WellFlo_Quick_Start_Guide_20090130.pdf

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WellFlo™

Petroleum Engineering Software

Quick Start Guide

Software Version 4.0

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W e l l F l o

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C

OPYRIGHT

AND

W

ARRANTY

WellFlo 4.0 © 2008 Weatherford International This document contains information proprietary to Weatherford International, with all rights reserved worldwide. Any reproduction or disclosure of this publication, or any part hereof, to persons other than Weatherford International personnel is strictly prohibited, except by written permission of Weatherford International.

D

ISCLAIMER

Information in this guide is subject to change without notice and does not constitute a commitment on the part of Weatherford International. It is supplied on an “as is” basis without any warranty of any kind, either explicit or implied. Information may be changed or updated in this guide at any time.

T

HIRD

-P

ARTY

S

OFTWARE

The following products and organizations have been mentioned in this documentation. Various trademarks are owned by the respective owners. Microsoft®, Windows 95®, Windows 98®, Windows 2000®, Windows NT® and Windows XP® are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries, http://www.microsoft.com.

U

SING

T

HIS

M

ANUAL

This manual is designed to address the needs of both the new and advanced user. It assumes you have knowledge of basic oil field terminology and have minimal familiarity with Microsoft Windows®.

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C

ONTENTS

CHAPTER 1: Overview ... 5 Introduction ... 6 Deliverability Applications ... 6 Diagnostic Applications ... 7 WellFlo Interface ... 8

CHAPTER 2: Tutorial I: Building a Well Model ... 11

Building a Model ... 12 Creating a New Model ... 13 Setting Flow Correlations ... 17 Setting Reference Depths ... 18 Setting Fluid Parameters ... 19 Reservoir Layers ... 24 Setting General Parameters ... 24 Plotting IPR ... 25 Relative Permeability ... 25 Wellbore Data ... 29 Wellbore Equipment ... 30 Surface Data ... 34 Surface Equipment ... 35 Temperature Model ... 38 Gas Lift Data ... 40

CHAPTER 3: Tutorial III: Systems Analysis ... 43

Systems Analysis ... 44

Setting Operating Conditions ... 44

Running Sensitivities ... 48

Plotting ... 50

CHAPTER 4: Tutorial IV: Gas Lift Design ... 53

Gas Lift Data ... 54

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Designing Gas‐lift Systems ... 57

Sizing ... 75

Sample Gas‐Lift Plots ... 76

CHAPTER 5: Tutorial V: ESP Design ... 79

ESP Design and Analysis Overview ... 80

Designing an ESP Installation ... 82

Analyzing an ESP Installation ... 86

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Chapter 1 O

VERVIEW

This chapter gives an overview of WellFlo and describes its basic features. This chapter also describes the WellFlo interface and how to use it to set up and run a WellFlo model, including well configuration, tuning, analysis and results. Introduction ... 6 Deliverability Applications ... 6 Diagnostic Applications ... 7 WellFlo Interface ... 8

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OVERVIEW Introduction

I

NTRODUCTION

WellFlo is a Nodal Analysis program designed to analyze the behavior of petroleum fluids in wells. This behavior is modeled in terms of the pressure and temperature of the fluids, as a function of flow rate and fluid properties. The program takes descriptions of the reservoir, the well completion (i.e. the hardware within the well), and the surface hardware (i.e. pipelines etc.), combined with fluid properties data. The program then performs calculations to determine the pressure and temperature of the fluids. Different modes of operation can be employed to either solve for flow rate given controlling pressures (typically deliverability calculations), or solving for pressure drops given measured flow rates (typically diagnostic calculations).

Deliverability Applications

• Calculating the Flow Potential (or Deliverability) of a Well: A technique for determining the Operating Point is used, whereby the pressures at a point (i.e. node) in the system are calculated for a range of flow rates, by calculating downwards from the top of the system and upwards from the bottom. Only one flow rate will provide the same pressure at the solution node calculated in both directions — this is obtained from an intersection of curves. This flow rate and the corresponding pressure determine the Operating Point of the system. • Designing the Completion of a Well: This is an extension of the previous application, where deliverability can be calculated as a function of different sizes of tubing, different perforations, etc., allowing the optimum completion to be chosen, given that a more expensive completion must justify itself in terms of higher production. Design facilities also include gas lift parameters like valve positioning, valve sizing and setting, and ESP selection. • Modeling the Sensitivity of a Well Design to Different Factors That May Affect it in the Longer Term: These factors may include increasing water production or decreasing reservoir pressure. Sensitivity modeling may encompass the reservoir, well, surface configuration, or the operating conditions.

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OVERVIEW Diagnostic Applications

Diagnostic Applications

This alternative mode of calculation is simpler: this is where the flow rate is known and the pressure at one point is required, given the pressure at another point. This is useful for the following reasons: • Comparing measured and calculated data, which could be for one of several purposes, such as evaluating the best flow correlation within WellFlo, evaluating Match Parameters, which are impossible to measure, such as pipe roughness, or determining if a well is behaving as it is expected to (i.e. to detect faulty components). • Monitoring work, such as predicting reservoir pressure from measured surface pressure and flow rate. This will enable the engineer to see if the system is behaving as predicted, even though they may not be able to measure all parameters at one time. This contrasts with the above application, where diagnostics are done by comparing measured and calculated data. • Design work where it is required to calculate the pressure drop in a system (e.g. to determine whether a given system will be able to flow to surface and still leave enough pressure to operate surface equipment). Optional facilities also are available to select ESPs and motors appropriate to the conditions specified, or to space out and size Gas‐Lift valves.

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OVERVIEW

WellFlo Interface

W

ELL

F

LO

I

NTERFACE

The main WellFlo window (see Figure 1‐1) contains a navigation pane and a Workbench. The Navigator is the pane on the far left of the application window and is used to navigate the system and open the main program menus. The Workbench is the main content pane with which you interact with the system. When a file is opened initially, the current Dashboard configuration for that file is shown in the Workbench. Open each of the following menus through the Navigator: • Configuration. Lets you enter all data necessary to create a well model, including the well and flow type, flow correlations, reference depths, fluid parameters, reservoir layers data, wellbore and surface equipment, and specific artificial lift type data. • Analysis. Lets you perform various nodal analysis tasks, such as calculating flow curves and performing operating point and pressure drop calculations. You also can export data through the Analysis menu. • Design. Lets you design ESP and Gas Lift applications. • Output. Lets you load previous saved data without having to re‐run the calculations.

