机械工程学报

Microbial Composition and Significance of Lower Pliocene Sedimentary Globigerinid Limestone Facies in the East Java Basin

MoZhen GUO, FuLiang LÜ, FuDou Hou, Lin LI, TaoTao YANG, Dong LI

2020, 38(4): 747-758. doi: 10.14027/j.issn.1000-0550.2019.070

[Abstract](247) [FullText HTML] (124)

Abstract:

Globigerinid limestone is well developed in the Pliocene Series of the East Java Sea Basin, and has become one of the main exploration targets in this area. Many oil and gas fields have been discovered in Globigerinid limestone reservoirs. Globigerinid limestone is dominated by Foraminifera tests, particularly of the planktonic genus Globiegerina, which may form up to 50 percent of the limestone. Pore space in the limestone comprises foraminiferal test pores and intergranular pores. The porosity of the grainstones may exceed 50 percent, which represents a high⁃quality reservoir. Due to the lack of reliable facies markers, however, opinions differ as to its origin and depositional environment, seriously affecting knowledge of the control factors and distribution of such reservoirs, and limiting exploration in the area.This study examined the depositional environment of Globigerinid limestone based on thin sections of casts, core observations and microbial data, together with the ecological environment of planktonic Foraminifera. It is concluded that the Globigerinid limestone consists of different species, including shallow⁃water species, middle⁃water species and deep⁃water species, as well as tropical⁃, subtropical⁃ and temperate⁃water species. Globigerina bulloides and Globorotalia menardii were found in large quantities, indicating the existence of upwelling. The combined characteristics of the paleosedimentary environment and paleocurrents indicate that the formation of Globigerinid limestone in the study area was closely related to upwelling, and occurred in two stages: firstly, the planktonic foraminiferal species living in the shelf slope and middle ocean were deposited on the sea bed after their death. The bottom current and upwelling current carried the different species to the shelf margin where the energy is weakest and they accumulated there, influenced by offshore currents. Secondly, they were winnowed and transported by waves or storm⁃associated currents, eventually forming one of the primary high⁃quality reservoir exploration targets in the East Java Bain.

Quantitative Paleotemperature Reconstruction of Late Cretaceous Nenjiang Formation in Songliao Basin: A case study of the LD6⁃7 Core

JianMing QIN, JiQuan CHEN, Yuan GAO, DangPeng XI, ChengShan WANG

2020, 38(4): 759-770. doi: 10.14027/j.issn.1000-0550.2019.079

[Abstract](193) [FullText HTML] (105)

Abstract:

The Nenjiang Formation Members 1+2 (K₂n¹⁺²), which formed during the Late Cretaceous in the Songliao Basin, is a lacustrine mudstone deposition, on which abundant terrestrial paleoclimate information is preserved. This study examined mineralogy, as well as the major elemental and trace elemental geochemistry, of K₂n¹⁺² and attempted to reconstruct the terrestrial paleotemperature quantitatively. Results show that the bulk rock mineralogy is mainly composed of clay mineralogy (46.2% average), minor quartz (21.7% average). and negligible plagioclase and K⁃feldspar. Values of the Chemical Index of Alteration (CIA, 63 average), Mafic Index of Alteration for Oxidative condition (MIA⁃O, > 64), Plagioclase Index of Alteration (PIA, > 53), and Weathering Index of Parker (PIA, > 44) indicate medium chemical weathering intensity of K₂n¹⁺². The analysis of the sediment chemical composition by provenance, transportation, and diagenesis satisfies the precondition of calculating the annual mean temperature (MAT) by element geochemistry: (1) High annual precipitation rate (> 400 mm/yr), (2) moderate physical erosion rate, (3) no significant sedimentary sorting and recycling, (4) weak diagenesis, and (5) Chinese acid rock as the protolith. This study suggests a MAT of ~14.19 °C based on the τ_Na-MAT transfer function from K₂n¹⁺² of the LD6⁃7 core in Songliao Basin. This estimated MAT is consistent with previous research results, which is a subtropical climate. It is proven that the method of reconstructing paleotemperature by means of element geochemistry is feasible for K₂n¹⁺² of the LD6⁃7 core in Songliao Basin, which can provide a reference for the quantitative study of the terrestrial paleoclimate concerning "deep time" in the future.

