amethyste guided session #1 - kappa eng · pdf fileecrin v4.20 - doc v4.20.01 - © kappa...

Ecrin v4.20 - Doc v4.20.01 - © KAPPA 1988-2011 Amethyste Guided Session #1 • AmeGS01 - 1/19

Amethyste Guided Session #1

A01 • Initialization

This document is an introduction to Amethyste and illustrates the principles of Well

Performance Analysis (WPA).

We will carry out a Vertical Lift Performance (VLP) and an Inflow Performance (IPR) on a

producing oil well. We will also illustrate how the improvement of the well performance can be

investigated by conducting a sensitivity analysis.

Note: Unless you work in high resolution, it is preferable to uncheck the ‘Always show scale’

option in Settings – Plot Aspect - Plots tab.

Click on the icon in the application toolbar and then new .

This opens in succession 3 dialogs:

Fig. A01.1 • Initialization dialog 1 of 3

This dialog allows you to enter general information about the well, define the units to be used

in the document and type comments.

Click .



Here, you can edit the case name, select the fluid of reference and the type of well. Keep all

values at their suggested defaults.

Click to enter the PVT data.


In this window, we leave all the parameters at their default values. This defines a ’Saturated

Oil’ fluid, corresponding to the ’Oil’ reference phase selected in the previous dialog.

Click . The main Amethyste screen is displayed.


Fig. A01.4 • Main screen

The Control Panel displays the WPA page with the highlighted Well icon . The series of

icons from top to bottom follow the default path of the basic workflow used in a Well

Performance Analysis, the highlighted icon materializing the next recommended step.

B01 • Well data

B01.1 • Loading data

Click on . The window shown below (Fig. B01.1) pops up.

Fig. B01.1 • Load data


It is used to enter wellbore data, flowline data, create a well sketch and load some production

data in terms of rate and pressure if available.

In our example, we will study the flow in the wellbore and disregard the flowline section. In the

Wellbore tab, we enter the roughness 0.0006 in and the bottom hole depth 12650 ft.

By convention, all measured depths (MD) along the wellbore are counted positive, starting

from the wellhead down to the bottom hole. If a flowline is defined, all measured depths along

the flowline are counted negative, starting from the wellhead up to the flowline top.

The fluids are flowing out of the reservoir into the casing section, then into the tubing. This is

equivalent to a fluid flow within a varying ID section defined by f(MD). It can be represented

by selecting the Tubing flow option, and by defining a varying ID.

Click on Type Constant for the ID. A drop down menu opens and select f(MD). A icon

appears next to the ID value. Click on it and the following window allows to enter the

diameters, depths and relevant information:

- A 2.441 in tubing from 0 to 8779 ft (MD).

- A 3.965 in casing from 8779 to 12650 ft (MD).

Fig. B01.2 • Loading depths and IDs

Check ‘Show length’ for verifying the data.

Some comments can be added in the info lines as ‘tubing shoe’ line 2. These comments will

appear in the plot representing the fluid path (see Fig. B01.4 below).

Once done, exit with OK.


B01.2 • Making a Well Sketch

It is possible to associate a well sketch to the geometrical description of the well. This will only

be qualitative information as it will not be used further in subsequent calculations.

Select the Well Sketch tab and create a well sketch by dragging the elements as follows, from

the components library on the right to the tree view on the left:

- Add a casing to the wellsketch by selecting the ‘casing’ element in the components

library on the right, and dropping it on the ‘Well’ node in the tree view on the left. This

creates a ‘Casing’ node below the ‘Well’ node.

- Add a casing shoe by dropping the corresponding element on the ‘Casing’ node.

- Add a tubing by dropping the corresponding element on the ‘Casing’ node.

- Add a packer to seal the tubing-casing annular, by dropping the corresponding element

on the ‘Casing’ node.

At the end of this operation the well sketch is designed, but its elements are missing their

geometrical definition. Activate the geometry tab on the right. Select each element in the tree

view on the left, and enter the following geometrical information:

- casing ID: 3.965 in from 0 to 12650 ft

- casing shoe ID: 4.5 in at 12650 ft

- tubing ID: 2.441 in from 0 to 8779 ft

- packer: from 8500 to 8700 ft (not realistic length but ensures a clear display)

Fig. B01.3 • Making the well sketch

When pressing OK, the well sketch plot is created as well as the well geometrical information

entered in the Well geometry dialog (see Fig. B01.4 below). Note that to obtain a similar

figure, the ‘deviation’ and ‘tubing roughness’ plots, given by default, were removed with a drag

of the plot title bars outside of the main plot window (a hand appears when hovering on the

plots title bars).


