Migration Rule of Crude Oil in Microscopic Pore Throat of the Low-Permeability Conglomerate Reservoir in Mahu Sag, Junggar Basin

Tan, Fengqi; Ma, Chunmiao; Zhang, Xu-Yang; Zhang, Jigang; Tan, Lei; Zhao, Dandan; Li, Xiankun; Jing, Yuqian

doi:10.3390/en15197359

Cited by 5 publications

(3 citation statements)

References 45 publications

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“…Many scholars have studied the structure [14], sedimentation [15], rock [16], and minerals [17] in the Fengcheng Formation reservoir in Mahu Sag. In terms of reservoir pore structure characteristics, Chinese and foreign scholars have conducted many studies [18][19][20], but most of the studies focus on pore and fracture, and the research scale is singular, and few studies separate pore and fracture and multi-scale pore and fracture. On the basis of previous studies, this paper combines large-scale core characterization with small-scale characterization using scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) technology, and studies the reservoir structure of the Fengcheng Formation in Mahu Sag through the multi-scale characterization of pores and fractures separately, and expounds the genesis of pores and fractures to a certain extent, in order to enrich the reservoir research of the Fengcheng Formation in Mahu Sag.…”

Section: Introductionmentioning

confidence: 99%

Characteristics and Genesis of Pore–Fracture System in Alkaline Lake Shale, Junggar Basin, China

Jiao,

Tang,

et al. 2024

Applied Sciences

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Unconventional oil and gas resources are indispensable, and shale oil is one of them. The Junggar Basin is a typical superposition oil and gas basin in China, with reserves of 100 million tons in many areas and various types of oil and gas reservoirs. The Permian Fengcheng Formation in Mahu Sag has great potential for oil generation, making the study of the Fengcheng Formation reservoir in Mahu Sag particularly important. Based on previous studies, the core sample from well Maye-1 is divided into four lithologies according to mineral composition: felsic shale, dolomitic felsic shale, clay-bearing felsic shale, and siltstone interlayers. Through core observation and description, it is found that the macroscopic porosity of each lithology is well-developed, with felsic shale exhibiting the highest macroscopic fracture density, followed by siltstone interlayers, and clay-bearing felsic shale showing the least development. Argon ion polishing scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) techniques show that the siltstone interlayer pore development is the best, with pore sizes ranging from 100 to 4000 nm. The fracture development of dolomitic felsic shale is the most significant, with fractures contributing up to 80.14%. The porosity of clay-bearing felsic shale is only 1.12%. The development of pores and fractures in the study area is related to sedimentary tectonic factors and diagenesis. It mainly exhibits three types of subfacies deposits, namely semi-deep lake subfacies, shallow lake subfacies, and lakeshore lake subfacies, predominantly composed of felsic shale. Strong tectonic movements contribute to the formation of macroscopic fractures. Diagenesis plays a crucial role in the formation of microscopic pores. The Fengcheng Formation is primarily influenced by compaction, pressure dissolution, dissolution, and metasomatism. These various diagenetic processes collectively promote the formation of pores, ultimately leading to the development of a multi-scale porosity system in the Fengcheng Formation.

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Section: Introductionmentioning

confidence: 99%

Characteristics and Genesis of Pore–Fracture System in Alkaline Lake Shale, Junggar Basin, China

Jiao,

Tang,

et al. 2024

Applied Sciences

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“…For conglomerate reservoirs, the content of sand and shale is relatively high, the gravel is suspended in the sand and mud, the pore throat distribution is extremely uneven, the average throat radius is small, the pore throat ratio is large, the pore throat coordination number is low, and the overall characteristics are multipeak biased fine state. The complex pore structure has a relatively large impact on oil recovery under different displacement methods [4][5][6]. At present, the conglomerate reservoir has been developed through a long period of waterflooding, with a limited swept volume of injected water, increasing water content, and rapidly decreasing oil production.…”

Section: Introductionmentioning

confidence: 99%

Study on Compatibility between Complex Mode Micropore Structure and Polymer Solution of Different Formulation for Conglomerate Reservoir

