三维VSP技术的研究及应用

Today, because of high petroleum consumption of our country, society steady development and difficulty increase in new resources exploration, deep exploitation of the existing oilfield is needed. More delicate reservoir imaging and description, such as thin layer identification, interlayer exploitation monitoring, subtle structure imaging, reservoir anisotropy recognition, can provide more detail evidence for new development adjustment scheme and enhanced oil recovery. Now, the people have already realized the 3D VSP technique more effective than the general methods in solving these aspects. But VSP technique especially 3D VSP develop slowly due to some reasons. Carrying out the research of VSP technique, it will be very useful to the EOR service. 3D VSP techniques include acquisition、data processing and interpretation. In this paper, the author carried out some researches around acquisition and processing. The key point of acquisition is the survey design, it is critical to the quality of the data and it will influence the reservoir recognition as follows. The author did detailed researches on the layout pattern of shot point and geophone. Some attributes relate to survey design such as reflectivity, incidence angle, observation area, reflection points distribution, fold, minimum well source distance, azimuth angle and so on are studied seriously. In this geometry design of 3D-VSP exploration in deviated wells, the main problems to be solved are: determining the center position of shots distribution, the effect of shots missing on coverage areas and coverage times，locating the shots and receivers of multi-wells. Through simulating and analyzing, the above problems are discussed and some beneficial conclusions are drawn. These will provide valuable references to actual survey design. In data processing, researches emphasize on those relatively key techniques such as wavefield separation, VSP-CDP imaging, the author carried out deep researches around these two aspects. As a result, variant apparent slowness wavefield separation method developed in this article suit the underground variant velocity field and make wavefield separation well, it can overcome reflection bending shortage aroused by conventional imaging method. The attenuateion range of underground seismic wave is very important for amplitude compensation and oil/gas identification.In this paper, seismic wave attenuateion mechanism is studied by 3D-VSP simulateion and Q-inversion technique. By testing with seismic data, the method of VSP data attenuateion and relationship of attenuateion attribute variant with depth is researched. Also the software of survey design and data processing is developed, it fill the gap of VSP area in our country. The technique developed applied successfully in SZXX-A Oilfield、QKYY-B Oilfield、A area and B area. The good results show that this research is valuable, and it is meaningful to the VSP technique development and application of offshore oil industry and other areas in our country.

陆地三分量三维地震勘探技术研究与应用

With the development of oil and gas field exploration, it becomes harder to search new reserves. So a higher demand of seismic exploration comes up. Now 3C3D seismic exploration technology has been applied in petroleum exploration domains abroad. Comparing with the traditional P-wave exploration, the seismic attributes information which provided by 3C3D seismic exploration will increase quickly. And it can derive various combined parameters. The precision of information about lithology, porosity, fracture, oil-bearing properties, etc which estimated by above parameters was higher than that of pure P-wave exploration. These advantages mentioned above lead to fast development of 3C3D seismic technology recently. Therefore, how to apply the technology in petroleum exploration field in China, how to obtain high quality seismic data, and how to process and interpret real data, become frontier topics in geophysical field nowadays, which have important practical significance in research and application. In this paper, according to the propagation properties of P-wave and converted wave, a study of 3C3D acquisition parameters design method was completed. Main parameters included: trace interval, shot interval, maximum offset, bin size, the interval of receiving lines, the interval of shooting lines, migration aperture, maximum cross line distance, etc. Their determination principle was given. The type of 3C3D seismic exploration geometry was studied. By calculating bin attributes and analyzing parameters of geometry, some useful conclusions were drawn. With the method in this paper, real geometries for continental lithology stratum gas reservoir and fractured gas reservoir were studied and determined. In the static method of multi-wave, the near surface P-wave, S-wave parameter investigation method has been advanced, and this method has been applied for the patent successfully; the near surface P-wave, S-wave parameter investigation method and the converted refraction wave first arrival static techniques have been integrally used to improve the effectiveness of converted wave static. In the aspect of converted wave procession, the rotation of horizontal component data, the calculation of converted wave common conversion bin, the residual static of converted wave, the velocity analysis of the common conversion point (CCP), the Kirchhoff pre-stack time migration of converted wave techniques have been applied for setting up the various 3C3D seismic data processing flows based on different geologic targets, and the high quality P-wave, converted-wave profiles have been acquired in the actual data processing. In the aspect of P-wave and converted-wave comprehensive interpretation, the thoughts and methods of using zero-offset S-wave VSP data to calibrate horizon have been proposed; the method of using P-wave and S-wave amplitude ratio to predict the areas of oil and gas enrichment has been studied; the method of inversion using P-wave combined with S-wave has been studied; the various P-wave, S-wave parameters(velocity ratio, amplitude ratio, poisson ratio) have been used to predict the depth, physical properties, gas-bearing properties of reservoirs; the method of predicting the continental stratum lithology gas reservoir has been built. The above techniques have all been used in various 3D3C seismic exploration projects in China, and the better effects have been gotten. By using these techniques, the 3C3D seismic exploration level has been improved.

