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The Study On Crucial Techniques For Neogene Hydrocarbon Prediction Around Chengdao Region

Posted on:2016-05-08Degree:DoctorType:Dissertation
Country:ChinaCandidate:J F BiFull Text:PDF
GTID:1220330482980569Subject:Earth Exploration and Information Technology
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Neogene channel sandstone is the dominant reservoir in coastal regions ShengLi Oil Field.It is the potential reservoir for quality reserves because of its wide distribution, shallow burial depth and high yield. With the constantly advancing of the exploration, the exploration direction of channel sandstonehas transformed tolimb where reservoir conditions are more complex from the body section with structural settings. It’s difficult to predict and evaluate the oil-bearing of channel sandstone for its thin single layer thickness, rapid lateral change and low oil-bearing height, which lead to a poor success rate of annual wildcat and restrict the further exploration. According to statistics, the drilled wells aimed at Neogene channel sandstone in Chengdao area have failedin past two years, and the success rate was less than 30 percent. Two aspects need to be strengthened in Neogene channel reservoir exploration around Chengdao Region. On the one hand, we should further deepen the understanding of oil and gas migration and accumulation rules. On the other hand, there is an urgent need to develop a set of key geophysical techniques for oil-bearing according to different seismic geological conditions and predict the dominant oil area, improve the success rate of shallow wells.There are three reasons to choose the surrounding area of ChengdaoOil field for technical research. Firstly, the burial depth of Neogene strata in this area is shallow, and the exploration degree is low relatively, which have made the surrounding area of Chengdao Oilfield a potential exploration position. Secondly, the Neogene meander sand body is the main exploration target for increasing reserve and production in the past few decades and even in the near future.Lastly, the results of the research on the technology of oil-bearing prediction and evaluation can be obtained through the drilling, which are propitious to the formation and popularization of the technology series.In this paper, aiming at the technical difficulties in oil-bearing prediction and evaluation of the channel sand bodies, based on the theory of modern oil and gas accumulation andby means ofgeophysical technologies, hydrocarbon accumulation geologic factors of channel sand body reservoir have been studied deeply, the distribution of sand body reservoir has been predicted and evaluated, and the key technologies of oil-bearing prediction and evaluation have been established.In this paper, we started researchfrom the structural background, sedimentary facies characteristics and the distribution characteristics of hydrocarbon accumulation zones. The dissection about known reservoir had pointed that the oil source faults, the structural ridges, the channel sand bodies and the spatial matching of them were the main controlling factors of channel sand body reservoir. In order to describe the oil source fault network, the fault image enhancement processing technique and theimproved third generation coherence technique had been developed. According to the research of the oil source fault network and the relationship between source and reservoir, the faults had been divided into oil source fault, oil source fault branch and nonoil source fault. In order to master the structural bridges characteristics, the new simulation technique of hydrocarbon migration and accumulation based on the changes of gradient had been developed and its application had indicated the limited pathway of lateralhydrocarbon migration. The study on the oil-bearing prediction techniques of channel sand bodies was the most important part of this article and three techniques had been developed based on statistical analysis of reservoir geological model, drilled oil-bearing sand bodies thickness, velocity and the surrounding rock mass, the seismic reflection characteristics and elastic parameters.Developedthe attenuation spectralanalysis technique based on the wavelet cepstrumestimation through parted time window, which has been realized by means ofsetting time window atthe upper and lower layers of the oil layer, extracting the cepstrumwith more abundant information than the conventional power spectrum. The research production could enlarge the spectral difference between oil-gas layer and adjacent strata, which had predicted the thick sand bodies with stable lateraldistribution.And developedthe multi-attributes inversion technique based on spectral decomposition and the relationship between amplitude and frequency at different time thicknesses. The pure wave seismic data was processed bythe spectral decomposition technique and the wells information and seismic data had been combined throughnonlinear inversion algorithm named SVM support vector algorithm, which could effectively establish the relationship between different frequency properties of seismic data and the sensitivity curves indicating the existence of hydrocarbon. The research production could predict the potential oil and gas distribution zone, which had improved the lateral prediction accuracy of thin oil-bearingsandbody. Another was the direct inversion technique of pre-stack fluid factor for Gassmann Fluid factor. By constructing the sensitive coefficient of fluid factor, the most sensitive fluid factor to the oil-bearing channel sand body was optimized and the most sensitive fluid factor could be obtained by one step inversion by adding variable number of points to the initial objective function. The direct inversion of fluid factor had reduced the accumulated error and improved the sensitivity of the oil and gas detection. The results of the model verification and the practical application showed that the method could extract the results and the stability was very good. Through the research of this paper, the prediction methods of oil-bearing channel sand body with different petrophysicalcharacteristics and different lithologic combination structure have been established.The research and exploration well deployment have been linked closely, and quickly realized the technology transformation to yield and reserves. The application of developed techniques in Neogene strata of many areas including the Minghuahen group in the West Wing of Chengbei fault belt and the Lower Guantao segment in Zhuanghai area have achieved good exploration results. Not only the distribution range of oil-bearing areas has been predicted, but also the potential exploration areas have been indicated and the results have been in good agreement with the practical drilling results. Compared with conventional oil and gas detection results, they have a great improvement, which fully demonstrates the progressiveness and effectiveness of the developed techniques in this paper. Well Chengbei208 and Well Chengbei209 aiming at Minghuahen group in the West Wing of Chengbei fault belt had been submitted and drilled in 2014. Well Chengbei208 drilled out 16 oil layers, which existed in reservoir 67.3 meters thick, and 2 oil-water layers in reservoir 10.5 meters thick. Well Chengbei209 drilled out 9 oil layers, which existed in reservoir 49 meters thick, and 3 water layers in reservoir 40 meters thick. The result of testing for oil existed commercial oil flow, and 16 million tons probable reserves had been submitted in 2015. In addition, the research results of oil-bearing channel sand bodies in this paper have guided the deployment of wells in other areas such as Chengbei262, Chengbei374, Chengbei342 and etc. And the three wells above would submit forecast geological reserves about 900 million tons.There are three innovations in this paper as follows. The first one is that the direct inversion technique of pre-stack fluid factor controlled by variable number points. The most sensitive fluid factor is optimally choised by constructing the sensitive coefficient of fluid factor. Then, the direct inversion for fluid factor had been performed by adding variable number of points to the initial objective function, which reduced the accumulated error and improved the sensitivity and accuracy of the oil and gas detection. The second one is that the attenuation spectra analysis technique has been developed based on the wavelet cepstrum estimation through parted time window, which can detect the oil-bearing thick sand bodies with vertical concentration distribution and horizontal wide range. The third one is that the multi-attributes frequency-divided inversion technique based on AVF has been developed. The relationship between different frequency properties of seismic data and the sensitivity curves indicating the existence of hydrocarbon could be effectively established by nonlinear inversion algorithm and the lateral prediction accuracy of thin oil-bearing sandbody could be improved.
Keywords/Search Tags:Neogene, Hydrocarbon accumulation geologic factor, Structural ridge, Hydrocarbon detection, Fluid factor
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