Origin and formation mechanisms of low oil saturation reservoirs in Nanpu Sag, Bohai Bay Basin, China

Lai, Jin; Pang, Xiaojiao; Xu, Feng; Wang, Guiwen; Fan, Xuejun; Xie, Weibiao; Chen, Jingying; Qin, Z.; Zhou, Zhong‐Zhen

doi:10.1016/j.marpetgeo.2019.07.021

Cited by 27 publications

(14 citation statements)

References 33 publications

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“…The core plugs were firstly saturated with brine and then evaluated to obtain the T 2 spectrum. Then, the samples were kept in the MnCl 2 brine with a salinity of 15 000 mg/L to remove the water (only oil remained), and the NMR measurements were performed again to obtain the T 2 distribution of the residual oil …”

Section: Samples and Methodsmentioning

confidence: 99%

“…Pore structure significantly influences storage capabilities, transport properties, and oil‐bearing property in rock reservoirs . Sandstones typically have a wide range of pore‐throat sizes, spanning from the nanoscale (<1 μm) to the microscale; therefore, various techniques and theories must be applied to qualitatively and quantitatively describe the complex pore geometry and pore‐throat structure in sandstones . Mercury injection capillary pressure (MICP) experiments are widely used to determine the complexity and heterogeneity of pore‐throat distribution .…”

Section: Introductionmentioning

confidence: 99%

“…Laboratory NMR measurements provide uncalibrated pore‐size distributions and determine fluid mobility in reservoir rocks . Additionally, NMR measurements can be used to identify oil‐bearing pore‐size distribution . Therefore, a combination of core and microscopic observations, as well as MICP and NMR analyses, allows the determination of pore structure characteristics and their effect on oil‐bearing property …”

Section: Introductionmentioning

confidence: 99%

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Effect of pore structure on oil‐bearing property in the third member of Paleogene Funing Formation in Subei Basin, East China

Liu

Xie

Shu

et al. 2020

Energy Science & Engineering

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Mercury injection capillary pressure (MICP) tests, nuclear magnetic resonance (NMR), (fluorescence) thin section, X-ray diffraction (XRD), and scanning electron microscope (SEM) analyses were used to describe the size and distribution of entire pore-throat structures in the sandstones of the E 1 f 3 (the third member of Paleogene Funing Formation) in the Subei Basin. The lithologies of E 1 f 3 in the Subei Basin are mainly dark-gray, very fine-grained sandstones and siltstones, interbedded with dark mudstones. The pore systems predominantly feature secondary intergranular and intragranular dissolution pores, micropores coexisting with minor amounts of intergranular pores, and microfractures. The high threshold pressure and bulk volume of irreducible fluids values and the significant variation in the NMR and MICP parameters indicate that the E 1 f 3 reservoirs are characterized by complex and heterogeneous microscopic pore structures. Microscopic pore-throat parameters are linked with macroscopic properties through the reservoir quality index (RQI). The NMR T 2 (transverse time relaxation) spectrum is unimodal or bimodal but with weak right peaks, indicating the rarity of large intergranular pores. However, large-scale pore throats, though only account for a minor part of the total pore volume, significantly contribute to the total permeability. The abundance of small-scale pore-throat systems (short T 2 components) results in high irreducible water content. Therefore, the oil saturation in E 1 f 3 sandstones is low, and the pore structure, especially the number of micropores, determines the oil-bearing property. Oil primarily occurs in the intragranular dissolution pores with minor amounts occurring in the large intergranular pores. Most of the micropores are bound by capillary water. The sandstones with chlorite clay minerals tend to be oil-wet and have high oil-bearing potential, while the abundance of detrital clay or illite contributes to a low oil-bearing grade. The combination of core and microscopic observations and the MICP and NMR analyses have allowed the determination of the pore structure characteristics and their coupling effects on oil-bearing property. |

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Section: Samples and Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of pore structure on oil‐bearing property in the third member of Paleogene Funing Formation in Subei Basin, East China

Liu

Xie

Shu

et al. 2020

Energy Science & Engineering

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“…[28][29][30][31] The Nanpu Sag is a typical dustpan-shaped faulted sag ( Figure 1). 1,30,32,33 The Nanpu Sag experienced a rifting stage during the Paleogene and then a postrifting stage since Neogene. 1,2 The Nanpu Sag contains many northwestern to nearly east-west faults.…”

Section: Geologic Settingsmentioning

confidence: 99%

“…1,30,34,35 The Cenozoic stratigraphic units in the Nanpu Sag include the Eocene Kongdian (Ek), Paleogene Shahejie (Es), Paleogene Dongying (Ed), Miocene Guantao (Ng), Minghuazhen (Nm), and the Quaternary Pingyuan Formation (Qp) ( Figure 1). 25,27,33,36 The Dongying Formation is in unconformable contact with the underlying Shahejie Formation. The lithology of Dongying Formation in Nanpu Sag consists of mudstones, fine to medium-grained sandstones, peppy sandstones, and conglomerates.…”

Section: Geologic Settingsmentioning

confidence: 99%

In‐situ stress determination and fracture characterization using image logs: The Paleogene Dongying Formation in Nanpu Sag, Bohai Bay Basin, China

Niu

Liu

Lai

et al. 2019

Energy Science & Engineering

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Fracture detection and in‐situ stress determination via well logs are important for exploration and exploitation of subsurface hydrocarbons. Cores, thin sections, and image logs are used to describe and interpret the subsurface fractures and in‐situ stress in the Paleogene Dongying sandstones in Nanpu Sag, Bohai Bay Basin, China. The maximum horizontal stress (SHmax) indicates a nearly east‐west trend according to the borehole breakouts and drilling‐induced fractures. Natural fractures in the Dongying sandstones are classified into: (1) open fractures and (2) closed fractures. The cement‐filled (closed) fractures are commonly detected by image logs as bright discontinuous sinusoidal waves due to resistive filling materials, while the open fractures are evident on image logs appearing as dark sine waves. The open fractures are of dominantly high dip angles, and the rose diagrams confirm the presences of two sets of fractures: northwest‐southeast and northwest‐southeast orientation. Fractures with strikes approximately parallel to the SHmax have good connectedness, making a significant contribution in hydrocarbon production. In addition, the oil‐bearing layers are mainly associated with the intervals with open fractures. The presence of natural fractures provides important pore spaces and fluid flow conduits. Insights can be provided into the subsurface fracture (natural and induced) detection and characterization using image logs.

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Characterization of Pore Electrical Conductivity in Porous Media by Weakly Conductive and Nonconductive Pores

Zhu

Zhang

et al. 2023

Surv Geophys

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Origin and formation mechanisms of low oil saturation reservoirs in Nanpu Sag, Bohai Bay Basin, China

Cited by 27 publications

References 33 publications

Effect of pore structure on oil‐bearing property in the third member of Paleogene Funing Formation in Subei Basin, East China

Effect of pore structure on oil‐bearing property in the third member of Paleogene Funing Formation in Subei Basin, East China

In‐situ stress determination and fracture characterization using image logs: The Paleogene Dongying Formation in Nanpu Sag, Bohai Bay Basin, China

Characterization of Pore Electrical Conductivity in Porous Media by Weakly Conductive and Nonconductive Pores

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