Experimental investigation of thermal expansion of organic-rich shales

Gabova, Anastasia; Чехонин, E.; Popov, Y.; Savelev, E.; Romushkevich, R.; Popov, Evgeny; Kozlova, Elena

doi:10.1016/j.ijrmms.2020.104398

Cited by 16 publications

(7 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Shale contains organic matter and inorganic minerals and the physical and chemical properties of these components are different, such that their structural changes during heating were also different (Hajpál and Török, 2004). The shale bedding assessed in this work was relatively well developed and showed variations in thermal conductivity depending on direction (Gabova et al, 2020), meaning that changes in the shale structure in different directions were also varied.…”

Section: Changes In Organic and Inorganic Components During Heatingmentioning

confidence: 90%

“…In addition, striped organic matter can be observed in the SEM images, indicating that the bedding direction was nearly horizontal (Figure 2), and the development of the bedding had a significant effect on the heat transfer within the material. Specifically, the thermal conductivity of the shale was different in different directions, such that the thermal conductivity of the parallel bedding was higher than that of the vertical bedding (Gabova et al, 2020). As inorganic minerals in the sample shrank due to the loss of water, they contracted in both the horizontal and vertical directions during the initial stage of heating and then expanded with temperature, although the magnitude of change was different in both directions (Figure 6).…”

Section: Structural Changes In Different Directions During Heatingmentioning

confidence: 99%

See 1 more Smart Citation

Temperature-Driven Hydrocarbon Generation-Expulsion and Structural Transformation of Organic-Rich Shale Assessed by in situ Heating SEM

Yuan

Yang

2021

Front. Earth Sci.

View full text Add to dashboard Cite

Mud shale can serve as source or cap rock but also as a reservoir rock, and so the development of pores or cracks in shale has become of great interest in recent years. However, prior work using non-identical samples, varying fields of view and non-continuous heating processes has produced varying data. The unique hydrocarbon generation and expulsion characteristics of shale as a source rock and the relationship with the evolution of pores or cracks in the reservoir are thus not well understood. The present work attempted to monitor detailed structural changes during the continuous heating of shale and to establish possible relationships with hydrocarbon generation and expulsion by heating immature shale samples while performing in situ scanning electron microscopy (SEM) imaging and monitoring the chamber vacuum. Samples were heated at 20°C/min from ambient to 700°C with 30 min holds at 100°C intervals during which SEM images were acquired. The SEM chamber vacuum was found to change during sample heating as a consequence of hydrocarbon generation and expulsion. Two episodic hydrocarbon expulsion stages were observed, at 300 and 500°C. As the temperature was increased from ambient to 700°C, samples exhibited consecutive shrinkage, expansion and shrinkage, and the amount of structural change in the vertical bedding direction was greater than that in the bedding direction. At the same time, the opening, closing and subsequent reopening of microcracks was observed. Hydrocarbon generation and expulsion led to the expansion of existing fractures and the opening of new cracks to produce an effective fracture network allowing fluid migration. The combination of high-resolution SEM and a high-temperature heating stage allowed correlation between the evolution of pores or cracks and hydrocarbon generation and expulsion to be examined.

show abstract

Section: Changes In Organic and Inorganic Components During Heatingmentioning

confidence: 90%

Section: Structural Changes In Different Directions During Heatingmentioning

confidence: 99%

Temperature-Driven Hydrocarbon Generation-Expulsion and Structural Transformation of Organic-Rich Shale Assessed by in situ Heating SEM

Yuan

Yang

2021

Front. Earth Sci.

View full text Add to dashboard Cite

show abstract

“…8). This finding, while preliminary, may help us understand the significant anisotropy of mechanical properties (e.g., elastic modulus (E)) and thermal properties (e.g., thermal conductivity (TC)) within oil shale [33][34][35].…”

