Fault Automatic Recognition And Intelligent Interpretation In 3-D Seismic Data

The earth is the basic space of human's living and development. Since the emergence of the human society, human has never stopped exploring the earth. As society advances, human's requirement of resource is increasing. Geophysics has unique advantage at the problems such as resources prospecting etc. which are closely related to social development. Seismic exploration method is an indispensable technology in hydrocarbon resources exploration. Seismic exploration method has been improved increasingly, from the two-dimensional seismic has developed to the three-dimensional seismic. From the emergence to the present, the three-dimensional seismic exploration method has been widely used in this 30 years, the three-dimensional seismic has almost replaced the position of traditional two-dimensional seismic in hydrocarbon resources exploration.Faults could not only be a channel of hydrocarbon migration, but also could have sealed effect in hydrocarbon migration. With the theory of exploration developing to the deep-level, the quantitative study of carrier system has become the important component of hydrocarbon accumulation. As one of the three carrier systems, the research of faults has the greatest difficulty. Traditionally faults are picked in 3D seismic volumes as discontinuities in seismic amplitude on sections and time slices, this method is through visual recognition of reflector's discontinuity to achieve fault interpretation. The drawback of this conventional interpretation method is its inefficiency and strong subjectivity, this method greatly depends on the experience of interpreter and geological priori information, as the exploration for oil and gas goes deep, the geologic targets are also becoming more complex, traditional interpretation method is difficult to merge fault surface. In order to improve the accuracy and efficiency of fault interpretation, interpreters hope to extract potential structural information from seismic data. For a long time, people has made a lot of efforts for the accurately description of fault system, a number of description methods has been presented and applied, and plenty of discontinuity attributes which emphasize the fault information are extracted from 3-D seismic date successfully, such as fault slicing,coherence cube,variance cube,dip-azimuth attribute and edge enhancement attribute and so on. The present of coherence cube has improved the discontinuity technology to a whole new level, and also makes auto recognition of faults being possible. But no matter what kinds of discontinuity attribute, the application effects are affected by parameters in various degrees, all the attribute impossible to completely remove the noises and remains of the strata. Therefore, another method should be exploited based on these discontinuity attributes in order to achieve the real auto recognition of fault.Reducing the cycle of oil and gas exploration has significant economic benefits, as the data has shown, Oil companies have suggested that for each 6 months saved,5% of the total costs of the development of the oilfield are saved. In the exploration phase, some of the most time consuming tasks involves the geological interpretation of seismic data. This is today done manually by interpreters, and much time could be saved by automating these tasks, therefore, seeking a method of fault auto recognition is very important. Recently, the study of fault automatic recognition and intelligent interpretation has become one of the hot issues which are focused on the many scholars and researchers.In order to effectively overcome the problems of the existing fault recognition methods, the author proposed a fault auto-tracking and recognition scheme based on ant colony algorithm which is the latest bionic simulated evolutionary algorithm. Focused on the research of fault autotracking and recognition which is based on orientation constraint ant tracking algorithm, this paper consists of five parts as follows.The first part of this dissertation introduces the purpose and significance of this topic based on the analysis of current relevant researches both at home and abroad, including fault interpretation methods, fault enhancement attributes, Technology of fault automatic recognition and ant colony algorithm (ACA). Partâ… also points out the shortcomings of current technology in Fault automatic recognition. Overall, this part describes the main contents, contribution and innovative points of this dissertation.The second part begins with a brief introduction to the origins of ant colony algorithm, and then discusses some improvements and applications on basic ant colony algorithm, on the basis of detailed study of mathematical model and implementation process of ACA. Considering the similarities between fault recognition and image edge detection, the second part makes a fully analysis of the principles and implementation process about how ACA is applied into the image edge detection with noise, and then tests the real images, which successfully verified the feasibility that ACA can be used for fault automatic recognition from indirect sources.The third part is the core of this dissertation. It begins with the introduction to Improved C3 Algorithm, then compares the processing effect of it from that of C3 Algorithm and C2 Algorithm through real-world data, confirming that Improved C3 Algorithm can help to get data with higher resolution and SNR(Signal to Noise Ratio). Improved C3 Algorithm is chosen as the Fault Attribute so as to achieve better results in Fault Automatic Recognition.. Then, grounded on the application of ACA in image edge detection with noise, orientation constraint ant tracking algorithm is proposed to solve the problems existing in fault enhancement attributes. It also makes a detailed introduction to the principles, tracking strategies and implementation processes of this Algorithm. At last, part III focuses on presenting the application of this algorithm to a multi-fault 2-D synthetic model in order to verify the validity and reliability, and the discussion on impact and optimization of parameters in this algorithm. The forth part firstly introduces the fault-line optimization methods, including expansion, corrosion, opening operation and closing operation in mathematical morphology, graph thinning technology of image processing, and then applies these methods to optimize the results, thus getting more accurate data. What's more the calculation method for transient occurrence of fault points on the 3-D fault surfaces is also presented in this part; finally, part IV presents the auto-extraction and adaptive separation methods according to transient occurrence.The fifth part is centered on real experiment. Based on the analysis of real data from Shengli oil field, it makes a further research on the impact of tracking control parameters, proposes the different tracking strategies which should be used for tracking vertical section and horizontal section respectively, and the final results are projected to the original seismic section to demonstrate the effectiveness and accuracy. It also carries out comparative analysis between the effect using this method and the one with Petrel software, which presenting the strengths of our method.The original contributions in this dissertation are as follows:1. The proposed scheme is first successful attempt to fault automatic recognition by orientation constraint ant tracking algorithm worldwide. Results from both synthetic models and real-world data demonstrate that orientation constraint ant tracking algorithm applied to fault automatic recognition should be considered good not only in terms of noise suppression but also in terms of fault continuity enhancement, some controlling strategies are proposed to solve the problem of time-consuming search due to large amount of seismic data, thus improving search efficiency. There is comparative analysis between the effect using this method and the one with Petrel software, which demonstrates the advantage of this method.2. Fault Adaptive Separation method which is based on the calculation of 3-D transient occurrence is brought forward for the first time in China. Grounded on space distance, this method makes a preliminary separation among the faults, and then conducts a further separation between intersectional faults by instantaneous dipping angle and instantaneous dipping tendency of three dimensional faults.