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OVERVIEW WellFlo Interface

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1

OVERVIEW

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Chapter 2 T

UTORIAL

I: B

UILDING

A

W

ELL

M

ODEL

This Tutorial explains how to build a well model in WellFlo. Building a Model ... 12 Creating a New Model ... 13 Setting Flow Correlations ... 17 Setting Reference Depths ... 18 Setting Fluid Parameters ... 19 Reservoir Layers ... 24 Setting General Parameters ... 24 Plotting IPR ... 25 Relative Permeability ... 25 Wellbore Data ... 29 Wellbore Equipment ... 30 Surface Data ... 34 Surface Equipment ... 35 Gas Lift Data ... 40 Temperature Model ... 38

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TUTORIAL I: BUILDINGA WELL MODEL Building a Model

B

UILDING

A

M

ODEL

This Tutorial covers the basic data entry required to set up a well and reservoir description. The lessons in this Tutorial walks you through the Configuration process using the screens under the Model Navigator in the Configuration menu (see Figure 2‐1).

Figure 2-1: Configuration Menu

In this Tutorial, you will re‐create the example well, TEST1 (Test1.wfl), supplied in the WellFlo installation (Tutorials folder).

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TUTORIAL I: BUILDINGA WELL MODEL Creating a New Model

Creating a New Model

To start a project, you must create a new WellFlo model and enter, at a minimum, the initialization data into the General Data and Well and Flow Type configuration screens.

T

OSTART ANEWMODEL

:

1 Launch WellFlo from its stored location or go to

C:\Program Files\Weatherford\WellFlo 4.0 and double‐click

WellFlo4.exe to start the program from the default location. The initial WellFlo Getting Started screen is displayed (see Figure 2‐2).

Figure 2-2: WellFlo Getting Started

2 Click Create a new model under the Project Tasks menu.

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TUTORIAL I: BUILDINGA WELL MODEL

Creating a New Model

Figure 2-3: New WellFlo Model

3 Go to File > Save As... to save the WellFlo model as a *.wfl file.

4 For the Save in: location, navigate to

C:\Program Files\Weatherford\WellFlo 4.0\Example.

5 Enter Sample Well in the File name: box, and click Save.

You are prompted to choose whether to save the model in 3.x format to keep only the compatible data, or 4.0 format to keep compatible and incompatible data.

You now can follow the Configuration menu to set up the well model. A red X indicates screens that have not been configured sufficiently. A green check mark indicates that the screen has been configured. A

n amber check mark

indicates that the screen has not been fully configured, but has

sufficient data for calculations to run

Incomplete configuration screen. Mouse over to view a description of the invalid or missing data.

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TUTORIAL I: BUILDINGA WELL MODEL Creating a New Model

To configure a new well model, follow the items sequentially from top‐down in the Configuration Model Navigator tree.

6 Select General Data from the Configuration Model Navigator. The General Data configuration screen is opened (see Figure 2‐4).

Figure 2-4: General Data

7 Fill in the basic data entry fields.

Completed configuration screen

Incomplete configuration screen, with sufficient data for calculations.

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For more information, or for specific definitions of the fields in this configuration screen, click Help at the bottom right of the screen to view the WellFlo Help

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Creating a New Model

8 Click Apply to save your changes.

Note that a green check mark appears beside General Data in the Model Navigator.

9 Click Forward to advance to the next configuration screen: Well and Flow Type. The Well and Flow Type configuration screen is opened (see Figure 2‐5).

Figure 2-5: Well and Flow Type

The Well and Flow Type configuration screen is used to select the fluid flow

direction and type for the well. The well type can be set to Producer, Injector or

Pipeline, and fluid flow can occur in the tubing, annulus or both. Artificial Lift

Method and Fluid Type are selected here also.

10 Make the selections shown in Figure 2‐5.

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When you select Continuous gas lift as the Artificial Lift Method, an additional configuration screen, Gas Lift Data, is added to the Well Model Navigator.

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TUTORIAL I: BUILDINGA WELL MODEL Setting Flow Correlations

12 Select Dashboard in the Model Navigator.

The Sample Well Dashboard displays the current well and flow type as well as default values for the remaining configuration properties (see Figure 2‐6).

Figure 2-6: Sample Well.wflx Dashboard

Setting Flow Correlations

The Flow Correlations configuration screen is used to select the correlations for the pressure drop calculations.

T

OSET FLOWCORRELATIONS

:

1 With Sample Well.wflx open, select Flow Correlations in the Model Navigator.

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Setting Reference Depths

Figure 2-7: Flow Correlations

2 Make the selections shown in Figure 2‐7 for all Correlations.

3 Click Apply.

4 Click Forward to advance to the next configuration screen, or go to File > Save to save the model.

Setting Reference Depths

The Reference Depths configuration screen contains the information necessary to link the downhole and surface components to a common reference location from where depths are measured (Zero Depth). Depending on the well type — Onshore, Subsea or (offshore) platform well — the reference point selection varies.

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For more information, or for specific definitions of the fields in this configuration screen, click Help at the bottom right of the screen to view the WellFlo Help System.

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TUTORIAL I: BUILDINGA WELL MODEL Setting Fluid Parameters

T

OSET REFERENCEDEPTHS

:

1 With Sample Well.wflx open, select Reference Depths in the Model Navigator.

The Reference Depths configuration screen is opened (see Figure 2‐8).

Figure 2-8: Reference Depths

2 Select Kelly Bushing/Rotary Table in the Zero Depth section. This is the reference point from which all vertical depths are taken. This selection enables the Distance from area above.

3 Enter 105.4 for the Distance from Kelly Bushing to Wellhead (see Figure 2‐8).

4 Click Apply.

Setting Fluid Parameters

The Fluid Parameters configuration screen is used to enter fluid data and select correlations to be used for estimating fluid properties.

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Setting Fluid Parameters

There are facilities for checking and calibrating computed Fluid Properties against measured data. Most of the PVT Fluid Parameters can be Tuned individually. The Tuning Coefficients are stored as part of the WellFlo data file and will be applied in any subsequent calculation made here or in any other part of the program.