Fig. B01.4 • Well Plot

C01 • Vertical Lift Performance

The next step is the evaluation of the Vertical Lift Performance. The idea is to proceed in two

steps:

1- Identify the correlation that best represents the flow conditions in the well. It can be

done by determining the flow correlation that best fits in situ pressures.

2- Use this correlation when achieving the Well Performance analysis.

Click on the VLP icon . A dialog is displayed, with a series of five tabs allowing the

definition of the outflow model and conditions.

C01.1 • Input: Wellbore tab

The ‘Input: Wellbore’ tab is where the flow correlation(s) applied to the wellbore section must

be defined. Within the list of available correlations press ‘select none’ and after select only:

Hagedorn & Brown (ref)

Kaya et Al

Petalas & Aziz

Stanford Drift Flux LG

This will make the plots clearer and the calculations faster. The correlation selected as the

reference is the correlation that will be used when conducting the Well Performance Analysis.

C01.2 • Input: Temperature tab

The ‘Input: Temperature’ tab is where the temperature model applied to the well is selected.

The temperature profile can be selected as linear from top to bottom (‘Linear’), imposed from

a temperature survey (‘Survey’) or simulated based on a geothermal profile and a quantified

heat transfer between the well and the reservoir (‘Calculate’). Keep the default choice to force

a linear temperature profile. The end-points temperature will be entered further, in the

‘Output: Traverses’ and ‘Output: VLP’ tabs.


C01.3 • Input: global settings

The ‘Input: Global settings’ tab is where specific model settings can be selected, such as the

erosional velocity calculation method, the static liquid column height or the integration scheme

along the flowstring. There, additional calculation nodes can be defined at locations where the

results are required. By default, Amethyste creates a calculation node for the wellbore and

flowline end points.

Add 1 additional calculation node at 8779 ft (MD) as shown in Fig C01.1. Call it ’tubing shoe’.

Fig. C01.1 • adding 1 node

Check the erosional velocity box and pick the Salama (solid free) model.

C01.4 • Output: Traverses

The ‘Output: Traverses’ tab is where different production conditions can be specified. The well

response to these conditions will be given in detail along the flow string (e.g. traverses), and a

comparison will be possible with measured pressure data.

Add 2 production tests as shown in the next picture (the GOR is automatically calculated):

Test A: [qo: 500 STB/D, qg: 400 Mscf/D, WHP: 180 psia, WHT: 75 °F, BHT: 212 °F]

Test B: [qo: 1000 STB/D, qg: 900 Mscf/D, WHP: 190 psia, WHT: 75 °F, BHT: 212 °F]

Fig. C01.2 • adding 2 tests


Select each test, and enter the user data as follows in the bottom part of the window:

Test A: [2000 ft, 450 psia and 8400 ft, 1800 psia]

Test B: [4600 ft, 900 psia and 12000 ft, 2500 psia]

Fig. C01.3 • adding user data

When accepted with OK, the Well Traverses plot is created and displayed on the screen.

Fig. C01.4 • Well Traverses plot

Maximize the plot by double clicking in its header. Curves for both tests A and B are shown.

The velocity plot shows the mixture velocity, the erosional velocity and the unloading velocity.

The curves labels are visible when moving the cursor on the curves.

The Well Traverses plot can display numerous information. Selecting ‘List’ in the Test drop

down menu of the toolbar or pressing the ‘Edit display settings’

button opens a window that allows to customize the display to better understand the well

flow. For instance, all well geometrical information can be added to this plot. Depending on the

user choice, these data can be displayed for a given flow correlation and several production

tests, or for a single production test and several flow correlations.


Fig. C01.5 • plots display settings

The activity log (tab ‘messages’) located at the bottom of the screen, displays the details of

the calculation during the Traverse tests. To see less detailed messages, go to Settings,

Interpretation, Activity log, select the Amethyste stone and set the verbosity level to a lower

level. This will be effective for the next run.

