The Paleogene Hothouse climate significantly affects the paleoenvironment and regional climate of lake basins globally. A Hothouse climate is recorded in the Paleogene Shuangyang Formation within Yitong Basin. The first member of the Shuangyang Formation forms excellent hydrocarbon source rocks. Under the influence of a Hothouse climate state during the Paleogene, the paleoenvironmental controls on organic matter accumulation within the Shuangyang shale remain to be fully understood. This study employs an integrated analysis of mineralogy, lithology, and organic/inorganic geochemistry to divide the Shuangyang shale into three parts: lower, middle, and upper. Paleoenvironmental conditions for each part are reconstructed using diverse geochemical proxies, and the differential accumulation of organic matter is explored. The findings indicate that the Shuangyang shale is rich in quartz mineral (average = 49.35 %), with the proportion of organic-rich shale (total organic carbon, TOC >= 2 wt. %) accounting for 60 %. A reducing environment and suitable salinity are the basic conditions for the preservation and accumulation of organic matter. The development of organic-rich shale is driven by a humid paleoclimate, strong terrigenous detrital concentration, and high paleoproductivity. Organic matter accumulation in the lower and upper parts is driven by middle-high paleoproductivity and strong terrigenous detrital concentration, respectively. The stable development of organic-rich shale in the middle part is driven by a humid paleoclimate, moderate terrigenous detrital concentration, and medium paleoproductivity. This study reveals the driving mechanisms behind organic matter differential accumulation in various sedimentary paleoenvironments, providing valuable insights for lacustrine shale oil exploration.

Shale oil exploration has achieved a breakthrough in the first member of the Paleogene Shuangyang Formation in the Luxiang fault depression of Yitong Basin. However, the characteristics and evolution of medium-high maturity siliceous shale in this lacustrine basin remain to be fully understood. The coupled evolution of organic matter (OM), quartz, different types of clay, and pore space in the Shuangyang shale is investigated considering differences in pore structure compared to marine and continental shales with low-medium maturity. The Shuangyang shale (depth greater than 3400 m), mainly argillaceous-rich siliceous shale, significantly influences pore volume and specific surface area through the effect of mesopores (2-50 nm). Ink-bottle-shaped pores are dominated by OM pores and dissolved interparticle pores. Parallel plate-shaped pores are predominantly OM shrinkage fractures and intracrystalline pores. Shale pore volume and specific surface area decrease with increasing kaolinite content. The presence of chlorite in foliated form and the ordered distribution of illite/ smectite mixed layers (I/S) enhances the specific surface area. Pore overpressure from smectite dehydration during the transformation of I/S to illite helps preserve the primary pores. Pore volume increases as I/S decreases and illite increases. In the middle-high maturity stage (Ro = 1.24-1.34 %), OM content emerges as the primary factor influencing pore formation. The coupling effect of siliceous mineral skeleton (quartz) and overpressure is crucial for pore preservation. This study expands our understanding of shale pore systems in argillaceous-rich siliceous shale within the medium-high maturity range and reveals significant discrepancies in shale pore evolution concerning OM and mineral components.

研究区基岩储层为变质岩,岩性复杂,利用测井资料预测基岩岩性成为亟需解决的技术难题.为此,从测井岩性解释出发,对基岩岩性进行分析归类,结合多种测井曲线交会分析,寻找对不同基岩岩性响应特征敏感的测井曲线,依据交会图中不同岩性关键测井参数的变化,给出不同岩性的测井响应区域,进而区分不同的岩性.最后运用叠前、叠后多属性反演技术开展基岩岩性识别.