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OENTER FLUIDPARAMETERS

:

1 With Sample Well.wflx open, select Fluid Parameters from the Model Navigator.

The Fluid Parameters configuration screen is opened (see Figure 2‐9).

Figure 2-9: Fluid Parameters

2 Enter the parameters shown in Figure 2‐9.

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Oil Specific Gravity and Oil API Gravity and Water Salinity (NaCl Equivalent) and Water Specific Gravity are linked pairs of fields (i.e. changing one automatically updates the other of the pair, so that data remain consistent).

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3 Make the Black Oil Correlation selections shown in Figure 2‐9 for

Bubble‐Point Pressure (P_b), Solution GOR (R_s), Oil Formation Volume Factor (Bo), Oil Viscosity (µo) and Gas Viscosity (µg).

4 For the Surface Tension of water (S_w), select Advanced. This option uses a correlation incorporating pressure and salinity _{effects on water surface}

tension, as opposed to Basic, which uses a simplistic correlation with no dependence on pressure and salinity.

5 Click Tune Correlations to PVT data.

The P‐V‐T Parameters screen is displayed. Any existing fluid models are listed under the Fluid Parameters.

6 In Fluid Model 1, enter the measured produced Gas/Oil Ratio at which the tuning will take place (i.e. this should be the value of Produced GOR (Rsp) at which all the test data were acquired.)

Adding Experiment Data

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O

A

DD

E

XPERIMENT

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ATA

1 Right‐click Fluid Model 1, select Add [Fluid Type] Experimental Data. A new empty experiment is added (see Figure 2‐10).

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Setting Fluid Parameters

Figure 2-10: PVT (Tuning Matching) Workbench

1 Enter the values of Saturation Pressure and Temperature.

2 To enter observed values, select the table and click the Insert Row button.

3 Observed data are entered into the table. You can also add PVT data by copying the data from Excel spreadsheet and pasting it in. 4 Click on Match. A message box confirmation box is displayed if the correlations are tuned successfully. 5 Click OK to close the message box. The results are viewed under Tuning Output (see Figure 2‐11). Insert Row: Adds a new, blank row to the table.

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Figure 2-11: P-V-T Parameters - Tuning Results

6 Click Accept. The PVT Tuning window closes.

The Check tab may be used to examine the results of the selected correlations.

7 Enter the check Pressure, Temperature, produced GOR (Gas/Oil Ratio (Rsp)) andproduced CGR (Condensate/Gas Ratio (Condensate only)) shown in

Figure 2‐9.

8 Click Calculate to get the values of properties out. 9 Click Apply.

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The calculations made in this section are not carried through to any other part of the program and are purely for reference only. All Fluid Properties for Nodal Analysis are calculated at prevailing conditions wherever necessary, based on the data contained in the Fluid Parameters configuration screen.

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TUTORIAL I: BUILDINGA WELL MODEL Reservoir Layers

R

ESERVOIR

L

AYERS

In this Tutorial, you will enter Reservoir Layers data in Test Point mode. In this mode, the Productivity Index (PI) and/or Flow Coefficient/s will be computed from one or two measured Bottom Hole Flowing Pressures (BHFPs) and flow rates.

Setting General Parameters

T

OSET GENERALPARAMETERS

:

1 With Sample Well.wflx open, select Reservoir from the Model Navigator. A new layer is opened in the Reservoir Layers Data configuration screen (see Figure 2‐12).

Figure 2-12: Reservoir Layers Data - General

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TUTORIAL I: BUILDINGA WELL MODEL Plotting IPR

3 Enter the values shown in Figure 2‐12. You can also enter the data by selecting

Layer Parameters or Manual at the top of the configuration panel.

4 Click Apply.

Plotting IPR

5 Open the IPR tab.

The Layer IPR Plot is produced from the data you configured (see

Figure 2‐13).

Figure 2-13: Plotting the Layer IPR

Relative Permeability

Relative Permeability data are used in the computation of the Productivity Index (J), in the IPR Layer Parameters entry mode.

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Relative Permeability

Figure 2-14: Relative Permeability

7 Click Plot.

The relative permeability is plotted in the chart at the right (see Figure 2‐15).

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These parameters will create a plot of Krg and Krw (Y-axes) versus Water Saturation (Sw) in the WellFlo Graphing Window.

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TUTORIAL I: BUILDINGA WELL MODEL Relative Permeability

Figure 2-15: Gas/Water End-Point Parameters Plot

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You can click the pin icon at the top right of the chart to unpin the plot and view or move it in a floating window (see Figure 2-16). This floating window remains in the foreground of your screen even when switching applications.

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Relative Permeability

Figure 2-16: Gas/Water End-Point Parameters Plot (unpinned)

8 Go to File > Save to save the model.

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TUTORIAL I: BUILDINGA WELL MODEL Wellbore Data

W

ELLBORE

D

ATA

The Wellbore Deviation configuration screen is used to view, enter and edit well deviation data. You may chose to enter data in one of three ways, by entering or importing information in two of the three columns. The main deviation data three‐column table allows you to enter data from a deviation survey or import it in from a spreadsheet or other external source.

T

OENTER WELLBOREDEVIATIONDATA

:

1 With Sample Well.wflx open, select Deviation under Wellbore in the Model Navigator.

The Wellbore Deviation configuration screen is opened (see Figure 2‐17).

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The Segment Deviation from Vertical angle is the component deviation angle, not the average angle from the Wellhead/Xmas Tree to this point.

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Wellbore Equipment

Figure 2-17: Wellbore Deviation

2 Click the Add a new row button to insert one blank row into the table. Enter deviation data shown in Figure 2‐17.

WellFlo translates this tabular well deviation data into an equivalent string of nodes for the Nodal Analysis.

3 Click Apply.

4 Click Forward to advance to the Wellbore Equipment configuration screen.

Wellbore Equipment

The Wellbore Equipment configuration screen is used to view, enter and edit information on tubing, casing and restrictions, like SSSV.

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TUTORIAL I: BUILDINGA WELL MODEL Wellbore Equipment

Figure 2-18: Wellbore Equipment

This option is used to add a length of Tubing to the well. The Segment Length increment is the measured length of the component. The Measured Depth refers to the total depth down to the node (i.e. at the bottom of the component or at the deepest fluid entry point (bottom‐most component — nominally the middle of the perforations)).

