Research Of 3D High-Precision Seismic Exploring Data Acquisition Technology In Shengli Oil Field Paralic Zone

Paralic zone means coastal mud flat, intertidal zone and shallow sea with depth of water lower than 10 meters. It is such special surface condition that the modes of seismic exploring are different from that in land and marine. At present, the effects of high-accuracy seismic exploring in paralic zone are little in the world. And existing seismic exploration achievements generally have the problems that the SNR and resolution ratio of gathering data are low. The paralic zone of Shengli Oil Field has abundant oil & gas resources, wide area and enormous exploring potentiality, but complicated surface condition and surface layer structure influence exciting and receiving of the seismic wave seriously. The requirements of the fine geological structure interpretation are unable to meet. So, researching the methods of high-accuracy three-dimensional seismic exploring in complicated surface areas of paralic zone is significant.The seismic characteristics of the paralic zone in Shengli Oil Field are researched in detail at first. Four key technologies for seismic exploring in paralic zone are provided, through analyzing synthetically the factors of seismic exploring in paralic zone and the characters of old seismic data in the paralic zone of Shengli Oil Field. After that, the paper focuses on researching the four technologies, and some innovative technological achievements are got.The author describes the target designing technologies of no split concatenation in seismic gathering, by researching the mutual surface characters of the land and water and the underground geological characteristics in paralic zone, considering the geological task, and referring the current state of seismic gathering equipments. As a integrated applied technology, on the base of fully analyzing geological and seismic condition in the target district of seismic exploring project, it includes three parts: the seismic gathering designing technique of demonstrating seismic gathering parameters based on a geophysical model, the survey system attributes analysis technique based on numerical model design, and the forward modeling technique of ray tracking and synthetic traces making based on underground geological model. Applying theseintegrated technologies and drawing lessons from the designing methods of the land and marine in target exploring designing, a flexible and changeable survey system is obtained. But, some methods must be done to improve fold number in the target region of seismic gathering, and the survey system must be changed with the variation of target layer depth.The receiving technique and secondary localization technique being suitable to paralic zone are studied. By the theory analysis and experiment contrast between velocity receiver and bender hydrophone, different model receivers must be used together so as to receive seismic wave well in the complicated surface layer structure region of paralic zone. Further more, the tail cone structure of the geophones are improved to enhance the coupling effect between geophone and the earth's surface. In the course of improving geophone, some means prove the performance of the geophone, such as, indoor vibration platform test, outdoor modeling test, and field test data contrast, etc. Meanwhile, new type geophone is developed to solve the problem of receiving seismic wave in the mudbank area. Because a receiver will swift with water flow, which brings on the problem of localization precisely, research on sonar localization and first break localization is involved. Especially, the question of then-errors is discussed detailedly. Moreover, secondary localization software using first break is developed.The exciting way in paralic zone is also presented. Key research has been made between explosive energy source and air gun source on comparing with their characteristics of exciting, mode of combination, exciting way, impact on seismic wave, different exciting sources match, and the choice of the source parameters, etc. And the rational view is introduced, which the combination of using explosive energy source and air gun source can produce the seismic wavelet of wide band and strong energy, according to surface characteristics of paralic zone and the tide law.The seismic gathering operation way in. paralic zone is finally proposed, which choosing rationally the mode of exciting and receiving can improve the quality of seismic data effectively, reduce the excessive interference of transition zone, depending on the tide characteristics. In addition, the consistency and validity ofseismic gathering factor are also involved.Applying the comprehensive technologies mentioned above to two paralic zones in Shengli Oil Field, Guojuzi project and Zhuanghai project, gets better result, by target designing of seismic exploring and field seismic gathering. The seismic data processing result shows, that every marker bed is linked up accurately, the geological phenomenon is clear, the geological structure is accurate and rational, SNR and resolution ratio of seismic data are much higher, the fracture system is known. So, It can meet the requests for the geological task. As a conclusion, the differences are eliminated among frequency, phase, energy, etc. of seismic data in land, mud flat and shallow sea, using all the technologies discussed in the paper. High quality and high accuracy seismic section are got. And the good geological results and economic benefits has been made.The research has higher directive significance and extensive application value to three-dimensional seismic exploring in all paralic zones of Shengli Oil Field and around Bohai Bay.