Study Of Multiple Elimination Techniques In The Deepwater Area Of South China Sea

Seismic multiple, which is a kind of interference wave, is due to the earth’ssurface or some strong reflection coefficient interface which is underground makesthe primary reflection turn back more than one time and finally received by thegeophones. Seismic multiple is serious in the marine seismic data especially for thedeepwater data. In recent years, more than50%of the global oil and gas discoverycame from the sea, particularly, the deepwater domain. With the rapid development ofthe exploration and development of the deepwater oil and gas, it is transiting fromconventional deepwater (below1500m) to ultra-deepwater. China has beenconcerned the development of blue ocean resources and has discovered the Liwan oiland gas fields in the Baiyun sag;3Cenozoic oil and gas basin of Jianfengbei, Bijiaand Xisha trough in the deepwater continental slope; and has discovered Mesozoic ofcontinental slope of northern South China Sea is target area with exploration potential.As the main method of deepwater oil and gas exploration, seismic exploration facedone major issue, multiples. Multiple covers the primary wave and severely impactsthe seismic profile and thus, contributes to the ambiguity of interpretation and the lowsuccess rate of drilling. To sum up, for the purpose of increasing the accuracy ofinterpretation and reducing the risk of exploration, furtherly studying the multiplesurppression techniques and improve the data S/N ratio and resolution has importantpractical significance and application value.By means of forward numerical simulation and analysis, simple model trial,complex theory model processing, this paper discusses multiple suppressiontechniques, aiming at South China Sea deepwater multiple elimination. To examinethe methods and processing flow presented, we have processed Dongsha area seismicline in the deepwater continental margin of northern South China Sea and Liyue Basinseismic line in the southern South China Sea. First of all, by the method of numericalmodel of acoustic wave equation and elastic wave equation, we studied and analysedthe propagation law and wave field characteristics of multiple model; Next, we established simple models and processed the raw CSP (Common-Shot Point) gatherand analysed multiple elimination methods; And then we gave a transition fromsimple model to complex theory model and discussed the most effective methods andprocess. Finally, we applied the combined methods and flow summed to the Dongshaand Liyue data and thus proved the effectiveness and practicability.Aiming at deepwater multiple of South China Sea, the processing result of modeldata and actual data indicated that SRME+deconvolution in the τ-p domain+highresolution parabolic Radon transform or flexible use of Radon transform in the CRPgather, is a fruitful and very practical processing idea and methods flow. Whether forthe multiple suppression, the highlights of primary wave or deep structureidentification, we all achieved significant effect. Nonetheless, we should knowcircumstances alter case and do not apply mechanically. Besides, pay attention topreprocessing and random noise suppression before multiple processing.