5 Select Depth in the Enter Data For section. Segment Length values are calculated in this mode.

6 Click the Add a new row button to insert one blank row into the table. Enter the tubing data shown in Figure 2‐18

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Wellbore Equipment

7 Open the Casing tab (see Figure 2‐19).

Figure 2-19: Wellbore Equipment - Casing

This option is used to add a length of Casing to the well. The only difference between a casing and tubing is that the latter is considered to have an external casing. This detail is significant for Heat Transfer modeling and for the Annular Flow option; otherwise for nodal analysis calculations, both component types are just regarded as tubulars, where multi‐phase flow is concerned. The casing components may be replaced by tubing components where required.

8 Select Depth in the Enter Data For section. Segment Length values are calculated in this mode.

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The Flow Configuration column is used to specify whether the flow is in the Tubing or (tubing-casing) Annulus or both. This feature is useful for changing flow path even when tubular sizes are same.

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TUTORIAL I: BUILDINGA WELL MODEL Wellbore Equipment

9 Click the Add a new row button to insert one blank row into the table. Enter the casing data shown in Figure 2‐20.

10 Click Apply, then go to File > Save to save the model.

11 Open the Restrictions tab to enter the data of any Restriction or SSS valve.

12 Click the Add a new row button to insert one blank row into the table. Enter the data.

13 Open the Trace Points tab to enter the data of any Restriction or SSS valve (see

Figure 2‐20).

Figure 2-20: Wellbore Equipment - Trace Points

14 Click the Add a new row button to insert one blank row into the table. Enter the data as shown.

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TUTORIAL I: BUILDINGA WELL MODEL Surface Data

S

URFACE

D

ATA

The Terrain Data configuration screen is used to view, enter and edit Surface Deviation data. The convention for Surface Component measurement is different from the well components. Instead of Depth, WellFlo uses the more useful concept of Elevation; these are measured above the permanent datum of Mean Sea Level (MSL). A deviation of 0° means vertical upward flow; 0° to 90° means inclined upward flow; 90° means horizontal flow; 90° to 180° means inclined downward flow, and 180° means vertical downward flow.

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OENTER SURFACETERRAINDATA

:

1 With Sample Well.wflx open, select Terrain Data under Surface Data in the Model Navigator.

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TUTORIAL I: BUILDINGA WELL MODEL Surface Equipment

Figure 2-21: Terrain Data

2 Click the Add a new row button to insert a blank row into the table. Enter the terrain data shown in Figure 2‐21.

WellFlo translates any tabular terrain data into an equivalent string of nodes in the Terrain data chart.

3 Click Apply.

4 Click Forward to advance to the next configuration screen.

The Surface Equipment configuration screen is opened (see Figure 2‐22).

Surface Equipment

The Surface Equipment configuration screen is used to view, enter and edit Surface Equipment Data. This dialog can be used to specify the following items of Surface equipment: Bend, Choke, Downcomer, Flow Line, Gas Injector, Manifold, Riser, Surface ESP, Trace Point, or Wellhead Gauge.

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Surface Equipment

Figure 2-22: Surface Equipment

5 Click the Add a new row button to insert a blank row into the table. Select the

Choke type and enter the choke details shown in Figure 2‐22.

6 Click the Add a new row button to insert a second blank row into the table. Select the Flowline type and enter the flowline details shown in Figure 2‐23.

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TUTORIAL I: BUILDINGA WELL MODEL Surface Equipment

Figure 2-23: Surface Equipment - Flowline

7 Click the Add a new row button to insert a third blank row into the table. Select the Flowline type and enter the flowline details shown in Figure 2‐24.

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Temperature Model

Figure 2-24: Surface Equipment - Flowline

8 Click Apply.

T

EMPERATURE

M

ODEL

There are four models used in WellFlo for Temperature calculation: Manual, Calculated, Coupled and Calibrated.

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OCONFIGUREATEMPERATUREMODEL

:

1 With Sample Well.wflx open, select Temperature Model from the Model Navigator.

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TUTORIAL I: BUILDINGA WELL MODEL Temperature Model

The Calibrated Temperature model is selected to tune the calculated model to temperatures measured at a known flow rate at the wellhead (or gauge) and at the Outlet Node (e.g. Separator). The calibration applies one Tuning Factor from the Reservoir to the Wellhead (or Gauge), and another Tuning Factor from the Wellhead (or Gauge) to the Outlet Node, such that the calculated temperatures at the specified Flow Rate match the specified Wellhead (or T Gauge) temperature and Outlet Node temperature.

Figure 2-25: Temperature Model - Calibrated

2 Enter the values shown in Figure 2‐25 for the Flow Rate, Outlet Temp, and

Wellhead Temp.

3 For the Surface temperature, enter 60.0.

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For more information about the Calibrated Temperature Model, click Help at the bottom right of the screen to view the WellFlo Help System.

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Gas Lift Data

In the Wellbore table, Calculated indicates whether the Heat Transfer Coefficient is calculated or manually input for each segment. Calculated is checked to allow WellFlo to calculate it automatically.

4 Open the Flowline tab (see Figure 2‐26).

Figure 2-26: Temperature Model - Flowline

5 Enter values for the Air and Water Standard heat transfer coefficients.

6 Click the Add a new row button to insert two blank rows into the table. Enter the data shown in Figure 2‐26.

7 Click Apply, then go to File > Save to save the model.

G

AS

L

IFT

D

ATA

The tabular Gas Lift Parameters configuration screen is used to view, enter and edit Gas‐Lift data.

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TUTORIAL I: BUILDINGA WELL MODEL Gas Lift Data

Gas‐Lift is modeled in WellFlo by inserting one or more Gas‐Lift Valves in the well system; these are positioned at the bottom of the Tubing components. Gas‐Lift Valves can be declared as Active or Inactive. Gas‐Lift Valves may be selected by Manufacturer, Model and Port Size. Depending on the selection of Valve Type, either PPO (Production Pressure Operated) valves or IPO (Injection Pressure Operated) valves will be mutually excluded from the valve models that become available.

T

OSET GASLIFTPARAMETERS

:

1 With Sample Well.wflx open, select the Gas Lift Data configuration screen from the Model Navigator.

The Gas Lift Parameters configuration screen is opened (see Figure 2‐27).

