Scorpion Plot

Test Your Knowledge

Scorpion Plot Quiz:

Instructions: Choose the best answer for each question.

1. What does the "tail" of a Scorpion Plot represent?

a) The cost of the workover b) The well's production after the workover c) The well's production before the workover d) The overall production decline of the well

2. What does a long, impactful "stinger" in a Scorpion Plot indicate?

a) The workover was unsuccessful b) The workover was highly profitable c) The workover cost more than the production gains d) The well's production declined rapidly after the workover

3. Which of the following is NOT a factor to consider when evaluating a Scorpion Plot?

a) The well's production history b) The type of workover performed c) The oil price at the time of the workover d) The reservoir characteristics of the well

4. A Scorpion Plot with a "flat stinger" might suggest that:

a) The workover effectively addressed the production decline b) The workover was extremely expensive c) The workover did not address the root cause of the decline d) The well is nearing the end of its production life

5. Why is the Scorpion Plot a valuable tool for workover analysis?

a) It simplifies the analysis of complex well data b) It visually displays the economic impact of a workover c) It predicts future production trends after a workover d) It eliminates the need for detailed well history analysis

Scorpion Plot Exercise:

Scenario:

You are reviewing two Scorpion Plots for different wells that underwent workovers.

• Well A: Shows a gradual decline in production before the workover (tail), a significant investment in the workover (body), and a steep increase in production immediately after the workover, followed by a gradual decline (stinger).
• Well B: Shows a steep decline in production before the workover (tail), a moderate investment in the workover (body), and a slight increase in production after the workover, followed by a continued decline (stinger).

Task:

Analyze the two Scorpion Plots and answer the following questions:

1. Which well experienced a more successful workover based on the Scorpion Plot?
2. What insights can you draw about the potential causes of the production decline in each well before the workover?
3. Which well would you recommend for further investment in workovers based on the Scorpion Plots?

Techniques

Chapter 1: Techniques for Creating a Scorpion Plot

Creating an effective Scorpion Plot requires careful data collection and processing. The core components are pre-workover production data, workover cost data, and post-workover production data. Here's a breakdown of the techniques involved:

1. Data Acquisition:

• Production Data: Gather historical production data (oil or gas rate, water cut, etc.) for the well, ideally spanning several months before the workover. Data should be consistent and reliable, often sourced from SCADA systems or production databases. Regularly spaced intervals (e.g., daily, weekly, monthly) are preferred.

• Workover Cost Data: Compile a detailed breakdown of all costs associated with the workover. This includes direct costs (e.g., labor, materials, equipment rental) and indirect costs (e.g., engineering, permits, transportation). Accurate cost accounting is essential for reliable economic analysis.

2. Data Processing and Cleaning:

• Data Normalization: Ensure consistent units and data formats across all datasets. Address missing data points through interpolation or exclusion, documenting the method used.

• Data Cleaning: Identify and correct outliers or erroneous data points. This may involve statistical analysis or consultation with field personnel.

• Data Aggregation: Depending on the desired level of detail, production data might be aggregated (e.g., daily to monthly averages).

3. Plot Construction:

• Time Axis: The horizontal axis represents time, showing the pre-workover, workover period, and post-workover periods.

• Production Axis (Y-axis): The vertical axis represents well production (e.g., barrels of oil per day or cubic meters of gas per day).

• Cost Representation: The workover cost is typically represented by a vertical bar or rectangle positioned on the time axis, corresponding to the duration of the workover. The height of this bar represents the total cost.

• Plotting the Data: Plot the pre-workover production data as a line, showing the decline curve. The post-workover data is plotted as a continuation of this line, ideally showing an upward trend (the "stinger").

4. Analysis and Interpretation:

• Visual Inspection: Assess the length and steepness of the "stinger" relative to the "body" (workover cost) to evaluate the workover's economic viability.

• Quantitative Metrics: Calculate metrics such as the rate of production increase after the workover, the return on investment (ROI), and the payback period. These metrics supplement the visual interpretation.

Chapter 2: Models for Scorpion Plot Enhancement

While a basic Scorpion Plot provides a clear visual, incorporating additional models can enhance its analytical power and provide deeper insights into workover effectiveness.

1. Production Decline Curve Modeling:

• Pre-workover Decline: Fit a suitable decline curve model (e.g., exponential, hyperbolic, power law) to the pre-workover production data to extrapolate the expected production without the workover. This provides a baseline for comparison.

• Post-workover Decline: Similarly, model the post-workover production data to forecast future production and assess the long-term impact of the intervention. The model choice depends on the reservoir characteristics and production behavior.

2. Economic Modeling:

• Net Present Value (NPV): Calculate the NPV of the workover, considering the future revenue generated by the increased production, discounted by a suitable discount rate.

• Internal Rate of Return (IRR): Determine the IRR of the workover, representing the discount rate at which the NPV becomes zero. This provides a measure of the project's profitability.

• Payback Period: Calculate the time required for the increased production revenue to offset the workover cost.

