Development of a simulation program for natural gas pipeline system design with a graphical user interface

Modern pipeline systems require designs that ensure safe and cost-effective transportation of gas from the source to the processing facility. Front End Engineering Design (FEED) which is conducted after completion of conceptual design provides to configure technical issues and estimate rough investment costs of the project. "Final Investment Decision" is the point at which everything is in place to realize the project in Oil & Gas Industry. At this point, a new simulation program, NatGasDesign, to contribute FEED studies has been developed for flow analysis of buried natural gas pipeline system design including metering, block valve and compressor stations. The natural gas pipeline design program, NatGasDesign, with graphical user interface (GUI) was developed and tested in the present work. The NatGasDesign calculates the major pressure losses due to friction and pipeline's elevation profile as function of flow rate, pipe roughness, pipeline length and diameter and thermodynamic properties of natural gas. The elevation profile used for the predictions is captured from Geographic Information System (GIS). The velocity in pipeline is computed from the mass continuity. Density that is used in the continuity equation is evaluated from the computed local pressure, temperature and compressibility factor. Friction factor which is used for the major losses is calculated from the Haaland Equation for turbulent flow. The minor local losses are evaluated from pipeline local components and bends. The energy conservation of gas along the pipeline due to pressure, velocity, elevation above ground level is expressed by Bernoulli's Equation. The ideal gas law predicts adequately the behavior of natural gas at low pressure and temperature conditions. However, the typical flow conditions show that real gas equation must be employed as Equation of State to calculate the gas density. The Compressibility Factor to use in the equation of state is calculated from specific relations based on empirical constants. Predictions of temperature change are performed by considering heat transfer between gas and soil, and Joule Thomson cooling effect. Gas viscosity is determined as function of temperature and gas density. Isobaric specific heat capacity of natural gas is computed as a function of specific gravity, pressure and temperature. Compressor power should meet pressure losses along the pipeline up to the delivery point. Based on the operating design point, the required compressor power is calculated. NatGasDesign is based on steady-state flow analysis and computes the pressure drop along the pipeline successfully. A natural gas pipeline model is used as a test case for validation of the present methodology. A well-established commercial PIPESIM program was used to validate the present predictions. The pressure variation results predicted by NatGasDesign along the pipeline and the results obtained by the well-established PIPESIM software were compared with the available field data. For validation of the test case, TANAP which transports Azeri Gas through Turkey from Azerbaijan to Italy is used as the natural gas pipeline model. Pressure losses for an operating point of 1,9 billion m3 as annual flow capacity have been calculated using both NatGasDesign and PIPESIM programs and the comparison with the measured field data showed good agreement. As a second scenario, predictions of pressure losses for flow capacity of 16.2 billion m3/year where no field measurements were available, were compared only with the PIPESIM results and again, a good agreement was observed between the results.