The lithology and formation age of basement rocks are significant for the understanding of the nature of basin architecture, evolution and the potential of hydrocarbons of a basin. In this study, the basement lithology of the Cenozoic Yitong Basin is investigated through the petrological analysis of cores, cuttings, and thin sections. The results suggest that the basement rocks of the Yitong Basin are mostly composed of unique igneous rocks that are different from nearby basins’ sedimentary and metamorphic basement. The igneous rocks are dominated by intrusive monzonite granite and alkali feldspar granite. Additionally, U–Pb zircon geochronology of basement samples by LA-ICP-MS and the geological interpretation of apparent resistivity data indicate that the igneous basement in major part of the basin was mainly formed by a lateral intrusion of granite into the Permian sedimentary stratum in the Yanshanian period from 177 to 170 Ma. The results also reveal the two-layer basin architecture with coal-bearing Carboniferous–Permian strata below the igneous basement covered with Tertiary sediments, thus providing a new geologic horizon for deep natural gas exploration in the older coal-bearing sedimentary rocks beneath the current igneous basement.

Located in the middle south segment of the Jia-Yi graben and northeast Yitong Basin,the Shulan Basin is a NE-trending narrow faulted basin.Previous studies only carried out preliminary geological survey in the Shulan Basin,whereas researches on the structural characteristics and evolution of the basin were insufficient.This paper focused on the correlations of Cenozoic strata between the Shulan Basin and Yitong Basin on the basis of all research data collected,e.g.,sporopollens and stratigraphy.Moreover,the electrical and seismic profiles from the Shulan Basin suggest that the southern section of the basin shows half-graben type structure,the middle basin shows graben type structure,and the northern section becomes increasingly deep step by step southwestward.In addition,the basement of the basin is slightly different in different parts and characterized by upper Permian Yangjiagou Formation,Cretaceous granites and Cretaceous strata in the southern,middle and northern parts,respectively.A comprehensive analysis suggests that the Shulan Basin underwent three tectonic evolutional stages,e.g.,the initial faulted phase(Early Paleocene),the main faulted phase(Pale ocene-Oligocene),and the extrusion-reversion phase(Oligocene-Miocene).

Drilling has shown that there is a large petroleum reserve in the Sheling Formation in the Liangjia area of the Yitong Basin from reservoirs of the nearshore subaqueous fan facies. To reduce the risk associated with exploration, the updip pinch-out or isolated sandstone in the nearshore subaqueous fan should be identified and described. Analysis of the 3D seismic reflection, instantaneous phase and acoustic impedance was conducted to identify and interpret the sandstone. Seismic reflection, instantaneous phase and acoustic impedance alone can not clearly identify the updip pinch-out of sandstone in the nearshore subaqueous fan. However, the combination data of acoustic impedance and the instantaneous phase has better detectability (it indicates the ability for identifying sandstone distribution) and is a more reliable indicator of the sandstone distribution than these seismic data alone. The sandstone and the updip pinch-out of the sandstone in the nearshore subaqueous fan can be identified more clearly and directly by the combination data of acoustic impedance and instantaneous phase than the 3D seismic reflection data alone. Combined analysis of the acoustic impedance and instantaneous phase in the sedimentary system is a valid approach for identification and description of the updip pinch-out sandstone or the isolated sandstone that can reduce the risk associated with exploration of lithological traps. (C) 2011 Elsevier Ltd. All rights reserved.

The Yitong Basin, a typical strike-slip basin, is part of the northern segment of the world-famous Tanlu strike-slip fault area in China. Research is needed to understand how the strike-slip tectonic environment affects the development of structures and depositional systems within the basin. The aim of this paper is to analyze how the right-lateral strike-slip movement of the northwestern boundary faults in this region controls extensional faulting, and to analyze differences in two main sedimentary sequences (termed SYSQ1 and SYSQ2) that result from strike-slip movement. The study is based on geological and geophysical data. The following conclusions are drawn: (1) The two periods of strike-slip movement of the boundary fault generated two episodes of extensional fault inside the basin. The extensional faults have a characteristically episodic activity related to the episodic strike-slip movement. The extensional faults have small fault throw, and their activity lags behind the strike-slip movement of the northwestern boundary faults. (2) The strike-slip movement of the boundary faults generated the extensional faults inside the basin and changed the locus of depocenters, with complimentary changes in the paleogeomorphology and in the distribution of depositional facies. It is this strike-slip movement that caused the differences in sedimentary and structural characteristics between sequences SYSQ1 and SYSQ2. (C) 2012 Elsevier Ltd. All rights reserved.

