Decline Curve Analysis and Diagnostic Methods for Performance Forecasting - DCA

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Decline curve analysis has been called the most commonly used and misused technique for forecasting future production and remaining reserves. This course will give the learner a better understanding of how fundamental reservoir properties and drive mechanisms affect the shape of the production decline curve and how to avoid many of the mistakes commonly found in decline curve forecasts. The course also examines the use of modern production decline type-curves to evaluate reservoir properties and predict future performance. Students will make production forecasts and generate curve fit parameters for the common curve types. These exercises will be done using MS Excel spreadsheets. The course begins with an introduction and review of the classic exponential, hyperbolic, and harmonic decline curve equations using a variety of plotting techniques. Next, information is provided on how decline curve parameters relate to fundamental reservoir properties and drive mechanisms. Then, transient and pseudosteady-state (pss) flow regimes are identified along with how the classic decline equations apply only to pss conditions. The participants will be taught methods to constrain transient forecasts to a more realistic estimate of future production. Next, the class will review forecasting techniques for wells undergoing fluid displacement drives such as waterflooding. Popular techniques such as semi-log plots of water-oil ratio (WOR) versus cumulative oil production will be discussed. The effects of parameters such as mobility ratio on the shape of these trends will be reviewed. The effect of reservoir heterogeneities such as layering and compartmentalization on the shape of the decline trend will be reviewed. Methods to account for difficult situations such as downtime, well workovers, and facility constraints are presented. Problems related to forecasting groups of wells instead of individual wells are shown and ways to eliminate common forecasting mistakes are identified. The final portion of the course is dedicated to advanced decline curve and production data analysis. Historical background and development of the more popular techniques such as Fetkovich, Blasingame, and Agarwal-Gardner curves is presented. Example problems are used to illustrate how the decline type-curves can be used to estimate reservoir parameters during both transient and stabilized production and how these results are then used to forecast future performance. One personal computer is provided, at additional cost, for each two participants in non-virtual sessions.

Engineers or technical assistants who are responsible for making forecasts of future production using decline curves analysis. Economists, managers, or geoscientists who are interested in developing a greater working knowledge of decline curve methods and how to make better forecasts will also benefit from this course.

You will Learn:

  • Participants will learn how to:Use the exponential, hyperbolic and harmonic decline curve equations - including exercises to perform the calculations
  • See the relationships between reservoir recovery mechanisms and decline curve types
  • Identify and understand how the transient flow period can lead to an overestimation of reserves
  • Use multiple methods to avoid overestimating reserves
  • Recognize reservoir performance characteristics based on actual field examples
  • See the impact of reservoir heterogeneities such as faulting, permeability variance and layering
  • Account for changing operating conditions
  • Perform analysis on a multi-well basis without introducing common errors
  • Use alternative methods including diagnostic performance plots (e.g., log WOR vs. Np, Stagg's, P/Z vs. Gp, etc.) for rate and reserves analysis
  • Use advanced decline curve and production data analysis for reservoir characterization: flow regime, hydrocarbons-in-place, permeability, skin, drainage area, fracture properties, etc.

Course Content:

  • Conventional decline curve equations: exponential, hyperbolic and harmonic rate versus time and rate versus cumulative production relationships, selecting the proper equation based on reservoir properties and drive mechanisms
  • The effects of transient production: how to recognize transient production, how transient forecasts can overestimate remaining reserves, how to properly constrain transient forecasts
  • Forecasting during displacement processes: using trends like water-oil ratio and versus cumulative oil production to estimate ultimate oil recovery, converting these trends into an oil rate versus time forecast
  • Difficult situations: layered and compartmented reservoirs, downtime, workovers, changing facility conditions and facility constraints, forecasting groups of wells, common mistakes
  • Production decline type-curves: Introduction and historical background on production decline type-curve methods, how to use modern decline type-curves to determine reservoir properties during both transient and stabilized production, using type-curve methods for forecasting future production

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