Analysis of Casing Fatigue Failure During Multistage Fracturing Operations

Abstract

Tubular fatigue failures have been commonly reported in geothermal and heavy oil wells with cyclic steam injection operations. Recently, possible fatigue failures in casing connections during multistage fracturing operations have also been reported in the literature. These occurrences raised the question of whether casing fatigue is a real problem, even for shale plays. This paper describes fatigue modeling and analysis of the casing connections during fracturing operations to provide additional information about this issue. The varying casing temperature and temperature-dependent casing loads were obtained using numerical simulations of cyclic hydraulic fracturing operations, such as end of cementing → shut-in → plug and perforation → stimulation (stage 1) → shut-in → plug and perforation → stimulation (stage 2) etc. These simulations were accomplished using commercial software, including a thermal flow simulator and stress analyzer. The previously simulated casing loads were then used to calculate localized stress amplitude, strain amplitude, and maximum stress. Finally, the localized strain and stress values were used as input parameters of fatigue models to estimate the lifetime (cycles) of selected casing sections. The fatigue model was implemented in a computer program and integrated with the thermal flow and stress analysis commercial software, and a field case (shale oil/gas well) was studied with the integrated fatigue simulation. The predicted casing connection fatigue behavior closely correlates with failure field data, and the casing failure location was analyzed and explained in terms of environmental and cyclic stress/strain conditions. The corrosion fatigue appears important for the acidic environment during hydraulic fracturing. The field case study indicates that the fatigue analysis, coupled with numerical thermal-flow analysis and multistring stress analysis, can provide more insight into the failure of casing connections during fracturing operations. Consequently, it is valuable to include fatigue analysis during the wellbore tubular design when multistage fracturing and/or refracturing operations are involved.

Casing structural integrity and failure modes in a range of well types - A review

“…The industry tendency to go to slim-hole DwC, with ever increasing operating loads is not a foreseeable future. Also, according to Liu et al (2018) recent literature have reported casing fatigue during multistage hydraulic fracturing particularly at casing joints. The study attributed cause of casing fatigue loading to cyclic hydraulic fracturing with varying temperature between stages.…”

“…It also indicate formation slippage as the main reason for casing failure during waterflooding. Simulation Liu et al, 2018;Xi et al, 2018;Zhao et al, 2018;Zhang et al, 2016 Vertical /Drilling, completion and production Collapse pressure from salt rock creep, annulus pressure build-up owing to fluid thermal expansion in sealed annuli.…”

Strength analysis of perforated casing in ultra-deep horizontal shale wells during sublevel acidizing and hydraulic fracturing process

“…The casing under cycling loads are available to generate residual strain, and the accumulation of induced stresses from hydraulic fractures increases the maximum principal stress near the wellbore. [11][12][13] Moreover, in acidizing fracturing conditions, activation and slip of faults caused by fluid entering the formation can also seriously affect casing integrity. [14][15][16][17][18][19][20][21][22][23] At present, numerical simulation analysis is the main method of casing deformation and failure mechanism research.…”

Prediction of casing critical buckling during shale gas hydraulic fracturing

“…Another reason for casing deformation was proposed by Hagshenas et al (2017) and Liu et al (2017) who noted that additional load is exerted on the casing by fracture slip through the wellbore. Liu et al (2018) pointed out that local stresses and shear of weak formation are the main causes of casing deformation during fracturing. These local stresses are typically tangential, axial and radial resulting from in situ stresses.…”