Diagenesis and its controls on reservoir quality of the Tambar oil field, Norwegian North Sea

Bukar, Mohammed; Worden, Richard H.; Shettima, B.; Shell, Philip

doi:10.1016/j.engeos.2020.07.002

Cited by 32 publications

(9 citation statements)

References 37 publications

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“…During the deposition process, the overlying sediment thickens continuously, and under the action of the overlying load, the pore water is discharged (Bukar, Worden, Bukar, & Shell, 2021;Li, Zhou, Wang, Jiang, & Xue, 2020). In this process, the pores gradually shrink and the porosity gradually decreases, and this process is called compaction (Nelson, 2009).…”

Section: Compaction and Pressure Solutionmentioning

confidence: 99%

Diagenesis and reservoir classification criteria for Jurassic continental sandstone oil reservoir in the western Ordos Basin, China

Wei

Chen

et al. 2021

Geological Journal

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The marginal area of a sedimentary basin is closer to the provenance, so the sand body is generally more developed. For the Western Margin Thrust Belt of the Ordos Basin, the quality of the Jurassic sandstone reservoirs is still less studied. Diagenesis and reservoir evaluation are important research contents and hotspots in sedimentary geology. Therefore, in this paper, the diagenesis and reservoir properties of the Jurassic Yan 6 to Yan 10 members (Yan'an Formation) have been systematically studied based on the latest 3D seismic, well logging, cast thin section, scanning electron microscope and petrophysical property tests in this area. Furthermore, the vertical heterogeneity of petrophysical properties of the Jurassic reservoir has been discussed in detail, and the diagenetic evolution sequence and classification criteria of Jurassic sandstone reservoir have been proposed. The research results show that the lithologies of the Yan 6 to Yan 10 members are mainly lithic quartz sandstone, lithic feldspar sandstone and feldspar lithic sandstone. The pore types of sandstone are mainly intergranular pores, followed by dissolution pores, intercrystalline pores and a few microfractures. There are two high-value porosity zones in the buried depths of 1,950-2,050 m and 2,150-2,250 m, which are the coupling results of dissolution and palaeo-overpressure. Based on the comprehensive study of petrology, petrophysical properties and diagenesis, the diagenetic evolution sequence of the Jurassic sandstone was restored and a comprehensive classification standard for the Jurassic sandstone reservoirs is proposed. The Jurassic reservoir in the study area is a structurallithological reservoir, which has a unified oil-water interface, the Type I and Type II reservoir areas in the structural high positions are conducive to the large-scale accumulation of hydrocarbons.

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Section: Compaction and Pressure Solutionmentioning

confidence: 99%

Diagenesis and reservoir classification criteria for Jurassic continental sandstone oil reservoir in the western Ordos Basin, China

Wei

Chen

et al. 2021

Geological Journal

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“…Fractured reservoirs have strong heterogeneity, so traditional fracture evaluation methods face many challenges, such as the fine identifications of fractured segments and fracture sweet spots of tight reservoirs based on geophysical methods (Baecher., 1983;Bhatti et al, 2020;Chen., 2020;Fan et al, 2020a;Han et al, 2021;Liu et al, 2021a). At present, the conventional methods for identifying and evaluating reservoir fractures include core observations, conventional and imaging logging (Dowd et al, 2007;Casini et al, 2016;Li et al, 2019;Cao et al, 2020;Fan et al, 2020b;Liu et al, 2020a;Bukar et al, 2021). The cores obtained by drilling can be used to directly observe the development of underground fractures (Dcrshowitz and Einstein., 1988;Li et al, 2021;Yang et al, 2021;Xu and Gao., 2020;Nakaya and Nakamura., 2007;Dong et al, 2018;Hong et al, 2020;Liu et al, 2020b;Liu et al, 2021b).…”

Section: Introductionmentioning

confidence: 99%

Development Characteristics and Finite Element Simulation of Fractures in Tight Oil Sandstone Reservoirs of Yanchang Formation in Western Ordos Basin

Wang

et al. 2022

Front. Earth Sci.

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Structural fractures have a significant control effect on the large-scale accumulation of hydrocarbons in the Yanchang Formation. Previous studies have affirmed the important role of fractures in hydrocarbon accumulations in strongly deformed zones. However, for low-amplitude structural areas, the degree of fracture development is relatively low, and their control on sweet spots of hydrocarbons has not yet formed a unified understanding. In this paper, taking the Upper Triassic Yanchang Formation in the western Ordos Basin as an example, the development characteristics, prediction method, and the distribution of fractures in tight sandstone reservoirs in low-amplitude structural areas have been systematically studied using a large number of cores, thin sections, paleomagnetism, FMI logging, acoustic emission, productivity data, and finite element method. The research results showed that the Yanchang Formation in the study area mainly develop high-angle and vertical fractures, which were formed by regional tectonic shearing. Fractures are mainly developed in the fine-grained and ultra-fine-grained sandstones of the distributary channel and estuary bar microfacies, while the fractures in the medium-grained sandstones of the distributary channel and the mudstones of the distributary bay are relatively underdeveloped. The core fractures and micro-fractures of the Yanchang Formation all have the regional distribution characteristics, and the fracture strikes are mainly between NE50° and NE 70°. Moreover, the finite element method was used to predict the fractures in the target layer, and the prediction results are consistent with the actual distribution results of the fractures. The coupling analysis of fractures and tight oil sandstone distribution showed that the existence of fractures provided conditions for the accumulation of hydrocarbons in the Yanchang Formation. The confluence and turning areas of the river channels were repeatedly scoured by river water, and the rocks were brittle and easy to form fractures. The thickness of the fractured sandstone in these areas is usually greater than 0.4 m. Moderately developed fracture zones are prone to form hydrocarbon accumulation “sweet spots,” and the fracture indexes of these areas are usually distributed between 0.8 and 1.2. However, when the fracture index exceeds 1.2, over-developed fractures are unfavorable for the accumulation of hydrocarbons.

