Overpressure: Origin, Prediction, and Its Impact in the Xihu Sag, Eastern China Sea

Li Wang, Ruizhao Yang, Zhipeng Sun, Lingda Wang, Jialiang Guo and Ming Chen
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Li Wang: College of Geoscience and Surveying Engineering, China University of Mining and Technology-Beijing, Beijing 100083, China
Ruizhao Yang: College of Geoscience and Surveying Engineering, China University of Mining and Technology-Beijing, Beijing 100083, China
Zhipeng Sun: College of Geoscience and Surveying Engineering, China University of Mining and Technology-Beijing, Beijing 100083, China
Lingda Wang: College of Geoscience and Surveying Engineering, China University of Mining and Technology-Beijing, Beijing 100083, China
Jialiang Guo: College of Geoscience and Surveying Engineering, China University of Mining and Technology-Beijing, Beijing 100083, China
Ming Chen: Shanghai Petroleum Company, Shanghai 200041, China

Energies, 2022, vol. 15, issue 7, 1-20

Abstract: The complex relationship between deep overpressure, abnormal porosity, and hydrocarbon generation in the Pinghu Formation is interesting and challenging for hydrocarbon exploration and development in the East China Sea Shelf Basin. It shows three-stage pore pressure evolution based on the characteristics of logs in the west slope of the Xihu Sag. Disequilibrium compaction was identified as the dominant overpressure mechanism in stage II (1.0 < PC < 1.6). The fluid expansion was identified as the predominant mechanism of overpressure generation in stage III (PC > 1.6), and tectonic compression occurs in Well B. Pore pressure was predicated by the Fillippone method based on the combination of raw velocity spectra and high-resolution velocity parameters obtained by seismic inversion. The overpressure at the bottom of the Pinghu Formation is mainly distributed in the F2 and F3 fault blocks. The deep gas reservoir of the Pinghu Formation is controlled by both lithology and pressure. The overpressure distribution area is consistent with the center of hydrocarbon generation. The overpressure distribution illustrated that overpressure was positively correlated with the porosity and permeability of the reservoir. The first porosity and permeability inversion zone of the Pinghu Formation formed because the overpressure caused by under-compaction offsets the pressure of some overlying strata and slows down diagenesis. Due to a large amount of hydrocarbon generation in source rocks, the acidic fluid with high temperature promoted the development of secondary pores, resulting in the second pore permeability inversion zone of the Pinghu Formation. The index of porosity preserving (IPP) is proposed here to quantitatively describe the relationship between overpressure and porosity. The index of porosity preserving in the second stage is 1.16%/10 MPa, and in the third stage is 1.75%/10 MPa. The results can be used to guide the exploration of the deep-basin gas reservoir of the Xihu Sag in the Eastern China Sea Basin.

Keywords: overpressure; pore pressure prediction; porosity preserving; Xihu Sag; East China Sea Basin (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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