Recently, the researches on structure controls on sandbodies have provided a new method for predicting petroleum reservoirs. The Yitong ((sic)) graben is situated in the northern section of the Tan-Lu ((sic)) fault system in eastern China. It was characterized by dual properties of strike-slip and extension in Cenozoic. Two types of intrabasinal structures were identified as oblique fault and transverse uplift in the graben. The oblique faults arranged en echelon in plain and locally presented negative rosette structures on seismic profile, so they were closely derived from strike-slip movement of the northwestern boundary faults. Moreover, these oblique faults were divided to five zones. The three transverse uplifts, located corresponding to flattened southeast boundary faults, were mainly originated by displacement-gradient folding due to segmental extensional activities of southeast boundary faults. The large-scale sandbodies of subaqueous fan facies and fan delta facies had developed at the two types of intrabasinal structure zone. Based on analyzing the seismic facies, logging facies and seismic attribute extractions, and on discovering many incised valleys at the oblique fault zones, the two types of intrabasinal structures were revealed to have conducted drainage entering basin and further dispersing, and to have consequently controlled the development and distribution of sandbodies.

The bedrock buried hill is a mountainous peak formed by the arching up of the basement rocks in a sedimentary basin. The mountainous peak could be the ancient buried hill, known as buried-hill drape structure, present before the formation of sedimentary cover. In contrast, the late-formed buried hill comes into being after the deposition of the sedimentary cover due to the fold, fracture, volcanic eruption and other tectonic events in later stages. No matter what type of buried-hills, the reservoiring is comparable, with the dissolved pores formed by weathering and leaching of bedrocks as the reservoir, and the overlying sedimentary rocks as the source rocks and cover rocks. These are known as ancient reservoir but newborn sources. We present here, however, a different situation of the buried hill in Yitong basin in northeastern China. The bedrock in Yitong basin is the Yanshanian granite, which occurs as a sill underlain by Paleozoic marine strata of low electric resistivity. A right-lateral strike-slip extrusion of Yitong basin in Himalayan period leads to the diapiric ascent of the Lower Paleozoic argillite, which in turn causes the arching up of the granite bedrock to form the buried hill. It is concluded, on the basis of drill No. Chang 37, that the natural gas is sourced from Carboniferous-Permian argillite, and reservoirs in the cracks developed beneath 300m of the granite sill, with the upper part of granite as the cover.

在伊通盆地新牛代沉积岩层下的花岗岩储层中发现了烃类C藏,其气源岩与上覆新生界烃源岩无关.通过对该地区的电法、地震、烃源岩进行分析,结合邻区地表露头,认为伊通盆地深部存在石炭·二叠纪地层,具有较好的生烃能力,其上部覆盖较厚的花岗岩,既是良好的盖层,义是优质的储层,形成有利的牛储盖组合.依据基底岩性特征,结合基岩同位素测年资料,建立了盆地基底结构成因模式,对东北地区的构造演化历史、古地理研究及油气勘探具有重要意义.

This paper first divides the stages of diagenesis by thermal evolution of organic and the distribution of clay for different structural zones in Chaluhe depression.Then,it analyzes the factors affecting diagenesis based on the analysis of structure,sedimentary facies,clay distribution,chemical property of underground water,and the micro character by thin section and SEM.The results show that the depth of the same diagenesis stage in the different sub-structures becomes shallow from southwest to northeast and that there are three secondary porosity zones in Liangjia,Wanchang and Botai district,two secondary porosity zones in Gudian slope,but not clear in Xin′anpu sub depression.They also reveal that the secondary porosity zones are greatly related with organic acid,unconformity surface,ground water infiltration,and the alkalescence corrosion in deep formation and the percentage of porosity damaged by compaction and cementation is different within different district and facies.