Figure 2-27: Gas Lift Parameters

2 Click the Add a new row button to insert one blank row into the table. Enter the gas lift data shown in Figure 2‐27.

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Gas Lift Data

5 Click Dashboard in the Model navigator to view the completed Dashboard for this model.

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Chapter 3 T

UTORIAL

III: S

YSTEMS

A

NALYSIS

This Tutorial explains how to perform nodal analysis tasks in WellFlo, including setting operating conditions, running sensitivities and plotting. Systems Analysis ... 44 Setting Operating Conditions ... 44 Running Sensitivities ... 48 Plotting ... 50

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TUTORIAL III: SYSTEMS ANALYSIS

Systems Analysis

S

YSTEMS

A

NALYSIS

In “Tutorial I: Building a Well Model”, you configured a well model with the same parameters as the example well, Test1 (Test1.wfl), supplied with the WellFlo installation files. This well requires a minimum Gas Injection before production can kick‐off.

If you have not completed Tutorial I, go to File > Open and select Test1.wfl from the following location: C:\Program Files\Weatherford\WellFlo 4.0\example. Review the example well model before continuing the Analysis tutorial. The Analysis section of WellFlo consists of these main options: • Operating Conditions — There is a choice of Pressure Drop calculations (e.g. end to end pressure drop, knowing one end Pressure and a Flow Rate) or Operating Point determination (e.g. flow rate and pressure at a given node, knowing both end pressures). • Sensitivities — You can run a single base case, or up to two Sensitivities (i.e. study the effect on the results of two independent sets of variables ‐ 10 values per set). The choice of variable is limited to those appropriate for the models that have been selected.

Setting Operating Conditions

The operation mode and other operating conditions are set in the Operating Conditions configuration screen, under the WellFlo Analysis menu.

T

OSET OPERATINGCONDITIONS

:

WellFlo.exe to start the program from the default location. The initial WellFlo Getting Started screen is displayed.

2 If you completed “Tutorial I: Building a Well Model”, open

Sample Well.wflx from the WellFlo example folder. If you did not complete the previous tutorial, go to File > Open and select Test1.wfl to view the example well model (see Figure 3‐1).

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TUTORIAL III: SYSTEMS ANALYSIS Setting Operating Conditions

Figure 3-1: WellFlo Dashboard

3 Open the Analysis menu in the Model Navigator.

4 If necessary, select Operating Conditions in the Analysis menu.

The Operating Conditions menu is displayed in the center of the screen.

Operating is selected as the default Operation Mode (see Figure 3‐2).

This option is used to perform operating point nodal analysis for the current well. For Operating mode, this means running Pressure Drop calculations at a range of flow rates, starting from opposite end nodes and calculating Inflow and Outflow pressure curves at an intermediate point called the Solution Node. The intersection of the Inflow and the Outflow pressure curves provides the Operating Point (i.e. the Pressure and Flow Rate at the solution node) for the well under analysis. In Operating mode, there are two end nodes and a Solution Node. Logic is used to keep the node selection consistent (i.e. the Top Node must be above the Bottom Node, and the Solution Node must be between the two).

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Setting Operating Conditions

Figure 3-2: Operating Conditions

5 Select and enter Calculation Nodes data:

• Top Node. Select Outlet Node and enter 96.00 for the Top Node Pressure. • Bottom Node. Select Layer 1 @ 15413 and enter 2171.00 for the Bottom

Node Pressure

• Solution Node. Select Casing @ 15413.

6 Enter the Flow Rates at which the nodal analysis calculations will be

performed. The defaults are 11 flow rates in a range from 5% to 95% of the AOF. Click % of AOF above the Flow Rates table, and enter From 5 to 95 in 10

Steps, and click Fill. The Flow Rates table is filled (see Figure 3‐2). In an Operating point calculation, these will be arbitrary flow rates that (hopefully) span the actual operating point/s. The flow rates used should ensure that the intersection (if any) of Inflow and Outflow curves will be seen. At least two flow rates are required for an Inflow/Outflow Analysis.

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TUTORIAL III: SYSTEMS ANALYSIS Setting Operating Conditions

The Flow Curve is calculated (see Figure 3‐3).

Figure 3-3: Flow Curve

8 Open the Configuration menu in the Model Navigator, and select Temperature Model to review the Temperature Model configuration screen. The flowing temperature will be calculated at each of the production rates. The model is calibrated against temperatures that were measured at the wellhead and separator while the well was producing at 1332 STB/day (i.e. total liquid). Gas in the annulus will be assumed since this is a Gas‐lifted well. The inflow calculations will start from the Reservoir (i.e. using the layer pressure 2171 psia) and the outflow calculations from the Outlet node (i.e. base case pressure 96 psia). The Casing has been selected as the Solution Node so that the Operating point pressures computed will be the “Bottom Hole Flowing Pressures.”

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TUTORIAL III: SYSTEMS ANALYSIS Running Sensitivities Owing to the low reservoir pressure, the Sample Well will not produce without Gas‐lift. A Sensitivity Analysis will be performed to examine the productivity at different injection GLRs, for different outlet node pressures. The objectives here will be to: • Ascertain the minimum Injection GLR for production at each pressure. • Determine the performance curves for the well when producing.

Running Sensitivities

To run Sensitivity Analyses, you must select one or two sensitivities from the

Sensitivity 1 and Sensitivity 2 drop‐down lists. If no sensitivities are selected, only the base case values entered in the various input fields will be used in the Nodal Analysis. The Sensitivities and Sensitivity Groups offered when the Reservoir is included in a nodal analysis run are dependent on the current Reservoir Configuration. In this Tutorial, you will create two new sensitivities and run a Sensitivity Analysis using both.

T

ORUNASENSITIVITY ANALYSIS

:

1 Open the Analysis menu in the Model Navigator.

2 Select Sensitivities from the Analysis menu.

Existing sensitivities are listed in the Manage Sensitivities list and are available in the drop‐down lists under Sensitivity 1 and Sensitivity 2 (see Figure 3‐4).

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TUTORIAL III: SYSTEMS ANALYSIS Running Sensitivities

Figure 3-4: Manage Sensitivities

3 Click Create... under the Manage Sensitivities window. The Sensitivities section is activated below.

4 Select Lift gas/liquid ratio, under the Artificial Lift category. In the Range table, enter From: 500 To: 3500 Steps: 6. Click Fill, then click Apply to add the new sensitivity to the Manage Sensitivities window.

