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Article

Research on Diagenetic Evolution and Hydrocarbon Accumulation Periods of Chang 8 Reservoir in Zhenjing Area of Ordos Basin

by
Guilin Yang
,
Zhanli Ren
* and
Kai Qi
Department of Geology, Northwest University, Xi’an 710069, China
*
Author to whom correspondence should be addressed.
Energies 2022, 15(10), 3846; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103846
Submission received: 25 March 2022 / Revised: 17 April 2022 / Accepted: 19 May 2022 / Published: 23 May 2022
(This article belongs to the Special Issue Natural Gas Hydrate and Deep-Water Hydrocarbon Exploration)
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Abstract

:
The Mesozoic Chang 8 Section in the Zhenjing area is a typical low permeability-tight sand reservoir and is regarded as the most important set of paybeds in the study area. Guided by the principles of basic geological theory, the diagenetic evolution process and hydrocarbon accumulation periods of the Chang 8 reservoir in the study area were determined through various techniques. More specifically, core observation, scanning electron microscopy (SEM), X-ray diffraction (XRD), and vitrinite reflectance experiments were performed in combination with systematic studies on rock pyrolysis and the thermal evolutionary history of basins, the illite-dating method, and so on. The Chang 8 reservoir is dominated by feldspar lithic and lithic feldspar sandstones. Quartz, feldspar, and lithic fragments are the major clastic constituents. In clay minerals, the chlorite content is the highest, followed by illite/smectite formation and kaolinite, while the illite content is the lowest. The major diagenesis effect of the Chang 8 reservoir includes compaction, cementation, dissolution, metasomatism, and rupturing. The assumed diagenetic sequence is the following: mechanical composition → early sedimentation of chlorite clay mineral membrane → early cementation of sparry calcite → authigenic kaolinite precipitation → secondary production and amplification of quartz → dissolution of carbonate cement → dissolution of feldspar → late cementation of minerals such as ferrocalcite. Now, the study area is in Stage A in the middle diagenetic period. Through the inclusion of temperature measurements, in conjunction with illite dating and thermal evolutionary history analysis technology in basins, the Chang 8 reservoir of this study was determined as the phase-I continuous accumulation process and the reservoir formation epoch was 105~125 Ma, which was assigned to the Middle Early Cretaceous Epoch.

1. Introduction

Zhenjing Block is located at the intersection of the Tianhuan Depression, Northern Shaanxi Slope, Weibei Hump and thrust belt at the west edge of the Ordos Basin, which is in a unique geological position (Figure 1) [1,2,3,4]. In the study area, the Mesozoic Chang 8 reservoir forms the major paybed, which is rich in oil and gas resources [3,4,5,6]. With continuous developments of the oil field, high yields have been difficult to maintain and may even worsen, largely due to insufficient understanding of the reservoir quality. The formation of the reservoir is a complicated and time-consuming process, with the three essential geological processes—sedimentation, diagenesis, and tectonism—requiring thorough examination [7]. Of these processes, diagenesis plays an important role in reservoir reformation and, as a result, has been widely examined by the scientific community in the field [8,9,10,11,12,13,14,15,16,17,18,19]. The analysis of the accumulation period is an important part of the accumulation system study and key in the analysis of the accumulation process [20,21,22,23].
Previous studies on the Chang 8 Member in the Zhenjing area of the Ordos Basin mainly focused on sedimentary facies and reservoir characteristics. However, studies on the diagenesis and accumulation stages were relatively weak. It is therefore of great significance to clarify the diagenetic evolution and hydrocarbon accumulation stage of the Chang 8 Member—the main oil-producing layer—for deepening the theoretical understanding of reservoir evaluation and hydrocarbon accumulation [9,10,11,12,13,14,15,20,21,22,23]. In this paper, both the diagenetic sequence and hydrocarbon accumulation periods of the Chang 8 reservoir section, which is a low-permeability-tight sandstone reservoir, are discussed systematically. First, a brief analysis of the petrology and physical characteristics of the Chang 8 reservoir was carried out based on insights from the borehole core observation, scanning electron microscopy (SEM), and slice observation. On this basis, the diagenesis of the Chang 8 reservoir section was investigated by combining X-ray diffraction (XRD) measurements, vitrinite reflectance, and rock pyrolysis. Thus, it was divided into various evolutionary sequences. Meanwhile, the hydrocarbon accumulation periods of the Chang 8 reservoir were analyzed comprehensively by conducting a thermal history analysis of basins and applying the illite dating method. The hydrocarbon accumulation times and the specific time were determined both indirectly and directly. Our work provides reliable references to the follow-up exploration and exploitation of the study area [5].