Tan

Jing

et al. 2023

Geofluids

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In this paper, the conglomerate reservoir is selected as the object to investigate the micropore structure and the compatibility of polymer solutions. Firstly, the characteristics of complex mode pore structure are analyzed based on casting thin sections, scanning electron microscope, and capillary pressure curve. Then the conglomerate reservoir is divided into five types by use of the K-means clustering algorithm, and the differences in micropore structure among the different reservoir types are also clarified. Secondly, the dynamic light scattering technology is used to directly determine the hydrodynamic diameter of different polymer formulations. As the polymer molecular weight increases, the average hydrodynamic diameter becomes larger, and with the same polymer molecular weight, the average hydrodynamic diameter becomes gradually larger as the solution concentration increases. Based on the above research results, the matching relationship between five reservoir types and polymer solutions is determined through laboratory experiments. The experimental results show that when the polymer molecular weight is determined, the volume of pore volume that can be effectively swept by polymer hydration molecules gradually decreases as the concentration of the solution increases. When the polymer molecular weight and its concentration are both determined, the pore volume of effective displacement of polymer-hydrated molecules also gradually reduces with becoming worse reservoir pore structure. The scope of application of different polymer formulations becomes progressively smaller as the microscopic pore structure of type I to type V reservoirs becomes deteriorated. The compatibility between the micropore structure of different conglomerate reservoir types and polymer solution is determined to provide the geological basis for the reasonable formulation of the polymer flooding scheme.

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“…Due to the special depositional environment of conglomerate reservoirs, the microscopic pore structure of the reservoir shows complex mode characteristics, with extremely uneven pore throat distribution, poor connectivity, and strong anisotropy [ 20 , 21 , 22 , 23 ]. The complex pore structure controls the seepage characteristics and production rules of crude oil in different scale pore throats [ 24 ]. For the oil displacement process of different media, the microscopic manifestation is mainly the large difference in fluid flow patterns in different cores, which is reflected in the macroscopic phenomenon as the obvious difference in development characteristics, which in turn leads to significant distinctions in the final recovery rates of different types of reservoirs in conglomerate reservoirs [ 25 ].…”

Section: Introductionmentioning

confidence: 99%

Difference in Step-Wise Production Rules of SP Binary Flooding for Conglomerate Reservoirs with Different Lithologies

Liao

et al. 2023

Polymers

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The purpose of this study is to clarify the difference in oil production rules of conglomerate reservoirs with different pore structures during surfactant–polymer (SP) binary flooding and to ensure the efficient development of conglomerate reservoirs. In this paper, the full-diameter natural cores from the conglomerate reservoir of the Triassic Kexia Formation in the seventh middle block of the Karamay Oilfield (Xinjiang, China) are selected as the research objects. Two schemes of single constant viscosity (SCV) and echelon viscosity reducing (EVR) are designed to displace oil from three main oil-bearing lithologies, namely fine conglomerate, glutenite, and sandstone. Through comprehensive analysis of parameters, such as oil recovery rate, water content, and injection pressure difference, the influence of lithology on the enhanced oil recovery (EOR) of the EVR scheme is determined, which in turn reveals the differences in the step-wise oil production rules of the three lithologies. The experimental results show that for the three lithological reservoirs, the oil displacement effect of the EVR scheme is better than that of the SCV scheme, and the differences in recovery rates between the two schemes are 9.91% for the fine conglomerate, 6.77% for glutenite, and 6.69% for sandstone. By reducing the molecular weight and viscosity of the SP binary system, the SCV scheme achieves the reconstruction of the pressure field and the redistribution of seepage paths of chemical micelles with different sizes, thus, achieving the step-wise production of crude oil in different scale pore throats and enhancing the overall recovery of the reservoir. The sedimentary environment and diagenesis of the three types of lithologies differ greatly, resulting in diverse microscopic pore structures and differential seepage paths and displace rules of SP binary solutions, ultimately leading to large differences in the enhanced oil recoveries of different lithologies. The fine conglomerate reservoir has the strongest anisotropy, the worst pore throat connectivity, and the lowest water flooding recovery rate. Since the fine conglomerate reservoir has the strongest anisotropy, the worst pore throats connectivity, and the lowest water flooding recovery, the EVR scheme shows a good “water control and oil enhancement” development feature and the best step-wise oil production effect. The oil recovery rate of the two schemes for fine conglomerate shows a difference of 10.14%, followed by 6.36% for glutenite and 5.10% for sandstone. In addition, the EOR of fine conglomerate maintains a high upward trend throughout the chemical flooding, indicating that the swept volume of small pore throats gradually expands and the producing degree of the remaining oil in it gradually increases. Therefore, the fine conglomerate is the most suitable lithology for the SCV scheme among the three lithologies of the conglomerate reservoirs.

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Migration Rule of Crude Oil in Microscopic Pore Throat of the Low-Permeability Conglomerate Reservoir in Mahu Sag, Junggar Basin

Cited by 5 publications

References 45 publications

Characteristics and Genesis of Pore–Fracture System in Alkaline Lake Shale, Junggar Basin, China

Characteristics and Genesis of Pore–Fracture System in Alkaline Lake Shale, Junggar Basin, China

Study on Compatibility between Complex Mode Micropore Structure and Polymer Solution of Different Formulation for Conglomerate Reservoir

Difference in Step-Wise Production Rules of SP Binary Flooding for Conglomerate Reservoirs with Different Lithologies

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