| The point that basin areas are usually abundant of petrol and methane resources has been proved again with the exploration implemented in the Yitong basin. According to the phase III petroleum resource evaluation published by the CNPC (China National Petroleum Corporation), the oil resources in the basin is believed to be up to in equivalent 730 million tons of oil and gas. Consequently, the basin has become an important gas exploration and reserve replacement area of the Jilin Oilfield. In recent years, the oil and gas exploration in the Yitong basin has made substantive breakthroughs. For instances, the instantaneous flow rate of the C37 well, located at the Qijia buried hill, is as high as 25600 m3/h airflow, and the figure is 85000 m3/d airflow for the C51 well which is the northwest margin. These achievements have shown a promising potential of oil and gas exploration possessed by the Yitong Basin.The Yitong Basin is at the eastern part of Jilin province and its north part belongs to the Tan-Lu fault zone. The basin’s trend is 45～55°to east and shows a long and narrow banded distribution. The nature of the basin is the tertiary fault basin sedimentation. Over the years, in order to improve the understanding of the basin’s geological settings and to accelerate the pace of hydrocarbon exploration in this area, researchers have been devoted to the study of fracture structure system. Though many achievements have been obtained, yet it still cannot fulfill the requirement of oil and gas exploration. Therefore, there exists an urgent need to adopt new ideas and research methods to find out the deep geological structure which restricts basin oil and gas resources, clarify the basin fracture system to deepen the geological understanding of the basin, understand the regularity of hydrocarbon accumulation, found that the scale of oil and gas reserves, and make Yitong basin on the subsequent production as soon as possible to replace area of storage.So far, the study of fault basin is limited to the seismic data. Due to the complexity of fault basin, serious formation squeeze broken, causes distortions in seismic imaging. Consequently, it is unable to further the research on fracture system of basin using seismic data. This makes applying seismic data to restrict basin oil and gas exploration of deep geological structure seems even more impossible, especially in the basin basement insider, buried hill and recognize the distribution of the palaeozoic group.In this thesis, we implement integrated geophysical and physical methods and the explaining principle "one, two, three, multipile", proposed by prof. Liu Guangding, to study the Yitong Basin’s deep structure using gravity, magnetic, seismic, drilling and geologic data for research. The research carried out a variety of new integrated geophysical exploration methods and technologies and has carried on the extraction of deep structure’s geophysical feature. Combined with the geological, seismic and drilling data, we established a basin fracture mode and improve the understanding of the structure of fracture characteristics and the basin basement insider, which provide the fundament for deep oil and gas exploration. We formed a set of application of comprehensive geophysical study basin complex fracture system, deep geological structure of the new way of thinking and comprehensive interpretation of geophysical data processing flow. At the meantime, this work provides reference experience of data processing and interpretation for the similar research.In the aspect of integrated geophysical data processing and interpretation, this paper applied a variety of modern processing methods and techniques. Putting forward the distortion by using three dimensional density interface and 3D apparent depth of the total gravity gradient method to identify fault information. Creating application of gravity apparent depth filter processing method to establish the three-dimensional gravity field. The 3D total gradient processing effectively highlight the fault caused by the change of the gravity gradient anomalies in three dimensional space characteristic.3D density inversion theory was applied to the study of fracture system. And through the three dimensional density distortion surface to study the fracture structure. In basin to study the distribution of the volcanic rocks, the application of 3D inversion of magnetic susceptibility is obtained by new method of three-dimensional spatial distribution characteristics of magnetic susceptibility, combined with the drill in volcanic rocks well data, successfully predict the three-dimensional spatial distribution of the volcanic rocks. Using three dimensional density and 3D resistivity inversion results, using the difference of density and resistivity between glutenite and sedimentary rocks, the distribution of glutenite is predicted; By studying the basement lithology characteristics and geophysical response characteristics, combined with drilling data and geological research results of other researchers, research basement lithology distribution; Based on magnetotelluric sounding resistivity vertical variation characteristics of geological attribute recognition, using the drilling information and high quality seismic data calibrated using section, and the electrical layer transverse rolling exercised stratification, combining with the measured physical property data in the study area, geological and geophysical model is set up, Gravity electric constraint inversion, study of deep structure and basal insider structure characteristics.Through the above integrated geophysical interpretation methods in the application of Yitong basin, we obtain more deep geological structure information of geology, the fracture characteristics of the basin, volcanic rock distribution, distribution of glutenite, basal fluctuation characteristics and further understanding of the structure of basal insider. A series of achievements have been achieved about structure characteristics.(1) Further study of Gravity, magnetic, electric processing methods, we use 3D apparent depth of the total gravity gradient and 3D density method to identify the fault information distortion interface, which obtained the good geological effect.Conventional approaches focuses on two-dimensional magnetic and gravity separation of geophysical field, magnetic and gravity response research geologic body in the plane. In order to extract the linear structure of 3D gravity field information,3D apparent depth of the total gravity gradient processing,3D density inversion method of fracture structure geophysical identification, fault density of 3D model,3D density inversion and 3D apparent depth of the total gravity gradient trial, result in accordance with the model. In Sheling area of Yitong basin 3D density inversion and 3D apparent depth of the total gravity gradient processing, to obtain the three dimensional density and the three dimensional total gradient of gravity anomaly, the three dimensional gravity gradient extremum attachment distortion and high strength density interface are clearly reflect the three-dimensional structure of basin-controlling boundary faults, and three dimensional gradient extremum of attachment to the secondary fault information also has a good show.