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	JOPC 2012 Vol.14 Number 3
	2012, Vol.14 Num.3
	Online: 2012-06-01

	SPECIAL ISSUE ABOUT “Triassic Yanchang Formation in Ordos Basin” LITHOFACIES PALAEOGEOGRAPHY AND SEDIMENTOLOGY GEOCHEMISTRY AND SEDIMENTARY ENVIRONMENT GEOCHEMISTRY AND SEDIMENTARY ENVIRONMENTS PALAEOGEOGRAPHY AND MINERAL RESOURCES NEW TECHNIQUES AND NEW METHODS

SPECIAL ISSUE ABOUT “Triassic Yanchang Formation in Ordos Basin”

	269	Fu Jinhua, Li Shixiang, Liu Xianyang, Deng Xiuqin

		Sedimentary facies and its evolution of the Chang 9 interval of Upper Triassic Yanchang Formation in Ordos Basin
		Delta and lacustrine sedimentary facies are recognized from the Chang 9 interval of the Upper Triassic Yanchang Formation in the Ordos Basin.The deltaic plain distributaries channel sandbodies and deltaic front subaqueous distributaries channel sandbodies are high quality reservoirs.Based on the research of sedimentary facies，according to the single factor analysis and multifactor comprehensive mapping method，the sedimentary facies distribution of the upper and lower parts of Chang 9 interval of Yanchang Formation in the Ordos Basin were studied and mapped.The single factors include strata thickness，content of deep water sedimentary rocks，sandstone thickness，sandstone strata thickness ratio，authigenic chlorite development characteristics，paleontology characteristics，sedimentary structure combination characteristics.Discussion was made about the sedimentary evolution rule of the Chang 9 interval.The results show that the Chang 9 interval of Yanchang Formation was characterized by the deposition of multiple delta sedimentary system which surround the lake and have multiple water systems and multiple provenances.The meandering fluvial deltas were mainly developed in the northeastern Ordos Basin，and the braided fluvial deltas were mainly developed in the western Ordos Basin.The deltaic plain distributaries channel microfacies and deltaic front subaqueous distributaries channel microfacies were well developed.During the depositional period of the lower part of Chang 9 of Yanchang Formation，semi-deep custrine was only developed in the center of the Ordos Basin.During the depositional period of the upper part of Chang 9 interval of Yanchang Formation，the custrine basin began to expanded，lake shoreline moved to the land，lake area enlarged，and the semi-deep custrine deposition greatly developed.From the lower part to the upper part of Chang 9 interval of Yanchang Formation，the water depth changed from shallow to deep.Correspondingly，a set of oil shale with hydrocarbon generating potential are deposited in the study area.
		2012 Vol. 14 (3): 269-284 [Abstract] ( 2795 ) [HTML 1KB] [PDF 7736KB] ( 633 )

	285	Liu Haowei, Wang Jian, Liu Qunming, Zhao Xin

		Favorable reservoir distribution and its controlling factors of the Chang 8 interval of Upper Triassic Yanchang Formation in Jiyuan area，Ordos Basin
		The Chang 8 interval of the Upper Triassic Yanchang Formation is a typical low-porosity and low-permeability reservoir in Jiyuan area of the Ordos Basin.Researches of the main controlling factors，the formation conditions of high quality reservoirs and forecast of the favorable target have great significance for the exploration of potential oil and gas resources.Comprehensive analyses have been made on the sedimentary characteristics，property characteristics，rock thin sections，casting thin sections and so on.This paper discusses the distribution of favorable reservoir，the petrology characteristics，the pore texture and pore types，the physical property and the diagenesis types，which finally makes a comprehensive prediction of the distribution characteristics of favorable reservoir area.The results reflect that the lithic arkose is developed well and the cement，especially the ferrocalcite，is general in the Chang 8 interval of the study area.It is poor of the physical properties of the whole reservoir which is characterized by strong heterogeneity.The pore types mainly include residual intergranular pore and dissolution pore.The reservoir is controlled by the sedimentation，diagenisis and tectonism.Based on the above analyses，we forecasted the favorable reservoir in the Jiyuan area.
		2012 Vol. 14 (3): 285-294 [Abstract] ( 2293 ) [HTML 1KB] [PDF 2944KB] ( 641 )