储层评价目标驱动的地震叠前叠后综合反演方法研究

The exploration and development of natural gas in the north of Ordos basin have been one important part in China’s energy stratagem. Reservoir in upper Palaeozoic group is of lithological trap and its prediction is a crux in a series of works. Based on foregoing seismic reservoir prediction, seismic data are re-processed with some optical methods and pre-stack information is used in corresponding inversions. Through the application of diverse methods, a series of techniques for reservoir prediction come into being. Several results are achieved as flowing: 1. A set of log processing and interpretation methods is developed. Porosity, permeability and gas saturation models are rebuilt. 2. Based on the petro-physics analysis of reservoirs in upper Palaeozoic group, the equations about lithology, property, hydrocarbon and elastic parameters are established. 3. Forward modeling based on elastic wave theory is first applied in the study area and increases the resolution of modeling results. 4. A series of techniques such as pre-stack time migration and others are combined to improve the data quality. 5. Pre-stack seismic inversion is first employed in the north of Ordos Basin and brings the results of EI, P-impedance, S-impedance and other elastic parameters. 6. In post-stack inversion, logs indicating reservoir parameters are rebuilt and boost the resolution of lithology inversion. 7. Amplitude, coherence, frequency-discomposed amplitude, waveform and other sensitive attributes are extracted to describe sands distribution. Seismic modes standing for sands of P1x3, P1x2 are established. 8. Among 9 proposed wells, 8 wells encountered sands and became production wells. The output of DK13 amounts to 510,000 m3 per day. Keywords：the north of Ordos Basin, reservoir prediction, pre-stack inversion, post-stack inversion, seismic attributes．

东海陆架盆地复杂天然气藏地震勘探判别技术研究

Exploration study proves that East sea shelf basin embeds abundant hydrocarbon resources. However, the exploration knowledge of this area is very low. Many problems in exploration are encountered here. One of them is that the gas reservoir of this area, with rapid lateral variation, is deeply buried. Correlation of Impendence between sandstone, gas sand and shale is very poor. Another problem is that the S/N ratio of the seismic data is very low and multiples are relatively productive which seriously affect reservoir identification. Resolution of the seismic data reflected from 2500-3000 meter is rather low, which seriously affects the application of hydrocarbon direct identification (HDI) technology. This research established a fine geological & geophysical model based on drilling、well logging、geology&seismic data of East sea Lishui area. A Q value extraction method from seismic data is proposed. With this method, Q value inversion from VSP data and seismic data is performed to determine the subsurface absorption of this area. Then wave propagation and absorption rule are in control. Field acquisition design can be directed. And at the same time, with the optimization of source system, the performance of high resolution seismic acquisition layout system is enhanced. So the firm foundation is ensured for east sea gas reservoir exploration. For solving the multiple and amplitude preserving problems during the seismic data processing, wave equation pre-stack amplitude preservation migration and wave equation feedback iteratively multiple attenuation technologies are developed. Amplitude preservation migration technology can preserve the amplitude of imaging condition and wave-field extrapolation. Multiple removing technology is independent of seismic source wavelet and velocity model, which avoiding the weakness of Delft method. Aiming at the complicated formation condition of the gas reservoir in this area, with dissecting typical hydrocarbon reservoir, a series of pertinent advanced gas reservoir seismic identification technologies such as petrophysical properties analyzing and seismic modeling technology、pre-stack/post-stack joint elastic inversion, attribute extraction technology based on seismic non-stationary signal theory and formation absorption characteristic and so on are studied and developed. Integrated analysis of pre-stack/post-stack seismic data, reservoir information, rock physics and attribute information is performed. And finally, a suit of gas reservoir identification technology is built, according to the geological and geophysical characteristics of this area. With developed innovative technologies, practical application and intergrated interpretation appraisal researches are carried out in Lishui 36-1.The validity of these technologies is tested and verified. Also the hydrocarbon charging possibility and position of those three east sea gas exploration targets are clearly pointed out.

