WellFlo™ - Advanced Well Modeling Software

Quick Links to Information Below

• WellFlo Introduction
• Typical Applications for WellFlo
• Inflow and Completion Modeling
• PVT Modeling

• Pressure Traverse and Temperature Calculations
• Tuning of Well Models
• Data Export and Import
• Gas Lift Design and Analysis
• Electric Submersible Pumping Systems
• Pseudo-Pressure File Generator (PPFG)
• Document Management
• New to WellFlo 4.0 Software
• WellFlo Module
• Gas Lift Module
• ESP Module
• FieldFlo Module
• Well Data Manager

PDF Documents

• WellFlo Software Brochure
• WellFlo Software Brochure - Spanish Version
• EPS Software Brochure
• EPS Products At-A-Glance

WellFlo Introduction

WellFlo systems analysis software is a powerful and simple-to-use stand-alone application to design, model, optimize and troubleshoot individual oil and gas wells, whether naturally flowing or artificially lifted. With this software, the engineer builds well models, using a guided step-by-step well configuration interface. These accurate and rigorous models display the behavior of reservoir inflow, well tubing and surface pipeline flow, for any reservoir fluid. Using WellFlo software results in more effective capital expenditure by enhancing the design of wells and completions, reduces operating expenditure by finding and curing production problems and enhances revenues by improving well performance.

Typical Applications for WellFlo

WellFlo Analysis Section

The WellFlo software package is a single well tool which uses nodal analysis techniques to model reservoir inflow and well outflow performance. WellFlo modeling can be applied to designing, optimizing and troubleshooting individual wells. Specific applications for which the software can be used include:

• Well configuration design for maximum performance over life of well
• Completion design to maximize well performance over the life of well
• Artificial lift design
• Prediction of flowing temperatures and pressures in wells and flowlines and at surface equipment for optimum design calculations
• Reservoir, well and flowline monitoring
• Generate vertical lift performance curves for use in reservoir simulators

As well as these applications, the software has two key internal sub-applications which can be used stand alone from the rest of the program and offer the user an excellent engineering toolkit.

• Detailed reservoir inflow performance modeling
• Multiple completion and perforation models
• Detailed skin analysis
• Detailed fluid PVT modeling
• Black oil models for oil and gas
• Equation of State models for condensate and volatile oil

Inflow Performance Plot Comparing Multiple IPR Methods

Relative Permeability Interface

Pressure and Temperature Versus Depth Analysis for a Gas Lift Well

Tuning Inflow Performance Relationship to Measured Data

• Laboratory data matching
• Fluid behavior prediction

Inflow and Completion Modeling

Well inflow is an important factor in a well’s performance. The WellFlo interface allows you to enter a PI, reservoir pressure, and inflow model such as Vogel, if your information is limited. Alternatively, detailed completion data including damaged zone, well deviation, partial penetration, perforating specification, gravel pack information, and fracture geometry can all be entered to predict the effect on well deliverability (this can be done for both vertical and horizontal wells).

A multi layer model is included for composite systems, with each layer having its own fluid, completion and inflow model. This benefits petroleum engineers who are designing new completions or diagnosing problems in performance. A sophisticated constant mass flow rate inflow model can be used to include relative permeability effects. These can be entered through tables or Corey coefficients. This provides an extremely accurate technique for performance forecasting in condensate and gas cap drive reservoirs, and is especially useful in predicting performance as reservoir conditions and phase fractions change in these fields.

PVT Modeling

All pressure and flow modeling in hydrocarbon systems relies on accurate modeling of fluid properties as they vary with pressure and temperature. The WellFlo PVT package includes the important standard black oil correlations and allows these to be tuned to honor observed data. The tuned correlation is then used throughout the program to calculate fluid properties. As a result, you can rely on the accuracy of the software’s performance predictions and optimization operations which often depend on accurate calculations of fluid properties.

For near critical fluids, where the black oil correlations are unreliable, an equation-of-state technique is incorporated in the software with tuning facilities to allow accurate modeling of these fluid types. This approach holds great advantages because it requires only the limited data needed for a black oil model while retaining the higher accuracy of full compositional modeling.

