| In the field of basin analysis, sequence and sedimentary are influenced by tectonism, climate, environment and base-level changes, and the research has always been popular themes. In marine basins with stable structure, changes of sea level is the main factor affecting sequence and sedimentary; while in active continental rift basins, tectonic can affect sediment supply, accommodation space, and turns to be the main factor that affects sequence and sedimentary. Carrying out the study about the responses of sequence and deposition to tectonic activities and analyzing tectonic controls on sequence and deposition have important theoretical significance.Most basins in eastern China are Mesozoic-Cenozoic rift basins, and the current exploration mainly focuses on Cenozoic formations. Cenozoic exploration is now faced up with problems of high exploration density and limited resources, and oil and gas shortage is becoming the bottleneck which restricted the sustainable development of economic and affected Chinaese energy security. Liu Guangding(2002) once pointed that there got pretty potential oil and gas in the pre-Cenozoic residual basins. Though it is diffculty for residual basin exploration, more oil and gas can be found as long as making further study on basic geological research and carrying on the second startup of resources. Currently Cenozoic formations in Jiyang Depression is facing the bottlenecks of oil and gas production, as oil and gas discovery frequency and quantity have a tendency to decline, the exploration of Pre-Cenozoic (buried hill formations, especially Mesozoic) formations will receive more attention.Yihezhuang Salient is a secondary building unit of Jiyang Depression, formations inside the salient as the sedimentary basement of Cenozoic rift basin contains Paleozoic and Mesozoic formation. Since the discovery of oil and gas reservoirs in 1977, Ordovician carbonate rocklayers have been the main oil producing zone, although hydrocarbon also got found in Mesozoic basins. With the petroleum production decreasing, the layer above the Ordovician, especially the Mesozic layer, would become the next focus in Yihezhuang oilfield. Through later fine structural interpretation of three-dimensional seismic and re-calculation of reserves, there found 350.15 x104 t hydrocarbon reserves above Ordovician formations, showing large resource potential. However, the complexity of the structure system and lack of basic geological research made the study of Yihezhuang buried hill very difficult.This paper combines the exploration problems and the theorical hot point. According to detailed 3D seismic data, field outcrops, drilling and logging data, based on sequence stratigraphy and sedimentology, with the response of sequence and sedimentary to tectonic activities, sequence stratigraphic framework of the Mesozoic formations that in the east of Yihezhuang Salient, Jiyang Depression was established. Under the constraints of sequence stratigraphic framework, we analyzed the Mesozoic sedimentary systems, reconstructed the depositional environment, and finally analyzed the Mesozoic tectonic activities. Development and evolution characteristics of sequence and deposition were conducted, and their response to tectonic activities was discussed. The Mesozoic residual basin analysis was carried out by combination with tectonic, sequence and deposition features, in order to predict the potential oil and gas traps.The main work is as follows:Chapter 1 mainly discussed the origin, objective and scientific significance of this topic, then summarized the continental sequence stratigraphy and sedimentology as well as their response to tectonic activities. After analyzing the exploration present situation and existing problems, the content of this article was established. We choosed the second-order tectonic unit-Yihezhuang Salient as the research object, then in order to solve the above problems we analyzed the characteristics of sequence and sedimentary as well as forming and evolution mechanism of the Mesozoic basin, and discussed their response to tectonic activities. On the basis of geological, seismic, geochemical and outcrop data, the research methods were made out, namely according to the principle of "five-in-one", field outcrops, geological and seismic study, following the point-line-plane-body-time idea, a comprehensive analysis of Mesozic tectonic evolution of Eastern Yihezhuang Salient is carried out. Then we builded the Mesozoic sequence stratigraphic framework and analyzed the inside sedimentary filling. According to the above work, the responses of sequence stratigraphy and deposition to tectonic activities are discussed. Then combining reservoir evaluation, oil source data, etc., the types of potential oil and gas reservoirs of the Mesozoic residual basin were predicted. This study could make up for the shortages of the geological research for the Mesozoic residual basin in the east of Yihezhaung salient, Jiyang depression, and provide references for the study of similar residual basins in Jiyang depression, even