叠前叠后联合反演技术及其在QHD32-6油田的应用研究

What geophysical inversion studied includes the common mathematics physical property of inversion and the constitution and appraisal method of solution in geophysics domain, i.e. using observed physical phenomenon from the earth surface to infer space changing and physical property structure of medium within the earth. Seismic inversion is a branch of geophysical inversion. The basic purpose of seismic inversion is to utilizing seismic wave propagating law in the medium underground to infer stratum structure and space distribution of physical property according to data acquisition, processing and interpretation, and then offer the vital foundation for exploratory development. Poststack inversion is convenient and swift, its acoustic impedance inversion product can reflect reservoir interior changing rule to a certain degree, but poststack data lack abundant amplitude and travel time information included in prestack data because of multiple superimpose and weaken the sensitiveness which reflecting reservoir property. Compared with poststack seismic inversion, prestack seismic inversion has better fidelity and more adequate information. Prestack seismic inversion, including waveform inversion, not only suitable for thin strata physical property inversion, it can also inverse reservoir oil-bearing ability. Prestack seismic inversion and prestack elastic impedance inversion maintain avo information, sufficiently applying seismic gathering data with different incident angle, partial angle stack, gradient and intercept seismic data cube. Prestack inversion and poststack inversion technology were studied in this dissertation. A joint inversion method which synthesize prestack elastic wave waveform inversion, prestack elastic impedance inversion and poststack inversion was proposed by making fully use of prestack inversion multiple information and relatively fast and steady characteristic of poststack inversion. Using the proposed method to extract rock physics attribute cube with clear physical significance and reflecting reservoir characterization, such as P-wave and S-wave impedance, P-wave and S-wave velocity, velocity ratio, density, Poisson ratio and Lame’s constant. Regarding loose sand reservoir in lower member of Minghuazhen formation, 32-6 south districts in Qinhuangdao,as the research object, be aimed at the different between shallow layer loose sand and deep layer tight sand, first of all, acquire physical property parameters suitable for this kind of heavy oil pool according to experimental study, establishing initial pressure and shear wave relational model; Afterwards, performing prestack elastic wave forward and inversion research, summarizing rules under the guidance of theoretical research and numerical simulation, performing elastic impedance inversion, calculating rock physics attributes; Finally, predicting sand body distribution according to rock physics parameters, and predicting favorable oil area combine well-logging materials and made good results.

松辽盆地长岭断陷火山岩储层识别与勘探目标评价

Changling fault depression is the biggest fault subsidence in south of Songliao Basin. In its Lower Cretaceous Yingcheng and Shahezi formations developed thick source rocks of deep lake facies and developed poly-phase volcanic rock reservoirs as well. In recent years, significant breakthroughs have been obtained in hydrocarbon exploration of volcanic rock reservoir in the different fault depressions in Songliao basin. Lately, I have been involved in hydrocarbon exploration in the Changling rift depression, especially volcanic rock reservoirs and exploration targets research, participating in the deployment of well Yaoshen 1 which gained over 40 × 104m3 natural gas flow. As quick changes of lithology and facies in Changling area in the south of Songliao basin, and the volcanic rock interludes distribution in continental clastic rock and shale in 3D space, so the identification of volcanic rock types and distribution become a difficult problem. Thus, based on the integrated research of the wild outcrop observation, gravity, magnetic and seismic data, geophysical logging, drilling and coring, laboratory test, this paper carried out the reservoir identification, description and prediction of volcanic rocks in Changling fault depression. In this area, this paper analyzed the volcanic rocks litho-facies, the eruption period, and characteristics of cycles. At the same time, tried to know how to use logging, seismic data to separate volcanic rocks from sandstone and shale, distinguish between volcanic reservoir and non-reservoir, distinguish between intermediate-basic and acidic volcanic rocks, and how to identify traps of volcanic rocks and its gas-bearing properties, etc. Also it is summarized forming conditions and distribution of traps, and possible gas-bearing traps were optimized queuing management. Conclusions as follows: There are two faulted basements in Changling fault depression, granite basement in the southeast and upper paleozoic epimetamorphic basement in the northwest. The main volcanic reservoirs developed in Yingcheng period, which was the intermediate-basic and acidic volcanic eruptions, from the south to north by the intermediate-basic to acid conversion. The volcanic vents are gradually young from south to north. According to information of the re-processing 3D seismic data and gravity-magnetic data, the large volcanic vent or conduit was mainly beaded-distributed along the main fault. The volcanic rocks thickness in Yingcheng formation was changed by the deep faults and basement boundary line. Compared with the clastic rocks, volcanic rocks in Changling area are with high resistance and velocity (4900-5800), abnormal Gamma. All kinds of volcanic rocks are with abnormal strong amplitude reflection on the seismic stacked section except tuff. By analyzing the seismic facies characteristics of volcanic rocks, optimizing seismic attributes constrained by logging, using seismic amplitude and waveforms and other attributes divided volcanic rocks of Yingcheng formation into four seismic zones in map. Currently, most volcanic gas reservoirs are fault-anticline and fault-nose structure. But the volcanic dome lithologic gas reservoirs with large quantity and size are the main gas reservoir types to be found.