Fig. C01.6 • detailed messages

Displaying one correlation at a time, by using the Correlation drop down list in the plot toolbar,

it is possible to visually identify the correlation that best matches the entered data for each

production test.

Let’s select ‘Petalas & Aziz’ as the reference. For this, minimize the plot and go back to the VLP

dialog, ‘Input: Wellbore’ tab. Check the reference box in front of the Petalas & Aziz

correlation. This defines the correlation that will be used in the well performance analysis.

C01.5 • Output: VLP

Click on ‘Output: VLP’ in VLP option. This tab is where the Vertical Lift Performance production

conditions are defined. Enter the number of calculation steps (#Q), rate calculation range,

phase ratios, wellhead and bottom hole conditions as shown below (ensure that the rate type

is Oil rate):

[#Q: 20, qmin: 0 STB/D, qmax: 5000 STB/D, GOR: 800 scf/bbl, WHP: 180 psia, WHT:

75 °F and BHT: 212 °F]


Fig. C01.7 • rate calculation range

The ‘Detailed results’ option forces, for each of the ‘#Q’ production conditions, the output of

the traverses calculations to the activity log. This may help in troubleshooting specific well

conditions. Leave the box unchecked.

In addition, it is possible to specify some measured pressure data for different rates at any of

the calculation node depth. Add the user data Q= 400 STB/D and P= 3000 psia at the

bottom hole node. Click on OK.

The VLP plot is created. It shows that if only production Test A was considered, the Stanford

Drift Flux model would be a good candidate for the reference correlation. But Test B has helped

in discriminating both and selecting the best correlation for our well, thanks to the Traverses

calculations.

When the plot is maximised, it is possible to see the VLP curves at any of the calculation nodes

defined earlier, using the Node drop down menu in the toolbar.


Fig. C01.8 • VLP plot with 4 correlations

D01 • Inflow Performance Relationship

The selection of the model defining the outflow is now done. The next step is to define the

inflow model for analysis, Inflow Performance Relationship (IPR).

Minimize the VLP plot and click on the IPR icon . The following window opens:

Fig. D01.1 • IPR window

The first time entering this dialog, a default IPR model is selected at the well bottom hole

depth (if defined). The active row in the grid is highlighted in blue and the red cell indicates

that the IPR model is not correctly defined yet. When several IPRs are created for comparison,

this red mark helps to differentiate between well defined IPR models and others. In this case,

the IPR set as reference is the one that will be used in the Well Performance Analysis.

Modify the calculation depth to 12582 ft. Select ‘Top perforations’ for the Position label. A

calculation node will be automatically added, at the corresponding depth, into the list of VLP

calculation nodes.


In this example, the well is vertical and we keep the Darcy model. Click on the ‘parameters’

icon and enter the following:

Reservoir parameters:

Reservoir permeability, k: 25 md.

Average pressure, Pavg: 5000 psia.

Well radius, rw: 2.875 in.

Skin model: check Calculate damage skin from completion.

Completion model: select Cased hole in the drop list.

Keep all other parameters at their default values.

Fig. D01.2 • Reservoir parameters

To enter the Cased Hole parameters, use

Perforation shot density: 4 spf.

Perforated interval: 23 ft.

Compacted zone perm: click on and enter kc/k reservoir: 0.4.

Compacted zone turbulent coef: click on to compute it from kc.

Keep all other parameters at their default values.


Fig. D01.3 • Completion parameters

PVT parameters:

B and µ can be handled different ways:

Constant at P avg.

With a user entered pressure (manual pressure).

Adaptative pressure. In this case, the IPR model calculates the sandface pressure Psf

with B and µ at P = (Pavg + Psf) / 2, starting at B and µ at Pavg. This method involves

an iterative process until convergence is obtained. Let Adaptative pressure by default.

When choices are validated, the IPR plot is created. It displays the sandface pressure, Psf

(from the IPR model) and the wellbore pressure, Pwf (from the completion model). If there is

no completion model defined, the IPR plot displays only the flowing pressure from the IPR

model.

Fig. D01.4 • IPR plot


E01 • Well Performance Analysis

As there is a valid VLP and a valid IPR models, a Well Performance Analysis (WPA) plot is

created. This WPA plot is a cross plot of the inflow and the outflow at the IPR calculation depth.

The intersection point is marked on the plot and moving the cursor on top of it, displays

pressure and rate. The status window also indicates this information as well as the reference

flow correlation and inflow model.

