Shut-in Casing Pressure

Test Your Knowledge

Shut-in Casing Pressure Quiz:

Instructions: Choose the best answer for each question.

1. What does SICP stand for? a) Shut-in Casing Production b) Shut-in Completion Pressure c) Shut-in Casing Pressure d) Surface Casing Pressure

2. Where is SICP measured? a) Inside the tubing b) Inside the casing c) In the annulus between the casing and tubing d) At the wellhead

3. What is the primary reason for measuring SICP? a) To determine the flow rate of the well b) To assess the well's integrity and potential problems c) To calculate the reservoir's total volume d) To predict future production

4. Which of the following factors DOES NOT affect SICP? a) Reservoir pressure b) Fluid viscosity c) Wellbore depth d) Atmospheric pressure

5. A sudden drop in SICP could indicate: a) Increased production b) Reservoir depletion c) Casing leak or tubing leak d) Both b and c

Shut-in Casing Pressure Exercise:

Scenario:

A well is shut-in for a routine pressure check. The SICP is measured at 2500 psi. After 24 hours, the SICP is re-measured and found to be 2400 psi.

Task:

Analyze the situation and explain the possible reasons for the decrease in SICP. Consider the factors that might have contributed to the change in pressure.

Techniques

Understanding Shut-in Casing Pressure in Oil & Gas Operations

This document expands on the provided introduction to Shut-in Casing Pressure (SICP) by breaking down the topic into distinct chapters.

Chapter 1: Techniques for Measuring Shut-in Casing Pressure

Measuring SICP accurately is crucial for reliable well diagnostics. Several techniques are employed, each with its own strengths and limitations:

• Direct Measurement with Pressure Gauges: This is the most common method. A pressure gauge, typically a bourdon tube gauge or a digital pressure transducer, is installed on the casing head at a point above the annulus pressure monitoring location. The gauge should be calibrated regularly and its accuracy verified. The well must be completely shut-in for a sufficient period (allowing pressure stabilization) before taking the reading. The duration depends on factors like reservoir characteristics and wellbore geometry.

• Indirect Measurement using Downhole Pressure Sensors: In some cases, downhole pressure sensors within the casing can provide more detailed pressure profiles along the wellbore. This method offers a higher degree of accuracy and allows for identifying pressure variations along the casing. However, it's more expensive and requires specialized equipment.

• Pressure Transient Analysis: Analyzing the rate at which SICP builds up after shut-in can provide additional information about the reservoir. This technique requires careful data acquisition and sophisticated analysis using specialized software.

• Data Acquisition Systems: Modern data acquisition systems automate the process of SICP measurement and recording. These systems can continuously monitor SICP, providing real-time data and alerting operators to any significant changes in pressure.

Considerations for Accurate Measurement:

• Wellbore Cleanliness: Contamination in the annulus can affect pressure readings. Regular wellbore cleaning is important for accurate measurements.
• Gauge Accuracy and Calibration: Regular calibration and verification of pressure gauges are essential to ensure accurate readings.
• Temperature Compensation: Temperature changes can affect pressure readings. Pressure gauges should be temperature-compensated or the temperature should be considered when interpreting the data.
• Environmental Conditions: Extreme weather conditions can affect the accuracy of surface measurements.

Chapter 2: Models for Interpreting Shut-in Casing Pressure

Interpreting SICP data often involves using models that account for various reservoir and wellbore characteristics. Key models include:

• Material Balance Models: These models relate changes in SICP to changes in reservoir fluid volume, considering compressibility and expansion effects. They are particularly useful in assessing reservoir pressure depletion.

• Wellbore Pressure Transient Models: These models simulate pressure buildup or drawdown in the wellbore and surrounding formation. They can help identify leaks or formation communication based on the pressure response. Software packages often incorporate these models for complex wellbore geometry.

• Empirical Correlations: Simpler correlations exist which relate SICP to reservoir properties, but these are usually specific to certain reservoir types or well configurations and often less accurate than fully physics-based models.

The choice of model depends on the specific well conditions, data availability, and the objectives of the analysis. Sophisticated techniques often combine various models to provide a more comprehensive interpretation.

Chapter 3: Software for SICP Analysis

Several software packages are available for analyzing SICP data and simulating wellbore pressure behavior. These packages typically include:

• Reservoir Simulation Software: Comprehensive reservoir simulators such as CMG, Eclipse, and Petrel can simulate pressure changes in the reservoir and wellbore in response to various scenarios, including shut-in conditions.

• Well Test Analysis Software: These specialized packages are designed for analyzing pressure transient data, including SICP data, to estimate reservoir properties and identify wellbore issues. Examples include Saphir and KAPPA.

• Data Acquisition and Visualization Software: Software packages dedicated to data acquisition, logging, and visualization are also useful in managing and interpreting SICP data.

Chapter 4: Best Practices for SICP Monitoring and Interpretation

Several best practices ensure reliable SICP measurements and interpretation:

• Establish a clear procedure: Develop a standardized procedure for SICP measurement including the duration of shut-in time, the type of gauge used, and data recording methods.
• Regular calibration and maintenance: Regularly calibrate pressure gauges and perform routine maintenance to ensure their accuracy.
• Proper well preparation: Ensure the well is completely shut-in before taking measurements, and the annulus is free of debris or other contaminants.
• Data quality control: Implement procedures to check for data errors and inconsistencies.
• Use appropriate models: Select the most appropriate model for interpreting the data based on reservoir conditions and wellbore geometry.
• Consider all factors: Account for all factors that could influence SICP, such as reservoir pressure, fluid properties, and wellbore geometry.
• Expert interpretation: Interpreting SICP data is complex, and consulting experts in reservoir engineering or well testing can help ensure accurate and reliable results.

Chapter 5: Case Studies of SICP Applications

Several case studies illustrate the application of SICP monitoring and interpretation in diagnosing and resolving well problems:

• Case Study 1: Identifying a Casing Leak: A sudden drop in SICP during a workover operation indicated a casing leak. Further investigation using pressure transient analysis helped pinpoint the leak location, enabling timely repairs.

• Case Study 2: Assessing Reservoir Pressure: Monitoring SICP buildup after shut-in provided insights into reservoir pressure and helped assess the reservoir's productivity.

• Case Study 3: Diagnosing Formation Communication: Fluctuations in SICP during a stimulation treatment suggested communication between different zones in the formation. This information was crucial for optimizing the stimulation strategy.

These case studies emphasize the importance of SICP as a diagnostic tool for safe and efficient oil and gas operations. The details of specific cases would be confidential but the principles illustrated are broadly applicable.