多尺度分解与相位反褶积提高海上地震资料分辨率和信噪比

Offshore seismic exploration is full of high investment and risk. And there are many problems, such as multiple. The technology of high resolution and high S/N ratio on marine seismic data processing is becoming an important project. In this paper, the technology of multi-scale decomposition on both prestack and poststack seismic data based on wavelet and Hilbert-Huang transform and the theory of phase deconvolution is proposed by analysis of marine seismic exploration, investigation and study of literatures, and integration of current mainstream and emerging technology. Related algorithms are studied. The Pyramid algorithm of decomposition and reconstruction had been given by the Mallat algorithm of discrete wavelet transform In this paper, it is introduced into seismic data processing, the validity is shown by test with field data. The main idea of Hilbert-Huang transform is the empirical mode decomposition with which any complicated data set can be decomposed into a finite and often small number of intrinsic mode functions that admit well-behaved Hilbert transform. After the decomposition, a analytical signal is constructed by Hilbert transform, from which the instantaneous frequency and amplitude can be obtained. And then, Hilbert spectrum. This decomposition method is adaptive and highly efficient. Since the decomposition is based on the local characteristics of the time scale of data, it is applicable to nonlinear and non-stationary processes. The phenomenons of fitting overshoot and undershoot and end swings are analyzed in Hilbert-Huang transform. And these phenomenons are eliminated by effective method which is studied in the paper. The technology of multi-scale decomposition on both prestack and poststack seismic data can realize the amplitude preserved processing, enhance the seismic data resolution greatly, and overcome the problem that different frequency components can not restore amplitude properly uniformly in the conventional method. The method of phase deconvolution, which has overcome the minimum phase limitation in traditional deconvolution, approached the base fact well that the seismic wavelet is phase mixed in practical application. And a more reliable result will be given by this method. In the applied research, the high resolution relative amplitude preserved processing result has been obtained by careful analysis and research with the application of the methods mentioned above in seismic data processing in four different target areas of China Sea. Finally, a set of processing flow and method system was formed in the paper, which has been carried on in the application in the actual production process and has made the good progress and the huge economic benefit.

叠前地震数据规则化、重建及噪音压制

I address of reconstruction of spatial irregular sampling seismic data to regular grids. Spatial irregular sampling data impairs results of prestack migration, multiple attenuations, spectra estimation. Prestack 5-D volumes are often divided into sub-sections for further processing. Shot gathers are easy to obtain from irregular sampling volumes. My strategy for reconstruction is as follows: I resort irregular sampling gathers into a form of easy to bin and perform bin regularization, then utilize F-K inversion to reconstruct seismic data. In consideration of poor ability of F-K regularization to fill in large gaps, I sort regular sampling gathers to CMP and proposed high-resolution parabolic Radon transform to interpolate data and extrapolate offsets. To strong interfering noise--multiples, I use hybrid-domain high-resolution parabolic Radon transform to attenuate it. F-K regularization demand ultimately for lower computing costs. I proposed several methods to further improve efficiency of F-K inversion: first I introduce 1D and 2D NFFT algorithm for a rapid calculation of DFT operators; then develop fast 1D and 2D CG method to solve least-square equations, and utilize preconditioner to accelerate convergence of CG iterations; what’s more, I use Delaunay triangulation for weight calculation and use bandlimit frequency and varying bandwidth technique for competitive computation. Numerical 2D and 3D examples are offered to verify reasonable results and more efficiency. F-K regularization has poor ability to fill in large gaps, so I rearrange data as CMP gathers and develop hybrid-domain high-resolution parabolic Radon transforms which be used ether to interpolate null traces and extrapolate near and far offsets or suppress a strong interfere noise: multiples. I use it to attenuate multiples to verify performances of our algorithm and proposed routines for industrial application. Numerical examples and field data examples show a nice performance of our method.

