Skip to main content
AFA Documentation
Main navigation
AFA Documentation
Close navigation
Main
Main
About AFA
Predico Differentiators
AFA Applications
SPAD: autoDecline & Ratio Methods
GAZ & MASLO: autoRTA, Diagnostics, and Forecasting
TAHK: Multiphase Tank Models
RULON: Automation & Group Runs
TSAR: Machine Learning (M/L) Capability
Predico Company Profile & History
Predico Publications & Workshops
Data Requirements for AFA
Pressure Sources & Types of Pressures
User Manual
Getting Started
AFA Home page
The Main Menu
File Menu
Modules Menu
Project
Help
Wells (Master Well List)
Searching the Well & Project List
Projects (Project List)
Profile Menu
Admin Dashboard
Module Overview (Types of Modules)
Navigating & Selecting Modules
Create a Project
Create a Group in a Project
Set Forecast End Date
Set Forecast Start Date
Delete a Project
Copy a Project
Rename a Project
Saving a Project
Transfer a Project
Import Wells
Import Projects
Working with the Well Lists
Adding Wells to a Group/Project
Removing a Well from a Project
Types of Pressures
User Preferences
SPAD Modules
SPAD: Gas Decline
SPAD: Oil Decline
SPAD: WOR
Exit Rate
Navigating OPS and Profile Forecasts
Unsupervised Cluster Analysis Option
Limiting "b" Values
KOLDUN: CSG Monte-Carlo
TAHK: Coal Seam Gas (PSS) Forecast
Power Law: Custom Perm - Skin Relationship
OGIP Per Measure Calculations
CSG Pump & Wellbore Options
Production Constraints
Contract Rate (Rate Constraints)
Skin and Accelerated Recovery Options
Flowing Pressure and Incremental Recovery Options
GAZ Modules
GAZ: autoFMB
FMB: Productivity Index Plot
FMB P/z Plot
GAZ: autoRTA
autoRTA: Langmuir Isotherm
autoRTA: Wellbore Model
autoRTA Pre-Forecast Setting
Forecast Table and Smart Fill
RTA Sensitivities
GAZ: P/z
MASLO Modules
MASLO autoRTA
MASLO autoFMB
RULON: Roll-up, Group Runs, and Job-Queue
RULON: Group Run
RULON: Roll-Up
Job Queue
Forecasting Result Standards
Zooming & Resetting Plots
Downloading Plots
Downloading Tabulated Data
Interactive Well Map
Map Overlays
References and Attributions
GeoJSON Specification (2.9.0)
Shapefile Specification (2.9.0)
Virtual Wells
Demo Dataset
Predico Data Model
Database Integration Capabilities
Predico Model Inputs
Exiting AFA (Logging Out)
Theory & Reference Manual
Basic Petrophysical Parameters
Lithology
Porosity
Porosity: Beard & Weyl Data
Fluid Filled Porosity
Permeability
Permeability Anisotropy
Permeability Measurements
DST Measurements
Wireline Formation Tester (WFT)
Wireline (Traditional Flow & Buildup)
Cores
Isothermal Compressibility
Sorption Compressibility
Mechanics of Basic Compaction: Solids
Rock (Formation) Compressibility
Fluid Saturations
Irreducible Water
Net Pay
Homogenous Permeability and Porosity
Capillary Pressure
Core Photos
Shale Porosity: Montney
Heterogeneity & Net Pay
Vuggy Porosity 1
Vuggy Porosity 2
Shale Color
HorseShoe Canyon "Dry" Coals
Bioturbation: Bandanna Formation
PVT Correlations and Calculations
Basic Fluids
Gas PVT Correlations
Gas Specific Gravity
Apparent Molecular Mass
Acid Gases
