Predicting the present-day in situ stress distribution within the Yanchang Formation Chang 7 shale oil reservoir of Ordos Basin, central China

Abstract

The Yanchang Formation Chang 7 oil-bearing layer of the Ordos Basin is important in China for producing shale oil. The present-day in situ stress state is of practical implications for the exploration and development of shale oil; however, few studies are focused on stress distributions within the Chang 7 reservoir. In this study, the present-day in situ stress distribution within the Chang 7 reservoir was predicted using the combined spring model based on well logs and measured stress data. The results indicate that stress magnitudes increase with burial depth within the Chang 7 reservoir. Overall, the horizontal maximum principal stress (SHmax), horizontal minimum principal stress (Shmin) and vertical stress (Sv) follow the relationship of Sv ≥ SHmax > Shmin, indicating a dominant normal faulting stress regime within the Chang 7 reservoir of Ordos Basin. Laterally, high stress values are mainly distributed in the northwestern parts of the studied region, while low stress values are found in the southeastern parts. Factors influencing stress distributions are also analyzed. Stress magnitudes within the Chang 7 reservoir show a positive linear relationship with burial depth. A larger value of Young’s modulus results in higher stress magnitudes, and the differential horizontal stress becomes higher when the rock Young’s modulus grows larger.

Unreliable determination of in situ stress orientation by cross multipole array acoustic logging in fractured shale reservoirs

“…[1][2][3][4][5][6] After nearly a century of development, a variety of comprehensive methods can be used to determine the stress state in reservoirs. [7][8][9][10] Stress evaluation has become an indispensable basic method for reservoir engineering [4][5][6] ; oil, gas, and coal exploration 8,[11][12][13][14][15] ; and oil and gas engineering design, drilling, and completion. [16][17][18][19] Stress evaluation also has important applications in the development of well pattern deployment, 4,6,20 prediction of reservoir fractures, [21][22][23][24] wellbore stability, 4,19,25 hydraulic fracturing, [26][27][28][29] and sand control in oil and water wells.…”

Determining the present-day in-situ stresses of tight-oil sandstones by conventional logs: An approach in the Triassic Yanchang Formation, southern Ordos Basin

“…Many scholars have studied the approaches of using conventional logs to determine the present-day in-situ stresses, and they have concluded a variety of different calculation models with different practicability (Anderson et al, 1973; Cheng et al, 2014; Ju et al, 2020b; Katahara et al, 1996; Mohaghegh et al, 2004; Pal et al, 2015; Yin et al, 2017; Zhang et al, 2019). However, most calculation models are proposed for the present-day in-situ stress calculation of shales, which have limitations for tight-oil sandstones.…”

“…However, most calculation models are proposed for the present-day in-situ stress calculation of shales, which have limitations for tight-oil sandstones. In addition, rock elastic parameters and intermediate parameters, such as tectonic stress coefficient and effective stress coefficient, are related to tectonic movement and lithology of specific areas, and thus obtaining these parameters accurately is critical to calculate the present-day in-situ stress (Cheng et al, 2014; Ju et al, 2020b). Therefore, it is crucial to create a more applicable approach for the present-day in-situ stress calculation in tight-oil sandstones.…”

Prediction method and distribution characteristics of in situ stress based on borehole deformation—A case study of coal measure stratum in Shizhuang block, Qinshui Basin

“…In situ stress analysis can intuitively reflect the variation law of in situ stress field in vertical and plane and provide basic information for drilling engineering and oil and gas reservoir development (Daniel and Christoph, 2016;Farshid et al, 2020;Zhang et al, 2021;Yang et al, 2022). It is an important reference for the selection of perforating and fracturing scale and parameters and prediction of sand production in production layers (Zou and Kaiser, 1990;Feng et al, 2019;Ju et al, 2020). In situ stress is the fundamental force that causes deformation and failure of mining and other underground engineering; in addition, its magnitude and direction have a great influence on the stability of the surrounding rock.…”