地震数据波动方程反演方法研究

Geophysical inversion is a theory that transforms the observation data into corresponding geophysical models. The goal of seismic inversion is not only wave velocity models, but also the fine structures and dynamic process of interior of the earth, expanding to more parameters such as density, aeolotropism, viscosity and so on. As is known to all, Inversion theory is divided to linear and non-linear inversion theories. In rencent 40 years linear inversion theory has formed into a complete and systematic theory and found extensive applications in practice. While there are still many urgent problems to be solved in non-linear inversion theory and practice. Based on wave equation, this dissertation has been mainly involved in the theoretical research of several non-linear inversion methods: waveform inversion, traveltime inversion and the joint inversion about two methods. The objective of gradient waveform inversion is to find a geologic model, thus synthetic seismograms generated by this geologic model are best fitted to observed seismograms. Contrasting with other inverse methods, waveform inversion uses all characteristics of waveform and has high resolution capacity. But waveform inversion is an interface by interface method. An artificial parameter limit should be provided in each inversion iteration. In addition, waveform information will tend to get stuck in local minima if the starting model is too far from the actual model. Based on velocity scanning in traditional seismic data processing, a layer-by-layer waveform inversion method is developed in this dissertation to deal with weaknesses of waveform inversion. Wave equation is used to calculate the traveltime and derivative (perturbation of traveltime with respect to velocity) in wave-equation traveltime inversion (WT). Unlike traditional ray-based travetime inversion, WT has many advantages. No ray tracing or traveltime picking and no high frequency assumption is necessary and good result can be got while starting model is far from real model. But, comparing with waveform inversion, WT has low resolution. Waveform inversion and WT have complementary advantages and similar algorithm, which proves that the joint inversion is a better inversion method. And another key point which this dissertation emphasizes is how to give fullest play to their complementary advantages on the premise of no increase of storage spaces and amount of calculation. Numerical tests are implemented to prove the feasibility of inversion methods mentioned above in this dissertation. Especially for gradient waveform inversion, field data are inversed. This field data are acquired by our group in Wali park and Shunyi district. Real data processing shows there are many problems for waveform inversion to deal with real data. The matching of synthetic seismograms with observed seismograms and noise cancellation are two primary problems. In conclusion, on the foundation of the former experiences, this dissertation has implemented waveform inversions on the basis of acoustic wave equation and elastic wave equation, traveltime inversion on the basis of acoustic wave equation and traditional combined waveform traveltime inversion. Besides the traditional analysis of inversion theory, there are two innovations: layer by layer inversion of seimic reflection data inversion and rapid method for acoustic wave-equation joint inversion.

Pg震相走时的各向异性影响及各向异性结构成像

As the first arrival of seismic phase in deep seismic sounding, Pg is the important data for studying the attributes of the sedimentary layers and the shape of crystalline basement because of its high intensity and reliable detection. Conventionally, the sedimentary cover is expressed as isotropic, linear increasing model in the interpretation of Pg event. Actually, the sedimentary medium should be anisotropic as preferred cracks or fractures and thin layers are common features in the upper crust, so the interpretation of Pg event needs to be taken account of seismic velocity anisotropy. Traveltime calculation is the base of data processing and interpretation. Here, we only study the type of elliptical anisotropy for the poor quality and insufficiency of DSS data. In this thesis, we first investigate the meaning of elliptical anisotropy in the study of crustal structure and attribute, then derive Pg event’s traveltime-offset relationship by assuming a linear increasing velocity model with elliptical anisotropy and present the invert scheme from Pg traveltime-offset dataset to seismic velocity and its anisotropy of shallow crustal structure. We compare the Pg traveltime calculated by our analytic formula with numerical calculating method to test the accuracy. To get the lateral variation of elliptical anisotropy along the profiling, a tomography inversion method with the derived formula is presented, where the profile is divided into rectangles. Anisotropic imaging of crustal structure and attribute is efficient method for crust study. The imaging result can help us interprete the seismic data and discover the attribute of the rock to analyze the interaction between layers. Traveltime calculation is the base of image. Base on the ray tracing equations, the paper present a realization of three dimension of layer model with arbitrary anisotropic type and an example of Pg traveltime calculation in arbitrary anisotropic type is presented. The traveltime calculation method is complex and it only adapts to nonlinear inversion. Perturbation method of travel-time calculation in anisotropy is the linearization approach. It establishes the direct relation between seismic parameters and travetime and it is fit for inversion in anisotropic structural imaging. The thesis presents a P-wave imaging method of layer media for TTI. Southeastern China is an important part of the tectonic framework concerning the continental margin of eastern China and is commonly assumed to comprise the Yangtze block and the Cathaysia block, the two major tectonic units in the region. It’s a typical geological and geophysical zone. In this part, we fit the traveltime of Pg phase by the raytracing numerical method. But the method is not suitable here because the inefficiency of numerical method and the method itself. By the analytic method, we fit the Pg and Sg and get the lateral variation of elliptical anisotropy and then discuss its implication. The northeastern margin of Qinghai-Tibetan plateau is typical because it is the joint area of Eurasian plate and Indian plate and many strong earthquakes have occurred there in recent years．We use the Pg data to get elliptical anisotropic variation and discuss the possible meaning.

