Elastic Reverse Time Migration Method Study Based On Crosswell Seismic Data

The technology of crosswell seismic has been partly used in oilfield development, but asthe dominant technology in the production seismology, still needs further improvement. Whenthe production seismology has been gradually accepted by the petroleum engineers, crosswellseismic, especially reflected wave imaging, naturally becomes the focus of the study ofdomestic seismic technology. However, there are great differences between crosswell seismicand conventional seismic. Crosswell seismic often uses three-component geophones to recordthe information of the wave field, and in the crosswell seismic records, P-wave and transverseS-wave are relatively rich. How to take full advantage of this information to determine thegeologic structure is extremely crucial. Reverse time migration was first proposed in the1983by whitmore, and after thirty years of development, has made a great deal of progress.Nonetheless, the researches of reverse time migration are mainly focused on conventionalseismic, and this technology is seldom used in crosswell seismic. Elastic reverse timemigration is currently the most accurate imaging method, since considering the vectorcharacteristics of the wave, in theory elastic wave migration is superior to the scalar wavemigration. Thus the study of elastic reverse time migration based on crosswell seismic data issignificant.The records acquired in crosswell seismic are quite complex. We first analyze the wavefield, and basing on this, we research the processing flow of crosswell seismic. We introducereverse time migration applied in surface seismic imaging to crosswell seismic imaging.Using finite difference technique, we derive an arbitary-order accurate space, second-orderaccurate time, two-dimensional acoustic finite-difference scheme based on the rectangulargrid. Comparison of several commonly used artificial boundary conditions, summarize theiradvantages and disadvantages, and ultimately select the mixed boundary conditions for calculating. In the finite-difference reverse time migration of acoustic wave, we adoptcross-correlation imaging condition. During the imaging process, we consider the imagingnoise, take appropriate measure to eliminate it, and ultimately get satisfying imaging results.The data recorded in crosswell are multiple components, and then we research elastic reversetime migration: derive the velocity-stress equations for modeling and two-dimensional elasticfinite-difference scheme based on the staggered grid, and give the imaging condition of elasticreverse time migration.Applying acoustic RTM and elastic RTM to crosswell seismic, we can image theup-going and down-going wave without separation, and avoid the noises caused byuncompleted separation. Through the model and real data test, satisfactory results have beenachieved.