(2) According to the content of the research, the establishment of the Yitong basin comprehensive geophysical methods to application system, effectively extract the Yitong geophysical characteristic information of deep structure, provides reference for the similar basin research work of data processing and interpretation.1) Using sliding varible order intending trend analysis to extract the steep gradient of gravity with local gravity anomaly;2) Using 3D apparent depth of the total gravity gradient processing and 3D density inversion fracture three-dimensional structure information;3) Using gravity, magnetic, electric 2D and 3D inversion, determine the rock density, magnetic susceptibility and resistivity 2D and 3D spatial structure variation characteristics;4) Resistivity inversion results of magnetotelluric sounding data wave field transform migration imaging, residual method and gradient method, extraction of cap rock resistivity difference between information;5) Gravity, electric and seismic data combined constraint inversion, deep geological structure research.(3) We extract the target field from gravity, magnetic and electric geophysical field characteristics to study the deep basin structure characteristics, which reveals the palaeozoic group of the Yitong Basin tectonic framework and provides theoretical fundament to find oil and gas exploration in the palaeozoic group in the next step.1) The relationship between oil and gas and fracture structure characteristicsThe fractures in the northwest margin is straight and continues peace activity for a long time with large scale. The fracture is of high angle from north to east and it changes dramatically along the strike. It shows slows wave S reservation in local parts and presents as a normal fault towards the basin in all. There are parallel to the main faults in the development of the secondary fracture, almost as the thrust fault, near the backer chariot tend to invert the flare to the basin. Their combinations have two forms "plough type" and "y" combined with the "y" thrust. Due to Neogene basin inversion and squeezing action, it forms a parallel to the thrust in the fracture distribution near the northwest edge of the basin with 2～4 km widen, with basically run through the whole basin. Thrust extruding inversion with footwall good of fault traps conditions and sealing ability, the nearshore subaqueous fan body development, better properties, reservoir thickness, larger near the center of hydrocarbon generation, have good oil and gas accumulation conditions, is one of the important favorable zones for oil and gas exploration.The fault boundary in the southeast margin is distorted distribution, which formed in the early ages and breaks into the deep lithosphere basement. This fault plays coordinating pull-apart effect in the formation and evolution of the Yitong Basin. The fracture shows obviously sectionally distribution, especially in the Maan Mountain town and the Dagu Mountain town and its strike and tendency varies considerably.The No.2 fracture mainly experienced early strong extensional activities and late extrusion adjusting the ChaLuHe and LuXian fault depression tectonic activities. The fracture controls the LiangJia structural belt on heading wall and the WuXing tectonic belt on the fault footwall. There is a huge vertical slip between the two plates. The No.2 fracture characterized as extensional fault in early phase, which plays as an significant role in basin sedimentary control, and as pressure torsion effect in later phase,which is in the nature of thrust and makes main channels for hydrocarbon migration.2) The distribution of glutenite regularities and its oil and gas potentialThrough research of C49 and C51 glutenite well drilling physical characteristics, we discovered glutenite and surrounding mudstone density and resistivity have bigger difference, often density, resistivity, respectively,0.14 g/cmJ and above 15 Ω.m. Using three-dimensional density, resistivity inversion and get to know the density and resistivity change in three-dimensional space, we combining glutenite sedimentary environment to predict the distribution of glutenite, combined with regional tectonic characteristics at the same time, we puts forward the Wanchang stratum two groups of glutenite of oil and gas exploration target zone.3) Basal inside structure and oil and gas potentialThe mainly mass types distributed in the basin basement lithology are hercynian, indo-chinese epoch, Yanshan period acidic intrusive mass. Give priority to with granite at the top of the basement lithology, pre-tertiary basement sedimentary strata are mainly distributed in the northwestern margin and tertiary basement before southeast margin fault zone inside with a zonal distribution. Metamorphic rocks are mainly distributed between the MaAn Mountain and the DaGu Mountain town, which is distributed around the crater of the volcano.Evidences found in the Yitong Basin deep structure prove the exist of palaeozoic group: There exist the perm-carboniferous rocks out of the basin controlling fracture in the nature of mudstone, limestone, slate, sandstone. Magnetotelluric deep resistivity section generally have low resistivity exists. Seismic are layered reflection in basal. The Yitong basin C37 well’s natural gas is coal-type gas. C27 well side drilling in bedrock section of drilling in the carbonate rocks of Yitong basin, effectively firm and clear Yitong basin deep with permo-carboniferous formation.Basal insider holds two layers of structure:the upper for the granite, the lower Permo-carboniferous formation. On the whole, permo-carboniferous formation depth is more than 2000 m, generally between 3000-4500 m. Permo-carboniferous formation mainly develops in the northwestern and southeastern margin of the basin, middle between Maanshan-Luxiang as granite intrusion, massive permo-carboniferous formation residual is not much, the southeastern margin of permo-carboniferous formation shallower than in the buried depth. Permo-carboniferous structure in the northeastern to the zonal distribution, permo-carboniferous in the top of the basement structural belt, fault terrace zone, there are local uplift under slope belt.By the means of gravity, magnetic, electric, seismic and drilling data, a comprehensive study thinks that there are four buried within the basement:the Xiaogushan-Jianshan high buried hill zone, Wanchang-Qijia low buried-hill zone, the Wuxing high buried-hill zone, Soudengshan high buried hill zone, the total area of 565 km2, wanchang-Qijia low buried hill zone industrial air flow, have been obtained. C27 sidetracking well carbonate Ro distribution between 0.7-1.6%, enter the mature-high maturity stage, is a good hydrocarbon source rocks, thus Yitiong basin has palaeozoic group new formations of oil and gas exploration potential. |
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