Erosion characteristics and simulation charts of sand fracturing casing perforation

Large-scale sand fracturing is a necessary means in the efficient exploitation of shale gas/oil.However,in the process of fracturing operation,the sand carrying fluid and proppant easily causes scouring and wear to production strings,especially the casing perforation system,which damage the wellbore integrity and deformation to affect the subsequent fracturing.For this problem,taking the actual construction conditions and perforation technology of an oilfield in western China as an example,the structural parameters of the downhole string were measured and the wall thickness reduction model of casing perforation suitable for large-displacement sand fracturing in horizontal well section was established.With software ANSYS-FLUENT,the casing perforation erosion under the conditions of different displacements,sand content and perforation sand-passing quantity in the process of sand fracturing was simulated and calculated.The influences of three parameters on perforation erosion and expansion were analyzed and the prediction chart of the influences of three main control factors on perforation erosion and expansion was established.The perforation erosion images after fracturing construction were obtained with the downhole eagle perforation logging technology.The logging chart results were compared with the downhole eagle perforation data.The error between the established numerical simulation calculation charts and the real logging data was about 5%,indicating that the simulation charts were the valuable reference.

Numerical Analysis of Residual Strength in the Perforated Casing of Ultra Deep Wells

A three-dimensional model for the numerical simulation of casing-cement behavior is used to investigate residual strength in the perforated casing of ultra deep wells.The influence of the hole diameter,hole density and phase angle on the residual strength of the casing under non-uniform stress and fracturing conditions is revealed through the consideration of different perforation parameters.It is shown that the residual strength of the casing increases with the hole diameter and periodically changes with the hole density;the phase angle is the main factor that affects the residual strength of the perforated casing,and the perforation should be avoided in the direction of the minimum principal stress to reduce stress concentration at the perforation hole.Moreover,as shown by a companion orthogonal experiment,the descending order of influence of the different influential parameters is:phase angle,hole diameter,hole density and the thickness of casing.

Simulation of the erosion of casing and perforation under staged sand fracturing conditions in horizontal sections

The new fracturing technology of intensive stages and high-intensity proppant injection shows significant advantages of cost reduction and high efficiency in the volume fracturing of unconventional reservoirs,but it also intensifies the erosion of the casing and the perforations,with a perforation diameter expansion and the casing wall thinning.To solve this problem,in view of the applications of the perforation fracturing technology under the construction conditions in Mahu Area in Xinjiang,China,the structure parameters of the downhole strings are measured and a calculation model of the perforation casing erosion is established for the large-displacement sand fracturing process in horizontal sections.The software ANSYS-FLUENT is used to simulate the casing and perforation erosion under different conditions of the displacement,the sand content,the proppant particle size,and the fracturing fluid viscosity in the sand fracturing process.The particle size of the proppant and the viscosity of the fracturing fluid mainly affect the erosion area,but they have little influence on the erosion rate.The sand content and the displacement significantly affect the erosion rate.Among these factors,the sand content has a more significant effect on the erosion rate and the displacement has a more significant effect on the erosion area.Due to the influence of gravity,the perforation erosion rate is larger when the phase angle ranges from 120°to 240°.