5 Select Top/start node pressure, under the Pressure and Temperature category. Enter 50, 100 and 150 in the first three rows of the Values table, then click

Apply to add the new sensitivity to the Manage Sensitivities window.

6 In the Sensitivity 1 drop‐down list, select Lift gas/liquid ratio. The seven values entered (500 to 3500 SCF/STB with a view to identifying kick off) will override the base case value in the Gas Lift Parameters configuration screen.

7 In the Sensitivity 2 drop‐down list, select Top/start node pressure. The three values entered span a reasonable operating range and will override the base case value entered for the Start Node pressure under Operating Conditions.

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TUTORIAL III: SYSTEMS ANALYSIS Plotting The calculations will be performed using both Sensitivities, making a total of 11*7*3 (= 231) runs, from which a maximum of 7*3 (= 21) operating points could be determined if stable intersections were found in all cases.

Plotting

9 Open Include in Plot on the Analysis menu.

The results of the sensitivity analysis are displayed.

10 Drag the row selector to select the values you want to plot in the chart. 11 Click Plot Selected.

The values selected are plotted in the chart windows (see Figure 3‐5).

Figure 3-5: Inflow/Outflow Plot

The Inflow/Outflow curves are plotted in the Flow Curves plot. Separate plots can be produced of the Sensitivity 1 curves and Sensitivity 2 curves versus the first case of the other sensitivity.

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TUTORIAL III: SYSTEMS ANALYSIS Plotting

12 For an overall view of the effects of all the values of GLRi and Outlet Pressure

on the Production Rate, open the Lift gas/liquid ratio performance tab (see

Figure 3‐5). The Operating Point Rate can now be plotted for each case against both sensitivities.

Figure 3-6: Well Performance Plot for Lift-gas GLR

From this plot, it is clear that the well kicks off at a certain minimum Lift‐gas GLR and that the kick‐off requirement increases the Outlet pressure. There is no production at 500 SCF/STB from the well at the highest Outlet pressure (150 psia).

13 Open the Top/start node pressure performance tab (see Figure 3‐7). This plot illustrates a different way of looking at the same scenario. The curve shows a decline in production with increasing Top/start node pressure.

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Plotting

Figure 3-7: Well Performance Plot for Outlet Pressure

14 Select the 2500 scf/STB Lift‐gas/liquid ratio and the 100 psia Top/start node

pressure from the table, and click Calculate.

15 Open the Report tab to view the Analysis report.

The Analysis Report contains a summary of the input data and system description, followed by the calculated results. For Operating Point calculations, the pressures calculated at the Solution Node in the inflow direction and outflow direction will be listed for each flow rate, along with the Operating Point, and Depth of Gas‐Injected (i.e. provided a Gas‐Injection Analysis is being performed), on a case by case basis. The Operating Point report lists the flow rates of each Layer at each Operating Point. For Cross‐Flowing Layers in a production well, the Cross‐Flow Rate is listed, with a negative sign.

16 Click the Save Report button to save this report to the WellFlo Output sections.

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Chapter 4 T

UTORIAL

IV: G

AS

L

IFT

D

ESIGN

This chapter how to configure and design a Gas Lift well model in WellFlo. Gas Lift Data ... 54 Adding Valves ... 54 Gas Lift Design ... 56 Designing Gas‐lift Systems ... 57 Sizing ... 75 Sample Gas‐Lift Plots ... 76

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TUTORIAL IV: GAS LIFT DESIGN

Gas Lift Data

G

AS

L

IFT

D

ATA

For this Tutorial, you will use a pre‐configured WellFlo model, Gldesign.wfl located in the WellFlo Tutorials folder. The Gas Lift Parameters configuration screen is used to view, enter and edit Gas‐Lift data. Gas‐Lift Valves may be selected by Manufacturer, Model and Port Size from those listed in the gasvalve.csv file. Depending on the selection of Valve Type, either PPO (Production Pressure Operated) valves or IPO (Injection Pressure Operated) valves will be mutually excluded from the valve models that become available.

Adding Valves

T

OSET GASLIFTPARAMETERS

:

WellFlo4.exe to start the program from the default location. The initial WellFlo Getting Started screen is displayed.

2 Go to File > Open and select Gldesign.wfl from the following location:

C:\Program Files\Weatherford\WellFlo 4.0\example. 3 Open the Configuration menu in the Navigator.

4 Select Gas Lift Data from the Model Navigator. This configuration screen is added to the Model Navigator when Gas‐lift is selected as the Artificial Lift Method in the Well and Flow Type screen.

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TUTORIAL IV: GAS LIFT DESIGN Adding Valves

Figure 4-1: Gas Lift Parameters

New valves are added to the system at set depths. The Temp. column is used to set the temperature at the valve when the Manual Temperature Model is selected. The Tro column represents the Test Rack Opening Pressure for

Gas‐Charged and Spring‐Loaded Valves only.

The Port column lets you select a port size for the selected Manufacturer and Model (see “Port Size Calculation” on page 75 for more information on sizing). R displays either the Port‐to‐Bellows Ratio of the selected Port size for an IPO Valve (where Apt is the Port Area), or its complement (R = 1 ‐ Apt/Ab), for a PPO Valve. For an Orifice Valve, this column is blank.

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Gas Lift Design

The valve differential pressure is the quantity by which Casing Pressure must exceed Tubing Pressure at the valve in order for a valve to open. WellFlo models a Differential Gas Valve assuming a fixed differential. In case several valves could be open by this criterion, only the deepest is assumed to be open.

Use GLRi is selected to enable the Injection GLR field. The value entered here will be the base case Injection GLR. This Deepest Point of Injection data is used only if the Analysis mode is Deepest Point of Injection: Operating Point, Deepest Point of Injection: Pressure Drop or Gas‐Lift Design ‐ Valve Positioning, where WellFlo is computing Gas‐Lift Valve depths rather than using specified depths. These fields are used to indicate the Deepest Point in the Well that a Gas‐Lift Valve can be inserted.

Use Tubing Shoe is checked to limit Gas‐lift valves to be as deep as the

downstream end of the first Tubing Node above the shallowest Active Layer.