Provenance Analysis and Reconstruction of the Climate Change for the Holocene Loess profile in the Zhuanglang Country of Gansu Province, China

ZhaoDuo WANG, ChunChang HUANG, JiangLi PANG, AnNa LIU, YaLi ZHOU, XiaoChun ZHA

2020, 38(4): 781-789. doi: 10.14027/j.issn.1000-0550.2019.077

[Abstract](232) [FullText HTML] (85)

Abstract:

Through detailed field investigation of the loess area on the western side of Liupan Mountains, a loess paleosol profile with a thickness of 3 m was found on the flat ground of the third⁃level terrace of the Shuiluo River in northern Zhuanglang county, Gansu province. The paleosol provenance analysis, paleoclimate restoration, and loess reconstruction were determined. Based on the observation and analysis of the macroscopic characteristics of the soil and sedimentology of the profile, 170 samples were obtained from top to bottom and continuously sampled every 2 cm. Physical and chemical index analysis and OSL dating, particle size component end⁃member analysis, and time⁃process wavelet analysis were performed in the laboratory. The results show that four endmembers can be identified from the Holocene loess paleosol in the study area, and it represents the weathering and pedogenesis under the action of the East Asian summer monsoon after sediment deposition, the late eluviation dynamic characteristic, northwest winter monsoon, and regional north wind. Furthermore, the summer monsoon end member components on the Holocene time scale with oscillation periods of 0.3 ka, 0.7 ka, 1.2 ka, 1.5 ka, 1.8 ka, and 2.4 ka can be divided on the corresponding time scales. The results of this study are of great significance for promoting quantitative analysis of the Holocene paleosol provenance in the Loess Plateau of the Liupan Mountains and restoring and reconstructing the climate change laws of the region. It can also provide reference materials for the restoration and reconstruction of the Holocene climate change process and regional comparison in other regions.

Lithofacies and Sedimentary Model of Tidal⁃dominated Estuary: A case study of LU interval from Upper Cretaceous Napo Formation, northern Oriente Basin, Ecuador

Yang LI, ZhenKui JIN, XiaoEr ZHU, ShuTing SHI, Kun YUAN, Rui LI, JinYi WANG

2020, 38(4): 826-837. doi: 10.14027/j.issn.1000-0550.2019.068

[Abstract](137) [FullText HTML] (107)

Abstract:

A predominantly tidal estuary is the main reservoir type in the Upper Cretaceous Napo Formation, northern Oriente Basin, Ecuador, although its identification, lithofacies and sedimentary distribution are unclear at present. Establishing a reliable sedimentary model of the estuary is of great significance for predicting the presence of oil and gas reservoirs. A comprehensive analysis of the core, including grain size, well logging, thin section and geochemical data, found that: (1) The combination of lithofacies, geochemical and vertical sequence characteristics indicates the development of a tidal⁃dominated estuary⁃shelf sedimentary system. (2) The tidal⁃dominated estuary contains middle⁃and outer estuary subfacies. The middle estuary contains tidal channels with an overbanked mixture of flat and salt⁃marsh microfacies, the distribution shown as bell-shaped on the logging curve. Along the axis of the outer estuary, tidal sand bar and upper⁃flow⁃regime sand flat microfacies were developed, producing a box⁃shaped logging curve. Muddy tidal flat microfacies occur on both flanks of the outer estuary, shown as finger⁃shaped logging curve. A muddy shelf and storm⁃formed glauconitic sheet sand developed under the normal wave base. (3) The paleogeography of the study area leans towards the southwest. Tidal channels developed in the middle estuary in the northeast. The southwestern channel gradually widened and north⁃south tidal bars were distributed along the axis of the outer estuary. A sheet⁃like muddy tidal flat developed on the flanks of the estuary.