Pressure Traverse and Temperature Calculations

The pressure drop and temperature change between the bottom of the well and the surface is normally the largest drop in the system. WellFlo pressure drop analysis incorporates all the important correlations for this calculation. The temperature modeling options include manual definition of temperature at each node, calculated and calibrated heat loss models and a coupled temperature-pressure model. This allows you to define heat loss factors either through the system’s calculation or by direct input.

Plots of measured data and predictions can be shown simultaneously on-screen allowing rapid matching. When performing pressure traverse calculations you have the option to capture other data instead of pressure and temperature, such as in situ phase densities and velocities, flow regime, and hold-up plus the gravitational, frictional and acceleration terms of the pressure drop. This data can be very useful in determining, for example, if erosional velocity limits are being exceeded.

Tuning of Well Models

In order to be certain that analysis results can be trusted to match reality, users need a way to tune their well model to measured data. With many software packages, this task can prove to be labor-intensive and challenging. In the redesigned WellFlo 4.0 software release, this task has been greatly simplified through the development of an all-new “Tuning” mode. In this mode, users are able to tune PVT correlations using PVT data; they can use flowing pressure gradient surveys to tune their outflow performance model; they can use production well test data, at either surface or downhole conditions, to tune their inflow performance model; and, they can use multi-rate well test performance data to tune a variety of well parameters. In each of these cases, data can either be entered manually or imported from an external source through a wizard-based data import tool. Once the measured data is entered, it can then be used to tune a variety of parameters using a powerful non-linear regression algorithm. This ensures that well models will be as accurate as possible with a minimum of effort from the user.

Data Export and Import

WellFlo data export tools generate vertical flow table data in DOS or UNIX format for use in Eclipse™, VIP™ and other reservoir simulators. These files are simply pasted into the control decks for the simulator. Therefore, it becomes practical to generate a vertical flow profile table for every well in a field appropriate to that particular well. Without this direct link to simulators, a ‘typical’ table is used for all wells due to the shear impracticality of generating one table per well.

Data Export Interface

Report files can be generated in tab-separated form to allow easy export of data to word processing and spreadsheet packages. The ability to ‘cut and paste’ in the Windows™ environment allows very efficient generation of reports including graphs and other screen captures. A graphics export option also allows plots to be saved directly to file in a number of formats.

• UNIX and DOS flowing pressure file generation for Eclipse, VIP, CHEARS, SimBest I and II, IMEX, MoRes, GCOMP, COM4, sensor reservoir simulators and a multi-well batch mode is available for some outputs
• Key-worded file output available for data transfer to other applications
• Graphics export facility saves plots directly to file (BMP, GIF, JPG and TIF formats)
• Reports can be opened directly in Word, Excel, etc.

Measured pressure-depth or pressure and rate data can be imported into the WellFlo data repository and plotted on the same graphs as the model’s prediction. This significantly reduces the time taken to produce a matched data model. An auto-regression option will estimate the optimum flow correlation tuning factor by a least-squares fit to the measured data.

Gas Lift Design and Analysis

Using the program’s specialized capabilities for gas lift, engineers can design and model gas lift installations and determine the number and position of the gas lift valves, as well as the optimum injection rate taking account of the available injection pressure.

Gas Lift Design Section Showing Gas Lift Valve Spacing and Valve Calculations

AGVM Injection Pressure Sensitivity for an IPO Valve

Gas lift design and diagnosis is a particular strength of the software making it (with its link to the only commercially available dynamic gas lift simulator, the EPS DynaLift™ program) a uniquely powerful gas lift system. This is critical in a tool used for full gas lift system modeling and optimization.

This program will allow you to incorporate gas injection rate or gas-liquid ratio terms as preferred. Together with the casing head pressure, these factors are input as sensitivity variables. For every rate specified, the program will determine which valve is being used for gas injection so that the system’s predictions are always accurate.

WellFlo features include the following modes of operation for analyzing and designing gas lift systems:

• Continuous gas lift design–deepest point of injection
• Gas lift design–valve spacing for continuous and intermittent gas lift installations
• Gas lift design–valve sizing
• Gas lift performance analysis–for continuous gas lift
• Advanced gas lift valve modeling (AGVM)–for continuous gas lift, true valve performance

Advanced Gas Lift Valve Modeling

The pressures at which gas-lift valves allow gas to pass and the amounts of gas they pass depend upon the way they are constructed.