Based on the boundaries and interior depositional evolutions of second-order sequences in the continental extensional basins and their coupling relations with the tectonic actions and subsidence histories,the Paleogene strata in the Cenozoic basins of the eastern China can be divided into 4 or 5 second-order sequences.The boundaries of those second-order sequences generally belong to the regional angular unconformities.The fossil assemblages and sedimentary characteristics of a single second-order sequence in upper interface are much different from the underlying ones.Some large-scale low-stand fans are usually developed at the bottom of sequence,and a large-scale transgress-regressive succession is presented in the second-order sequences.The second-order sequences are corresponding to the episodic stages of tectonic evolution,and their boundaries are resulted from the tectonic affairs such as reverse of tectonic,tilting and rotating of fault block,intruding of magma,breaking forth of volcanic and change of tectonic stress field.The second-order sequences in the continental extensional basins are controlled by the regional tectonic actions.So,the genetic relationship of sequences with tectonic actions can be used to determine the second-order sequences.

Yitong graben is a strike-slip and extensional basin in Meso-Cenozoic,the eastern China.After seismic profile explaining and well core observing,a large-scale sublacustrine fan complex with an area of 400 km2 and thickness of 250 m was identified at the bottom of Member Yong1,Paleogene of the graben.As the low-stand fan of three-order sequence Yong1,It was mainly composed of fine to middle-grained sandstone and a little gravel stone which bore many sandstone breccias,mudstone shivers or muddy gravels together with various pene-contemporaneous deformation structures such as convolute bedding,liquefied distortion,ball and pillow structure,microfault etc.,so it was determined to be dominantly subaqueous debris flow deposit due to slump.After underlying Sheling Formation had developed,the research area suffered reverse tectonic extrusion,denudation,and then violent normal-faulting accompanied with volcano breaking forth and earthquake activity.The fan at Member Yong1 was synthetically caused by above tectonic affairs,and it indicated that a new episode of tectonic subsidence occurred and that the garben came into a new evolution stage.Owing to the farraginous lithology composite and very poor reservoir capacity,this sublacustrine fan was not favorite to oil and gas accumulation although its size was very large.

Chaluhe faulted depression of Yitong Basin,an inland graben,has experienced multiple phased tectonic activities from the Late Cretaceous to the present.By means of microthermometry combined with the analysis of burial history,thermal history,and integrating hydrocarbon generation and expulsion history of major source rocks with tectonic movements,the hydrocarbon filling process can be subsequently divided into three episodes.While the GOI technology proves that the earlier filling hydrocarbon has been destructed at the peak of the structural closures,and the later filling hydrocarbon at the deeper structural closures are still preserved.This shows a favorable prospective for the future exploration.

According to traditional hydrocarbon genesis theory,it is accepted that organic maturity is affected by temperature,time and pressure.After summarizing exploration practices,it reveals that thermal maturity of organic matter is mainly controlled by temperature.So long as the temperature is high enough,substantial hydrocarbon can be generated from source rock.Tectonic movements do not only produce great amount of heat,but also make hydrocarbon generation and expulsion abruptly.Compressive process promote the hydrocarbon generation and migration.In addition,tectonic movements can form a set of traps,which shorten the time from generation to accumulation.Therefore,in areas where tectonic compression are well developed,though shallow buried source rock,they also have the capacity for hydrocarbon expulsion,and can form economic oil reservoirs.Based on these findings,the traditional theory that shallow source rock can not expulse oil should be broke,and regions of marginal basin with intense structural deformation should be taken into the exploratory frontier.