3. Reservoir Simulation Integration:

• For more complex scenarios, integrate reservoir simulation results into the Scorpion Plot. Simulation can provide a more accurate prediction of post-workover production and help assess the impact of different workover strategies.

4. Incorporating Uncertainty:

• Use probabilistic methods (e.g., Monte Carlo simulation) to account for uncertainty in production forecasts and cost estimates. This creates a range of possible outcomes, providing a more robust assessment of workover viability.

5. Sensitivity Analysis:

• Conduct sensitivity analyses to determine the impact of key parameters (e.g., oil price, production decline rate, workover cost) on the workover's economic viability. This helps identify critical uncertainties and potential risks.

Chapter 3: Software for Scorpion Plot Creation

Several software packages can be used to create and enhance Scorpion Plots. The choice depends on the available data, the desired level of sophistication, and user expertise.

1. Spreadsheet Software (Excel, Google Sheets):

• Suitable for simple Scorpion Plots with basic data visualization. Functions and charting tools can be used to create the plot and perform basic calculations.

• Limitations: Limited capabilities for advanced modeling and complex data analysis.

2. Reservoir Simulation Software (Eclipse, CMG, etc.):

• Advanced software packages capable of integrating reservoir simulation results into the analysis. They provide a sophisticated platform for modeling and forecasting production.

• Requires specialized expertise and may be overkill for simpler workover analyses.

3. Production Data Analysis Software (Petrel, KAPPA, etc.):

• These specialized software packages offer advanced tools for data processing, visualization, and analysis. They often include functionalities for decline curve analysis and economic evaluation.

• Usually more expensive than spreadsheet software, but provide greater functionality and efficiency for managing large datasets.

4. Custom Programming (Python, Matlab):

• Provides maximum flexibility and control over the entire process, allowing for the development of customized tools and workflows. Requires programming expertise.

• Allows for seamless integration with other data sources and tools, enabling sophisticated analysis.

5. Specialized Workover Analysis Software:

• Some companies offer specialized software specifically designed for workover analysis, which may include tools for creating and interpreting Scorpion Plots.

Chapter 4: Best Practices for Effective Scorpion Plot Analysis

The effectiveness of a Scorpion Plot depends not only on its construction but also on the best practices employed during its creation and interpretation.

1. Data Quality:

• Use accurate and reliable data from trusted sources. Data validation and quality control are crucial.

• Address missing data points appropriately. Document the methods used for data imputation or exclusion.

2. Model Selection:

• Choose appropriate decline curve models that reflect the reservoir characteristics and production history. Justify the model choice.

• Consider the limitations of the chosen model and account for potential uncertainties.

3. Cost Accounting:

• Develop a comprehensive and accurate cost breakdown for the workover. Include both direct and indirect costs.

• Consider potential cost overruns and contingencies when evaluating the economic viability.

4. Economic Assumptions:

• Clearly define all economic assumptions, such as discount rate, oil/gas price forecasts, and operating costs.

• Conduct sensitivity analyses to assess the impact of variations in these assumptions.

5. Interpretation and Communication:

• Present the Scorpion Plot clearly and concisely, using appropriate labels and legends.

• Explain the key findings and implications of the analysis. Avoid overinterpreting the results.

6. Integration with other Analyses:

• Consider the Scorpion Plot as part of a broader workover evaluation process. Integrate it with other analyses, such as reservoir simulation, production forecasts, and risk assessments.

Chapter 5: Case Studies of Scorpion Plot Applications

Several case studies illustrate the practical applications and value of Scorpion Plots in workover decision-making. (Note: Specific case study details would require confidential data, which is not available here. However, the following outlines potential scenarios.)

Case Study 1: Comparing Workover Techniques:

• Two different workover techniques are considered for a well experiencing a production decline. Scorpion Plots for both techniques are compared, showing the cost and production response for each. The plot highlights the superior economic viability of one technique compared to the other.

Case Study 2: Evaluating the Effectiveness of a Stimulation Treatment:

• A well receives a stimulation treatment as part of a workover. The Scorpion Plot illustrates the cost of the stimulation and the subsequent production response. The plot indicates whether the stimulation was cost-effective.

Case Study 3: Assessing the Impact of Different Completion Strategies:

• Multiple wells with different completion strategies undergo workovers. Scorpion Plots are generated for each well, illustrating the impact of the completion strategy on workover effectiveness and economic viability.

Case Study 4: Predicting Workover ROI:

• Using pre-workover decline curve modeling and post-workover production forecasts, a Scorpion Plot is created to predict the future ROI of a proposed workover. This helps make informed decisions about whether to proceed with the intervention.

Case Study 5: Optimizing Workover Spending:

• Analysis of several workovers using Scorpion Plots helps identify trends and potential areas for cost optimization in future interventions. This reduces overall spending while maintaining productivity.

In each case study, the Scorpion Plot provides a clear visual representation of the cost-benefit relationship, facilitating informed decision-making and maximizing the return on investment from workover activities. The plots should be accompanied by detailed cost breakdowns and production data to support the analysis.