When unchecked, the Max MD of Injection is used.

In Deepest Injection Point and Gas‐Lift Design modes, WellFlo Analysis is only allowed to position valves above the specified depth. It follows that the default Use Tubing Shoe option allows complete freedom, while Maximum MD of injection applies a depth constraint.

G

AS

L

IFT

D

ESIGN

The Gas Lift Design screen is used to determine the positions of the Unloading Valve/s and Operating Valve to produce the Well at a prescribed Flow Rate for a specified set of Casing and Gas‐Lift conditions, initial static Wellbore Fluid, etc.

i

If users decide later to select GLRi as a Sensitivity Variable (Go to Analysis > Sensitivities > Create > Artificial Lift > Lift gas/liquid ratio. See “Running Sensitivities” under the “Systems Analysis”section), the Injection GLRs entered there will override this value.

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TUTORIAL IV: GAS LIFT DESIGN Designing Gas-lift Systems

Any specified Gas‐Lift Valve Depths that may already have been entered via the Gas‐Lift Data configuration screen (see “Gas Lift Data” on page 54) will be ignored in a Design run. Normally, users will have made a reasonable estimate of the Operating Conditions from an Inflow/Outflow Analysis, using the Deepest Point of Injection: Operating Point option, to identify the optimum Operating Valve Depth and Operating Rate. Users should also have an idea of the range of Valve Depths (i.e. bracketing envelope) that might be required to allow for changing Operating Conditions (i.e. declining Reservoir Pressure, increasing Water‐Cut, Well Stimulation, etc.). This can be achieved by a careful Sensitivity Analysis of all relevant variables. Set‐up the input data as described below, and run the Design option. The Valve Depths will be computed, and the results of the Design Analysis are plotted in the graphing window.

Designing Gas-lift Systems

T

OENTER GASLIFT DESIGNDATA

:

1 With Gldesign.wfl open, open the Design menu in the Navigator. The Gas Lift Design screen is opened (see Figure 4‐2).

i

The Gas-Lift Valve (GLV) and Electrical Submersible Pump (ESP) Design options are separately licensed within WellFlo; users with a basic WellFlo license will not have access to these. This Design option will be disabled if your Software License is not configured (and activated) for WellFlo/Gas-Lift.

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Designing Gas-lift Systems

Figure 4-2: Gas Lift Design — Design Options

Design Options

2 Select Design Options from the menu at the left.

2a Enter Valve Type data: — Select the type of Gas‐lift valves to size, either Injection (Casing) Pressure Operated (IPO) or Production (Tubing) Pressure Operated (PPO). 2b Enter Unloading Valve data: — Model. This field displays the manufacturer and valve model to be used for the unloading valves in the design.

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The choice of Valve Type does not affect the Valve Spacing methodology, but does affect the Valve Sizing calculations.

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— Browse Catalog. The Browse Catalog button allows users to browse the gas lift valve catalog and select the valve manufacturer, model, port size and correlation to use for sizing unloading valves in the design.

— Port Size. This field displays the default port size used in unloading valves for the given design. When gas passage requirements dictate that a different port size be used to meet the conditions, WellFlo will select a valve with the most suitable port size from same manufacture and model.

— Load Default.This option allows users to load the default unloading valve specified under Settings > Options >Preferences > Default Gas Lift Valves.

— Correlation. This field displays the gas passage correlation used for sizing the unloading valves. Note: certain correlations are only available to users who have licensed the data from the Valve Performance Clearinghouse.

— Check Use Catalog Discharge Coefficient. This option enables users to use the discharge coefficient (Cd) specified in the catalog for sizing the unloading valves. Note: this only applies when Thornhill‐Craver is selected for the gas passage correlation.

— Discharge Coefficient. This displays the discharge coefficient that is used in calculating gas passage for the unloading valves using the Thornhill‐Craver gas passage relationship.

2c Enter Casing Pressure Drop data:

— Check Pressure Drop at Top Valve (delta P line). This option enables users to apply a fixed differential pressure between available casing pressure and maximum casing head pressure for the purposes of spacing out the top gas lift valve. This additional differential pressure is intended to ensure that sufficient gas passage is available for the well to unload past the first gas lift valve.

— Select Constant Casing Pressure Drop to enter the Casing Closing Pressure Margin (optional): This correction reduces the casing pressure required to open each valve successfully down the hole. This helps ensure that the valve above will be closed when the next valve below is opened. This design margin is usually applied to

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appropriate range of values (e.g. 20 ‐ 50 psi) should be entered.

— Check Use Recommended Casing Closing Pressure Margins. This option allows users to set casing closing pressure drops based on values specified in the gas lift valve catalog.

— Select Pt max - Pt min to enter the Safety Factor. This option allows users to base their design on the Ptmax – Ptmin method. The corresponding safety factor is used in the calculation of Ptmax in conjunction with this method. For more information on the Ptmax – Ptmin gas lift design method, refer to API RP 11V6: Recommended Practice for Design of Continuous Gas Lift Systems Using Injection Pressure Operated Valves, Second Edition, July, 1999. 2d Enter Deepest Point of Injection data:

— Check Use Tubing Shoe to limit Gas‐Lift valves to be as deep as the

downstream end of the first Tubing Node above the shallowest Active Layer. When unchecked, the Max MD of Injection is used. — Maximum MD. This is the maximum Measured Depth (MD) that the Operating Valve is expected to be set during the life of the well. This value must be between the Wellhead/Xmas Tree and the Tubing Shoe (at the downstream end of the first Tubular Node above the shallowest Active Layer). The default value (i.e. nominally Tubing Shoe Depth) is transferred from the Deepest Point of Gas Injection section of the Gas‐Lift Data configuration screen.

— Valve Differential Pressure. This is the quantity by which casing pressure must exceed tubing pressure for a Gas‐lift valve to open (i.e. for the operating valve to pass the required volume of gas). This value is shared between this screen and the Gas Lift Parameters configuration screen (see “Gas Lift Data” on page 54).

2e Enter Minimum Valve Spacing data.

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It is usually left at zero for Production Pressure (Tubing) Operated (PPO) Valves.

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The minimum True Vertical Depth (TVD) spacing between Gas‐Lift valve positions to be used in the Design process. If the valve spacing is too close, in practice this will lead to unstable Gas‐lift.