Section: Cross Section Orientationmentioning

confidence: 99%

Pore types of oil shale in Jilin Province, Northeastern China

Lu¹,

Zhou²,

Jia³

et al. 2023

View full text Add to dashboard Cite

To better understand and characterize pores in oil shale systems, samples from four significant oil shale-bearing formations of the Songliao, Huadian and Luozigou basins in Jilin Province, Northeastern China, namely Qingshankou (QSK), Nenjiang (NJ), Fengtai (FT) and Longteng (LT), were prepared by breaking fresh surfaces and argon (Ar) ion polishing both perpendicular and parallel to bedding and imaged using a field emission scanning electron microscope (FE-SEM). Interparticle (interP), intraparticle (intraP) and organic matter (OM) pores are the three types of pores between or within particles of oil shale, i.e., fossils, minerals and OM. All four samples contain interP and intraP pores, but only minor OM pores occur in sample QSK. Sample FT has significant amounts of intrafossil and dissolution (intraparticle) pores due to the abundance of microfossils and the dissolution possibly caused by OM decarboxylation. Sample NJ has the highest pyrite content and contains the greatest amount of pyrite intercrystalline (intraparticle) pores, differently from sample QSK, whose amount of these pores is the lowest. Sample LT enriched with clastic particles has a large number of intercrystalline (interparticle)pores. These pores are primarily at micro-to nano-scales with various shapes, from irregular to elongated to triangular to polyhedral to rounded to elliptical, etc. There are differences in the contents of particles and OM pores between oil shales in Jilin Province and gas shales in North America. The reasons for these differences may be due to the diverse sedimentary environments and levels of maturity of oil shales. Besides, high-resolution scanning electron microscope imaging can be used to describe the diagenetic processes of oil shale.

show abstract

“…The effect of cryogenic damage after LN 2 preconditioning is affected by not only the environmental factors such as reservoir temperature, ground stress, and moisture content but also the internal structure factors such as mineralogical composition, microcracks, and bedding orientation [31,32]. The cryogenic damage extent of frost heave is controlled by initial moisture content [33].…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation on Cracking Characteristics of Dry and Saturated Shales in Nitrogen Fracturing after Liquid Nitrogen (LN2) Injection

Zhang

Вадимовна

et al. 2023

Geofluids

View full text Add to dashboard Cite

Cryogenic LN2 fracturing is one of the environmentally friendly waterless fracturing technologies that promote the fracture complexity of shale gas reservoir. The water-ice phase transition under freezing condition causes frost heave in saturated shale. The effect of moisture in shale should be taken into account during cryogenic damage process. Therefore, the differences of cracking characteristics between dry and saturated shales were studied in this paper. A laboratory triaxial and high temperature fracturing system was developed for nitrogen fracturing dry and saturated shale after LN2 injection. The influence of moisture on breakdown pressure was studied under different confining pressures (3 MPa, 6 MPa, 9 MPa, and 12 MPa) and bedding directions (parallel bedding and vertical bedding). The experimental results demonstrated that when the confining pressure increased from 3 MPa to 12 MPa, the breakdown pressure of dry parallel bedding after LN2 preconditioning decreased 7.12 MPa, 6.06 MPa, 4.58 MPa, and 3.11 MPa, respectively. Therefore, LN2 preconditioning could damage shale resulting in a lower breakdown pressure, but the effect of cryogenic damage decreased with the confining pressure increasing. The moisture in shale had little impact on nitrogen fracturing without LN2 injection because the breakdown pressure difference between dry and saturated shales was small. However, the breakdown pressure of saturated shale after LN2 preconditioning was always lower than that of dry shale. The breakdown pressure of saturated parallel bedding shale after LN2 injection decreased 8.62 MPa, 7.67 MPa, 6.08 MPa, and 4.63 MPa, respectively, with the confining pressure increasing from 3 MPa to 12 MPa. The breakdown pressure difference between dry and saturated shales was impacted by the migration of unfrozen water and frost heave. In addition, the extent of cryogenic damage varied substantially between different bedding directions. When the confining pressure was 3 MPa, the breakdown pressure of saturated parallel bedding shale reduced by 69.18% after LN2 preconditioning, but that of saturated vertical bedding shale only decreased by 22.49%. The tensile strength of shale had a greater influence on the breakdown pressure. According to the Brazilian disc test results, the tensile strength of matrix was much higher than that of bedding planes. As a result, it is useful to wet the shale in order to reduce the breakdown pressure. The fracturing direction of horizontal drilling should be consistent with the bedding direction for better cryogenic fracturing effect.

show abstract

Experimental investigation of thermal expansion of organic-rich shales

Cited by 16 publications

References 13 publications

Temperature-Driven Hydrocarbon Generation-Expulsion and Structural Transformation of Organic-Rich Shale Assessed by in situ Heating SEM

Temperature-Driven Hydrocarbon Generation-Expulsion and Structural Transformation of Organic-Rich Shale Assessed by in situ Heating SEM

Pore types of oil shale in Jilin Province, Northeastern China

Experimental Investigation on Cracking Characteristics of Dry and Saturated Shales in Nitrogen Fracturing after Liquid Nitrogen (LN2) Injection

Contact Info

Product

Resources

About