Orifice valves are simple: if there is sufficient pressure in the casing to reach the valve, then the major limitations on how much gas can be passed through the valve are the port size and the casing pressure.

Pressure controlled, or “live,” valves open at a pressure that is dependent upon overcoming a resisting force (bellows or spring). These mechanisms also allow the valve to be fully or partially open and to pass variable amounts of gas depending upon the balance of tubing and casing pressures and the valve port size.

The AGVM facility in the software introduces true valve performance into the computation of operating points.

Electric Submersible Pumping Systems

EPS engineers have worked extensively with pump suppliers to ensure that the calculations performed by WellFlo–ESP software are rigorously accurate. The program has a complete database of pump performance curves for all the models from leading manufacturers. These performance curves are used as the basis for the head calculations which are then adjusted for fluid density, pump frequency, number of stages and other system variables. This means that a reliable calculation of pump performance is performed at all operating conditions. The benefit of including pump modeling within the software is that it allows a pump to be modeled as installed in the real well, such as in a horizontal well, with a particular fluid type. This is more accurate than modeling the pump performance without considering other well characteristics.

ESP Design Mode

Output Mode

Pseudo-Pressure File Generator (PPFG)

The multiphase PPFG (link with 3rd party PVT packages) is an additional application which creates a table of multiphase pseudo-pressures from the customer’s own PVT. This allows the client to use his own PVT modeling package where he prefers to do so. The multiphase pseudo-pressures generated by PPFG can then be imported into WellFlo software for use in IPR calculations.

The PVT data are generated by the user’s preferred PVT package and supplied to the software in the form of an ASCII file containing a table of phase properties versus pressure at a specified (reservoir) temperature. Properties required are viscosity, density and, for oil and condensate systems, gas mass fraction.
PPFG interfaces with WellFlo software via an external API link to extract the relative permeability data which are part of the well and reservoir model contained in the well file.

The generator then creates a multiphase pseudo-pressure file. This can be imported into the software and used as the basis for layer IPR calculations. The use of external PVT data is an alternative to the use of the software’s own internal PVT models (4-component EoS, black oil correlations, etc).

Each layer in the WellFlo model can be assigned its own pseudo-pressure file and each pseudo-pressure file can be generated from a different set of PVT data so the accurate modeling of variations in fluid properties with depth and their effect on IPR becomes possible.

Document Management

The latest software version addresses one of the most important, yet often-overlooked, tasks facing users of the program, through the development of a unique document management system. Upon completion of an analysis or design, users generally want to display and then save their work in the form of a chart or report. Unfortunately, most software packages do not provide an easy way of doing this. In most cases, the chart or report is only available for viewing for as long as it is displayed on the screen. The creators of the WellFlo systems analysis platform have developed a new feature called “Output’, which addresses this need head-on. Users can now save and organize any chart or report that is generated in the software. Once the item is saved, it is available for viewing in the Output section, where it can easily be recalled using the document management feature that is provided. This means that users can easily display, print or e-mail any analysis results from any well model, regardless of which model is active at the time. This can save the user hours of frustration and wasted effort while providing a seamless way of viewing the results of prior analysis runs.

New to WellFlo 4.0 Software

This new version represents a major step forward in systems analysis, providing a new level of power, sophistication, flexibility and ease of use. All of this in a modern, intuitive, workflow-based user interface. The following is a sampling of features that users will find in the latest release.

• Completely new graphical interface
• Data input de-coupled from creation of nodes
• Improvements to temperature model
• Major enhancements to equipment catalogs
• Internationalization support which provides easy translation to any language
• All new, interactive gas lift design tool incorporating true valve performance
• Improvements to reporting and plotting
• Ability to retain and organize any report or plot for future reference
• Dashboard showing overview of well parameters and model selections
• Sachdeva choke model support for OLGAS 2000 steady-state multiphase flow correlation
• Enhancements to liquid loading calculations including addition of Coleman method
• Pressure and temperature survey matching
• Tuning of inflow performance relationship to measured data, including THP to BHP calculation
• Tuning of PVT parameters
• Tuning of well parameters to match well performance measurements
• Ability to import and filter data from Excel spreadsheets
• COM interface to external utilities and engineering applications
• Ability to create custom charts from calculated profiles including wellbore flow regime distribution

