ABSTRACT This paper provides an overview of Pacific Gas and Electric Company's (PG&E) In-Line Inspection (ILI) process from start to finish. PG&E's integrity management program encounters numerous operational challenges as it expands its in-line inspection program to include more challenging pipelines than previously inspected. The company has addressed these challenges by developing a rigorous hydraulic feasibility study process that evaluates risks associated with a respective ILI run before making the decision to proceed with pipeline retrofits to accommodate in-line inspection tools. Several new operating methods have been developed to increase the number of pipelines hydraulically capable of in-line inspections, while reducing risk. Two tools that PG&E has developed to analyze ILI system operations will be discussed. PG&E's Batch Analysis Tool (BAT) is used to conduct complex, multiple-scenario hydraulic analysis. Data results are then processed through an ILI BAT Results Tool, which summarizes BAT data into easily-viewed charts and tables. This allows engineers to consistently analyze and document predicted ILI run gas velocities and system response to varying operations during the inspection. Once detailed analysis is conducted, preparation for the ILI is required. This paper will discuss upgrading pipelines to accommodate inspection tools, developing detailed operating plans, directing real-time operations, and preparing to respond to operational impacts due to anomalies identified on the line. A case study of an ILI on Distribution Feeder Main (DFM) 0617-06 is presented to exemplify PG&E's ILI process from start to finish.

ABSTRACT: The purpose of this work is to present a simplified explicit model to assist the gas controllers during pig run operations. The model considers the mass balance to obtain an approximation of the transient flow profile and calculates the gas velocity using analytical equations to estimate pressure and temperature profiles, while the gas density is calculated by an explicit equation of state for real gas. The effect of seven different models for natural gas compressibility factor are verified on the Pig tracking model. Additionally, the influence of the temperature profile on the pig velocity is analyzed by varying of heat transfer coefficient. A total of five real test cases of pig run in two different section of the pipeline are used to test the model. The results revealed that the heat transfer coefficient slightly impacts the pig velocity. A maximum of 5.8% difference in the average pig velocity is found among the natural gas compressibility equations. As a general observation, the model was able to predict pig position within 8% of error. INTRODUCTION It is well established the importance and benefits of pigging during the many phases of a pipeline life, from commissioning to operation and this includes cleaning, inspection and data acquisition as pointed out by McDonnell et al. (2004). Routinely, as required by the maintenance and integrity programs, is necessary to promote a Pig run to remove lubricants carried out from compression stations or dust and many other times to find corrosion points, dents or cracks. However, a significant amount of time is spent by operational staff during pigging operations. In remote control stations, operators must have adequate monitoring information about pig location to take the necessary actions in order to have safe and reliable pipeline operation.

ABSTRACT When wet gas is transported in a pipeline, liquid (condensate and water) will drop out due to temperature and pressure changes along the pipeline. The prediction of liquid holdup inside a pipeline is very important, as it will affect the prediction of pipeline pressure drop, downstream slug catcher design, scraping operation, etc. In performing pipeline steady-state liquid holdup and pipeline pressure drop calculations, one can choose either multiphase dynamic simulator or multiphase steady-state simulator. It was found that there could be significant differences in liquid holdup prediction when comparing the calculation results from different simulation methods. Using a typical hilly terrain, this paper presents the calculation results for wet gas pipeline liquid holdup and pressure. Different water and condensate loadings are considered. Gas flowrate is varied and different calculation methods are used. INTRODUCTION Heavy component and water exists in the gas produced from gas production wells or gas-oil separation facilities. The pipeline can be in multiphase flow conditions when this wet gas is transported. It is very important to accurately calculate the pressure drop and liquid holdup in the multiphase flow pipeline for the design of the pipeline and other processing facilities. The accurate prediction of liquid holdup inside pipeline is also important for pipeline operation as the accumulated liquid inside the pipeline can potentially flood its downstream slug catcher due to slugging flow, gas flowrate rampup, or scrapping. Two different approaches have been practically used to Model pipeline multiphase flow. Ellul [1] has summarized these two approaches as Steady-State Approach and Transient Approach. Over the years, multiphase flow inside a pipe has been widely studied and correlations have been proposed to model the multiphase flow phenomena. These correlations include Beggs & Brill [2], Oliemans [3], Eaton [4], flanigan [5], etc. These correlations have been used for describing steady-state multiphase flow. Another method that used in steady-state calculations is the so-called Mechanistic Method [1]. The representatives for this method are OLGA Steady-State [6], Tacite Steady-State, and Xiao [7]. Empirical correlations and mechanistic methods are used in the softwares that are specifically designed for pipeline multiphase steady-state flow calculations.Dynamic simulations for pipeline multiphase flow have become more popular. The advance of computer power has made the dynamic simulation less time consuming. Dynamic simulation is based on solving the fundamental fluid flow equations in conservation of momentum, mass, and energy. Liquid holdup and pressure prediction can have significant differences among different calculation methods as well as in comparison with experimental data [6]. Shea [6] has compared several empirical correlations, mechanistic methods, and dynamic simulation results with experimental data. Ellul [1] summarized different approaches in multiphase flow modeling and compared the calculation results using an example. Steady-state and transient cases (ramp-up, scrapping) are studied. This paper studies multiphase pipeline pressure and liquid holdup predictions from different calculation methods that are available in commercial software using a typical hilly terrain. Different flowrates and liquid loading (for both condensate and water) are used.