THE STUDY OF THE LOW-FREQUENCY SECTION IN THE NEAR-SURFACE MICRO-LOGGING RECORD OF THE TAHE OILFIELD

There generally exists the record of a low-frequency band characterized by low frequency,strong energy and fat wave form in the near-surface micro-logging data of the Tahe oilfield,which usually occurs near the top of the high-velocity layer.The reason for the formation of this special low-frequency band and its influence on the selection of IP well depth are important problems that geologists have to face in seismic data acquisition in this area.The low-frequency band was previously considered to be produced by lithological change,and hence in well depth design,the low-frequency band was intentionally avoided.Based on practical data,theroretical analysis and well depth test,the authors hold that the low-frequency band results from ghosting,and that the IP in the low-frequency band will not change the single gun quality.The characteristics and the formation mechanism of the low-frequency band as well as its impact on the selection of IP well depth are analyzed in detail,and it is considered that the influence of the low-frequency band can be ignored in the IP well depth design.