WellFlo Module

Types of Wells

• Production well with/without Pipeline, or Pipeline only (all fluid types); Injection (gas or water).
• Oil; Dry Gas (with inorganics); Condensate; Volatile Oil - all with or without water production.
• Vertical, slant or horizontal well completions.
• Multi-layer (vertical/slant well) or multi-unit (horizontal well) reservoir completion options (up to 36).
• Tubular, Annular and Tubular & Annular flow options.

General Functionality

• Operating point or pressure drop calculation mode options
• Up to 21 flow rates for operating point or pressure drop analysis
• 2 simultaneous sensitivity variables
• 10 sensitivity values for each variable
• Oilfield and various SI units systems supplied, plus custom options
• Unix and DOS flowing pressure file generation for Eclipse, VIP and other reservoir simulators
• Graphical and tabular well and pipeline model building
• Batch operation for multiple sensitivity and multiple well studies using the Well Data Manager

Graphical Output Available From Pressure Drop Calculations (vs measured or true vertical depth)

• Profile along the wellbore for Pressure; Temperature; Phase flow rates; Phase densities; Phase viscosities; Total, gravitational, friction and acceleration pressure gradients; No-slip and in situ phase holdups; Flow regimes; Erosional velocity; Deviation angle; Horizontal travel; Turner unloading velocity; In-situ phase and superficial velocities
• Measured pressure and temperature data can be plotted

IPR Models (Dependent on Well Type)

• Straight-line; Vogel (can be customized); Fetkovich; Tabulated
• Goode & Wilkinson (semi-steady state) and Joshi (steady state) for horizontal wells
• Back pressure and  P² form (gas wells)
• Multi-phase pseudo pressure for oil, gas, condensate and volatile oil wells (with or without water production)
• Upward cross flow between layers at different pressures

Skin Analysis

• Damaged Zone; Perforation Skin (Locke, Egan, Tariq and Muscat models); Crushed zone skin; Deviation Skin; Convergence skin (partial penetration); vertical and areal convergence skins (horizontal wells); Gravel Pack Skin; Fractured Well Models; Frac-and-Pack completion skins.

Fluid Properties

• Black oil correlations available are Glaso; Lasater; Standing; Vazquez-Beggs; Petrosky & Farshad; Macary; Beal et al,  Beggs et al (oil viscosity); ASTM Method (dead oil viscosity calibration); Carr et al, Lee et al (gas viscosity)
• Dranchuk, Purvis and Robinson (z-factor)
• Emulsion viscosity correction (user-defined)
• Correlations can be tuned to measured data
• Internal 4-pseudo-component Equation of State used for condensate and volatile oil systems

Vertical Flow Correlations

• Beggs and Brill (standard and modified); Beggs and Brill (no slip); Duns and Ros (standard and modified) Orkizewski; Gray; Fancher-Brown; Dukler-Eaton-Flanigan; eP Mechanistic model
• Different correlations can be used for different sections of the well model
• Correlations can be tuned using an L-factor, either manually or automatically by regression on a gradient survey or wellhead pressure
• Tuning table option allows different tuning factors to be applied according to flow rate and fluid ratios and for custom correlations based on the existing supplied correlations.

Temperature Modeling

• Choice of manually input, calculated or calibrated (Hasan and Kabir), coupled pressure-temperature model
• Time-dependent temperature profiling

Choke Correlations

• Ros; Gilbert; Baxendell; Achong; Customized for critical two-phase flow systems
• Separate model for sub-critical for two-phase flow systems
• Combined critical and sub-critical model for dry gas systems

Gas Lift Module

Continuous Gas Lift design - Deepest Point of Injection

• Specify:
  • Casing head pressure
  • GLR or Qgi - Desired pressure drop across valve
• Calculates maximum depth of injection and well performance for continuous gas lift
• Sensitivity to CHP, Qgi, GLR and all other WellFlo sensitivities