the North China platform.Chapter 2 mainly described regional geological conditions of Yihezhuang salient in the background of Jiyang depression. Yihezhuang salient is located in the North of Jiyang depression, and belongs to the footwall of Yinan fault and hanging wall of Chengnan fault. The activities of these two faults both influenced the formation and evolution of Yihezhuang salient much. The sedimentary strata of Jiyang depression, in ascending order, mainly includes lower Paleozoic Cambrian and Ordovician, upper Paleozoic Carboniferous and Permian, Mesozoic Jurassic and Cretaceous as well as Cenozoic Tertiary and Quaternary. The whole Yihezhuang salient was raised up and suffered from weathering and explosion with the effect of late Triassic Indo-China movement and late Cretaceous Yanshan movement, the Mesozoic only remained the Jurassic strata, namely Fangzi formation (J1+2), Santai formation(J2) and Mengyin formation(J3). Jiyang drepression was Mesozoic-Cenozoic rift basin formed above the Palaeozoic basement, and suffered five periods of tectonic evolution, namely Precambrian movement, Caledonian movement, Hercynian movement, Indo-China movement, Yanshan movement, and Himalayan movement. Indo-China and Yanshan movements occur in Mesozoic. The deposition paleogeography of the Mesozoic continental basin in Luxi where Jiyang depression located can be divided into two stages. The first stage contained early-middle Jurassic. In early-middle Jurassic, Fangzi formation got mainly reduced color fluvial sediment; in middle Mesozoic, sediments were mainly fine elastics and showed oxide color as the climate became drier. The second stage was late Jurassic, during this period, with the dclaminating and thinning of lithosphere, the rifting basin got formed, where could develop lake facies and fan delta in the margins.In Chapter 3, based on seismic profiles and well logs,3 main unconformity interfaces (Tg, Tgm, Tr) of Mesozoic were identified, the tectonic framework was built, and structural layers were divided. Taking structural layers as the research object, through the analysis of balanced cross section, palaeotopography, fault activity rate, fault negative reversal rate and fault displacement-distance curves, the Mesozoic tectonic activities and evolution in the research area have been researched. The Mesozoic tectonic activity in the research area underwent two main tectonic movements (Yinzhi Movement and Yanshan Movement). During the Yinzhi Movement, the research area uplifted and was eroded, forming the Tg. During the Yanshan Movement, the tectonic activity was subdivided into 2 stages (the main stage and the last stage) and 3 cycles (the early cycle, the middle cycle and the late cycle). The early cycle, corresponding the lower-middle Jurassic, inherited the tectonic framework of the Indo-Chinese epoch and was characterized by weak squeeze and limited distribution of sedimentary strata. The main stage of the Yanshan Movement corresponded the last phase of the middle Jurassic, when mountain making movement formed the regional unconformity interface (Tgm). Subsequently, the middle cycle began, corresponding the late Jurassic epoch-early Cretaceous epoch. The research area was under tensional stress field, and uplifted because of negative reversal. After the middle cycle, the subsequent last stage of the Yanshan movement was orogenic period and the whole area uplifted. Then, the late cycle of the Yanshan Movement began. It was characterized by obvious compressional structures and uplift-erosion in the research area. The structures positively inverted. The Mesozoic erathem and Paleozoic erathem were eroded, forming the regional unconformity interface (Tr).In Chapter 4, based on the tectonic framework, using seismic profiles, well logs and outcrops, the sequence boundaries were identified and the Mesozoic isochronous stratigraphic framework in the east area of the Yihezhuang Uplift was built.5 sequence boundaries can be identified in the Mesozoic erathem totally. From bottom to top, they are Tg, Tmz3, Tmz2, Tgm and Tr. Tg, Tgm, Tr resulted from regional tectonic movements, and are first-order sequence boundaries. The Mesozoic erathem can be divided into 2 first-order sequences, which correspond 2 tectonic layers:middle-lower Jurassic (J1+2) and upper Jurassic (J3), and contains 4 third-order sequences, which correspond to the lower member of the Fangzi Formation (J1fl), the upper member of the Fangzi Formation (J2f2), Santai Formation (J2s) and Mengyin Formation (J3m), respectively. Based on the analysis of sequence stratigraphic framework across different tectonic units, two Mesozoic sequence stratigraphic patterns were concluded. They were Yigu 991 sequence stratigraphic pattern and Yidong sequence stratigraphic pattern.The chapter 5, on the basis of the substantial materials, the integration of point-line-plane, by using outcrop, drilling cores, well logging and seismic date, was employed to reveal the depositional characteristics in the residual basin. Based on the understanding of basin property, the depositional