2. Lithological Characteristics and Physical Characteristics of the Reservoir

Based on the statistical studies of borehole core observation, SEM and slice observation data were analyzed. At the same time, the analysis of lithologic triangulation diagram was carried out (Figure 2a). Region I represents quartz sandstone, Region II denotes feldspathic quartz sandstone, Region III stands for the rock debris quartz sandstone, Region IV signifies arkose, Region V is the rock debris arkose, Region VI represents feldspar rock debris sandstone, and Region VII is the rock debris sandstone. It was found that feldspar rock debris sandstone and rock debris arkose are the dominant lithologies in the Chang 8 reservoir (Figure 2a). With respect to the clastic constituents, quartz accounts for the highest proportion (29%), followed by feldspar (26%), which is mainly composed of potash feldspar and plagioclase. The content of rock debris is the lowest, averaging at 24%. Among them, the magmatic rock debris mainly consists of neural acidity and the metamorphic rock debris is mainly composed of quartzite, followed by phyllite. The sedimentary rock debris is mainly siltstone and silty mudstone, followed by mudstones and flint. In addition, the content of mica is the lowest (Table 1) [24].
According to SEM and XRD analysis, the illite content in sandstones of Chang 8 reservoir in the study area is the lowest, ranging from 4% to 11% and averaging at 6.85%. Under the microscope, the thin-film, schistose, hair, and fiber modes are the major adhesion modes on the particle surfaces. Chlorite content is the highest (21~45%), averaging at 36.3%. Insights from SEM analysis indicate that chlorite mainly presents as thin-film mode and foliated mode, while the cementation mode is mainly presented as the looped lining mode and pore-lining mode, followed by illite/smectite formation and kaolinite. It is interesting to notice that the illite/smectite formation looks like a honeycomb under SEM imaging and the content of kaolinite ranges from 21% to 45%, averaging at 36.3%. It was developed on a large scale as filling in the pores and is presented with good crystal form. Under SEM imaging, the crystals look like book pages and worms (Figure 2b and Figure 4c–g).
According to the core data test and analysis, the porosity of the Chang 8 reservoir distributes between 1.8~17.9%, averaging at 10.9%. The permeability ranges between 0.037~0.79 mD, averaging at 0.45 mD (Figure 3). Thus, it belongs to a low-porosity and low-permeability reservoir.

3. Diagenetic Evolution Analysis of the Reservoir

Diagenesis is defined as the evolution process where sediments solidify into rocks through a series of physical, chemical, and biological reactions. This process is affected by many factors, such as burying rate, pressure, local temperature distribution, and sediment composition. Hence, it can greatly influence the physical properties of the reservoir. Therefore, diagenesis is closely related to the hydrocarbon accumulation mechanism [10,11,12,13,14,25].
Zhenjing area is located in the continental facies lacustrine deposit environment. There are many types of diagenesis of the Chang 8 reservoir [5,6]. In this work, both the diagenesis and the diagenetic sequence of the Chang 8 reservoir were studied systematically by using slice authentication, SEM and XRD measurements, as well as vitrinite reflectance and rock pyrolysis. The major diagenesis effects include compaction, cementation, dissolution, metasomatism, and rupturing. Among them, dissolution and rupturing have a positive impact on the improvement of the physical properties of the reservoir, while compaction and cementation facilitate the compactness of the reservoir.

