Study Of Mechanical Properties Of Perforated Casing Due To Formation Sand Production And Compaction

Due to formation sand production, cavities will be formed in perforated interval resulting in noncontinuous and nonhomogeneous loads as well as stress concentration of perforated casing. At the same time, due to formation compaction, axial force of casing will be developed and the perforated casing may be demotion on the buckling section. Therefore, different sand producing degree and different forms of cavities due to formation sand production and compaction are consided to analyse the strength safety of perforated casing in this text.First of all, reservoir sand production and compaction mechanism, casing damage mechanism caused by sand production and compaction and configurations of sand production cavities of perforation casing in the sanding and compaction well section are respectively analyzed. In addition, the axial compressive force of the perforated casing due to sand production and compaction is analyzed to establish the three dimensional finite element mechanical model of perforated casing in which sizes and shapes of cavities in perforated sections resulting from different sand producing degree are considered. Then, the influence which different cavities, sanding producing degrees and sanding production distributions had on perforating casing strength safety, and the relationships between different production pressure differentials, stimulation pressures and perforating parameters, perforating casing equivalent stresses are derived through loading areas and loading forms of FEM models of different sanding producing degrees being taken into consideration.In order to achieve the collapse strength directly, formulae to calculate the collapse strength of casing and hole-edge stresses distribution of perforated casing exerted by bending moment and differential pressure were derived and optimized with the methodology of shell theory. The analysis results shows that the collapse strength formulae of unperforated casing and hole-edge stress distribution formula of perforated casing can be applied in the engineering.