	295	Feng Juanping, Li Wenhou, Ouyang Zhengjian

		Sedimentary characters and geological implication of turbidite of the Chang 6 and Chang 7 intervals of Upper Triassic Yanchang Formation in Huangling area，Ordos Basin
		Based on cores，thin sections，grain size analyses，the sedimentary characteristics of turbidite and its geological significance of the Chang 7 and Chang 6 intervals of Upper Triassic Yanchang Formation have been studied systematically in Huangling area of the Ordos Basin.The study results indicated that the turbidites are angular and sub-angular arkose and has the typical characteristics of turbidite deposition according to the results of grain size analysis.The turbidites are characterized by erosion surfaces，synsedimentary deformation structures，graded sequence and the Bouma sequences including ABC、AB、ADE、AE、CDE and A overlaying models which are the typical sedimentary characteristics of turbidite.The turbidite intervals mainly include two types，one is thin bedded and the other is medium-thick bedded.The tubidites are formed by the slump sediments of delta-front and can be divided into two sedimentary facies belts， i.e. the central and marginal microfacies.Turbidity sandstone is regarded as good reservoir formed in semi-deep lacustrine to deep lacustrine environments and becomes important oil-gas exploration target.
		2012 Vol. 14 (3): 295-302 [Abstract] ( 3800 ) [HTML 1KB] [PDF 3538KB] ( 739 )

	303	Tian Jingchun, Wang Wenzhi, Wang Feng, Wang Weihong, Zhang Jinquan

		Palaeoearthquake deformation structures of the Chang 6 interval of Upper Triassic Yanchang Formation and superimposed relationship between sandbodies in Huachi-Qingyang area of Ordos Basin
		The Chang 6 interval of the Upper Triassic Yangchang Formation in the Ordos Basin is one of the most important interval of the Mesozoic section.The Chang 6 interval are characterized by the development of reservoir sandbodies and multiple genetic types.During the sedimentary evolution of the Chang 6 interval of Yanchang Formation in Huachi-Qingyang area of the Ordos Basin，liquefaction deformation structures related with palaeoearthquake are developed extensively.The authors，based on many previous research results，by detailed description and observation of drilling cores of Chang 6 interval in the research area，studied the characteristics of liquefaction deformation structures systematicly.The structures mainly include: Load and sand ball structure，vibrational liquefaction curl deformation structure，sand invasion mushroom，liquefaction dike，such as liquefied swing structure.The difference of deformation structures formed by seismic events and gravity slumping are distinguished，mainly as: The advantage deformation direction of deformation structures，the existence of the sliding surface and the existence of uniform layer. Based on the above analyses，the vertical relationship between the delta front sandbody formed by normal deposition or slump turbidite sandbody and seismite sandbody are also studied which include two types: The overlay between seismic events sandbody and the normal deposition sandbody(delta front sandbody); the seismic events sandbody and slump turbidite sandbody formed from delta front.At the end，the origin models are established.
		2012 Vol. 14 (3): 303-310 [Abstract] ( 2769 ) [HTML 1KB] [PDF 2573KB] ( 861 )

	311	Wang Lan, Li Wenhou, Lin Tong, Wang Ruogu

		Diagenesis and its influencing factors of the Chang 6 interval of Upper Triassic Yanchang Formation in Ordos Basin
		The reservoir of the Chang 6 interval of Upper Triassic Yanchang Formation in the Ordos Basin，controlled by deposition and diagenesis，is characterized by low porosity and extraordinary low permeability.Its rock types mainly include feldspathic sandstone，lithic arkose and feldspathic litharenite.The sandbodies are rich in feldspar and low in quartz in the southern basin，but low in feldspar and rich in quartz and argillaceous matrix in the southwestern basin.The reservoir spaces are mainly residual intergranular pore and dissolution pore.The diagenetic types controlling the reservoir include compaction，cementation and dissolution，in which the chlorite cementation，feldspar dissolution and laumontite dissolution are favorable to form high quality reservoirs，while the compaction and carbonate cementation are the main contributors to decreasing the intergranular pore and reservoir compaction.There are two kinds of diagenetic facies models which are the Ansai and Huachi.The controlling factors on diagenesis are provenance，sedimentary environment，tectonic activity，hydrocarbon generation，meteoric water etc.，and the sedimentary environment controlled the sandbody development firstly，then influence the type of diagenesis and physical property of the reservoir.
		2012 Vol. 14 (3): 311-320 [Abstract] ( 2424 ) [HTML 1KB] [PDF 3264KB] ( 643 )

