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��As a result of study, it is proved that to explorate natural gas by contrasting the acoustic velocity obtained from acoustic velocity logging with that obtained from seismic prospecting to explorate natural gas is superior and feasible. In all strata below the groundwater table. the stratum With logging acoustic velocity obviously bigger than the vertical se ismic acoustic velocity is a gas reservoir and the continuous opposite direction extension area of vertical seismic acoustic velocity belongs to the same gas-bearing trap.     

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��The design of centralizer assembly is the basic and key job for directional drilling.According to the theory equation of bend beam,using the computer to solve the performance parameters in the design of centralizer assembly is a new,simple and reliable method.This paper derives the equation,describes the use of centralizer assembly taking the well Zhong-48 as an example and presents the attentions for appling this method.     

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��The method of "running the drill pipe into the big diameter casing's interior" is suitable for the cementing of big diameter casing at the interval with many thief zoner By use of this method,the quantity of cement can be exactly eontroled,the quantity of the mud used for replacing the cement slurry is lesser,the time for cementing operation is shortened and the return velocity of mud and cement slurry in annular space can be effectively controled,thus,it can decrease the mud damage and exactly guarantee the quality of the cement plug and annular cement column. The equipment,operation and the usege result in field are briefly stated in this article.