多波多分量地震资料走时近似方法的研究与应用

Compared with the conventional P wave, multi-component seismic data can markedly provide more information, thus improve the quality of reservoir evaluation like formation evaluation etc. With PS wave, better imaging result can be obtained especially in areas involved with gas chimney and high velocity formation. However, the signal-to-noise of multi-component seismic data is normally lower than that of the conventional P wave seismic data, while the frequency range of converted wave is always close to that of the surface wave which adds to the difficulty of removing surface wave. To realize common reflection point data stacking from extracted common conversion point data is a hard nut to crack. The s wave static correction of common receiver point PS wave data is not easy neither. In a word, the processing of multi-component seismic data is more complicated than P wave data. This paper shows some work that has been done, addressing those problems mentioned above. (1) Based on the AVO feature of converted wave, this paper has realized the velocity spectrum of converted waves by using Sarkar’s generalized semblance method taking into account of AVO factor in velocity analysis. (2)We achieve a method of smoothly offset division normal method.Firstly we scan the stacking velocities in different offset divisions for a t0, secondly obtain some hyperbolas using these stacking velocities, then get the travel time for every trace using these hyperbolas; in the end we interpolate the normal move out between two t0 for every trace. (3) Here realize a method of stepwise offset division normal moveout.It is similar to the method of smoothly offset division normal moveout.The main difference is using quadratic curve, sixth order curve or fraction curve to fit these hyperbolas. (4)In this paper, 4 types of travel time versus distance functions in inhomogeneous media whose velocity or slowness varies with depth and vertical travel time have been discussed and used to approximate reflection travel time. The errors of ray path and travel time based on those functions in four layered models were analyzed, and it has shown that effective results of NMO in synthetic or real data can be obtained. (5) The velocity model of converted PS-wave can be considered as that of P -wave based on the ghost source theory, thus the converted wave travel time can be approximated by calculation from 4 equivalent velocity functions: velocity or slowness vary linearly with depth or vertical travel time. Then combining with P wave velocity analysis, the converted wave data can be corrected directly to the P-wave vertical travel time. The improvements were shown in Normal Move out of converted waves with numerical examples and real data. (6) This paper introduces the methods to compute conversion point location in vertical inhomogeneous media based on linear functions of velocity or slowness versus depth or vertical travel time, and introduce three ways to choose appropriate equivalent velocity methods, which are velocity fitting, travel time approximation and semblance coefficient methods.

