The mud film thickness on the outer surface of casing and its distribution laws are important factors affecting the cementation quality at casing-cement interfaces.So far,however,the distribution laws of mud film thic...The mud film thickness on the outer surface of casing and its distribution laws are important factors affecting the cementation quality at casing-cement interfaces.So far,however,the distribution laws of mud film thickness on the outer surface of casing at different inclinations and its effect on the interfacial cementing strength have never been reported in literatures.In this paper,the mud film thickness at different parts on the outer surface of simulated casing(steel pipe)was measured at the inclination of 0°,30°,60°and 86°,respectively,using the independently designed experimental device.Then,the distribution law of mud film thickness on the outer surface of casing and its effect on the interfacial cementing strength were summarized.And the following research results were obtained.First,when the inclination increases from 0°to 86°,the mud film thickness changes from uniform distribution to thin-and-thick distribution,and the area proportions of thinner and thicker mud films both increase.And especially at the inclination of 86°,the mud film thickness on the upper surface is very large,and there are large exposed areas on the left and right surfaces of the steel pipe.Second,the cementing strength at the casing-cement interface of the exposed casing is much higher than that at the interface with mud film.And with the increase of inclination,the interfacial cementing strength with mud film tends to increase.Third,with the increase of inclination,the interfacial cementing strength increases successively,which is closely related to the area proportion of the exposed steel pipe to the solid mud film on the outer surface.In conclusion,the exposed area of the simulated casing on the outer surface is a key factor affecting its interfacial cementing strength.展开更多
For mitigating the hazards of slurry flowing back into the casing after liner cementing,the deficiency of slurry backflow prevention structure of current liner hangers at home and aboard was analyzed in this paper.The...For mitigating the hazards of slurry flowing back into the casing after liner cementing,the deficiency of slurry backflow prevention structure of current liner hangers at home and aboard was analyzed in this paper.Then,a structurally new casing plug,i.e.,a semi-hollow casing plug was designed and developed.And it,combined with the hanger,was tested on site.And the following research results were obtained.First,the deficiency of the slurry backflow prevention structure of liner hanger,is that the locking mechanism on the drill pipe plug is damaged before it reaches the casing plug and matches with each other.Second,the inner bore of the semi-hollow casing plug is designed as a bend hole,which has a hollow round hole in its upper part and a solid column in its lower part.Third,during the cementing operation,the drill pipe plug enters into the semi-hollow casing plug once it gets to the position of hanger.And it is stuck at the bend and cannot go down anymore.Consequently it is integrated with the casing plug as a whole part.Fourth,when the shear pin goes down to the setting seat through the casing string under the force of drilling fluid,the solid column at the lower part of the semi-hollow casing plug is squeezed into the inner hole of the seat.In this situation,the backflow of cement slurry can be prevented only by using sealing elements and locking device on the casing plug instead of by using drill pipe plug.Fifth,field tests show that the cement top of test wells is only 24 m higher than the designed value while that of offset wells is 59 m higher.Obviously,the former is 50%less than the latter.In conclusion,this newly developed semi-hollow casing plug matches well with hangers,having no negative effects on cementing operation,so the cement top after cementing can be well controlled.展开更多
Cement bond model wells （1：10 scaled-down） were made with a gradually degrading cement annulus for cement bond evaluation of the first interface （between the casing and the cement annulus） and the second interfa...Cement bond model wells （1：10 scaled-down） were made with a gradually degrading cement annulus for cement bond evaluation of the first interface （between the casing and the cement annulus） and the second interface （between the cement annulus and the formation）. Experimental simulation on cement bond logging was carried out with these model wells. The correlation of acoustic waveforms, casing wave energy and flee casing area before and after cement bonding of the second interface was established. The experimental results showed that the arrival of the casing waves had no relationship with the cement bonding of the second interface, but the amplitude of the casing head wave decreased obviously after the second interface was bonded. So, cement bonding of the second interface had little effect on the evaluation of the cement bond quality of the first interface by using casing head wave arrivals. Strong cement annulus waves with early arrivals were observed before the second interface was bonded, while obvious ＂formation waves＂ instead of cement annulus waves were observed after the second interface was bonded.展开更多
基金Project supported by the Sub-project of National Major Science and Technology Project(No.:2017ZX05009003-003)the National Natural Science Foundation of China(No.:51774258,41572142).