3.1. Diagenetic Analysis

3.1.1. Compaction

Due to the pressure of the overlying rocks, the process that makes the reservoir structure tighter and tighter is called compaction. It is regarded as the most influential and the most common diagenesis type in the diagenetic evolution of the reservoir [26,27,28,29,30,31,32,33,34,35]. The manifestation of the compaction effect of the Chang 8 reservoir in the Zhenjiang area is obvious, especially as the bending deformation of the plastic mineral particles is concerned, due to compaction in the early diagenesis. For example, minerals such as mica developed deformation of plastic particles after experiencing strong mechanical compactness (Figure 4a). Mineral particles are also compacted and filled into spaces among primary pores, thus decreasing the physical properties of the reservoir significantly. As the compaction continues, the lattices at the particle contact points may be deformed and even be dissolved. As a result, the contact relation among the particles may change from the original point contact to the linear contact and even to the linear-concave-convex contact. Many clastic particles like mica are aligned in a direction that forms texture layers (Figure 4b). Compaction is the major cause of tightening and sharp reduction of the primary pores, and could lead to the deterioration of the physical properties of the Chang 8 reservoir in the Zhenjing area.

3.1.2. Cementation

The change during the process of minerals precipitation in the pores of fragmental deposits into authigenic minerals is called cementation, which renders sediments solidified into rocks [36,37]. The role of cementation is to fill the pores and it is considered an important cause of decreasing the porosity in the reservoir layer. However, volumes along particles may not decrease due to cementation, which is obviously different from compaction [28,30,31,32,33,34,35]. From a general point of view, the inter-granular pores are filled by authigenic minerals, which has a negative impact on changes in the physical properties of the reservoir. However, the early filling of authigenic minerals can inhibit compaction to some extent. In the retained inter-granular pores, solvent-sensitive types of cement from secondary pores are formed as a response to dissolution. Hence, cementation has some positive influence on changes in the physical properties of the reservoir to some extent. In particular, early cementation has dual contributions to the physical properties of the reservoir. As an important factor of compaction of the Chang 8 reservoir in the Zhenjing area, the cementation procedure can be divided into authigenic clay mineral cementation, siliceous cementation, and carbonate cementation according to the types of the cement. It is mainly influenced by the fluid features in pores, the sedimentation environment, and composition [32,35].
①
Authigenic clay mineral cementation
According to the casting slice and SEM analysis, chlorite and kaolinite are authigenic clay minerals in the Chang 8 reservoir of Zhenjing area, accompanied by some illite/smectite formation and illite. Chlorite, which was developed in the early diagenetic periods, was found in slice and foliated structures, manifested as looped lining cementation and pore-lining of cementation (Figure 4c,d). The supporting framework that was formed by the looped lining cementation has the ability to protect pores from cement filling effectively and it can also inhibit mechanical compaction to some extent. Moreover, it can be used as a separation layer between the silica-containing fluid and quartz particles to inhibit the nucleation of SiO2 on quartz granules, as well as the secondary expansion of authigeneic quartz, and promote the storage of primary pores. This mechanism has a constructive effect on the evolution of pores (Figure 5a).
Kaolinite cement appeared as book-like and worm-like under SEM imaging (Figure 4e). Its formation is closely related to the alteration of feldspar. Feldspar is one of the most commonly observed clastic particles in the region and it may produce kaolinite after dissolving in acid water. In other words, the occurrence of kaolinite is accompanied by the dissolution of feldspar.
The authigenic illite has a relatively low content in the Chang 8 reservoir of the Zhenjing area and it is frequently adhered onto particle surfaces as thin films, schistose, hair-like, and fibrous structures (Figure 4f). Montmorillonite illite may cause illite/smectite formation, which appeared as honeycomb shapes under SEM imaging (Figure 4g) [28].
②
Siliceous cementation
Siliceous cement is the product precipitated by siliceous materials in acid fluid and it is formed by the surrounding quartz particles or regions with poor development of chlorite film. In the study area, there’s a universal development of siliceous types of cement in the Chang 8 reservoir, which is mainly manifested as the secondary expansion of quartz (Figure 4h). The thickness of the expanded sides ranges between 0.02~0.2 mm. The quartz particles still exist in residual inter-granular pores after the second expansion is generated.
③
Carbonate cementation
In the study area, calcite is regarded as the major carbonate cement in the Chang 8 reservoir, with an average content of 9.56%. Carbonate types of cement produced substrate cementation, which were formed after the pore-lining chlorite in early diagenesis. Calcite is cemented among clastic particles (Figure 4i), thus forming a compacted reservoir. According to an intersecting analysis of the porosity and carbonate cement, a negative correlation was discovered (Figure 5b). Hence, it is believed that carbonate cement is the major cause of the compactness of the Chang 8 reservoir in the study area.