Fig. E01.1 • WPA plot

F01 • Sensitivity

Following the characterization of the well behavior under different flow conditions, the next

step is to optimize the well deliverability. This can be performed with a sensitivity analysis.

Click on the Sensitivity icon . The dialog that follows (Fig. F01.1) will allow specifying the

parameters to run the sensitivity on. In this example, we will do a sensitivity study on the

geometrical skin and the well head pressure. We will also generate the well traverses.

For each VLP sensitivity value (e.g. wellbore parameter, flowline parameter or production

condition), Amethyste calculates the well response to the different production conditions

defined in the VLP section, keeping unchanged any parameter but the selected sensitivity

variable. Amethyste will do the same for each IPR sensitivity value (e.g. reservoir or

completion parameter), calculating the inflow for different rates up to the Absolute Open Flow

Production (AOFP).

In the IPR list of sensitivity variables, select the Geometrical skin and enter the values [-1,

-3, 1, 3] as shown in picture F01.1. Proceed the same way with the WHP sensitivity variable

[250, 500, 750] of the VLP list of sensitivity variables. Require the sensitivity calculation on

the traverses by checking the corresponding box.


Fig. F01.1. • Sensitivity dialog

On OK, two sensitivity plots are created: a WPA sensitivity plot and a traverses sensitivity plot.

In the WPA sensitivity plot, the intersections are highlighted and the corresponding values

displayed when placing the cursor on the intersection points.

Fig. F01.2 • Sensitivity WPA plot


As the above plot is created, the activity log lists the intersection points.

All or parts of the contents of the activity log can be copied to the clipboard with Ctrl-C.

Fig. F01.3 • Activity log sample

The sensitivity plots display can be modified via the sensitivity plot toolbar icon or with

the right click menu of the plot. This allows to show the intersection rate values versus the

sensitivity variable values, as shown in the pictures below:

Fig. F01.4 • Q vs Geometrical skin


Fig. F01.5 • Q vs WHP

Fig. F01.6 • Sensitivity Traverses plot

The Sensitivity Traverses plot displays the curves (pressure and velocities in the above

example) for each value of the VLP sensitivity parameter selected (WHP).

Several sensitivities can be performed in the same case, along with the corresponding plots,

and an existing sensitivity plot can have its sensitivity parameters or values modified using the

icon of the sensitivity plot tool bar.


G01 • General document Features

In an Amethyste document, it is possible to create an unlimited number of cases,

corresponding to different situations encountered along the well life or different scenarios. Any

new case can be created with elements coming from an existing case.

The bold ‘Case’ tab displays the active case information.

The ‘Browser’ tab displays the document structure in a tree view and gives the user a clear

representation of the current document content. The information relative to the different

sections of the cases can be quickly accessed by selecting the corresponding element in the

tree view. The information is then displayed on the right side of the working area, as shown

below for the case ‘Case 1’.

Fig. G01.1 • Browser window

The drag and drop of the browser elements is also available, for easy copy/paste operation

between cases.

H01 • Links with other Ecrin applications

A well model defined in Amethyste can be copied into a Saphir, Topaze or Rubis documents.

The target document will then use the geometrical information and the reference flow

correlation defined in a selected Amethyste case, to compute the pressure drop along the well.

The transfer from Amethyste to another Ecrin document uses a specific option in each module:

- For Saphir and Topaze documents, selecting the ‘Well intake’ option in an ‘Analysis’

opens a window where the user is given the option to load an Amethyste case in any of

the opened Amethyste document.

- For Rubis documents, any existing well can have its ‘Wellbore definition’ loaded from an

Amethyste case (this opens a window where the user selects an Amethyste case in any

of the opened Amethyste document).

The transfer can also be done using the Ecrin browser, by drag and drop of an Amethyste case

directly into Saphir or Topaze (on an ‘Analysis’ node) or into Rubis (on a ‘Well’ node), as shown

in Fig. H01.1.


Fig. H01.1 • Browser window

The IPRs can be transferred between Amethyste and Saphir, using the Ecrin browser: drag and

drop operations can be performed from/to the ‘IPRs’ and/or ‘IPR’ nodes of both modules.

The PVTs can be exchanged between Amethyste and any other Ecrin application.

Pressure and rate data can be transferred to Amethyste by any other application.

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