In seismic exploration methods, imperfect spatial sampling at the surface causes a lack of illumination at the target in the subsurface. The hampered image quality at the target area of interest causes uncertainties in reservoir monitoring and production, which can have a substantial economic impact. Especially in the case of a complex overburden, the impact of surface sampling on target illumination can be significant. The target-oriented acquisition analysis based on wavefield propagation and a known velocity model has been used to provide guidance for optimizing the acquisition parameters. Seismic acquisition design is usually a manual optimization process, with consideration of many aspects. In this study, we develop a methodology that automatically optimizes an irregular receiver geometry when the source geometry is fixed or vice versa. The methodology includes objective functions defined by two criteria: optimizing the image resolution and optimizing the angle-dependent illumination information. We use a two-step parameterization in order to make the problem more linear and, thereby, solve the acquisition design problem by using a gradient descent algorithm. With simple and complex velocity models, we demonstrate that the proposed method is effective, while the involved computational cost is acceptable. Interestingly, the optimization results in our examples show that the conventional uniform geometry already satisfies the resolution requirement, while optimizing for angle coverage can provide a large uplift and is strongly dependent on the velocity model.

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Imperfect spatial sampling causes lack of illumination at the target in the subsurface. The hampered image quality at the target area of interest can cause high uncertainties in reservoir monitoring and production, which can have a high economic impact. Previously we have presented a method that optimizes the receiver geometry while the source side is carpet shooting. In this work, we develop a method that optimizes both the source and receiver geometries in order to obtain a good illumination of a chosen target point, such that they can compensate the missing illumination for each other. With numerical examples, we demonstrate that the proposed method is effective.@en

Seismic data acquisition is a trade-off between cost and data quality subject to operational constraints. Due to budget limitations, 3D seismic acquisition usually does not have a dense spatial sampling in all dimensions. This causes artefacts in the processed images, velocity models, or other physical properties. However, we rely on, for example, the accurate images in determining the location of oil and gas-bearing geological structures, and the accurate elastic properties to characterise the reservoir. In this thesis, we propose new methods to improve existing technologies that can optimise marine seismic acquisition. In Part I, we aim at obtaining dense data in less time by improving the so-called blended seismic acquisition techniques. In Part II, we aim at obtaining an improved target illumination with a limited number of sources and receivers by developing an acquisition optimisation framework. @en

In blended seismic acquisition, or simultaneous source seismic acquisition, source encoding is essential at the acquisition stage to allow for separation of the blended sources at the processing stage. In land seismic surveys, the vibroseis sources may be encoded with near-orthogonal sweeps for blending. In marine seismic surveys, the sweep type of source encoding is difficult because the main source type in marine seismic exploration is the air-gun array, which has an impulsive character. Another issue in marine streamer seismic data acquisition is that the spatial source sampling is generally coarse. This hinders the deblending performance of algorithms based on the random time delay blending code that inherently requires a dense source sampling because they exploit the signal coherency in the common-receiver domain. We have developed an alternative source code called shot repetition that exploits the impulsive character of the marine seismic source in blending. This source code consists of repeated spikes of ones and can be realized physically by activating a broadband impulsive source more than once at (nearly) the same location. Optimization of the shot-repetition type of blending code was done to improve the deblending performance. As a result of using shot repetition, the deblending process can be carried out in individual shot gathers. Therefore, our method has no need for a regular dense source sampling: It can cope with irregular sparse source sampling; it can help with real-time data quality control. In addition, the use of shot repetition is beneficial for reducing the background noise in the deblended data. We determine the feasibility of our method on numerical examples.

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Imperfect spatial sampling causes lack of illumination at the target in the subsurface. The hampered image quality at the target area of interest can cause high uncertainties in reservoir monitoring and production, which can have a high economic impact. Especially in the case of a complex overburden, the relation between surface sampling and target illumination is not trivial. Target-oriented acquisition analysis based on wavefield propagation has been used to provide guidance for optimising the acquisition parameters. The acquisition design is usually a manual optimisation process, with consideration of many aspects. In this work, with a specific acquisition scenario, we develop a methodology that automatically optimises an irregular receiver geometry in order to obtain a good illumination of a chosen target point. With numerical examples, we demonstrate that the proposed method is effective.@en

In a blended acquisition, source encoding is needed for the separation of the blended source responses. The source ghost introduced by the strong sea surface reflection can be considered as a virtual source located at the mirror position of the actual source. In this abstract, we propose an acquisition concept that includes the source ghost as a natural source encoding such that it can be used for deblending, where the end result is deblended as well as deghosted. This acquisition method is easy to combine with man-made source encoding and also the concept of using the source ghost provides an interesting alternative to deal with the current depth distributed source for the broadband seismic data. @en

The source ghost introduced by the sea surface reflection is usually considered noise which needs to be removed before imaging. We propose to utilize the source ghost in deblending as a natural blending code such that the end result is both deblended and deghosted. This method is easy to combine with other temporal source codes and provides an interesting alternative to deal with the current depth distributed source for a broadband solution. In this abstract, we discuss how to use the source ghosts in the case of lateral blending and vertical blending to deblend and deghost with illustrations of simple synthetic models. We applied the method to field data where two sources are blended in the same lateral position but at different depths. The results obtained show that it is possible to deblend and deghost in one step in the variable depth source setting. @en

The applicability of a deblending method is directly related to acquisition parameters, such as source and detector locations. We formulate focal deblending in two alternative ways. In the first case, the double focal transform is used, which relies on a well-sampled source and detector dimension. In the second case, the single-sided focal transform is used, which does not depend on a well-sampled source dimension. Comparing the deblending results, we find that although the double focal transform is superior, blending noise can be significantly attenuated using the single-sided focal transform, which allows application to more practical acquisition geometries. By combining with shot repetition, the deblending result can be further improved. @en