intrusion. Furthermore, the dyke intrusion might transform organic pores in surrounding shales into inorganic pores. There were two shale porosity peaks: one appeared when VRo = 2.0%, caused by the increase of organic pores as thermal maturity increased, the other occurred when the VRo value was between 3% and 4%, caused by the increase of inorganic mineral pores. It can be concluded that dyke intrusion can be an effective tool with which to study how deep fluid affects instantaneous hydrocarbon generation and pore space in shale.

Section: Pore Characteristics From Low-temperature Nitrogen Adsorptionmentioning

confidence: 98%

Process and Mechanisms of Deep Fluid Effects on Hydrocarbon Generation and Pore Space in Shale: A Case Study from the Mesoproterozoic Xiamaling Formation in the Zhaojiashan Section

Meng

Pang

et al. 2022

“…Organic-rich shale is a proven new type of oil field with great resource potential, thus has been receiving increasing attention (Zhao et al, 2019;Zhang et al, 2021b;Jia et al, 2022;Li et al, 2022;Wang et al, 2022a, b;Khan et al, 2023). At present, the industrial production of shale oil has been successful in many basins in North America, such as the Eagle Ford shale in the Gulf of Mexico Basin (Bodziak et al, 2014;Pommer and Milliken, 2015;Gottardi and Mason, 2018), the Wolfcamp shale in the Permian Basin (Heij and Elmore, 2019;Hackley et al, 2020), the Bakken shale in the Williston Basin (Pollastro et al, 2012;Donohue and Barrie., 2021), the Niobrara shale in the Denver Basin (Han et al, 2019b) and the Barnett shale in the Fort Worth Basin (Han et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Petroleum Retention, Intraformational Migration and Segmented Accumulation within the Organic‐rich Shale in the Cretaceous Qingshankou Formation of the Gulong Sag, Songliao Basin, Northeast China

HUANGFU

ZHANG

Zhang

et al. 2023

In this study, organic geochemical and petrological analyses of 111 shale samples from a well were conducted to understand the retention, intraformational migration and segmented accumulation (shale oil enriched in different intervals is unconnected) features of shale oil within the organic‐rich shale in the Qingshankou Formation of the Gulong Sag. Our study shows that retained petroleum characteristics in the investigated succession are mainly influenced by three factors: organic richness, intraformational migration, and segmented accumulation. Organic matter richness primarily controls the amount of retained petroleum, especially the “live” component indicated by the S2 value rather than the total organic carbon (TOC) alone. The negative expulsion efficiencies determined by mass‐balance calculations of hydrocarbons reveal that petroleum from adjacent organic‐rich intervals migrates into the interval of about 2386–2408 m, which is characterized by high free hydrocarbon (S1), OSI and saturated hydrocarbons content, and a greater difference in δ13C values between polar compounds (including resins and asphaltenes) and saturated hydrocarbons. The depth‐dependent heterogeneity of carbon isotope ratios (δ13C) of mud methane gas, δ13C of extracts gross composition(SARA), δ13C of kerogen and SARA content of extracts suggest that the studied succession can be subdivided into four intervals. The shale oil sealing enrichment character in each interval is further corroborated by the different δ13C values of mud methane gas in different intervals. Due to the migration of petroleum into the 2386–2408 m interval, the S1, OSI, and saturated hydrocarbons content of the interval show relatively higher values. And the maturity of organic matter in the 2471.0–2500 m interval is at the highest with the smaller size molecular components of the retained petroleum. Thus, favorable sweet spots may be found in the 2386–2408 m interval and the 2471.0–2500 m interval according to the experiment results in this study.

Geological and Engineering ‘Sweet Spots’ in the Permian Lucaogou Formation, Jimusar Sag, Junggar Basin

Lai

Bai

et al. 2023

Unconventional oil and gas resources require petrophysical logs to answer the question “How to optimize the geological and engineering sweet spots?”. Therefore the establishment of key well with comprehensive descriptions of lithology, reservoir property, hydrocarbon bearing property, electronic well log responses, source rock property, brittleness, and in situ stress magnitude and direction is important for exploration and production of unconventional hydrocarbon resources. Cores, thin section, scanning electron microscopy (SEM) and comprehensive well log suits are used to build a key well of the Permian Lucaogou Formation, Jimusar Sag of Junggar Basin. The results show that there are mainly three types of lithologies including siltstone, mudstone, and dolostone. Lithologies can be predicted using the combination of conventional well and image logs. The pore spaces consist of interparticle pores, intragranular dissolution pores, and micropores. Nuclear Magnetic Resonance (NMR) T2 components longer than 1.7 ms are superposed as effective porosity. Permeability is calculated using the Coates model from NMR T2 spectra. The ratio of T2 components >7.0 ms to the T2 components >0.3 ms is used to calculate oil saturation. TOC is calculated using ΔlogR method. Brittleness index is calculated using Poisson‐ Young's method, and brittleness index ranges from 13.42%–70.53%. In situ stress direction is determined, and in situ stress magnitudes (Maximum horizontal stress SHmax, Minimum horizontal stress Shmin, Vertical stress Sv) are calculated using density and sonic logs. The strike‐slip stress type (SHmax>Sv>Shmin) is encountered. The key well which comprehensively includes the above seven properties is established. Then geological and engineering (geomechanical) sweet spots are optimized from the key well by fully analyzing lithology, reservoir property, oil bearing potential, in situ stress magnitude and brittleness. The results are hoped to support engineers' and geologists' decisions for exploitation of unconventional hydrocarbon resources.