Characteristics of Lacustrine Shale Reservoir and Its Effect on Methane Adsorption Capacity in Fuxin Basin

Abstract

The Lower Cretaceous Shahai and Jiufotang Formation in Fuxin Basin, located northwest of Liaoning Province, with stable planar distribution contains abundant shale gas reserves, which are key horizons in the exploration breakthrough of the Mesozoic continental shale gas in northeastern China. FuYe-1 (FY-1) well was recently drilled, and it is an important shale gas parameter well in the Fuxin Basin area. A total of 60 shale samples were collected from Shahai and Jiufotang Formation of FuYe-1 well and DY-1 well in this work. A series of experiments including organic matter vitrinite reflectance, X-ray Diffraction (XRD) analysis, total carbonate content (TOC) measurement, scanning electron microscopy, low-temperature nitrogen adsorption, and methane isothermal adsorption were conducted through the samples. The final results revealed that in FuYe-1 well, the shale of the Lower Cretaceous Shahai and Jiufotang Formations has a maturity of 0.46−1.68% (average of 0.92%), which is at the immature-high maturity stage. The kerogens are mostly of types II−III. The mineral components are dominated by clay minerals and quartz, with an average of 21.39% and 30.89%, respectively. The main controlling factors of the methane adsorption capacity are the TOC content, the total clay content, and the shale pore structure. Langmuir's volume (V L ) of the shale ranges between 0.17 and 1.98m 3 /t (with an average of 1.21 m 3 /t). The methane adsorption capacity is positively correlated with the content of the total clay minerals and quartz, but varies in different clay minerals. The specific surface area of the shale and the total pore volume were calculated by BET and BJH, the macropore ratio of which is negatively correlated with the methane adsorption capacity, whereas the specific surface area and the total pore volume of the mesopores and micropores ratio are positively correlated with the methane adsorption capacity, indicating that the content of the micropores and mesopores is the major contributor to the specific surface area of shale.

Tectonic Controls on the Sedimentation and Thermal History of Supra‐detachment Basins: A Case Study of the Early Cretaceous Fuxin Basin, NE China

“…Without exception, the fan delta deposits in the whole basin were considered to be broadly developed on the western gentle slope and eastern steep slope (Cai et al., 2011; Chen et al., 2019; Li et al., 1985; Xu et al., 2020), due to the lack of integrally visual sedimentary stratigraphic evidences in different locations. However, we recognize a series of widespread subaqueous gravity flow deposits from K 1 jf to K 1 sh in the central‐eastern part of the basin from the recent borehole and seismic data (Figures 3–5), which have not been previously reported in the Fuxin Basin (Chen et al., 2018, 2019).…”

“…This study established a new evolution model of sedimentary facies during the whole early Cretaceous deposition in the Fuxin Basin (Figure 5). Although such models have been reported in a series of early Cretaceous half‐graben basins (NE China) (J. Jia et al., 2014; Yin et al., 2008), widely developed subaqueous fans in the eastern Fuxin Basin have never been demonstrated (Chen et al., 2018, 2019). We reveal the development of two depositional systems, a fan delta–slump fan–shore‐shallow lake and a subaqueous fan–semi‐deep lake (Figures 5 and 8).…”

“…The sedimentary strata of the Fuxin Basin contain coal, coalbed methane, conventional petroleum, shale gas, and other energy resources (Chen et al., 2018; J. L. Jia & Ji, 2017; Jiang et al., 2014; Wang et al., 1998, 2007, 2012). Understanding the thermal history of rocks is fundamental for evaluating the hydrocarbon generation potential of source rocks (Haile et al., 2018).…”

“…The Fuxin Basin was filled with early Cretaceous volcanic and sedimentary strata (Figure 1c) (X. R. Wang et al., 2007; B. W. Wu et al., 2015). This basin is a typical Mesozoic continental coal‐ and oil‐bearing supra‐detachment basin (Figure 1a) (X. R. Wang et al., 2007), where substantial breakthroughs in discoveries of petroleum and shale gas resources have been made in recent years (Chen et al., 2018; J. L. Jia & Ji, 2017). However, a lack of knowledge exists regarding the thermal record and its kinetic mechanism in the Fuxin Basin (Jiang et al., 2014; H. Wang & Liu, 2013; Zhu et al., 2007), due to the unclear basin‐range relationship associated with detachment tectonism (Li et al., 2013; Liang et al., 2020).…”

Continental chemical weathering during the Early Cretaceous Oceanic Anoxic Event (OAE1b): a case study from the Fuxin fluvio-lacustrine basin, Liaoning Province, NE China

“…Previous studies have shown that mudstones of the Shahai Formation were mainly composed of clay minerals, quartz, feldspar and carbonate minerals, with pyrite present in small amounts or absent. Identified clay minerals include mixed-layer illite-smectite, illite, chlorite and little kaolinite (Chen et al 2018;Kang et al 2019). Mudstones contain abundant chemical weathering products derived from their source rocks, allowing the chemical weathering history in the source area to be revealed (Garzanti et al 2013).…”