Sequence Architecture and Reservoir Distribution of the Cretaceous Mishrif Formation in M Oilfield, Iraq

FengFeng LI, Rui GUO, LiFeng LIU, YiChang YU, ShiQi SONG

2020, 38(4): 838-850. doi: 10.14027/j.issn.1000-0550.2019.078

[Abstract](140) [FullText HTML] (110)

Abstract:

In order to clarify the distribution rules and control factors of the Cretaceous Mishrif Formation carbonate reservoir in M oilfield, Iraq, based on the core, logging, and cast thin sections, lithofacies analysis was carried out under the control of the regional third⁃order sequence. The Mishrif Formation was divided into six quaternary sequences (SQ1⁃SQ6) by identifying the exposed interface of the carbonate rock, the lithologic transition surface, and the maximum flooding surface. The result shows that there were four types of sequences: the exposure of the restricted platform, the exposure of the shoal, the non⁃exposure of the shoal, and the long weathering and erosion. Different sequences had different sedimentary environments, system tracts, sequence boundaries, and exposure times. The exposure of the shoal developed high⁃energy sediments, such as the rudist shoal, bioclastic shoal, and front shoal in the high system tract. The exposure boundary of the restricted platform was characterized by the formation of thin carbonaceous mudstone. The spot shoal located mainly in the high system tract and the dense cemented layer formed in the late stage of the high system tract could be used as a good barrier. The sequence boundary for the non⁃exposure of the shoal was the lithological transition surface, and the reservoir mainly formed in the tidal channel and the bioclastic shoal in the high system tract. The long weathering and erosion developed bioclastic shoal in the high system tract, and the weathered breccia zone in the low system tract could be the high⁃quality barrier. In addition, the dolomitization associated with the bioturbation effectively improved the properties of sediments in the lagoon of the transgressive system tract, forming a number of thin reservoirs.

Determination Method and Application for the Conversion Period of Fault⁃caprock Configuration Leakage and Sealing

Guang FU, JinMeng DONG, WanTao PENG

2020, 38(4): 868-875. doi: 10.14027/j.issn.1000-0550.2019.090

[Abstract](381) [FullText HTML] (237)

Abstract:

In order to study the control effect of faults on hydrocarbon accumulation in petroliferous basins, we examine the fault⁃caprock configuration leakage, sealing mechanism, and its transformation period. By determining the growth period of connection and the period for which the fault ancient displacement pressure is equal to the reservoir ancient displacement pressure, we can confirm the leakage and sealing transformation period of the fault⁃caprock configuration. We then apply the results to fault F1 and the east 2 mudstone caprock configuration in the Nanbao No. 5 structure, Nanpu Sag, Bohaiwan Basin. In lines L1, L3, L4, L5, L6, L7, and L9, the F1 fault and east 2 mudstone caprock configuration are in a closed condition, there is no leakage, and it is beneficial to oil and gas accumulation and preservation. In line L2, the F1 fault and the east 2 mudstone caprock configuration began to shift from closure to leakage around 16 Ma and from leakage to closure at 7.4 Ma. In line L8, the F1 fault and east 2 mudstone caprock configuration began to shift from closure to leakage around 13.6 Ma and for leakage to closure around 8.0 Ma. At present, in lines L8 and L2, the F1 fault and east 2 mudstone caprock configuration are in the closed condition, and leakage time is relatively long, which is beneficial to oil and gas accumulation and preservation in the east 2 reservoir. This is consistent with the distribution of oil and gas in east 2 near the F1 fault of the Nanbao No. 5 structure at present, showing that this method is feasible for determining the conversion period between fault⁃caprock configuration leakage and closure.

