Design Of Expansible Casing Used In Small-Diameter Borehole And Study On The Hydraulic Expansion Process

Expansible casing technology can plug complex formation and repair damaged casing while keeping borehole diameter unchanged.It has been widely used in the petroleum field.In order to promote the application of this technology in small-diameter geological drilling,on the basis of a comprehensive review of the research status at home and abroad,through theoretical analysis,numerical simulation and experimental research,the section form of 8-shaped casing was optimized,the pipe material and wall thickness parameters were optimized,the design principles of small-diameter casing were summarized,and a perfect laboratory test system for hydraulic expansion of casing was formed.The evaluation system,the matching drilling tools and welding aids for casing have been developed,and the feasible field construction scheme has been worked out.In order to optimize the material and wall thickness of casing,on the basis of fully comparing the mechanical properties,metallographic structure and chemical composition of the candidate materials,a two-dimensional model of hydraulic expansion of casing is established by using finite element analysis method.The material and wall thickness are used as single variables to simulate and analyze respectively.The stress distribution and deformation during the expansion process are compared,and the wall thickness and material are summarized,and the influence of wall thickness and material on the expansion performance of casing is summarized.Based on the simulation results and theoretical analysis results,the casing made of TG02 were optimized.Two specifications of 4 mm wall thickness and 4.5 mm wall thickness were processed for indoor expansion test.An indoor hydraulic expansion test system is developed.The system adopts digital control,which can accurately set test parameters and realize real-time monitoring and recording of hydraulic expansion of casing.Aiming at the problem of insufficient compressive strength of weld seam in expansion process,port shaping tool and welding clamping tool were developed,and casing before and after welding were heat treated.After process optimization,the weld strength has been greatly improved.After constrained and unconstrained hydraulic expansion test andmechanical expansion test,the final inner diameter of TG02 casing with wall thickness of 4.5mm exceeds 120 mm,which meets the design requirements and has good expansion performance.In order to verify the practical application value of the research results in this paper,field tests were carried out in Jiangshan Well 1,Zhejiang Province.The tests were carried out in two sections with depths of 23m~55m and 60m~72m,respectively.After expansion,the inner diameter of the tube string has reached 122.5mm,and the test has been successful,which promotes the application of casing technology in the field of small-diameter geological exploration more widely.