Submitted By 5165M
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A.1 Purpose of the Program

This program was developed to calculate the critical gas velocity in gas wells. With required input data, the user can determine the inception of liquid loading with different models. This program was programed in .net framework using c sharp. Note that .net framework (4.0 or 4.5) is needed to run this program. We will describe how to use this program below.

A.2 Program Structure

The program consists of two tab pages: single well page and multiple wells page, as can be seen in Figure A.1. In the single well page, the user can analyze a single well; while in the multiple wells page, the user can process batch data.
We will start with the single well calculation. There are only two buttons in this page, “Calculation” button and “Exit” button. The input data area is on the upper left part of the page, where all the necessary information is needed to determine the critical gas velocity. Input data needed for the calculation is liquid density, gas gravity (gas density), surface tension, surface or bottom hole pressure and temperature, tubing size, gas production rate, liquid/gas ratio (or liquid production rate), and inclination angle. The default value for input data will be shown in the textbox when the user runs the program for the first time. If uncertain about any input data, the user can use the default value. For the unit, the user can choose field unit, SI unit or user defined unit. By default, the input data unit is the field unit. The unit can be changed by clicking appropriate button. The value of the input data will automatically change if the unit is changed. The input value in the textbox will be saved and will be available the next time the program is run.

Figure A.1: Single Well Calculation Page

Once all input data is ready, the user will click the “Calculation” button to see the results. The results are shown in Figure A.2. Now we can see the calculation results of the droplet model and the film model. In the droplet model, critical gas velocity from Turner’s equation and Coleman’s equation will be presented. Note that, in the results, the user can also convert the units between SI unit and field unit. For the film model, results from Barnea’s model and our new model will be shown.
On the lower right area of this page, a flow pattern map is plotted with different transition boundaries. In the plot, we show Turner’s boundary, Barnea’s boundary and the new model’s boundary. Also, current gas velocity is plotted as a blue square. To the left of the boundaries is loading region, and unloading region is on the right. In Figure A.2, this gas well is plotted on the left of the boundaries, so this well should have a liquid loading problem. The user can also choose to plot only one boundary by choosing prediction methods.

Figure A.2: Single Well Calculation Results

Figure A.3: Single Well Calculation Data

In addition to the plot, the user is able to obtain the calculation results in a spreadsheet, as shown in Figure A.3. This spreadsheet lists all the methods and corresponding critical velocities (in both SI and field units). The loading status of the current condition is shown in the last column. For this well, liquid loading is predicted by all the models.
A snapshot of the multiple wells calculation page is shown in Figure A.4. There are three buttons, which are “Choose Input”, “Calculation” and “Exit”. The “Calculation” button is greyed out since data input is needed first. Basically, the input data requirement is the same as the single well. It only needs…