A common reservoir engineering workflow is identifying production decline model(s) suitable for the production profile of wells or reservoirs; and quite frequently, asset management experts are tasked with calculating values of determining factors, and applying those factors in decline curve equations to establish forecast methodologies applicable to different periods in an asset’s production history.
The Decline Model Identifier is a simple Spotfire solution designed to rapidly assist reservoir engineers in visually identifying decline models using basic logarithmic and linear plots of production data.
Production data can be plotted in different ways to identify a representative decline model:
If the graph of flow rate plotted on a logarithmic scale against normalized time of production on a linear scale shows a straight line, the decline data follow an exponential decline model.
If the plot of flow rate on linear scale versus cumulative production on linear scale shows a straight line, an exponential decline model should be adopted.
If the plot of flow rate on a logarithmic scale versus normalized time on logarithmic scale shows a straight line, the decline data follow a harmonic decline.
- If the plot of cumulative production on a linear scale versus flow rate on a logarithmic scale shows a straight line, the harmonic decline model should be used.
If no straight line is seen in these plots, the hyperbolic decline model may be verified by plotting the relative decline rate versus production rate on linear scales.
The Decline Model Identifier dynamically displays these five (5) plots for any given asset’s production history thereby providing a visual guide to asset management analysts to easily establish appropriate technique for production forecasting and EUR estimation without recourse to solving mathematical equations.
It is important to note that much very often, different models are applicable at different periods of an asset’s production life. For instance, one model might be suitable for the first few years while another is representative of the next number of years. Leveraging Spotfire’s marking feature the Decline Model Identifier allows the user to select different production intervals during the model identification analysis. Some points in the production data can be included/excluded by simply marking/unmarking.
Also, with Spotfire’s marking feature, the Decline Model Identifier presents the user with the unique ability to diagnose decline for either a well or group of wells. This proves important for both production engineering and reservoir management workflows in the sense that production decline of a single well can be analyzed and that of an ensemble of wells representing a given sand, reservoir, pattern or zone can also be evaluated.
How to Use
The Decline Model Identifier is simple to use. It is a single-page Spotfire template in which user-action is either by clicking a data point, or by selecting a group of data points using a mouse. There are basically two data tables that feed the system:
- Well Data – this should have columns for name of the well, longitude, and latitude data
- Production History – this should contain columns for name of well, production date, and rate. The production date can be daily, monthly or annually.
There is a sample Well Data and Production History data tables for a few imaginary wells. To get started, replace the data tables with your well data and production history data as appropriate.
Once the data have been loaded, click well(s) on the Well Location map to display the production history of the selected asset in the Production History plot. In the Production History plot, select a range of data points. The system responds with the diagnostic plots. Identify in which of the plots a straight line is established from the production data.
Why Use the Decline Model Identifier
The ability to select multiple well objects and to analyze production data of a group of wells as a single profile makes the Decline Model Identifier stand out from most traditional model identification methods using decline software and Excel spreadsheets. Also, simplicity, ease of loading data, adaptability and extensibility to include more plots or features is unrivalled by most other decline model identifying tools.
More Decline Functions
It is possible to grow the features of the Decline Model Identifier tool to include determination of decline curve parameters, and forecasting future production. These functionalities are however not included in the present scope of the tool.
The Decline Model Identifier is developed by Ruths.ai and is available for download at the Analytics Marketplace:
Theodore Etukuyo holds a Bachelor’s Degree in Mathematics and an Associate Degree in Petroleum Engineering Technology.