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Using the Avalon Nodal Analysis Module

Avalon can creates nodal analysis tables, and then seamlessly migrate the data to the wells in the simulator.   The nodal curves can be generated for a wide variety of oil and gas correlations, include temperature gradient effects, and work with both subsurface and pipe line segments.  Alternatively, Avalon can be used as a stand alone program to generate stand alone nodal analysis tables.

Generating Nodal Curves in Avalon - The first step to creating nodal analysis tables is creating a new file in Avalon, and then opening the Merlin file within Avalon that will receive the nodal curves. The user next specifies basic data including PVT, pipe roughness, minimum and maximum production rates, water cuts, gas-oil ratios, and correlations for vertical and horizontal sections. Next the user creates a series of nodal curves for each different well arrangement in the simulator, including horizontal segments.  A graphical interface displays the piping for each well. The user can click on segments to view the pipe specifications. The example below shows a well with two vertical and two horizontal segments.

If a horizontal pipe line length is to be modified then a button called Design flow Lines is clicked, and the user then interactively designs the flow line segments. For example in the example below two different separator facilities are shown, along with the curved paths from two different wells to each respective separator facility. The well locations are taken from the Merlin file that has been opened, and a button in Avalon assigns the Avalon nodal curves to corresponding wells in the Merlin file. The separator locations and horizontal segment locations/lengths were placed by pointing, clicking, and dragging with the mouse. After the window is saved the lengths and widths of each horizontal segment on the picture are reassigned to the wells.

Next the user clicks a calculate button to generate the nodal curves that will be used by the wells in Merlin. A typical nodal analysis curve is shown below.

Lastly, the user saves the Merlin file and the tubing curves are integrated into the Merlin file.

If recorded pressure drop/rate information is available the calculated pressure drops can be adjusted by factors to match the recorded pressure drops.

The last step requires opening Merlin and assigning the tubing curves to different well startup times. A tubing curve selection option now resides on the Well Recurrent Data form.  In the Merlin post processor when a tubing constrained well is selected either cell pressure, flowing bottom hole pressure, or surface pressure can be displayed.

Avalon is not designed to replace a sophisticated compositional nodal analysis package.  However, it is designed to give the everyday engineer a remarkably simple to use tool for generating nodal analysis curves, and integrate the curves seamlessly into a simulation file. We have successfully used Avalon on large international gas prospects with long subsea tie backs, or equally well on tight West Texas gas fields.

How Do I Get It ?  Call us for our current price. Once you are signed up we will send you a bit lock update, and you can download the software from our site.

Avalon Technology Application Examples

Several technology examples for Avalon are presented below.

Offshore Subsea Tieback with Flow Lines and Risers

Avalon can quickly build tubing curves including flow lines for different wells going back to either a platform or subsea manifold. It is routinely used to compare the economic benefits of different subsea tubing and flow line arrangements. More than 20 reservoirs have been evaluated with Avalon in combination with Merlin within the last 12 months.

In many onshore tight gas reservoirs there are few if any reliable buildup pressures. In these reservoirs flowing tubing pressure is often the only history match variable that can be used along with the recorded production rates. Including tubing curves for the individual wells allows these reservoirs to be successfully history matched. Following the history match many operators are using this improved reservoir description to optimally place horizontal wells. In one application the recoverable gas was more than doubled, and recovered in a third the time of vertical wells. Our recent publication in World Oil illustrates this technology.

Avalon can help operators optimally design tubulars to maintain target deliverability rates over the life of a gas field. The Merlin simulator provides a much more accurate predictor for the reservoir module than analytic reservoir models

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