| As the time of oilfield development has increased,a large number of oil and water wells have experienced casing damage.Sidetracking and liner reinforcement are two management methods for casing damage wells.The most onshore wells are equipped ?139.7 mm casing as production casing in Chinese oilfield.The inner diameter range of ?139.7 mm casing is 118.13-124.13 mm,both sidetracking and liner enforcement needs slim hole casing to be fitted in a limited space.In the early stage,clearance between ?101.6 mm slim hole casing and ?118 mm annulus is small,and the pressure loss caused by friction when cement slurry flow back to surface accounts for 97.09% of the total cementing pressure.The cementing quality is poor,and cementing accidents frequently occur.The cementing problem is solved when use ?89 mm tubing as slim hole casing,but its inner diameter is only 76 mm,the matching 60 perforating gun can not penetrate deep enough,and the matching ?48.3 mm small tubing has low strength,small liquid flow section,and it is difficult to carry out increasing production processes such as plug,sand control and block removal.On the basis of demonstrating the causes of casing damage,the frequently occurring parts of casing damage in wells,and the detection methods of casing damage,this paper combines the problems of using ?101.6 mm slim hole casing and ?89 mm tubing as slim hole casing in the early stage to optimize the design of ?95 mm slim well casing.The optimization follow the API manufacture and usage standards,although the outer diameter and inner diameter of the designed new slim hole casing are non-API standard products,but the thread is 3-1/2″UPTBG,it is manufactured,inspected according to API5 B,convenient for manufacture and filed application.According to field test,when the pressure reaches 180 MPa,the thread does not slip off even the pipe body burst.In order to avoid the problem of perforation rupture,the material selection and heat treatment are carried out according to the API casing standard.The?95 mm slim hole casing can equip with optimized bow spring centralizer according to standard,to ensure the sting centralization.Through the cement rheology calculation and verification,the pressure drop distribution ratio between the pipe and the annulus tends to be reasonable during cementing,to ensure the cementing quality.The internal diameter of the ?95mm slim hole casing is up to 82 mm,which can meet the field general used mm tubing entry requirements.On the premise of ensure the inner diameter as same as the ?60.3 mm tubing and the strength is up to standard,the Y221,Y341,K341 packers and sand control packing tools with an outer diameter of 76 mm are optimized as precondition for multilayer production,multilayer water injection and multilayer operation.Optimized and matched 68 synergistic perforating guns.The one shot success rate of perforation was increased from 75% when use 60 guns to 100%;the application area was expanded to cementing in the lower open hole section to form a new wellbore,workover process was optimized,and operation success rate reach 100%;In the case of casing damage well use slim hole casing as liner,807 oil,water and gas wells have been counted with a success rate of98.3%. |
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