油气勘探中的弱磁异常提取与区域场分析

Petroleum and natural gas is an important strategic resources. The short of the reserves will block the development of economy and threaten the safety of nation, along with the main oil fields of our country coming to the height of power and splendor of the exploitation and exploration. Therefore, it makes a great sense to inaugurate new explorative field and increase the reserves of petroleum and natural gas. Magnetic exploration is a main method of geophysics exploration. the developing observation apparatus and the perfect processing method provide wide space for magnetic exploration in these years. The method of magnetic bright spot is an application of magnetic exploration. The vertical migration of the hydrocarbon changes physical and chemical environment above the hydrocarbon reservoir, the new environment make tervalent iron translate into bivalent iron, that produce small scale magnetic anomaly, that is magnetic bright spot. The method of magnetic bright spot explores oil and gas field by the relation between the hydrocarbon and magnetic anomaly. This paper systemically research to pick-up and identify magnetic bright spot combining an oil field item, then point out advantaged area. In order to test the result, the author use the seismic information to superpose the magnetic bright spot, that prove the magnetic bright spot is reliable. then, the author complete a software to pick and identify the magnetic bright spot. The magnetic basement is very important to research forming and evolvement of the basin, especially, it is a crucial parameter of exploring residual basin in the research on pre-Cenozoic residual. This paper put forward a new method to inverse the interface of the magnetic layer on the basis of previous work, that is the method of separation of magnetic field step by step. The theory of this method is to translate the result of magnetic layer fluctuation to the result of magnetization density change, and the magnetic layer is flat, the paper choose thickness of magnetic layer as unit thickness, and define magnetic layer as a unit-thickness layer in order to convenient calculation, at the same time, define the variational magnetization density as equivalent magnetic density. Then we translate the relation between magnetic field and layer fluctuation to the relation between magnetic field and equivalent magnetic density, then, we can obtain the layer fluctuation through calculating equivalent magnetic density. Contrast to conventional parker method, model experimentation and example checkout prove this method is effective. The merit of this method is to avoid flat result in a strongly fluctuant area because of using a uniform average depth, the result of this method is closer to the fact, and this method is to inverse equivalent magnetic density, then translate equivalent magnetic density to layer fluctuation, this lays a foundation to inverse variational magnetic density in the landscape orientation and portrait.

残留盆地分布综合地球物理研究——以大港地区为例

Macro-distribution of residual basins is a basic question in residual basin research，the main object of macro-distribution study is to build strata framework, compute thickness of residual strata and analyze characteristics of residual basins. With the guidance of the theory of integrated geology and geophysical research, the paper assembled series of methods and established the technical chart based on gravity and magnetic data, with restriction of geology, seismic and drilling data. Based on potential field data processing and analysis, forward and inverse computation, region potential field analysis and potential field separation, etc. it computed depth of gravity/magnetic basement and got strata framework. It had got effective results in the research of macro-distribution of residual basin research in the Dagang area. It did the wavelet transform of gravity/magnetic data with multi-kind of wavelet basis using a trou algorithm. From comparison of processing result and their spectral of wavelet analysis, up continuation and filter method, the wavelet approximation is better to fit the regional potential field, and it is an effective method to separate gravity/magnetic effect caused by deep geology bodies. The experiment of matching pursuit shows that te transform domain methods have great advantage in potential data analysis. From the integrated geophysical study of rock property study, gravity/magnetic basement inversion and fault system analysis of the Dagang area, it gets the strata framework and the thickness of pre-Cenozoic residual strata. Comprehensive study with gravity and magnetotelluric profile inversion and interpretation, three prospect plays of macro-distribution of residual basins are fingered out. It has great residual strata thickness in the northern part of Chengning Uplift and there is thrust fault in the deep zone and good up-Paleozoic hydrocarbon source rocks in this area. With integrated analysis, this area will be the most prospective hydrocarbon location of pre-Cenozoic residual basins.