3.1.3. Dissolution

Secondary pores, which are produced upon dissolution of mineral components and cement in the reservoir, facilitate the large-scale expansion of the reservoir spaces. It is the most important diagenesis process to improve the physical properties of the reservoir [5,26,31,34]. After experiencing tectonic lifting and oil–gas emplacement in the Chang 8 reservoir section of the Zhenjing area, feldspar and rock debris will be dissolved and eroded by organic acids (Figure 4j), thus forming mold pores, intragranular pores, and inter-granular pores. This effect mainly occurs at the end of early diagenesis and Phase-A of middle diagenesis.

3.1.4. Metasomatism

The occurrence of metasomatism is closely related to the local temperature and pressure distributions, as well as the fluid properties in pores and it occurs in all diagenetic periods [29,32,35]. Metasomatism is a process of mutual replacement of minerals. It is accompanied by the dissolution and sedimentation effects. Hence, the influence of the metasomatism process on the physical properties of the reservoir is very small and even can be ignored. Calcite metasomatism is regarded as the most common type of metasomatism in the study area (Figure 4k), with local metasomatism of kaolinite and clay minerals.

3.1.5. Rupturing

According to the core observation and analysis of slice data under SEM imaging, microcracks that are produced by rupturing in the Chang 8 reservoir were developed greatly (Figure 4l). These microcracks connect pores in the reservoir effectively, which play an important role in the improvement of the physical properties of the reservoir (decompaction), especially the migration and settlement of oil and gas [5,30].

3.2. Diagenetic Sequence and Diagenetic Periods

The various diagenesis types in each diagenetic period are different and the duration of diagenesis also varies. Based on the SEM analysis and the casting slicing observation, a comprehensive analysis of the diagenetic sequence of sandstones in the Chang 8 reservoir of the Zhenjing area was carried out by combining the diagenesis theoretical knowledge [29,30,31].
In the early diagenetic period A, the Chang 8 reservoir section in the study area becomes more and more compact, thus resulting in the plastic deformation of minerals such as mica. The contact relation among particles changes from the original point contact into the linear contact. According to SEM observation, clastic particles such as mica align toward oriented array to form a texture layer. In this period, the porosity of the reservoir declines sharply due to compaction. In the early diagenesis period B, compaction continues to increase and chlorite film begins to produce in pores. In this period, the production of cement-like kaolinite and sparry calcite decreases the porosity of the reservoir continuously. Compared with the early diagenetic period, the influence of compaction in the middle diagenetic period A on the physical properties of the reservoir has been very small and the secondary quartz development expands. In the reservoir, production of organic acids occurs, while carbonate cement and feldspar are dissolved, thus forming multiple secondary pores. The dissolution that consumes acid water and pore water becomes increasingly alkaline, thus facilitating changes in illite/smectite formation toward illite. During this period, diagenesis plays an important role in improving the physical properties of the Chang 8 reservoir. In the middle diagenetic period B, illite/smectite formation continues to change toward illite. Cementation and dissolution occur alternatively, while the porosity tends to be stable gradually. To sum up, the diagenetic sequences of the Chang 8 reservoir in the study area are determined as follows: mechanical compaction → early sedimentation of chlorite clay mineral → early cementation of sparry calcite → authigenic kaolinite precipitation → quartz secondary expansion → dissolution of carbonate cement → dissolution of feldspar → late cementation of minerals like ferrocalcite (Figure 6).
In this work, the J&M TIDAS PMT IV&MSP200 vitrinite reflectance test system was applied to test the vitrinite reflectance of ten rock samples (including mudstone, oil shale and coal) in the study area. The minimum and maximum reflectance values are 0.67% and 1.34%, respectively, averaging at 0.90% (Table 2). The maximum paleogeotemperature in the rock burying process was tested by acoustic emission, which ranges between 109.3~125.3 °C, averaging at 120.32 °C (Table 3). The extracted Tmax of mudstone in the Chang 8 reservoir of the study area ranges between 445~463 °C, averaging at 454 °C [38]. According to the XRD analysis, the montmorillonite content in the illite/montmorillonite formation is between 15~30%, averaging at 20% (Table 4). Moreover, according to the comprehensive analysis of the diagenetic sequence, both vitrinite reflectance and paleogeotemperature tests were performed based on the acoustic emission. With references to the relevant literature and industrial standards, it is believed that the Chang 8 reservoir in Zhenjing area is currently in the middle diagenetic period A (Figure 6).