	321	Chen Fei, Hu Guangyi, Sun Lichun, Fan Tailiang, Gao Zhiqian, Yu Xitong, Pang Zhenglian, Li Rangbin

		Characteristics of sedimentary facies and evolution in sequence stratigraphic framework of the Upper Triassic Yanchang Formation in southern Ordos Basin
		According to the theory and approach of high resolution sequence stratigraphy and sedimentology，combining with core，drilling well，well-logging and seisimic data，detailed studies has been carried out on the Upper Triassic Yanchang Formation of the southern Ordos Basin.Totally five sequence boundaries，four 3rd and eleven 4th sequences were identified and the sequence stratigraphy framework was built up.Four types of sedimentary facies were developed in this area，including meandering fluvial delta，braided fluvial delta，lacustrine and deep-water gravity flow facies.The characteristic distribution of sedimentary facies in sequence stratigraphic framework was illustrated，and the law of evolution and distribution of sedimentary facies in sequence stratigraphic framework was established and the distribution of sandbodies in sequence stratigraphy was generalized.Taking the constantly deepening understanding of the sedimentary facies as the guidance，great breakthrough has been made in the petroleum exploration of the Yanchang Formation in the Ordos Basin.
		2012 Vol. 14 (3): 321-330 [Abstract] ( 2737 ) [HTML 1KB] [PDF 1049KB] ( 744 )

LITHOFACIES PALAEOGEOGRAPHY AND SEDIMENTOLOGY

	331	Wu Shenghe, Fan Zheng, Xu Changfu, Yue Dali, Zheng Zhan, Peng Shouchang, Wang Wei

		Internal architecture of alluvial fan in the Triassic Lower Karamay Formation in Karamay Oilfield，Xinjiang
		Based on abundant borehole data of close-spacing wells and outcrop analogue，this paper mainly deals with the hierarchical system of internal architecture of alluvial fan and establishes the corresponding architectural model in the Triassic Lower Karamay Formation in Karamay Oilfield.Three orders of architectural elements are divided in each subfacies belt within alluvial fan to further demonstrate its depositional complexity.Inner fan，which can be dividied into main trench，sheet-flood belt，and overbank，is characterized by main trench-fill and sheet-flood sand-gravel deposits with thin discrete fine layer，resulting in a kind of pano-connective sand-gravel body.And in the main trench，gravel body(gravel bar and gulley deposits)and debris flow deposits are developed.In the sheet-flood belt，sand-gravel deposits(gravel bar and gulley deposits)are developed.In the overbank belt，sandbody and fine deposits are developed.Middle fan，which can be divided into braided-stream belt and overbank，is characterized by the pattern of lateral apartment and vertical interbedding of channel sand-gravel deposits with overbank fine ones.Braided fluvial belt mainly consists of braided channels，which can be divided further into sandy bar and gulley deposit.Outer fan，which can be divided into runoff belt and marshy，is characterized by narrow-belt runoff channel sandbodies inlaid into overbank and/or marshy mudstone.
		2012 Vol. 14 (3): 331-340 [Abstract] ( 2532 ) [HTML 1KB] [PDF 2500KB] ( 744 )

	341	Song Jinmin, Luo Ping, Yang Shisheng, Zhai Xiufen, Zhou Gang, Lu Pengpeng

		Carbonate rock microbial construction of the Lower Cambrian Xiaoerblak Formation in Sugaitblak area，Tarim Basin
		There are three kinds of carbonate rock microbial(cyanobacteria)constructions in the Lower Cambrian Xiaoerblak Formation in Sugaitblak area，Tarim Basin，including microbial mounds and laminated constructions at the lower part，microbial reefs in the middle and upper part and stromatolite constructions at the top.The microbial mounds or laminated constructions are characterized by the stromatactoid cavities and laminated texture formed in the subtidal high energy zone.The constructions with a wide and stable occurrence were related with sticky microbial mats.The microbial dendritic or shrub structure and its cohesive action are developed in reefs，formed by microbial growth and sticky microbial mats.They are widely spread in the study area.There are two stages of microbial reefs.At the first stage macroscopic massive buildups are developed during the regression setting，while at the second stage，two stages of point reefs are developed during the transgression setting.The stromatolite constructions are formed during a more broad transgression setting，overlapped on the point microbial reefs，when the hydrodynamic force was stronger.This type of microbial buildups is formed by microbial bonding and characterized by stromatolite and oncolite.They are only developed at the top of Su Ⅱ，Su Ⅲ and Su IV sections.
		2012 Vol. 14 (3): 341-354 [Abstract] ( 3071 ) [HTML 1KB] [PDF 4959KB] ( 818 )

