Present-day in-situ stress field within the Yanchang Formation tight oil reservoir of Ordos Basin, central China

Ju, Wei; Niu, Xiaobing; Feng, Shan; You, Yonghua; Xu, Ke; Wang, Geoff; Xu, Haoran

doi:10.1016/j.petrol.2019.106809

Cited by 32 publications

(17 citation statements)

References 48 publications

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“…The drop is 10-80m, and the extension is less than 16km. It can be inferred that the σ1 direction is roughly N40°E-N80°E (Ju et al, 2015;Ju et al, 2020;. Based on the research results of focal mechanism solution, HF, hole wall collapse, OC, fault sliding vector and earthquake surface rupture (Ju et al, 2017;Wang et al, 2018;Deng and Sheng, 2015;Sheng et al, 2015), it is considered that the present σ1 direction in north…”

Section: Comparison Of In-situ Stress Test Results In Burtai Minementioning

confidence: 99%

In-Situ Stress Measurements and Stress Accumulation Level Analysis of Coal Mines in Northern Ordos Basin

Yang¹,

Ning²,

Li³

et al. 2020

Preprint

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For non-directional drilling cores, the sample selection and test method for Kaiser effect (KE) in-situ stress measurement were proposed, and the magnitude and direction of its principal stresses were theoretically derived. Based on this method, the KE of 423 samples in Burtai and Baode coal mines in northern Ordos Basin (NOB) were tested. The results show that σH, σh and σv vary with depth and location, and their values increase with increasing of depths. Generally, horizontal stresses play a leading role. There are main stress regimes in NOB: σH > σh > σv (Burtai, <172m; Baode, <170m) and σH > σv > σh (Burtai, 170-800 m; Baode, 170-400 m), and the σv > σH > σh stress regime is mainly distributed in moderately deep to deep coal mines. For rock masses with a depth of 350m, k ((σH + σh) / 2σv) tends to 1, indicating that deep critical state will gradually emerge. The test results were compared with those of overcoring method (OC), elastic strain recovery (ASR) and micro-hydraulic fracturing (HF). The relative errors of σH, σh and σv are 14.90%, 19.67%, 15.47% (Burtai) and 10.74%, 22.76%, 19.97% (Baode), and they are all within a reasonable range required by the project, which verifies the reliability of KE method. The dominant orientation of σH (Burtai, NE-NNE; Baode, NEE) was obtained by using paleomagnetic technology, which is consistent with that (NE-NEE) of earthquake focal mechanisms in this area. Based on Byerlee-Anderson theory, the stress accumulation level of mine rock mass was discussed. Under dry rocks or hydrostatic pressure rocks, the friction coefficient of faults is both low, which is less than the lower limit (0.6) of strike-slip faults slip, indicating that the fracture stress with a low level around the study area is lower than the friction limit stress. The stress accumulation level in Baode mine is slightly larger than that in Burtai mine.

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Section: Comparison Of In-situ Stress Test Results In Burtai Minementioning

confidence: 99%

In-Situ Stress Measurements and Stress Accumulation Level Analysis of Coal Mines in Northern Ordos Basin

Yang¹,

Ning²,

Li³

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…The drop is 10-80 m, and the extension is less than 16 km. It can be inferred that the r 1 direction is roughly N40°E-N80°E (Ju et al 2015(Ju et al , 2020Li et al 2019). Based on the results for the focal mechanism solution, HF, borehole collapse, OC, fault sliding vector and earthquake surface rupture (Ju et al 2017;Wang et al 2018;Deng and Sheng 2015;Sheng et al 2015), it is considered that the present r 1 direction in the north Ordos area is NE-NEE.…”

Section: Comparison Of Results For In Situ Stress Testing In the Burtai Minementioning

confidence: 99%

In situ stress measurement and analysis of the stress accumulation levels in coal mines in the northern Ordos Basin, China