According to the geological data, the formation process of heavy oil in Taobao area is studied, by using geochemical techniques. It is considered that the crude oil of the area began from the Qingshankou Formation of the central sag in the east, migrated for about 50 kilometers and was hindered by the Taobao adverse fault and at last was accumulated in the area. Because of long distance migration, the bed absorbing process and filtration of the reservoir leads to the low freezing point and low asphaltene of crude oil. Meanwhile, the crude oil gets heavy and dense and of high resin, due to oxidation, water washing and biodegradation of formation water. Thus the crude oil has certain characteristics of heavy oil.

苏德尔特油田兴安岭群岩性复杂,测井响应差别较小,在岩性类别方面存在交互性和模糊性,使得识别困难.为了更好地开展储层研究和流体识别工作,探索其主要岩性的分类及识别方法成为关键问题,选取6个对岩性反应敏感的测井参数,应用模糊数学原理对其主要岩性进行分类,并在建立岩性模式基础上依据最大隶属原则识别岩性.与此同时,通过编制程序实现了对岩样的自动识别与分类.实践证明,岩性识别的应用效果较好,符合率达到90.1%.

The fault nature of north-west area in Yitong Graben used to be obscure,which heavily impedes the oil prospecting works in this area.By using outcrop,core,geophysical data,it is concluded that north-west fault zone in Yitong Basin is compressive and reversed faults which are well developed.A lot of fold structures are shaped at geological outcrops in north-west area of the basin.In prospecting wells near north-west boundary core data show that strata tilted at a large angle,and some even turn perpendicular.Gravity,magnetic and geo-electrical data also show that north-west area in Yitong Graben exits compressive phenomena.Fault composite characteristics are interpreted from high resolution 3D seismic.Fault nature and its characteristics are favorable for reservoir accumulation in the area.This study greatly guides oil exploration of north-west area in Yitong Graben,and also has a guiding meaning to oil prospecting vista of the entire Tancheng-Lujiang fault zone.

The characteristics and diagenetic types of Chaluhe reservoir were studied in terms of the data of drill cores,slices,scanning electron microscopy,X-ray diffraction.According to the criterion of division,the diagenetic phases are divided into early diagenetic A stage,B stage,and late diagenetic A stage and B stage,and the late diagenetic A stage is divided into A1 stage and A2 stage.By using the software of BasinMode,the burial history and thermal history of the primary structure were analyzed,and combined with the result of porosity evolution history,the reservoir diagenetic evolution was studied.The result is:before 30 Ma,the primary diagenesis was compaction and cementation.The porosity in the formation of Shanyang and Sheling reduced to 15% from 32% approximately,and that of Yongji and Wanchang reduced to 20% from 32% approximately;During the period of 30 Ma and 10 Ma,all the formations had been buried to the deepest depth and the feldspars in the sandstone formations of Shuangyang and Sheling began to dissolve,which caused the porosity to increase to 18%,providing space for the storage of oil and gas;but the porosity unchanged in the formation of Yongji and Wanchang during this period.Three diagenetic modes(alluvial fan,fan-delta,deep and half-deep lacustrine facies) are built in Chaluhe fault depression based on the study of burial history,thermal evolution history of organic,diagenetic evolution history,the rock type and sedimentary facies.

The Caluhe Depression of the Yitong Basin is a extension rift basin,due to the complex tectonics,particular morphology,sedimentary source from several directions,several depocenter and subsidence center and the rapid facies transition,there is much difficulty in the stratigraphic division and correlation.Based on the data of predecessor research,involved some methods and data of well lithology,geophysical,paleontology,combined with sequence stratigraphy,this paper deals with the Eocene stratigraphic division and correlation of the Chaluhe Depression in the Yitong Basin.It is suggest that Eo-cene is made of the Shuangyang Formation,the Shelin Formation and the Yongji Formation,and indicate the evidences of strata division and correlated,and analysis the correlation between the Yitong Basin and the Bohai Bay Basin.