CFD Simulation Investigation of Natural Gas Components through a Drilling Pipe RASEL A SULTAN HOUSSEMEDDINE LEULMI

CFD Simulation Investigation of Natural Gas Components through a Drilling Pipe Project overview:  CFD introduction  Physical properties and components of NG  Project Scope  Simulation Setup  Results comparison  Conclusion and Recommendations

Computational Fluid Dynamics (CFD)  CFD is commonly Used tool in different Technological studies, it’s a software base program that uses numerical analysis to perform the calculation required to simulate the interaction of liquid & gases defined by boundary conditions.

Natural Gas Properties  Natural Gas is a mixture of gases consisting mainly of methane, ethane and propane.  Natural gas is a colorless, tasteless, odorless, and non-toxic gas. Because it is odorless, Mercaptan is added to the natural gas, in very small amounts to give the gas a distinctive smell.

Moody Diagram  In 1944, Lewis Ferry Moody plotted the friction factor against Reynolds number Re for various values of relative roughness ε / D.

Project Scope  Simulate Pressure drop and Velocity drop across a chosen pipe and roughness of the three main components ( Ethane, Methane, Propane).  Compare the results with previous work done by Moody and validate the theory of pressure drop and velocity drop across different pipe roughness.

Flow Regimes throw a pipe Liquid -Gas

Project limitations  Multiphase flow system is really complex to simulate on CFD.  Ignoring Minor components of the gas mixture considering one simulation for one component takes 2 hours. (78 hour in total)  Ignoring changes from the outer boundary of the pipe such as Temperature, pressure.  Ignore results with similar incomes.

Simulation Approached to build a simulation model to analyze flow characteristics of natural gas in drilling pipe. Fluent, ver. 16.2, ANSYS Inc. is used to build a CFD simulation model of drilling pipe flow of natural gas. Validating the model, we tried to show the sensitivity analysis of different characteristics of flow especially velocity profile and pressure drop.

Simulation (Geometry) Assumed a portion of pipe of drilling string. Geometry with length 10m and inside diameter 0.15m. Main focus is the inner portion of the pipe so we neglect outer portion of geometry. Wall width is out of our contour and consideration as we are only focusing on pressure drop and velocity profile inside the pipe.

Simulation (Geometry) Isometric view of geometry

Simulation (Meshing) Used smooth meshing including inflation near wall to obtain fully developed velocity profile and pressure drop profile throughout the pipe (from inlet to outlet). Inflation near wall is added to observe more preciously the characteristics of different parameters near wall. Adding inflation is more time consuming and reliable. Statistics of meshing shows number of nodes are and number of meshing elements are

Simulation (Meshing) Cross Sectional view of meshing

Simulation (Modeling, Material and Boundary Condition) Assumed a steady flow condition. Methane, Ethane and Propane are working fluids. Aluminum with 0 mm roughness and steel with 0.5 mm roughness are wall materials. For viscous modeling Standard k–ε model is chosen. 1 m/s, 1.3 m/s, 1.5 m/s, 1.7 m/s, 2.0 m/s, 5.0 m/s and 10.0 m/s are taken as velocities with 0 Pa pressure at inlet. At outlet same pressure is assumed. At wall we take 0 mm and 0.5 mm roughness with no slip condition.

Validation Validation is done with Moody Chart which was plotted 1944 by Lewis Ferry Moody. We compare friction factor from simulation data with moody chart theoretical data at different Re number and roughness of pipe wall. The errors are very less and acceptable. Errors that are observed mainly due to natural gas characteristics. This shows our model is good enough to analyze sensitivity of different parameters.

Validation Pressure drop validation of Methane with theoretical data from Moody Chart at different Re Number

Validation Pressure drop validation of Ethane with theoretical data from Moody Chart at different Re Number

Validation Pressure drop validation of Propane with Moody Chart data at different Re Number

Sensitivity Analysis After validating our work, the approach was to collect data of different parameters at different condition and position to see the change of characteristics. Velocity profile graphical view with smooth pipe and 0.5 mm pipe roughness of three different fluids are presented in our analysis. The graphical view shows velocity profile across the diameter of the midway of pipe. Velocity contour of cross section view for different conditions are also shown in project work.

Sensitivity Analysis Velocity contour of cross section at midway of smooth pipe at 1.5 m/s velocity and 0 mm roughness condition with Methane

Sensitivity Analysis Velocity profile of methane with smooth pipe across pipe diameter

Conclusion Pressure drop and velocity drop results varies slightly with previous work due to various error sources. (deviation and standards) Gas mixture behavior may vary depending on the pipe roughness. Validating with theoretical data, building a model could be performed to help in further drilling flow work.

Recommendation for Future Work Perform simulation with different diameter of pipe. Perform research on velocity frequency. Use different type of gases on the simulation. Compare results with different theories similar to moody chart. Try to perform simulation with a multiphase flow combining gas and liquid.

Reference  Versteeg, Henk Kaarle; Malalasekera, Weeratunge (2007). An introduction to Computational Fluid Dynamics: The Finite Volume Method. Pearson Education.  Moody, L. F. (1944), "Friction factors for pipe flow", Transactions of the ASME 66 (8): 671–684.  ANSYS Lecture 7: Turbulence Modeling, version  Wallis, G. B. (1969). One-dimensional two-phase flow.  Mandhane, J. M., Gregory, G. A., and Aziz, K., 1974, ‘‘A Flow Pattern Map for Gas-Liquid Flow in Horizontal Pipes,’’ Int. J. Multiphase Flow, 1, pp. 537–553.

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