	365	Liu Jiaqiang, Mao Zhifang, Wang Xunlian, Zhou Hongrui, Gao Jinhan, Zheng Nan, Yu Lei

		Lithofacies palaeogeography of the Late Permian early Wuchiapingian in southeastern Yunnan Province
		Based on the quantitative and qualitative data of outcrops and well sections，according to the single factor analysis and multifactor comprehensive mapping method，the lithofacies palaeogeography of the Late Permian early Wuchiapingian in Wenshan，southeastern Yunnan Province，was studied and mapped.The research results are as following:（1）The Kangdian old land and the Pingma-North Vietnam old land was located to the western and southeastern of Wenshan during the Late Permian Wuchiapingian Age，and the sedimentary facies was distributed successively from the southwest to the northeast，including swamp-supratidal，intertidal，subtidal and restricted shallow sea facies;（2）The Kangdian old land and the Pingma-North Vietnam old land were the common material sources provider;（3）The sediments of Tianshengqiao area were deposited with large thickness，which constituted the depocenter;（4）The basin topographic center was located in the northeast of the study area；（5）Bauxites were mainly deposited in subtidal and restricted shallow sea area，and these sedimentary facies area should be the main perspective area for ore exploration.
		2012 Vol. 14 (3): 365-374 [Abstract] ( 2369 ) [HTML 1KB] [PDF 4315KB] ( 894 )

GEOCHEMISTRY AND SEDIMENTARY ENVIRONMENT

	355	Tang Xinping, Huang Wenhui, Deng Hongwen, Wang Wenyong, Mu Nana

		Formation mechanisms of the Paleogene lacustrine microbial carbonate rocks in Pingyi Basin，Shandong Province
		The origin of microbial carbonate rocks has become a hot issue of sedimentology，the Paleogene lacustrine carbonate rocks，however，are still rarely noticed and studied.In order to study the origin of the Paleogene lacustrine microbial carbonate rocks in the Pingyi Basin，field inspection as well as observations of plain microscope and scanning electron microscope，were carried out.The following results were obtained:(1)Microbial carbonate rocks in the studied section mainly consist of oncolites，thrombolites and stromatolites.(2)In each of these carbonate rocks，coccoid cells，sheet structures and clotted fabric were found，which illuminate the common microbial actions during their formation，including secretion，agglutination and calcification.(3)These 3 microbial carbonate rocks were formed in different environments，which play a great role in the development of textures and shapes of microbial carbonates，because microbial fabrics and microbial actions are sensitive to the instable lacustrine environment.（4）Based on the analyses of the common microbial actions and different forming environments，the genetic model of lacustrine microbial carbonate rocks was presented.
		2012 Vol. 14 (3): 355-364 [Abstract] ( 2809 ) [HTML 1KB] [PDF 2763KB] ( 703 )

GEOCHEMISTRY AND SEDIMENTARY ENVIRONMENTS

	375	Wang Yanyan, Zhang Biao, Shi Zhiqiang, Yi Haisheng

		Oxygen and carbon isotopic records of the Late Triassic Carnian pluvial event deposits in northwestern Sichuan Province
		Distinct lithological mutations from grey ooides，sponge reef limestone to grayish black shale，and then argillaceous siltstone are distinguished from the Upper Triassic Carnian marine sediments in the Mianzhu and Anxian counties in northwestern Sichuan Province，which is very similar to the sediments representing the Carnian pluvial event in western Tethys area.The stable oxygen and carbon isotopic compositions of the Carnian fossils of foraminifer，bivalve and brachiopodous shells and plant leaves are analyzed using laser micro-sampling technique.The analysis results indicate the slightly lowerδ¹⁸O values and remarkable lower δ¹³C values of the Upper Carnian than those of the Lower Carnian.Its believed that the isotopic compositions reflect that fresh water input into the Paleotethys ocean.We suggest that the Carnian pluvial event severely affected the deposits in the eastern Tethys area.The freshwater input in the humid conditions is one of the causes that triggered the periodic deaths and finally disappearing of the sponge reefs in the study area.
		2012 Vol. 14 (3): 375-382 [Abstract] ( 2894 ) [HTML 1KB] [PDF 1659KB] ( 805 )