evolution process was analyzed. Analyzing the types of the Mesozoic sedimentary facies by using above methods comprehensively, we found that the lower and upper sections of Fangzi as well as Santai formation was meandering river deposition, while Mengyin fonnation was fan delta sediment. Vertically, the lower and upper sections of Fangzi formation got meandering river coarse sediment with reduced color, and developed more channels showing topography with certain slope and water with certain depth; Santai formation mainly developed oxide colored fine meandering river sediment with less channels, reflecting that topography was flat and water depth was lower. Defferently from early-middle Jurassic meandering river sediment, Mengyin formation developed fan delta, showing the response of sedimentary facies types to tectonic evolution.Based on analyzing tectonic, sequence and sedimentary, the chapter 6 argued the relationship between tectonic evolution, sequence and types of sedimentary facies. Tectonic controlling on sequence firstly were reflected by the formation of sequence boundary: Indo-China movement controlled formation of Tg, the main episode of Yanshan movement controlled the formation of Tgm, respectively, the last episode of Yanshan movement controlled the formation of Tr. Tg, Tgm, and Tr were all first-order sequence boundaries. Second, the control wre reflected by tectonic evolution affecting sequence hierarchy:the early cycle of Yanshan movement happened in early-middle Jurassic and controlled the formation of intra-continental compressional basin which was a kind of prototype basin, namely a first-order sequence; the middle cycle of Yanshan movement happened in middle-late Jurassic and affected the formation of rift-related tensional basin, namely another kind of prototype basin and the first-order sequence in Mesozoic. Finally the control was reflected by affecting sequence patterns: early-middle Jurassic mainly developed the sequence pattern with fluvial facies sedimented inside, while late Jurassic developed sequence patterns of fan delta and lacustrine facies. For sedimentary, the tectonic evolution controlling deposition firstly was reflected by changing the depocenter:in the hanging wall of Yigu 991 Fault in the early cycle of Yanshan movement, the depocenter departed from the fault, while it was closed to the fault in the footwall. In the middle cycle of Yanshan movement, depocenter changed because of negative tectonic inversion, In the hanging wall of Yigu 991 fault, depocenter was closed to the fault while in the footwall it departed. Second, it was reflected in sedimentary types:in the early cycle of Yanshan movement, meandering river was the main type, while in the late cycle fan delta turned to dominant because of faulted basin forming. Finally, the tectonic evolution controlled the color changing and grain size of sediments, In the early stage of the initial cycle, owing to the consistent compression of Indo-China tectonic movement, the surface relief was characterized by a certain gradient. As a result, the channels of the meandering river was easily developed, and presented weak-braided, with relatively coarse and reduced colored sediments. While in the late stage of the initial cycle, the tectonic activity became weak, the sediments was marked by fine grained size and oxide colored as a result of shallow water environment. In addition, after infilling of the basin, the surface relief came to be gentle and the river came to be steady with relatively extensive development of point bar and few channels.Based on analyzing tectonic evolution, sequence, deposition, chapter 7 discussed the Mesozoic trap types. The lower and upper sections of Fangzi formation as well as Santai formation mainly developed lens-shaped lithologic traps and unconformity traps; while Mengyin formation mainly developed unconformity traps. Combined with reservoir evaluation and oil source data, we forecast the advantageous oil and gas region according to oil producing wells that have been successfully explorated.The paper closely tracks the hot topics of basin analysis including tectonic-sequence stratigraphy, tectonic-sedimentology, residual basin research etc., in recent years. Combining the structural setting and sedimentary background of easten Yihezhuang salient in Jiyang depression, we summarized a set of formulas to calculate fault activity rate and negative reverse rate as well as drawing displacement-interval curves according to the geological situation of study area. These formulas also can be used to study other Mesozoic residual basin with similar geological situation in the east of China, which may be worthy of be promoted. Divided by the main episode of Yanshan movement, lower and upper sequence architecture and sedimentary texture different characteristics and the response of tectonic evolution were analyzed, and the corresponding models were built, which may be pretty helpful for Mesozoic residual basin analysis in the eastern China and petroleum. |
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