Prediction of multiscale laminae structure and reservoir quality in fine-grained sedimentary rocks: The Permian Lucaogou Formation in Jimusar Sag, Junggar Basin

Pang, Xiaojiao; Wang, Guiwen; Kuang, Lichun; Lai, Jin; Gao, Yang; Zhao, Yidi; Li, Hongbin; Wang, Song; Bao, Meng; Liu, Shichen; Liu, Bingchang

doi:10.1016/j.petsci.2022.08.001

Cited by 15 publications

(9 citation statements)

References 71 publications

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“…In the P 2 l 2 2 (sweet spot of Lucaogou Formation in Jimsar Sag) interval at depths of 3,104-3,204 m, the ‗upper sweet spot' is 100 m thick and dominated by saltwater lacustrine carbonate deposits. The favorable lithologies here include laminated sand dolomite, laminated feldspar siltstone and laminated clayey sandstone, mainly containing calcite, quartz and feldspar, of which the feldspar is mainly albite and anorthite, with a small amount of K-feldspar (Carroll, 1998;Pang et al, 2022).…”

Section: Geological Backgroundmentioning

confidence: 99%

Differences in CO₂‐Water‐Rock Chemical Reactions among ‘Sweet Spot’ Reservoirs: Implications for Carbon Sequestration

Yang

Song

Wei

et al. 2023

Acta Geologica Sinica (Eng)

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The Lucaogou Formation, located in the Jimsar Sag, Junggar Basin, NW China, has great potential for shale oil resources. In the process of CO2‐EOR (CO2 enhance oil recovery), mineral dissolution, precipitation and transformation, leading to the local corrosion or blockage of reservoirs, have a significant influence on recovery. In this study, a combination of high‐temperature and high‐pressure laboratory experiments and coupled temperature/fluid‐chemistry multi‐field numerical simulations are used to investigate CO2‐water‐rock reactions under various reservoir conditions in the upper and lower ‘sweet spots’, to reveal the mechanisms underlying CO2‐induced mineral dissolution, precipitation and transformation. In addition, we quantitatively calculated the evolution of porosity over geological timescales; compared and analyzed the variability of CO2 transformation in the reservoir under a variety of temperature, lithology and solution conditions; and identified the main factors controlling CO2‐water‐rock reactions, the types of mineral transformation occurring during long‐term CO2 sequestration and effective carbon sequestration minerals. The results demonstrate that the main minerals undergoing dissolution under the influence of supercritical CO2 are feldspars, while the main minerals undergoing precipitation include carbonate rock minerals, clay minerals and quartz. Feldspar minerals, especially the initially abundant plagioclase in the formation, directly affects total carbon sequestration, feldspar‐rich clastic rocks therefore having considerable sequestration potential.

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Section: Geological Backgroundmentioning

confidence: 99%

Differences in CO₂‐Water‐Rock Chemical Reactions among ‘Sweet Spot’ Reservoirs: Implications for Carbon Sequestration

Yang

Song

Wei

et al. 2023

Acta Geologica Sinica (Eng)

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“…The Jimusar Sag has an area of 1300 km 2 and is located in the southeastern part of the Junggar Basin. The Jimusar Sag has experienced multistage tectonic activity (Zhang et al, 2019;Pang et al, 2022), rapidly subsiding in the early middle Permian (Qiu et al, 2016), the middle Permian to Cenozoic strata having a maximum thickness of 5000 m (Qiu et al, 2016;Cao et al, 2017). The Permian Lucaogou Formation (P 2 l) belongs to a lacustrine mixed fine-grained sedimentary rock deposited in a saline lacustrine environment (Zhang et al, 2019).…”