PALAEOGEOGRAPHY AND MINERAL RESOURCES

	383	Zhang You, Hou Jiagen, Li Na, Sun Haihang

		Reservoir characteristics and controlling factors of the lower part of Member 1 of Paleogene Shahejie Formation in Tang 34 Block，Huanghua Depression
		Based on core observation and sedimentary facies analyses，the reservoir characteristics of the lower part of Member 1 of Paleogene Shahejie Formation in Tang 34 Block and the main geological factors influencing its physical properties are systematically studied by using a large number of rock thin sections，thin sections，porosity and permeability properties and mercury-injection data, etc.The results indicate that the lower part of Member 1 of Paleogene Shahejie Formation reservoir belongs to middle to low porosity，low to extra-low permeability and fine throat reservoir.Reservoir properties of the study area are dominated by diagenesis，and combination pattern of sandstone and mudstone.Among them，carbonate cement，silica cement and clay mineral transformation are the main factors leading to the poor physical properties，while the corrosion produces substantial secondary porosity and provides favorable reservoir space.Authigenic kaolinite is the dissoluted product of feldspar and debris.Vertical distribution of reservoir properties are controlled by combination of sandstone and shale.
		2012 Vol. 14 (3): 383-392 [Abstract] ( 2389 ) [HTML 1KB] [PDF 2740KB] ( 610 )

	393	Sang Qin, Wei Yong, Cheng Chao, Huang Jing, He Shukun, , Guo Gui′an, Wu Changlong, Peng Zuoyuan

		Distribution of palaeokarst water system and palaeogeomorphic unit characteristics of the Permian Maokou Formation in southern Sichuan Province
		The Permian Maokou Formation in southern Sichuan Province is a set of thickly stable bioclastic limestone with dense and brittle matrix.The Dongwu Movement of the late Middle Permian leads to the development of the palaeoweathering crust-type karst on the apex face of Maokou Formation in this area. Palaeokarst water system controls the development and evolution of the palaeokarst.After studying the methods of recovering palaeogeomorphology，this paper analyzes all kinds of data to recover the palaeogeomorphology with impression method and researches the characteristics of the palaeokarst water system.On this basis，four second order landform units，such as karst platform，karst abrupt slope，karst gentle slope and karst basin and ten third order units，such as hill depression，karst trough valley and peak forest basin are subdivided，combined with eroding features of the upper surface，properties of sediments，configuration of geomorphology and data of drilling well and seismic.At last，the karst features of each unit are analyzed.So the research findings will provide reliable target for the reservoir predication in the next step.
		2012 Vol. 14 (3): 393-402 [Abstract] ( 2032 ) [HTML 1KB] [PDF 2204KB] ( 629 )

NEW TECHNIQUES AND NEW METHODS

	403	Qiao Yanguo, Shi Zhiqiang, Wang Yanyan, Zhang Biao

		The Late Permian-Early Triassic cyclostratigraphy in Shangsi section of Guangyuan area，Sichuan Province: Implications for P-T geological event based on wavelet analysis
		Based on the analysis of the GR energy spectrum collected from the Upper Permian to Lower Triassic carbonate rocks in Shangsi section at Guangyuan area，Sichuan Province，it was indicated that the sedimentary layers are controlled by Milankovitch cycles，whose scale ratio was 410：102.5：42.6：21.5.During the Late Permian，the Shangsi area was in a deep-water environment of the paleo-Tethys and the deposition rate was low to 5 cm/ka.During the P-T transitional period the tectonic movement was strong and terrestrial and marine fauna experienced mass extinction.At the same time，weathering rate increased sharply because of the acid rain and lack of terrestrial vegetation and mass terrigenous material fluxed into shallow sea in turn，which resulted in a rapid deposition rate of 25cm/ka in Shangsi section.The rapid rate of deposition displayed a strong influence on marine ecosystems，that is，it restrained the diversity of marine fauna and delayed the resuscitating of marine ecosystems.The cyclicity of the latest Permian sedimentary record was more obvious and stable in Shangsi section.However，the periodicity turned to be labile when it came to the Early Triassic.We concluded that the accelerated deposition rate and deteriorated sedimentary cyclicity were triggered by the turbulent paleoclimate and mussy marine environment.The perturbation of the terrestrial realm contributed to the change of marine conditions，which might be one of the major reasons for the marine ecosystem recovering relatively slowly in the Early Triassic.
		2012 Vol. 14 (3): 403-410 [Abstract] ( 2413 ) [HTML 1KB] [PDF 1892KB] ( 910 )

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