Lithofacies Palaeogeography and Source Rock of the Late Triassic in the Qiangtang Basin

WangZhong ZHAN, FuWen TAN

2020, 38(4): 876-885. doi: 10.14027/j.issn.1000-0550.2019.093

[Abstract](93) [FullText HTML] (46)

Abstract:

Lithofacies palaeogeography of the Late Triassic in the Qiangtang Basin was the basis for this study of the sedimentary evolutionary history and an evaluation of its hydrocarbon resources. By means of stratigraphic division and correlation, sedimentary facies analysis and sedimentary sequencing, combined with the most recent geological investigation and research data, the palaeogeographic lithofacies environment of the Late Triassic in the Qiangtang Basin was reasonably restored, and the basic characteristics of the hydrocarbon source rocks of the Late Triassic are discussed. During the Late Triassic, the Qiangtang Basin was subjected to both collisional orogenic and compression forces in the north, and the opening of the middle Tethys oceanic basin in the Bangong Lake⁃Nujiang River in the south. The northern Qiangtang foreland basin gradually contracted and disappeared, while the southern Qiangtang Basin began to receive sediment as a result of intracontinental rifting (subsidence). The three provenance areas in the basin during this period are the Kekexili orogenic belt in the north of the basin, the island chain uplift belt in the east, and the central uplift belt. At the northern and eastern margins of the central uplift zone and in the central and eastern parts of the basin, littoral⁃delta facies deposits of marginal facies were formed. Stable carbonate rocks were deposited in the central and western areas of the basin. In the southern part of the South Qiangtang Depression, shallow shelf deposits gradually deepened upward. Hydrocarbon source rocks that were developed in the gently sloping sedimentary facies zone of carbonate rocks during this period have the basic characteristics of high residual organic carbon, high maturity and low residual hydrocarbon generation potential. From a comprehensive evaluation of the medium⁃to⁃better source rocks, mainly generating gas, it was inferred that the Doggercuoren area is the preferred target area for future oil and gas exploration.

Geochemical Characteristics and Geological Significance of the Black Rock Series at the Bottom of the Mufushan Formation in the Lower Cambrian, Lower Yangtze Area

YangHong HOU, ZhiHong KANG, ChenJun ZHAO, XuDong YU, EnBo WANG

2020, 38(4): 886-897. doi: 10.14027/j.issn.1000-0550.2019.076

[Abstract](205) [FullText HTML] (146)

Abstract:

In order to investigate the provenance and tectonic setting for the source of the organic⁃rich black rock series from the Lower Cambrian Mufushan Formation in the Lower Yangtze area, samples were collected systematically from the bottom of the Mufushan Formation in the Mufushan section in Nanjing, and geochemical tests and analysis were conducted on the samples. The chemical alteration index (CIA) and Th/U values are important chemical parameters for judging the degree of weathering in the source region. The CIA and Th/U values of the sample indicate that the source rock has experienced weak⁃medium intensity weathering, and the Th/Sc⁃Zr/Sc diagram shows that the black rock series in the area has not experienced sedimentary recirculation. By analyzing the ratio characteristics of the major elements, the distribution patterns of rare earth elements (REE), δEu, (La/Yb)N, La/Th⁃Hf, and the La/Yb⁃∑REE diagrams, we find that the source rock of the Mufushan Formation black rock series is mainly upper crust felsic rocks such as granite and sedimentary rocks rich in felsic minerals, and there are mixed rocks of basic rocks. Considering the source property, geological age, and tectonic evolution process of the South China continent, the granite composition in the source rocks is mainly composed of magmatic rocks that formed during the Neoproterozoic period, and the source area is Ghiangnania. By analyzing the diagrams of K₂O+Na₂O⁃SiO₂, K₂O/Na₂O⁃SiO₂/Al₂O₃, La⁃Th⁃Sc, Th⁃Co⁃Zr/10, and Th⁃Sc⁃Zr/10, we determine that the tectonic setting of the black rock source area of the Mufushan Formation is the passive continental margin.

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