Normalizing A Gas Mixture
Gas Deviation Factor
Video: Z-Sensitivity to Specific Gravity & Temperature
Gas Viscosity
Formation Volume Factor (Bg)
Pseudo-Critical Properties
Gas Recombination Technique
Gas Density
Standard Conditions vs In-Situ Conditions
Oil PVT Correlations
Oil API
Water Correlations
Clays and Impact on Production
Field Example 1: Clay in Sandstones
Field Example 2: Clays in Sandstones
Hydrates & Flow Assurance
Hydrate Formation
Hydrate Removal & Inhibitors
Relative Permeability
Corey Relative Permeability Curves
Permeability Jail
CSG Relative Permeability
Pseudo Pressure
Classification of Reservoirs
Types of Reservoir Fluids
Phase Envelopes & Fluid Systems
Black Oil
Undersaturated vs Saturated
Associated Gas
Non-Associated Gas
Volatile Oil
Gas Condensate
Wet Gas Reservoirs
Dry Gas Reservoirs
Biogenic vs Thermogenic Gas
Reservoir Drive Mechanism
Depletion Drive Reservoirs
Gas Cap Drive Reservoirs
Water Drive Reservoirs
Compaction Drive
Imbibition Drive
Tight Gas and Shale
Shale Porosity
Shale Permeability
Organic Matter
Transport in Shale Reservoirs
Stimulated Rock Volume (SRV)
Field Example: Micro-Seismic
Tight Gas and Shale Completions
Hybrid Shale
Tight Gas and Shale Completion Examples
Montney Gas Well Performance By Year
Montney Completions by Year
Tight Oil
Coal Seam Gas (CSG)
CSG / CBM Basics
Transport in CSG
Isotherm
Adsorption/ Desorption Mechanics
Chemical vs Physical Adsorption
Moisture & Ash Content
AR vs DAF
Temperature Effects
Measurement of Adsorption Isotherms
Undersaturation (Dewatering)
Apparent Oversaturation
CSG Isotherm Examples
North American Examples
Field Example: Canadian Mannville
Australian Examples
Bowen Basin
Surat Basin
Sydney-Gunnedah Basins
Galilee Basin
CSG Permeability / Permeability Anisotropy
CSG Permeability and Anisotropy Examples
Field Example: Corbett Creek
Field Example: Narrabri CSG Project
Field Example Bowen Basin
Field Example: Sydney Basin
Field Example: Surat Basin
Field Example: Powder River Basin Cleats
CSG Permeability vs Depth
Cleat Porosity
Cleat Compressibility
CSG Cleat Compressibility Examples
Coal Density
CSG Bulk Density Examples
Gas Composition
Molecular Structure of Coal
CSG Material Balance
Water Material Balance
Field Example: Average Reservoir Pressure Diagnostics
Cleat (Formation) Compressibility
CSG Well Spacing & Completions
Well Spacing & Dewatering
CSG Well Spacing & Completion Examples
Field Example: Corbett Creek Well Spacing
Field Example: Apache & EnCana JV
Pinnate Well Design & Similar Designs
Field Example: Mahalo Gas Hub
Field Example: Powder River Basin
Field Example: Arrow Energy- Northern Bowen Basin
Galilee Energy Pilot
Field Example: Evolution of Westside Completions
2-Phase CSG Type Curves
CSG Formation Damage
Coal Measure vs Coal Layer
Coal Molecule
Comparison of Select CSG Projects
Gas Hydrate Resources
Geomechanics
Stress Dependence Models
Matrix Shrinkage Models
Poisson's Ratio
Bulk Modulus
CSG Matrix Shrinkage and SDP Examples
San Juan Basin
HorseShoe Canyon: Trident Exploration Corp.