Yang

Ning

et al. 2021

Int J Coal Sci Technol

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For non-directional drilling cores, selection of samples and the test methods for in situ stress measurements to evaluate the Kaiser effect (KE) were proposed, and the magnitude and direction of the principal stresses were derived from first principles. Based on this approach, the KE for 423 samples in the Burtai and Baode coal mines in the northern Ordos Basin (NOB), China, have been investigated. The results show that the maximum horizontal principal stress (σH), the minimum horizontal principal stress (σh) and the vertical stress (σv) varied with depth and location, and the values increase with increasing depth. Generally, the horizontal stresses play a leading role. For the main stress regimes in the NOB, σH > σh > σv (Burtai Mine, < 172 m; Baode Mine, < 170 m) and σH > σv > σh (Burtai Mine, 170–800 m; Baode Mine, 170–400 m), and the σv > σH > σh stress regimes are mainly distributed in moderately deep to deep coal mines. For rock masses with a depth of 350 m, k ((σH + σh)/2σv) tends to 1, indicating that a deep critical state will gradually emerge. The test results are compared with those for the overcoring (OC) method, the anelastic strain recovery (ASR) method and micro-hydraulic fracturing (HF). The relative errors for σH, σh and σv were 14.90%, 19.67%, 15.47% (Burtai Mine) and 10.74%, 22.76%, 19.97% (Baode Mine), respectively, and the errors are all within an acceptable range, thus verifying the reliability of the KE method. The dominant orientation for the σH (Burtai mine, NE-NNE; Baode Mine, NEE) is obtained via paleomagnetic technology, and the data are consistent with those (NE-NEE) of the earthquake focal mechanism solutions for the area. Based on the Byerlee–Anderson theory, a discussion is given on the levels of stress accumulation in the rock mass of the mines. For dry rocks or hydrostatic pressure rocks, the friction coefficients of the faults are low for both locations, and the values are less than the lower limit (0.6) of the strike-slip faults slip, indicating that the stress fractures at a low level around the study areas are lower than the friction limit stress. The stress accumulation levels in the Baode Mine are slightly larger than those in the Burtai Mine.

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“…Fractured oil and gas reservoirs are highly heterogeneous, and the key issue for their efficient development is the developmental law study of natural fractures (Holt, Fjaer, Stenebraten, & Nes, 2015;Hong et al, 2020;Ju et al, 2020a;Ju et al, 2020b;Stow et al, 2020;Yin & Gao, 2019). Large-scale tight sandstone gas reservoirs are widely developed in the Xu 2 Member (second member of the Upper Triassic Xujiahe Formation) in the West Sichuan Depression Zou et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Development mode of reverse fault‐associated fractures in deep tight sandstones: A case study in Xinchang Gas Field, Sichuan Basin, China

et al. 2021

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Evaluation of natural fractures is the key issue of the prediction of sweet spots in deep tight sandstones. In this article, taking the tight gas sandstone reservoir of the Xu 2 Member (second member of the Upper Triassic Xujiahe Formation) in Xinchang Gas Field, West Sichuan Depression as an example, we systematically studied the characteristics, formation periods, influencing factors, and developmental mode of fractures using testing results of cores, thin sections, rock mechanics, isotopes, fluid inclusions, and the structural curvature simulation method. The results show that the Xu 2 Member mainly develops vertical and high-angle fractures. The fractures are highly effective and mainly developed in medium-fine-grained sandstone. The secondary minerals in the fractures have multi-stage filling processes. The fluid inclusions are mainly gas-liquid two-phase brine inclusions (secondary inclusions), and with the same crystal, the temperature difference between the brine inclusion and the organic inclusion is 23.7 C. Carbon and oxygen stable isotope tests show that calcite has two mixing stages. In the end, the formation periods of the fractures in the Xu 2 Member were divided into five stages. The influencing factors of fractures in the Xu 2 Member include lithology, fault, layer thickness, and structural deformation. According to geomechanical analysis, we finally established the development mode of reverse fault-associated fractures in the Xu 2 Member.

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Present-day in-situ stress field within the Yanchang Formation tight oil reservoir of Ordos Basin, central China

Cited by 32 publications

References 48 publications

In-Situ Stress Measurements and Stress Accumulation Level Analysis of Coal Mines in Northern Ordos Basin

In-Situ Stress Measurements and Stress Accumulation Level Analysis of Coal Mines in Northern Ordos Basin

In situ stress measurement and analysis of the stress accumulation levels in coal mines in the northern Ordos Basin, China

Development mode of reverse fault‐associated fractures in deep tight sandstones: A case study in Xinchang Gas Field, Sichuan Basin, China

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