4. Determination of Hydrocarbon Accumulation Periods

In this work, hydrocarbon accumulation periods of the Chang 8 reservoir in the study area were studied systematically by applying the indirect limiting method of the thermal evolution history-inclusion temperature measurement and the direct dating method of illite [39,40,41,42,43,44]. First, the freezing-point and homogenization temperatures of rock samples from 12 wells (including HH188 and HH156) in the Chang 8 reservoir section were tested. The LINKM600 cold-heat table in the Thermal Chronology Laboratory of Northwestern University was used under the enforcement of 10.5 V of voltage, 26 °C of indoor temperature, and 65% of humidity. Meanwhile, the corresponding salinity was calculated. In this section, the saline inclusion, which coexists with the hydrocarbon inclusion was chosen as the test object. It is mainly reserved at the quartz expansion edges or inside of fracture and quartz. According to the analysis of the experimental results, the homogeneous temperature of inclusion has a wide range of 69~155 °C, with peaks ranging between 100~125 °C. This result and the reproduction diagram of the burying history were used together for mutual calibration, through which the accumulation period of the Chang 8 reservoir was 110~120 Ma (Figure 7).
When both oil and gas enter the reservoir, the growth of authigenic illite stops. Hence, this period is viewed as the time for hydrocarbon accumulation [44,45,46,47,48,49,50]. In this work, illite test analysis was accomplished in the Geochemistry Laboratory of China University of Petroleum (Beijing). The 38AR diluent was put in accurately by using the VG3600 mass spectrometer while melting the samples under 1500 °C. Later, the isotope ratios of (38Ar/36Ar) and (40Ar/38Ar) were tested. The radioactive factor 40Ar of the samples was calculated and the corresponding age was calculated according to the K content [44,47,48,49,50]. Based on the above principle, a dating analysis was carried out on the oil-containing sandstone illite in HH192 and HH198. The acquired results showed that the accumulation period of the Chang 8 reservoir was 105~115 Ma (Figure 7). Consistent with the inclusion analysis outcomes, it is concluded that the Chang 8 reservoir in the study area is a phase-I continuous accumulation process and the accumulation period is 105~125 Ma, which is the middle Early Cretaceous Epoch (Figure 7).

5. Conclusions

(1)
According to the borehole core observation, SEM and XRD analysis, the lithology of the Chang 8 reservoir section in the study area is mainly dominated by feldspar rock debris, and rock debris arkose. Quartz, feldspar, and rock debris are the major clastic constituents. Among them, quartz has the highest content (about 29%), followed by feldspar (26%). The content of the rock debris is the lowest, averaging at 24%. Among the sandstone clay minerals, chlorite content is the highest, averaging at 36.3%. The illite/smectite formation and kaolinite possess the lower content and the illite content is the lowest, averaging at 6.85%.
(2)
According to the SEM, XRD, vitrinite reflectance and rock pyrolysis analysis, the major diagenesis effects of the Chang 8 reservoir section in the Zhenjing area mainly include the following procedures: compaction, cementation, dissolution, metasomatism, and rupturing. Consequently, the proposed diagenetic sequence is the following: mechanical compaction → early sedimentation of chlorite clay mineral film → early cementation of sparry calcite → authigenic kaolinite precipitation → quartz secondary expansion → dissolution of carbonate cement → dissolution of feldspar → late cementation of minerals like ferrocalcite. Now, the reservoir is in the middle diagenetic period A.
(3)
Based on the thermal evolution history analysis and the illite dating method, the hydrocarbon accumulation periods of the Chang 8 reservoir are analyzed comprehensively. The Chang 8 reservoir in the study area is a phase-I continuous accumulation process and the accumulation period is 105~125 Ma, which is the middle Early Cretaceous Epoch.

Author Contributions

Supervision, Z.R. and K.Q.; Writing—review & editing, G.Y. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by National Natural Science Foundation of China (No. 41630312), National Key R&D Projects (No. 2017YFC0603106) and National Major Projects (No. 2017ZX05005002-008).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Informed consent was obtained from all subjects involved in the study.