Material Balance Methods
Gas Material Balance
P/z Abnormally Pressured Gas Reservoirs
Field Example: Anderson "L" Pool
Generalized Form of Gas Material Balance
Oil Material Balance
Initially Undersaturated
Initially Saturated (Gas Cap Present)
Inclusion of Formation & Water Expansion
Analysis Methods
General Reservoir & Production Engineering Workflows
Rate-Pressure Correlation
Reality Check: History Matching
Importance of Data Type
Unconventional Reservoir Workflows (SPEE)
Workflow For Evaluation of Developed Reserves in Unconventional Reservoirs
Analogs for Tight Gas Sands (& other Resources)
Scaling in Reservoir Engineering
Decline Analysis
Arp's Decline
Loss Ratio
Operational vs Profile Forecasts
Decline for Unconventional Reservoirs
Hyperbolic (Arps) and Flow Regime Identification
Probability Density Function
Pressure Normalized Decline Analysis
Multiphase Pressure Normalized Decline Curve Analysis
Rate Integral Function
FMB and Rate Transient Analysis (RTA)
Transient Models & Flow Regimes
Radial Flow Models
Hydraulically Fractured Vertical Wells
Uniform Flux & Infinite Conductivity Model
Finite Conductivity Fracture Model
Composite Models
Condensate (Liquid Drop Out)
Field Example: Gas Condensate
Field Examples: Composite Model Non-Unique Interpretation
Dual Porosity
Linear Flow Models
Multi-Fractured Horizontal Well
Linear Flow Examples
South Texas Example: Vertical Frac Well
Linear Channel Flow
Eagle Ford Shale Example
Barnett Shale Gas: Well 314
Radius of Investigation
Flow Regime Identification & Analysis Methods
Bourdet (Well Testing)
Bourdet Sensitivity to Skin
Bourdet Sensitivity to Permeability
Bourdet Sensitivity to Total Compressibility
Blasingame
Normalized Pressure Integral (NPI)
Beta
Chow Pressure Group (CPG)
Other Common Methods
Fetkovich & Carter Plots
Solutions for the Diffusivity Equation under Different Flow Regimes
Flowing Material Balance
Material Balance Time
Wellbore Skin and Formation Damage
Wellbore Radius & Equivalent Wellbore Radius
Skin Components
SEM Images of Clays
Damage Due to Hydraulic Fracturing
Choke Skin
Furui: Generalized Skin Equation
RTA vs PTA Permeability
RTA/PTA Field Examples
RTA: Alberta Colorado Shale Gas
RTA: Alberta Colorado Shale Gas 2
PTA: CSG Well in Australia
PTA: CSG Well in Australia 2
MDT: CSG Well in Australia 3
PTA of CSG Well Indonesia
PTA Challenges & Errors
PTA: Gauge Drift
PTA: Insufficient Shut-in Time
PTA: Super Charging? or Pressure Interference?
PSS Models
Vertical Models
Horizontal Well Models
Extension to a Generalized Well Model
Productivity Index (PI)
Cross Flow Calculations
Water Rate Constraint Crossflow Calculations
Gas Rate Constraint Crossflow Calculations
Aquifer Model
Type Wells
Modern Type Well Construction Methods
Concerns for Type Wells: Infill Drilling, Completion & More
Multiphase Wellbore Flow
Statistical Concepts
Weighted Percentiles Approach for P10, P50, P90, and Pmean
The Lorenz Coefficient (Lk)
Population Size
Maximum Iteration Number
Parameter Consistency in Monte-Carlo
Outlier Detection Techniques
Fitting and Repeated Median Regression
Error Messages
Glossary
AFA Data Dictionary
AFA
Boundary Condition
Bubble Point
CBM
CPG
CSG_
Drainage Radius
FMB
Formation Temperature
Initial Reservoir Pressure
NPI_
OGIP
OOIP
PVT
RTA_
Solution Gas Ratio
PTA_
RNP
PNR
Tubing Roughness
Releases Notes
2.8.2 - November 25th 2025
2.8.1 - October 2nd 2025
2.8.0 - September 11th 2025
2.7.0 - June 19th 2025
2.6.0 - April 8th 2025
2.5.0 - February 13th 2025
2.5.1 - March 4th 2025
2.4.0 - October 11th 2024
2.4.1 - November 21st 2024
2.4.2 - December 17th 2024
2.3.0 - June 28th 2024
2.3.1 - July 12th 2024
2.3.2 - August 7th 2024
2.3.3 - August 28th 2024
2.2.0 - May 17th 2024
2.1.0 - April 12th 2024
2.2.1 - May 31st 2024
2.0.0 - February 9th 2024
2.0.1 - March 1st 2024
2.0.2 - March 15th 2024
Version 1
Breadcrumbs
Home
Theory & Reference Manual
PVT Correlations and Calculations
Gas PVT Correlations
On this Page
Gas Density
Coming Soon!