文摘The mud film thickness on the outer surface of casing and its distribution laws are important factors affecting the cementation quality at casing-cement interfaces.So far,however,the distribution laws of mud film thickness on the outer surface of casing at different inclinations and its effect on the interfacial cementing strength have never been reported in literatures.In this paper,the mud film thickness at different parts on the outer surface of simulated casing(steel pipe)was measured at the inclination of 0°,30°,60°and 86°,respectively,using the independently designed experimental device.Then,the distribution law of mud film thickness on the outer surface of casing and its effect on the interfacial cementing strength were summarized.And the following research results were obtained.First,when the inclination increases from 0°to 86°,the mud film thickness changes from uniform distribution to thin-and-thick distribution,and the area proportions of thinner and thicker mud films both increase.And especially at the inclination of 86°,the mud film thickness on the upper surface is very large,and there are large exposed areas on the left and right surfaces of the steel pipe.Second,the cementing strength at the casing-cement interface of the exposed casing is much higher than that at the interface with mud film.And with the increase of inclination,the interfacial cementing strength with mud film tends to increase.Third,with the increase of inclination,the interfacial cementing strength increases successively,which is closely related to the area proportion of the exposed steel pipe to the solid mud film on the outer surface.In conclusion,the exposed area of the simulated casing on the outer surface is a key factor affecting its interfacial cementing strength.
文摘For mitigating the hazards of slurry flowing back into the casing after liner cementing,the deficiency of slurry backflow prevention structure of current liner hangers at home and aboard was analyzed in this paper.Then,a structurally new casing plug,i.e.,a semi-hollow casing plug was designed and developed.And it,combined with the hanger,was tested on site.And the following research results were obtained.First,the deficiency of the slurry backflow prevention structure of liner hanger,is that the locking mechanism on the drill pipe plug is damaged before it reaches the casing plug and matches with each other.Second,the inner bore of the semi-hollow casing plug is designed as a bend hole,which has a hollow round hole in its upper part and a solid column in its lower part.Third,during the cementing operation,the drill pipe plug enters into the semi-hollow casing plug once it gets to the position of hanger.And it is stuck at the bend and cannot go down anymore.Consequently it is integrated with the casing plug as a whole part.Fourth,when the shear pin goes down to the setting seat through the casing string under the force of drilling fluid,the solid column at the lower part of the semi-hollow casing plug is squeezed into the inner hole of the seat.In this situation,the backflow of cement slurry can be prevented only by using sealing elements and locking device on the casing plug instead of by using drill pipe plug.Fifth,field tests show that the cement top of test wells is only 24 m higher than the designed value while that of offset wells is 59 m higher.Obviously,the former is 50%less than the latter.In conclusion,this newly developed semi-hollow casing plug matches well with hangers,having no negative effects on cementing operation,so the cement top after cementing can be well controlled.
基金supported by the National Natural Science Foundation of China(Grant No.10534040 and No.40574049)key laboratory of well logging of China National Petroleum Corporation(CNPC).
文摘Cement bond model wells （1：10 scaled-down） were made with a gradually degrading cement annulus for cement bond evaluation of the first interface （between the casing and the cement annulus） and the second interface （between the cement annulus and the formation）. Experimental simulation on cement bond logging was carried out with these model wells. The correlation of acoustic waveforms, casing wave energy and flee casing area before and after cement bonding of the second interface was established. The experimental results showed that the arrival of the casing waves had no relationship with the cement bonding of the second interface, but the amplitude of the casing head wave decreased obviously after the second interface was bonded. So, cement bonding of the second interface had little effect on the evaluation of the cement bond quality of the first interface by using casing head wave arrivals. Strong cement annulus waves with early arrivals were observed before the second interface was bonded, while obvious ＂formation waves＂ instead of cement annulus waves were observed after the second interface was bonded.