Acknowledgments

We appreciate encouragement and guidance from Zhanli Ren, during the formulation and drafting of this paper.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Location map of the study area: (a) Structural location map of the study area; (b) exploration and development area map of the study area.
Figure 1. Location map of the study area: (a) Structural location map of the study area; (b) exploration and development area map of the study area.
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Figure 2. Comprehensive analysis of rock characteristics of the Chang 8 reservoir: (a) Triangular map of rock classification; (b) distribution histogram of clay minerals.
Figure 2. Comprehensive analysis of rock characteristics of the Chang 8 reservoir: (a) Triangular map of rock classification; (b) distribution histogram of clay minerals.
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Figure 3. (a,b) Histogram of the porosity–permeability frequency distribution of the Chang 8 reservoir.
Figure 3. (a,b) Histogram of the porosity–permeability frequency distribution of the Chang 8 reservoir.
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Figure 4. Thin-section microscopic analysis of the casting of the Chang 8 reservoir in Zhenjing area: (a) Plastic deformation of mica, Well JH36, 1376 m, orthogonal light, 100×; (b) directional arrangement of mica, forming laminae, Well HH157, 2037 m, Orthogonal light, 50×; (c) chlorite film is attached to the surface of the detrital particles and filled inside the intergranular pores, Well HH92, 2267 m, SEM, 1300×; (d) leaf-like chlorite film is attached to the surface of the detrital particles, Well HH92, 2267 m, SEM, 430×; (e) book-like kaolinite filled in intergranular pores, Well HH78, 2400 m, SEM, 1400×; (f) flake-like and hair-like illite filled between detrital particles, Well HH107, 2436 m, SEM, 1000×; (g) honeycomb-like illite mixed layer, Well HH111, 2035 m, SEM, 3000×; (h) secondary enlargement of quartz, Well HH193, 2298 m, positive cross light, 100×; (i) Calcite pore cementation, Well HH193, 2299 m, orthogonal light, 50×; (j) dissolution pores formed by dissolution of feldspar, Well HH193, 2295 m, single polarized light, 50×; (k) calcite metasomatic feldspar, Well HH188, 2413 m, single polarized light, 100×; (l) intersecting microfractures, Well HH166, 2396 m, single polarized light, 50×.
Figure 4. Thin-section microscopic analysis of the casting of the Chang 8 reservoir in Zhenjing area: (a) Plastic deformation of mica, Well JH36, 1376 m, orthogonal light, 100×; (b) directional arrangement of mica, forming laminae, Well HH157, 2037 m, Orthogonal light, 50×; (c) chlorite film is attached to the surface of the detrital particles and filled inside the intergranular pores, Well HH92, 2267 m, SEM, 1300×; (d) leaf-like chlorite film is attached to the surface of the detrital particles, Well HH92, 2267 m, SEM, 430×; (e) book-like kaolinite filled in intergranular pores, Well HH78, 2400 m, SEM, 1400×; (f) flake-like and hair-like illite filled between detrital particles, Well HH107, 2436 m, SEM, 1000×; (g) honeycomb-like illite mixed layer, Well HH111, 2035 m, SEM, 3000×; (h) secondary enlargement of quartz, Well HH193, 2298 m, positive cross light, 100×; (i) Calcite pore cementation, Well HH193, 2299 m, orthogonal light, 50×; (j) dissolution pores formed by dissolution of feldspar, Well HH193, 2295 m, single polarized light, 50×; (k) calcite metasomatic feldspar, Well HH188, 2413 m, single polarized light, 100×; (l) intersecting microfractures, Well HH166, 2396 m, single polarized light, 50×.
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Figure 5. Analysis of clay mineral cementation in the Chang 8 reservoir [28]: (a) Relationship between chlorite content and porosity and particle size; (b) relationship between carbonate cement content and porosity.