基于显式分形插值的高保真地震数据重建方法研究

Based on the fractal theories, contractive mapping principles as well as the fixed point theory, by means of affine transform, this dissertation develops a novel Explicit Fractal Interpolation Function（EFIF）which can be used to reconstruct the seismic data with high fidelity and precision. Spatial trace interpolation is one of the important issues in seismic data processing. Under the ideal circumstances, seismic data should be sampled with a uniform spatial coverage. However, practical constraints such as the complex surface conditions indicate that the sampling density may be sparse or for other reasons some traces may be lost. The wide spacing between receivers can result in sparse sampling along traverse lines, thus result in a spatial aliasing of short-wavelength features. Hence, the method of interpolation is of very importance. It not only needs to make the amplitude information obvious but the phase information, especially that of the point that the phase changes acutely. Many people put forward several interpolation methods, yet this dissertation focuses attention on a special class of fractal interpolation function, referred to as explicit fractal interpolation function to improve the accuracy of the interpolation reconstruction and to make the local information obvious. The traditional fractal interpolation method mainly based on the randomly Fractional Brown Motion (FBM) model, furthermore, the vertical scaling factor which plays a critical role in the implementation of fractal interpolation is assigned the same value during the whole interpolating process, so it can not make the local information obvious. In addition, the maximal defect of the traditional fractal interpolation method is that it cannot obtain the function values on each interpolating nodes, thereby it cannot analyze the node error quantitatively and cannot evaluate the feasibility of this method. Detailed discussions about the applications of fractal interpolation in seismology have not been given by the pioneers, let alone the interpolating processing of the single trace seismogram. On the basis of the previous work and fractal theory this dissertation discusses the fractal interpolation thoroughly and the stability of this special kind of interpolating function is discussed, at the same time the explicit presentation of the vertical scaling factor which controls the precision of the interpolation has been proposed. This novel method develops the traditional fractal interpolation method and converts the fractal interpolation with random algorithms into the interpolation with determined algorithms. The data structure of binary tree method has been applied during the process of interpolation, and it avoids the process of iteration that is inevitable in traditional fractal interpolation and improves the computation efficiency. To illustrate the validity of the novel method, this dissertation develops several theoretical models and synthesizes the common shot gathers and seismograms and reconstructs the traces that were erased from the initial section using the explicit fractal interpolation method. In order to compare the differences between the theoretical traces that were erased in the initial section and the resulting traces after reconstruction on waveform and amplitudes quantitatively, each missing traces are reconstructed and the residuals are analyzed. The numerical experiments demonstrate that the novel fractal interpolation method is not only applicable to reconstruct the seismograms with small offset but to the seismograms with large offset. The seismograms reconstructed by explicit fractal interpolation method resemble the original ones well. The waveform of the missing traces could be estimated very well and also the amplitudes of the interpolated traces are a good approximation of the original ones. The high precision and computational efficiency of the explicit fractal interpolation make it a useful tool to reconstruct the seismic data; it can not only make the local information obvious but preserve the overall characteristics of the object investigated. To illustrate the influence of the explicit fractal interpolation method to the accuracy of the imaging of the structure in the earth’s interior, this dissertation applies the method mentioned above to the reverse-time migration. The imaging sections obtained by using the fractal interpolated reflected data resemble the original ones very well. The numerical experiments demonstrate that even with the sparse sampling we can still obtain the high accurate imaging of the earth’s interior’s structure by means of the explicit fractal interpolation method. So we can obtain the imaging results of the earth’s interior with fine quality by using relatively small number of seismic stations. With the fractal interpolation method we will improve the efficiency and the accuracy of the reverse-time migration under economic conditions. To verify the application effect to real data of the method presented in this paper, we tested the method by using the real data provided by the Broadband Seismic Array Laboratory, IGGCAS. The results demonstrate that the accuracy of explicit fractal interpolation is still very high even with the real data with large epicenter and large offset. The amplitudes and the phase of the reconstructed station data resemble the original ones that were erased in the initial section very well. Altogether, the novel fractal interpolation function provides a new and useful tool to reconstruct the seismic data with high precision and efficiency, and presents an alternative to image the deep structure of the earth accurately.

地震波谱元法数值模拟和偏移研究

With the development of both seismic theory and computer technology, numerical modeling technology of seismic wave has achieved great advancement during the past half century. The current methods under development include finite differentiation method (FDM), finite element method (FEM), pseudospectral method (PSM), integral equation method (IEM) and spectral element method (SEM). They exert their very important roles in every corner of seismology and seismic prospecting. Large quantity of researches towards spectral element method in the end of last century bring this method to a new era, which results in perfect solution of many difficult problems. However, parts of posterior works such as seismic migration and inversion which base on spectral element method have never been studied widely at least up to the present whereas are of importance to seismic imaging and seismic wave propagation. Based on previous work, this paper uses spectral element method to investigate the characteristics and laws of the seismic wave propagation in isotropic and anisotropic media. By thoroughly studying this high-accuracy method, we implement a kind of reverse-time pre- and post-stack migration based on SEM. In order to verify the validity of the SEM method, we have simulated the propagation of seismic wave in several different models. The simulation results show that: (1) spectral element method can be used to model any complex models and the computational results are comparable with the expected results and the analytic results; (2) the optimum accuracy can be achieved when the rank is between 4 and 9. When it is below 4, the dispersion may occur; and when it is above 9, the time step-length will be changed accordingly with the reducing space step-length in order to keep the computation stability. This will exponentially increase the computation time and at the same time the memory even if simulating the same media. This paper also applies explosive reflection surface imaging technology, time constancy principle of wave-filed extrapolation and least travetime raytracing technology of surface source to SEM pre- and post-stack migration of isotropic and anisotropic media. All imaging results derived by the above methods agree well with the real geological models and the position of interface and inflexions can also return to their right location well. This indicates that the method proposed in this paper is a kind of technology with high accuracy and robust stability. It can serve as an alternative method in real seismic data processing. All these work can boost the development of high-accuracy seismic imaging, and therefore have significant inference value.