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“…Some scholars argue that hydrocarbon emplacement can well improve the physical property and pore structure of the reservoir, which is mainly attributed to two mechanisms: (a) emplaced hydrocarbons can extensively dissolve particles of the rock framework with the entrained organic acid, thereby generating numerous secondary pores (Daneshvar & Worden, 2018; Worden et al, 2018); (b) emplaced hydrocarbons can suppress cementation and thus protect primary pores via hindering the flow of pore water and avoiding contact between ions of pore water and detrital minerals; in this context, the oil film is concentrated on the detrital mineral surface (Rahman & Worden, 2016; W. Wang et al, 2019; Worden et al, 2018). Nonetheless, most scholars believe that such suppressing effect on diagenesis only exists in sandstone reservoirs with relatively high oil saturations, where pore water is trapped in a discontinuous isolated phase and the ion diffusion rate is greatly reduced (Bukar, Worden, Bukar, & Shell, 2021; Friis, Molenaar, & Varming, 2014; Sathar & Jones, 2016; Sathar et al, 2012; Worden et al, 2018). On the contrary, the interrelation between hydrocarbon emplacement and diagenesis is highly controversial in reservoirs with low oil saturation (fluorescence‐oil stain level).…”

Section: Introductionmentioning

confidence: 99%

Coupling relationship between reservoir densification and hydrocarbon emplacement in the Jurassic Badaowan Formation sandstone reservoirs of the southern Junggar Basin, China

Zhou

Guan

et al. 2022

Geological Journal

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Understanding the interrelationship between diagenesis and hydrocarbon emplacement is crucially important for investigating tight sandstone reservoir‐forming processes. In this paper, efforts were made to elucidate this interrelationship in the Jurassic Badaowan Formation tight sandstone reservoirs of the southern margin of the Junggar Basin (SJB), China. Four lithofacies were clarified, including quartz cemented‐dissolution facies (QCDF), carbonate cemented facies (CCF), authigenic clay mineral facies (ACMF), and matrix‐caused tightly compacted facies (MCTF). Weak hydrocarbon migration forces and poor hydrocarbon preservation conditions were identified to be the main reasons for the limited hydrocarbon accumulation scale. The reservoir densification process, mostly before 100 Ma, was associated with four aspects, including the high matrix content, the intensive carbonate cementation, the limited dissolution and alteration, and the development of authigenic clay minerals. Hydrocarbons in the Badaowan Formation reservoir were demonstrated to be emplaced after reservoir densification. Overpressure resulting from hydrocarbon expulsion and tectonic compression should have acted as the main driver for hydrocarbon migration. Particularly, the tight sandstone in the Qigu anticline was charged with overpressurized hydrocarbons sourced from the middle‐lower Jurassic source rocks at the footwall of the Qigu north fault since the early Jurassic. The tectonic compression in the late Neogene eroded the core of the Qigu anticline, which destroyed the initially large palaeo‐oil reservoir into smaller ones. The first‐stage hydrocarbon emplacement greatly affected the diagenesis and physical properties of the reservoir. It played an important role in inhibiting cementation, promoting dissolution, and altering the petrophysical properties of the tight sandstone reservoir. The densification process controlled the wettability and capillary pressure of pores in the tight sandstone. Specifically, the high kaolinite cement raised the hydrophilia, while the ubiquitous densification increased the capillary pressure of pores.

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Diagenesis and its controls on reservoir quality of the Tambar oil field, Norwegian North Sea

Cited by 32 publications

References 37 publications

Diagenesis and reservoir classification criteria for Jurassic continental sandstone oil reservoir in the western Ordos Basin, China

Diagenesis and reservoir classification criteria for Jurassic continental sandstone oil reservoir in the western Ordos Basin, China

Development Characteristics and Finite Element Simulation of Fractures in Tight Oil Sandstone Reservoirs of Yanchang Formation in Western Ordos Basin

Coupling relationship between reservoir densification and hydrocarbon emplacement in the Jurassic Badaowan Formation sandstone reservoirs of the southern Junggar Basin, China

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