Figure 5. Analysis of clay mineral cementation in the Chang 8 reservoir [28]: (a) Relationship between chlorite content and porosity and particle size; (b) relationship between carbonate cement content and porosity.
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Figure 6. Diagenetic evolution of the Chang 8 reservoir in the Zhenjing area.
Figure 6. Diagenetic evolution of the Chang 8 reservoir in the Zhenjing area.
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Figure 7. Analysis of thermal evolution history of Well HH155.
Figure 7. Analysis of thermal evolution history of Well HH155.
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Table
Table 1. Reservoir rock composition statistics of the Chang 8 oil layer group in the study area.
Table 1. Reservoir rock composition statistics of the Chang 8 oil layer group in the study area.
W 1Q (%) 2Feldspar (%) 3Debris (%) 4M (%) 5T (%) 6
OCPCTMRMPRSRT
ZJ535.213.617.831.415.83.41.6720.873.290.67
ZJ18407.51522.5143.5623.5490
ZJ1926.711.5517.228.7513.85.783.8323.415.5884.44
ZJ2125916.525.515.887.134.6327.635.7583.88
HH232812.6724.1936.8615.6241.821.42490.32
HH243210920146424580
HH2632.812.3816.528.8816.254.51.422.154.7588.53
HH10325.510.72030.716.37.95.8303.990.1
average29111626156424585
1 Well (W); 2 quartz (Q); 3 orthoclase (OC); plagioclase (PC); the total of feldspar (T); 4 magmatic rock (MR); metamorphic rock (MPR); sedimentary rock (SR); the total of debris (T); 5 mica (M); 6 the total of rock composition.
Table
Table 2. Table of vitrinite reflectance in Zhenjing area.
Table 2. Table of vitrinite reflectance in Zhenjing area.
WellLithologyDepth (m)Ro (%)
HH112Gray black mudstone2123.610.88
HH128-14Dark gray mudstone2294.660.91
HH128-15Dark gray mudstone2324.430.80
HH147Gray black mudstone2411.91.14
HH149Dark gray mudstone2354.350.95
HH156Dark gray mudstone1856.50.96
HH157Grey black oil shale2005.461.34
HH183Gray black mudstone2222.340.82
HH185Dark gray mudstone1794.830.88
HH198Black coal1819.241.00
Table
Table 3. Maximum paleo-geotemperature (acoustic emission) of Chang 8 reservoir.
Table 3. Maximum paleo-geotemperature (acoustic emission) of Chang 8 reservoir.
WellDepth (m)LayerT (°C)
HH1092335.12C81122
ZP12341.99C82109.3
HH1062418.63C82124.7
HH1072451.11C82125.3
Table
Table 4. Statistical table of X-ray diffraction data of Chang 8 clay minerals in Zhenjing area.
Table 4. Statistical table of X-ray diffraction data of Chang 8 clay minerals in Zhenjing area.
Sample NumberLayerI (%)I/SS (%)
HH78-2C81112620
HH78-12C81103420
HH78-21C8192120
HH78-31C8192420
HH78-41C8193020
HH92-4C8161420
HH92-9C816720
HH92-13C8191125
HH92-24C814520
HH92-32C817825
HH92-41C816920
HH107-03C81143620
HH107-11C81125730
HH107-17C81133920
HH107-26C81112820
HH107-35C81134120
HH107-39C81144315
HH107-52C81163820
HH107-65C82142420
HH107-78C82112615
HH107-91C82122015
HH107-104C82132015
HH109-3C8161320
HH109-14C817620
HH109-25C8161420
HH109-33C8172320
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Yang, G.; Ren, Z.; Qi, K. Research on Diagenetic Evolution and Hydrocarbon Accumulation Periods of Chang 8 Reservoir in Zhenjing Area of Ordos Basin. Energies 2022, 15, 3846. https://0-doi-org.brum.beds.ac.uk/10.3390/en15103846

AMA Style

Yang G, Ren Z, Qi K. Research on Diagenetic Evolution and Hydrocarbon Accumulation Periods of Chang 8 Reservoir in Zhenjing Area of Ordos Basin. Energies. 2022; 15(10):3846. https://0-doi-org.brum.beds.ac.uk/10.3390/en15103846

Chicago/Turabian Style

Yang, Guilin, Zhanli Ren, and Kai Qi. 2022. "Research on Diagenetic Evolution and Hydrocarbon Accumulation Periods of Chang 8 Reservoir in Zhenjing Area of Ordos Basin" Energies 15, no. 10: 3846. https://0-doi-org.brum.beds.ac.uk/10.3390/en15103846

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