Collapse Testing and Modeling of Perforating Guns Carriers. NAPS AUTHORS: Tomas Turkalj, Maurizio Bellingardi, Sebastian Cravero

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1 Collapse Testing and Modeling of Perforating Guns Carriers NAPS AUTHORS: Tomas Turkalj, Maurizio Bellingardi, Sebastian Cravero

2 Introduction Gun steel tubular carriers of the Perforating guns have to: Protect the gun core from Impacts and scratches. Survive to the gun detonation (minimal swelling /no ruptures). Avoid collapse of perforating gun under the high wellbore pressure. Scallops are often machined on the tubular carrier outer surface, so to provide a proper recess for burrs that may be generated during the bullet penetration towards the formation. Collapse rating of perforating guns primarily relies on the rating of the tubular steel carrier itself. The influence of material strength, pipe geometry and residual stresses on the collapse performance of a steel pipe is of great importance for casing and tubing. Tenaris has been investigating the matter since years, leading to the introduction in the industry of High Collapse grades for OCTG. In this study, the effect of scallops on Ultimate Collapse Pressure of Perforating Gun Carriers has been investigated. The primary objective is to find a correlation, also called derating, between the simple "unscalloped" geometry and several typical scallop patterns.

3 Agenda Introduction Finite Element Model Features Validation (Plain Pipe) FEM of Gun Carriers Results of Scalloped Gun Carriers Effect of Density on the Derating Effect of Pipe Geometry and YS on the Derating Conclusions Collapse Tests of Gun Carriers Final Remarks

4 Finite Element Model MODEL FEATURES Nonlinear post-buckling analysis using Riks method (ABAQUS) Full 3D Models with scallops (gun carriers) and without(plain pipe) Representative Boundary Conditions of an actual collapse chamber Pressure applied on the exterior Surface Zero Radial displacement at chamber O-ring locations One fixed side of the pipe ( including Pipe axial restriction) Elastic Plastic Material: true stress- true strain curves Pipe Ovality and Eccentricity Without Residual Stresses p U R =0 U R =0 U 1 =U 2 =U 3 =0 Applied Boundary Conditions 1 3 2

5 FEM Validation (Plain Pipe) MODEL VALIDATION FEM of Plain Pipes were compared with ISO10400 equation outputs with the same input parameters. Model OD av (in) Wt av (in) D/t Ov (%) Ecc (%) Rs (Ksi) YS (Ksi) P ult ISO (psi) P ult FEA (psi) Pipe Pipe e % Averaged Percentage Error = 3% Pipe ISO TR Ultimate Collapse Pressure (Pult)1 Pipe-1 Collapsed (1)Annex F.4 ISO/TR 10400:2007. Petroleum and natural gas industries Equations and calculations for the properties of casing, tubing, drill pipe and line pipe used as casing or tubing

6 FEM of Gun Carriers STUDIED SCALLOP PATTERNS AND GEOMETRIES Densities: 12spf, 6spf Phases : 90º, 135º, 180º The same scallop geometry was used in all models 31.6mm 2mm Scallop Geometry 5.5mm 90º 135º 180º 135º 180º 12 spf 6 spf

7 FEM of Scalloped Gun Carriers

8 FEM Results of Scalloped Gun Carriers ULTIMATE COLLAPSE PRESSURE DETERMINATION VIA FEM The derating on collapse was obtained for each scalloped configuration Group OD (in) Wt (in) D/t YS (ksi) Ov (%) Ec (%) Model Phase SPF P ult (psi) Derating P ult Gun/P ult Pipe Pipe Gun Gun Gun Gun Gun Pipe Gun Gun Pipe Gun º, 12 spf 180º, 12 spf

9 Effect of Density on the Derating Effect of Density: Derating curves of P ult depends on SPF and phase

10 Effect of Density on the Derating

11 Effect of Pipe Geometry and YS on the derating Effect of Geometry Effect of YS: YS slightly modify the effect of the scallops on P ult Effect of Pipe Geometry: Effect of Scallops pattern on P ult changes depending Pipe Dimensions. 12 SPF, Phase 135, YS=132 Ksi 12 SPF, Phase 135, D/t=14.3 (Ksi)

12 FEM Conclusions The FEM of plain pipes have been validated with the ISO TR10400 equation è Percent Error about 3%. Plain pipes and gun carriers with helical scallop patterns showed a correct post buckling behavior. The machining of the scallops produces derating of the collapse resistance, which depends on: Density ( quantity of removed material) AND Phase ( distribution of scallops). Pipe Geometry (The same pattern of scallops reduces P ult differently depending on pipe geometry) YS did not show a significant effect on the derating.

13 Collapse Tests of Gun Carriers The testing program included: Collapse Tests of Pipes and Scalloped PG Carriers 7 OD x 0.5 wt 4.5 OD x wt Scallop Density / Phase: 12 SPF, 135 Complementary tests Collapsed Pipes/Guns Residual Stress measurements (Slit Ring Method) Tensile Tests (Full Strip Tensile samples) 135º, 12 spf Scallop geometry

14 Collapse Tests of Gun Carriers RESULTS # Type OD x wt D/t YS and RS averaged from adjacent test samples (*)Second derating obtained from ISO P ult Av Actual YS (Ksi) Ov (%) Ec (%) Rs (Mpa) SPF Phase P ult (Psi) Average (Psi) ISO P ult (Psi) Av P ult ISO P ult Derating Test % Test-2 Pipe % Test % x Test % 16240? Test-5 Gun % Test % Test % Not Test-8 Pipe % Is it correct to assume that the residual Collapse Test x % Test-10 stresses 0.4 after the 11.9 machining of scallops % Test-11 remains Gun unchanged? %? * Test % RS YS P ult The derating obtained includes 2 effects: the effect merely referred to scallops ( Adressed by FEM) The effect produced by the change in residual stresses field

15 Final Remarks In the analyzed cases, the derating via FEM was more conservative than the derating obtained experimentally Collapse performance of a tubular is influenced by material strength, pipe geometry and residual stresses Collapse Derating Unknown RS of Guns ( both effects included) Modifies Geometry The machining of scallops Modifies RS fields FEM Change in geometry effect (RS=0) Diminishes P ult Unknown effect on P ult ( this work) Further investigation would be needed to fully understand the phenomenon of modification of RS due to Scallops and it interaction with the phenomenon presented in this work together.

16 QUESTIONS? THANK YOU NAPS AUTHORS: Tomas Turkalj, Maurizio Bellingardi, Sebastian Cravero