— Manual. This option allows users to manually specify the minimum allowable distance (in true vertical depth) between valves in the well. — Calculate (Valve Differential Pressure / Static Fluid Gradient). This

option allows WellFlo to automatically calculate minimum valve spacing based on the specified valve differential at the depth of injection.

2f Enter Valve Positioning data:

— Select Top/Bottom or Bottom/Top for the Numbering Method. — Enter the Round off Valve Depth (MD). This option allows users to

define a round‐off for spacing of gas lift valves. By specifying that valves be spaced to the nearest X feet, users are able to provide a more field‐friendly gas lift design. Often it is not practical or necessary to space valves to the nearest foot as defined in the design. (nearest 50 feet is generally OK)

Flow Parameters

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Figure 4-3: Gas Lift Design - Flow Parameters

3a Enter Design Conditions:

— Start Node. Select the node that the Design calculations will be started from. Users have the choice of starting at the Xmas Tree node or the

Outlet Node. The default node is the one used for the last Nodal

Analysis (Pressure Drop) mode calculation (if any).

— Start Node Pressure. After selecting the Start Node, enter the Flowing Pressure for this node at which the top‐down computations are to start.

— Casing Pressure. This value will be computed once the Operating Valve position has been calculated; its initial value is unimportant. It defaults initially to the Steady‐State Casing Head Pressure value (if any) entered in the Gas‐lift Data configuration screen, otherwise enter any value greater than 10 psia. Users will be given the opportunity to update the value from the Gas‐lift Data configuration screen (if any), with the new Design value, so it can be used for Nodal Analysis.

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— Max. CH Pressure. This value (usually larger than the Casing Head Pressure defined above), is the Casing Head Pressure that users expect to be available at the Wellhead for Gas‐lift operations, and is required for the Unloading Valve computations. WellFlo reports the

optimum Casing Head Pressure that follows from this maximum

Casing Head Pressure value.

— Kickoff Pressure. The value entered here is used for the computation of the upper‐most Unloading Valve position if it is greater than the Maximum Casing Head Pressure; otherwise, it is ignored.

3b Enter Design Rates:

— Liquid rate. The total Liquid Operating Production rate to be used in the Design study.

— To select rates from a performance curve, click the Select Rate button. — Select Use Qgi to use the Lift‐Gas Injection Rate.

— Gas Injection rate. The desired Operating Injection rate. This field is enabled only if Use Qgi is selected. The default value is transferred from the Gas‐Lift Parameters configuration screen.

— Select Use GLRi to use the Lift‐Gas/Liquid Ratio.

— Lift-Gas/Liquid. the desired Operating Injection Gas/Liquid ratio. This field is enabled only if Use GLRi is selected. The default value is transferred from the Gas‐Lift Parameters configuration screen.

3c Enter Gradients:

— Static Fluid Gradient. The Pressure Gradient of the Static Fluid (i.e. Kill Fluid) that is to be unloaded.

— Static Fluid Specific Gravity. the Specific Gravity of the Static Fluid (i.e. Kill Fluid) that is to be unloaded.

— Depth of Static Fluid Level. If this value is disabled (i.e. the associated

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For the upper-most Unloading Valve, this Maximum Casing Head Pressure value will be superseded by the Kick-Off Pressure value (described below) if this is greater.

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start at the Producing Wellhead Pressure. This will be the specified Start Node Pressure if the Wellhead is assigned as the Start Node (see “Flow Parameters” on page 61). If the Outlet Node is assigned as the Start Node, WellFlo will use a computed Wellhead Pressure. If this value is enabled (i.e. the associated checkbox is checked), the Static Fluid Pressure Profile for the unloading sequence is taken to start at corrected Atmospheric Pressure at the specified TVD from Reference Depth. This enables a Swab‐Out or other Static Fluid Removal process to be modeled.

Figure 4-4: Depth of static fluid level (TVD): 105.40

The setting above will start the Static Fluid Gradient at corrected Atmospheric

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Figure 4-5: Depth of static fluid level (TVD): 0

The setting above will start the Static Fluid Gradient at corrected Atmospheric

Pressure at the Reference Depth (i.e. unloading to the atmosphere).

— Injection gas gravity. This value is shared between this screen and the Gas‐Lift Data configuration screen (see “Gas Lift Data” on page 54); it does not have to be the same value as the Produced Gas Gravity.

3d Enter Extended Spacing Gradient.

— Check Display Extended spacing Gradient. This option allows the users to overlay a gradient that reflects a specified set of conditions. This is useful in depicting what future well conditions might look like in the context of the extended spacing region of the gas lift design. — Start Node Pressure. This is the pressure of the upper‐most node

(usually tubing head pressure) associated with the extended spacing gradient.

— Liquid Rate. This is the production rate associated with the extended spacing gradient.

— Water Cut. This is the water cut associated with the extended spacing gradient.

— GOR. This is the total produced gas‐oil‐ratio associated with the extended spacing gradient.

— List-Gas/Liquid. This is the gas injection rate (or injection gas to liquid ratio) associated with the extended spacing gradient.

Transfer Pressure Margins

4 Select Transfer Pressure Margins from the menu at the left (see Figure 4‐6).

i

The above two examples presume that Wellhead Depth is the same as

Reference Depth (e.g. if the Wellhead Depth was 80 ft from the Reference Depth, a Static Level of 180 ft would be 100 ft below the Wellhead). Unloading

can be represented against a back-pressure (i.e. flow lines) by entering a negative Depth here (i.e. so the pressure at the Wellhead is greater than zero).

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The Transfer Pressure Margins panel is used to specify a number of (optional) Design Safety Factors to be applied during a Gas‐Lift Design; these act to modify the valve transfer pressure that is used to position the gas lift valves and perform the valve sizing calculations. In order to accommodate the various design philosophies used in the industry, WellFlo provides the user with a variety of options for determining transfer pressure bias. The user has to choose only one of the options.

Figure 4-6: Gas Lift Design — Transfer Pressure Margins

4a Use Bracketing: The Bracketing option allows users to space gas lift valves based on the bracketing design methodology. This

methodology generates a design line based on a user‐specified error tolerance. This design line is drawn from the wellhead pressure to the target depth of injection at a pressure equal to (1 + error tolerance)* tubing pressure.