Section: Geological Settingmentioning

confidence: 99%

“…The two members are further subdivided into four sandbody units, P 2 l 2 1 , P 2 l 2 2 , P 2 l 1 1 and P 2 l 1 2 (Zhang et al, 2017). The lithologies mainly include siltstone or, occasionally, fine-grained sandstone, mudstone and dolostone (Wu et al, 2017;Zhang et al, 2019;Pang et al, 2022;Yang et al, 2023). Siltstone or fine-grained sandstone, as well as dolostones deposited in beach bar-lake or delta front environments, act as the reservoir rocks, while mudstones (shales), which were formed in semi-deep lacustrine to deep lake environments, act as the source rocks (Cao et al, 2017;Zhang et al, 2019;Lai et al, 2022a).…”

Section: Geological Settingmentioning

confidence: 99%

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

Lai

Bai

et al. 2023

Acta Geologica Sinica (Eng)

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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.

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“…The Lucaogou Formation in the Jimsar Sag has extensive development of argillaceous source rocks (Kuang et al, 2014), with TOC mostly of 1.29%-13.82% and averaging 5.34%. Fractures are created via the pressurization and dissolution processes during hydrocarbon generation and expulsion.…”

Section: Tocmentioning

confidence: 99%

Main controlling factors of natural fractures in tight reservoirs of the lucaogou formation in the jimsar sag, Xinjiang, China

et al. 2023

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Natural fractures act as critical flow channels and reservoir space in the Lucaogou Formation tight reservoir of the Jimsar Sag. It is essential to identify the main controlling factors of natural fractures in order to achieve efficient development of tight oil in this area. There are mainly three types of natural fractures, including tectonic fractures, diagenetic fractures, and abnormal overpressure-induced fractures. Diagenetic fractures are predominantly bedding seams. The fracture development is affected by multiple factors including brittle minerals, lithology, tectonic stress, bed thickness, and total organic carbon (TOC). Large tectonic stress, smaller bed thickness, and higher total organic carbon are all favorable for the development of tectonic fractures and bedding seams. The controls of brittle minerals and lithology on fracture development are different for tectonic fractures and bedding seams. Specifically, carbonate minerals stimulate the tectonic fracture development, while brittle minerals have no control over the bedding seam development; tectonic fractures are most developed in the dolomitic rocks, while bedding seams are most developed in the argillaceous rocks. The calculated fracture density variation coefficients reveal that tectonic stress and brittle minerals are the main controlling factors of tectonic fracture development; total organic carbon and lithology are the main control factors of bedding seam development.

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Prediction of multiscale laminae structure and reservoir quality in fine-grained sedimentary rocks: The Permian Lucaogou Formation in Jimusar Sag, Junggar Basin

Cited by 15 publications

References 71 publications

Differences in CO₂‐Water‐Rock Chemical Reactions among ‘Sweet Spot’ Reservoirs: Implications for Carbon Sequestration

Differences in CO₂‐Water‐Rock Chemical Reactions among ‘Sweet Spot’ Reservoirs: Implications for Carbon Sequestration

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

Main controlling factors of natural fractures in tight reservoirs of the lucaogou formation in the jimsar sag, Xinjiang, China

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Prediction of multiscale laminae structure and reservoir quality in fine-grained sedimentary rocks: The Permian Lucaogou Formation in Jimusar Sag, Junggar Basin

Cited by 15 publications

References 71 publications

Differences in CO2‐Water‐Rock Chemical Reactions among ‘Sweet Spot’ Reservoirs: Implications for Carbon Sequestration

Differences in CO2‐Water‐Rock Chemical Reactions among ‘Sweet Spot’ Reservoirs: Implications for Carbon Sequestration

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

Main controlling factors of natural fractures in tight reservoirs of the lucaogou formation in the jimsar sag, Xinjiang, China

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Differences in CO₂‐Water‐Rock Chemical Reactions among ‘Sweet Spot’ Reservoirs: Implications for Carbon Sequestration

Differences in CO₂‐Water‐Rock Chemical Reactions among ‘Sweet Spot’ Reservoirs: Implications for Carbon Sequestration