Finite Element Analysis And Application Of The Fracturing String

Fracturing operation was one of the effective way to improve hydrocarbon reservoir's permeability and raise oil and gas well's production. The mechanical analysis was the basis of designing the fracturing string and optimizing the construction parameters. This article was in view of the configuration about vague, graded fracturing string in deep well and the fracturing string in horizontal well. The overall fracturing string was selected as research objects. The load conditions and displacement boundary of the packer, hydraulic anchor and sand blasting sleeve was considered in the descent down hole, setting and fracturing operational mode. The nonlinear mechanical model about fracturing string was established. The gap element was adopted to simulate the contact condition between the fracturing string and the inside wall of the casing. The conditions of compatibility between the axial friction and the axial displacement was derived out. The forces and deformation status of the hydraulic anchor, packer and sand blasting sleeve were unified described under different operational mode. The dual nonlinear finite element methods was established. The software about the"deformation analysis of fracturing string"was developed by delphi language. It could compute the fracturing string's deformation, internal force and stress as well as the axial force displacement of the hydraulic anchor, packer and sand blasting sleeve under the different conditions of the displacement, pressure, card distance. In the vague fracturing string with well depth of 3800m, when the fracture pressure became form 60 MPa to 80 MPa, the hydraulic friction was form 9.81 MPa/1000m to 15.87 MPa/1000m, the axial force was form 826.85 kN to 1046.85 kN , the anchorage force was from 129.28 kN to 336.31 kN, the max equivalent stress became form 507.68 MPa to 655.33 MPa. In the horizontal dual grip fracturing string with the depth of 2087m, when the fracture pressure was 50 MPa, the axial displacement of the upper packer was 0.19 mm. For the card distance from the 10m to 30m at dual-card fracturing string, the axial displacement of the lower packer was respectively 11.17 mm, 23.78 mm, 36.46 mm. At graded fracturing string with the depth of 3800m,when lifting the string 0.2m, in primary fracturing, the sand blasting sleeve's axial displacement was 2.89 mm in the setting operational mode, while in the fracturing operational mode, the value was 1.21 mm. In the after fracturing, the axial displacement was respective 171.39 mm,4.64 mm. If the lifting distance of the fracturing string was greater than 176 mm, there was no contact between the sand blasting sleeve and the fixed packer. In order to guarantee a fixed packer fracturing safe in operations,0.2m was recommend. The axial displacement could accurately predict the location of fracturing. Therefore,it verify the accuracy of the theoretical methods and the practicality of the software.In order to further describe the impact of the fluid temperature and pressure on the fracturing string, the flow fracturing fluid, the static fluid outside the tubular and the fracturing string was selected as objects. The coupling analysis model of the physical field with the temperature field, flow field and stress field was set up. The inner wall temperature was 36.99℃. Its outer wall temperature was 50.55℃. The axial pressure drop with the fracturing fluid was 0.83 MPa. It would provide a theoretical basis for accurately describing the fracturing fluid temperature and pressure.