Gas Lift Design - Valve Spacing for Continuous and Intermittent Gas Lift Installations

• Specify:
  • Casing head pressure
  • GLR or Qgi - Desired pressure drop across valve
  • Kill fluid gradient
  • Maximum depth
  • Target operating rate
  • Design Margins
• Calculates depth of unloading valves, operating valve, tubing and casing pressures & temperatures at each valve
• Fallback and percent load methods available for intermittent gas lift design.
• Works for casing-controlled (IPO) and fluid-controlled (PPO) valve designs

Gas Lift Design - Valve Sizing

• Takes output from valve spacing calculations
• Calculates dome pressures/test rack opening pressures for unloading valves
• Calculates orifice sizes required
• Customizable database of gas lift valves with catalogue port/bellows ratio

Advanced Gas Valve Modeling (for Continuous Gas Lift)

• True performance of commercial gas lift valves modeled by correlations using data from the Valve Performance Clearinghouse.  Currently 18 valves available.
• True operating point of system obtained by intersecting well and in situ valve performance curves
• Sensitivity to valve type, port size, valve settings and gas injection parameters
• Gas-charged and orifice valve performance correlations currently available

Gas Lift Calculations (for Continuous Gas Lift)

• For a specified gas lift design, calculates well performance with gas lift
• Predicts valve actually operating at any condition or can force gas entry at specified valve
• Sensitivity to CHP, Qgi or GLR in addition to standard WellFlo sensitivities

Graphic Output

• Plots of well performance with operating conditions and gas lift data
• Pressure and temperature profiles vs depth for well stream and casing fluid
• Shows all valves and highlights the operating valve
• Unloading sequence plots
• Valve sizing calculations on spreadsheet
• Gas Lift Diagnostic Plot shows computed valve opening pressures and measured tubing pressures and temperatures for continuous gas lift
• Report files showing all data

ESP Module

ESP Calculations

• Pressure and temperature increase across pump (per stage or group of stages)
• Viscous fluid correction
• Gassy fluid correction and limits
• Gas separator including efficiency
• Pump efficiency as power or wear factor

Motor Calculations

• Mechanical power including shaft limit
• Electrical power
• Temperature rise
• Motor efficiency
• Fluid velocity past motor

Cable Calculations

• Voltage drop along cable

Design Mode

• At a given depth, flow rate and frequency
• List of suitable pumps
• Number of stages
• Cable recommended
• Power and current required
• Setting depth
• Optimize selected pump for Target frequency; Target number stages; Target efficiency

Calculation Mode

• With a selected pump installed, pressure and temperature profile generated
• Sensitivity analysis available including Pump and Motor wear factor; Number of stages; Frequency; Setting depth; Gas separator efficiency

Catalogue

• Pumps and motors from:  Reda; Centrilift; ODI; ESP Inc.; Alnas
• User-defined pumps may be entered

Output

• Plots of pump performance with operating conditions and limits superimposed
• Report (analysis mode) files showing all suitable pumps (design mode)
• Additionally all other standard WellFlo outputs
• Details of pump installed
• ESP Current and Power       

FieldFlo Module

General

• Graphical model building
• Performance curve import and export to spreadsheets
• Mixed natural producers, gas lifted wells
• Mixed fixed allocation or optimization wells
• Multiple separator trains
• Surface pipeline models may be added
• Water disposal and gas injection costs are modeled
• Maximum liquid rates can be specified at different nodes in the system

Types of Wells

• Oil (with water cut); Oil wells with ESP; Gas Lifted Wells; Gas (with water); Condensate/Volatile oil

Calculation Modes

• WellPCG – Generates well performance curves using WellFlo, with option to use true gas lift valve performance data.
• Build – Generates performance curves at all nodes above wells
• History Match – Used to tune the model, specified gas injection rates are used to determine production rates and pressures through the system
• Allocate -  Optimizes gas allocation or production based on produced oil rate or revenue

Calculated Data Display

• Oil and gas Rates; GOR; Water Cut; Revenue; Gas Injected; Operating Pressures; Operating Temperatures; ESP Variables (all as actual values or percentages if appropriate) reported at each node
• Any well or branch in the system can be masked to temporarily exclude it from the calculations

