## Reservoir Evaluation - Decline Curve Analysis

### Course overview

This popular course explores Reservoir engineering in relation to decline curves and the types of decline curves used and how they are applied throughout the industry.

The proposed discussion and workshop consists of 6 major subjects with attendant work problems.

- Begin with the Arps curves.They are simply equations of a line but the shape of the curve can infer meaning to the depletion process.
- Geology and changes within the producing system can profoundly affect production rate and expected reserves. The practical aspects of analyzing production are discussed and illustrated.
- Smoothing techniques may aid in the interpretation process.
- Of particular interest is Horner/ material balance time concept and normalizing pressures when available.
- Applying the quadratic equation calculation allows one to introduce the concept of substituting (FTHP’s) to replace static pressures when calculating (OGIP) in a gas reservoir’
- The technique for concurrently studying multiple coordinate system plots is introduced.
- The session discusses a variety of flow systems encompassing vertical and horizontal wells and un-fractured and fractured conditions. Plotting and analysis methods for analyzing these different situations are developed.
- The basic development of both Fetkovich and Blasingame type curves are discussed.
- The last segment discusses analyzing two phase flow production since one cannot apply normal Arps curve analysis methods for this case. The trend of the fluids producing ratio are of paramount importance in this case.
- Each section contains problems which the participant can work outside of class. The solutions of which are discussed at the beginning of the next session.

### The course is designed for

Reservoir engineers and professionals who work in collaboration with reservoir engineers, including well engineers, facilities engineers, process engineers, petrophysicists and geoscientists.

### Course outline

#### Advanced decline curve analysis

- Introduction
- Material Balance Time (t
_{mb}) or Horner Time (t_{p}) - Assumptions and Limitations

- Material Balance Time (t
- The Superposition Function
- Comparing Material Balance Time to the Equivalent Superposition Function
- Utility of the Poe Adjustment Method
- Coupling the Transient and Boundary Dominated Flow Stems
- Assumptions and Limitations

- Correlating Functions
- The Pseudosteady State Curve, Rate Integral and Rate Integral Derivative Functions

- The Composite Type Curve
- Type Curve Matching Procedure
- Method of Analysis

- Review of Decline Analysis Methods
- Problems
- MX4 Well – Blasingame and Lee Method
- Golden Zuma Well – Blasingame and Lee and Fetkovich

#### Horizontal wells

- Shale and Sandy Shale Reservoirs
- Production and Inflow Patterns
- Vertical, Horizontal Wellbores and Horizontal, Hydraulically Fractured Wells

- Production Characteristics of Fractured Horizontal Wells
- Flow Equations
- Idealized Performance Plots

- Analysis Methods
- Logarithmic Rate – Time, Square Root of Time Plot and Blasingame-Lee-Palacio Plots

- The Quadratic Equation
- Example Problems

**Production performance plots**

- Performance Plots
- The Water Oil Ratio Plot and Oil Water Ratio Plots

- Layering and Changes in Operations
- Example Problem

- Fluid Distribution and Capillary Mechanisms
- The Fluid Ratio Plotting Method
- Assumptions and Development of Concept
- Development of Relative Permeability Curves
- Predicting Performance
- Example Problem

- Problems
- Interpret Performance History – Regal Well
- Develop Relative Permeability Ratio Curves – Evans Well

- Well Diagnostic Plots
- Problem – Analyze Well Performance for the MR-321 Well

**Introduction to decline curves**

- Meaning of Curve Shapes
- Arps’ Equations –Exponential, Hyperbolic and Harmonic Equations
- Bounds of the Arps’ Equations and Curve Characteristics
- The Quadratic Model - Assumptions and Limitations, Development of Concept, Solution Procedure
- Introduction of Multi-Plot Well Analysis
- Problems
- Wafford Well
- Remedial Case – The Hollands Well
- West Virginia “A” Well – Quadratic Equation

#### Arps Interactive program

- Setting up excel program
- Performing case history studies

#### Reservoir and wells models

- The Vertical Wellbore Case
- Boundary Conditions
- Van Everdingen and Hurst Solutions to Diffusivity Equation
- Constant Rate and Constant Pressure Solutions
- Vertical Hydraulically Fractured Wells
- Horizontal Wells
- Depletion Models

- Linear Flow Equations

- Hydraulically Fractured Horizontal Wells
- Problems

**Application of decline curves**

- Constant Operating Conditions and Absence of Mechanical Restrictions
- Application to Field Conditions
- Likely Reservoir and Poor Candidates
- Knowledge of Field Character
- Effects of Adding and Abandoning Wells
- Production Segments
- Annotating Decline Curves
- Production Relationships
- Production and Pressure Data
- Correcting for Well Downtime
- Problems
- Gulf of Mexico Field – Correcting for Downtime
- North Texas Gas Condensate Well

**Fetkovich type curves**

- Fundamental Relationships and What are Type Curves?
- The Transient Curves,, Information Obtained, Utility, Example Problem
- The Arps’ Curves, Information Obtained, Example Problem
- Problems
- Curve Fit An Arps Curve
- Curve Fit the Transient Side
- Fit Oklahoma Well History to Fetkovich Curves

**The Exponential decline**

- The Constant Percentage - Effective Decline
- Analysis Procedure and Example Problem

- The Continuous – Nominal Decline
- Analysis Procedure and Example Problem

- Comparing the Two Exponential Decline Curves
- The Rate - Cumulative Recovery Curve
- Problems
- Analyze the Turner Lease Performance History
- Constant Rate and Then Exponential Decline Profile – Offshore Field

**Hyperbolic and harmonic curves**

- The Arps Hyperbolic Equation
- Determining the Coefficients and Analysis Procedure
- Example Problems
- Solution – Rectangular Plot Approach
- Solution – Type Curve Approach

- Problem – Type curve match for the Redfish Point well.

#### Interpretation of field curves

- Transition and Transient Flow
- Layering, Crude Oil Properties and Compressibility and Relative Permeability Effects

- Defining Reservoir Character, Infinite Acting, Low to Moderate GOR, High GOR, Gas Wells
- Field Rules - Analysis of Multi-well Field Curves
- Initializing Decline Curves - Glenn Pool Field
- When b>1
- Rules for Amending the Transient Curve

- Problems
- Re-initialize a Stimulated Well.
- Hyperbolic – Exponential Attenuation
- Analyze a Production History

Location | Start Date | End Date | Cost | Trainer | Book |

Upon request | Professor Emeritus Steven Poston | Make enquiry |