Data Transfer

• Update production variables in WellFlo models (reservoir pressure; produced GOR; water cut; casing head pressure)
• Tune well models to measured production test data
• Update well and pipeline models with data from last allocate run
• Export/import of reservoir data in ASCII files (layer pressure, water cut and PI)

Well Data Manager

WellFlo a tool used worldwide for well analysis, design and troubleshooting. It is used by reservoir engineers for its extensive range of reservoir modeling capabilities, whereby detailed analysis and design of reservoir inflow is powerful but simple to use due to WellFlo's GUI and navigation. Production engineers make use of its strength in artificial lift design and troubleshooting capabilities. It is an invaluable tool for field planning and design by allowing the reservoir and well performance to be modeled, generating vertical lift performance tables for use in reservoir simulators, material balance programs (MatBal™) and production simulators and optimizers (ReO™).

With the addition of the Well Data Manager (WDM) into WellFlo, the benefits to production and reservoir engineers are greatly enhanced. So what does WDM do for you?

WDM is a "supervisory" module that resides above WellFlo. It uses WellFlo as a calculation engine to generate results for a range of different scenarios of the WellFlo model - these can either be different "what-ifs" for the same well or for a range of wells. It even allows you to carry out multiple scenario calculations for many wells, simultaneously. It expands upon the "sensitivity analysis" already present in WellFlo by allowing multiple WellFlo models to be sensitized simultaneously, without the user having to open and work with multiple files. It is therefore a supervisory calculation manager for multiple wells.

How Does it Work?

The flowchart illustrates the workflow for WDM. The program works with pre-existing WellFlo files and allows you to change some of the sensitivity variables and calculate a result.

Application Map of Oil and Gas Upstream

There are three modes of operation of WDM.

• Vertical Lift Performance
• Layer Inflow Performance
• Eclipse VFP Table Generation

Each of these modes is similar in operation and purpose. The user chooses a set of parameters to vary and WDM then calculates a result for each well for those new variables. In Vertical Lift Performance the parameters are production variable, in Layer Inflow Performance they are Layer parameters and in VFP Table Generation the user selects a range of VFP well variables for WDM to generate the appropriate table to be used in MatBal or Eclipse.

A description of how WDM is used and results it generates, for the case of Vertical Lift Performance follows.

Vertical Lift Performance

In Vertical Lift Performance (VLP) mode, the "analysis result" WDM allows to you calculate can be operating rate (liquid or gas depending on well type), wellhead pressure, outlet node pressure or bottom hole pressure. These calculations will be based upon the current WellFlo model for each well selected, with the new value of a "production variable" which you set within WDM.

Well Data Manager

Any number of compatible production variables can be selected for each well calculation. The example shown here is for liquid rate to be calculated given a wellhead pressure, for a number of wells, but you can also have multiple instances of the same well with different production variables.

Benefits of Well Data Manager

1. The primary benefit of Well Data Manager is to give multi-well control and analysis capability of WellFlo models to the user who has many wells under his supervision
2. Allows rapid tabular updating of single or multiple well WellFlo files. This is especially powerful when dealing with a large number of wells eg when predicting performance of a multi-well field over time.
3. Allows the user to carry out sensitivities to various production and layer parameters for individual wells
4. Allows the user to carry out sensitivities to various production and layer parameters for groups of wells
5. Permits VFP table generation for groups of wells simultaneously

Conclusion

The WellFlo well analysis package is a sophisticated well modeling tool with a wide application to all producing or injecting oil wells. With more than a decade of use in applications in all major hydrocarbon producing regions it has benefited from the wide range of technical environments in which it has been used. WellFlo 4.0 software builds on this pedigree, providing a new level of sophistication, flexibility and ease-of-use. As the product matures and future enhancements are made, this robust analysis tool will continue to provide unsurpassed capabilities for well modeling and optimization.

The software is part of Weatherford’s suite of production optimization software that includes:

• DynaLift dynamic gas lift simulator
• MatBal material balance software
• PanSystem™ well testing software
• PanMesh™ numerical simulator for well test analysis
• ReO network simulation and optimization software
• ReO Forecast™ production forecasting and field planning software
• Intelligent daily operations (i-DO™) system