SSP

Test Your Knowledge

SSP Quiz:

Instructions: Choose the best answer for each question.

1. What is the primary cause of Static Spontaneous Potential (SSP)?

a) The magnetic field of the Earth b) The gravitational pull of the Earth c) The difference in electrical potential between formation fluids and borehole fluid d) The pressure of the formation fluids

2. Which of the following is NOT a factor contributing to SSP?

a) Electrochemical Potential b) Electrokinetic Potential c) Magnetic Field Potential d) Formation Fluid Type

3. What type of formation typically displays a negative SSP?

a) Sandstone b) Shale c) Limestone d) Coal

4. What does a higher SSP signal generally indicate about a formation?

a) Lower permeability b) Higher permeability c) Lower porosity d) Higher water saturation

5. What is the main tool used for measuring SSP?

a) Seismic reflection survey b) Gamma ray log c) Spontaneous potential log (SP log) d) Induction log

SSP Exercise:

Scenario: You are reviewing a well log from a new exploration well. The SP log shows a large negative deflection in the middle of the well.

Task: Analyze the potential implications of this negative SSP reading. Consider what it might tell you about the lithology, fluid content, and permeability of the formation at that depth.

Techniques

Chapter 1: Techniques for Measuring Static Spontaneous Potential (SSP)

This chapter delves into the practical aspects of measuring SSP, outlining the commonly employed techniques and equipment used in the oil and gas industry.

1.1. Spontaneous Potential Logging (SP Log):

The primary method for acquiring SSP measurements is through spontaneous potential logging. This involves lowering a specialized tool, known as an SP log tool, into the borehole.

• SP Log Tool Components: The tool consists of two main components:

  • Reference Electrode: Typically, a metallic electrode placed in the borehole fluid. It acts as a reference point for measuring the potential difference.
  • Measuring Electrode: Another electrode, usually a porous pad, placed in contact with the formation. This electrode measures the electrical potential of the formation.

• Data Acquisition: As the SP log tool is lowered into the borehole, the potential difference between the reference and measuring electrodes is continuously recorded, resulting in an SSP log.

1.2. SSP Measurement Procedures:

• Mud Filtrate Invasion: The SP log is typically acquired after the borehole has been drilled and stabilized with drilling mud. The mud filtrate invades the formation, creating a zone of altered conductivity that impacts the SSP readings.

• Calibration and Standardization: To ensure accurate and comparable results, the SP log tool is calibrated and standardized against a known reference potential before and during the logging operation.

1.3. Other SSP Measurement Techniques:

While SP logging is the dominant method, other techniques can be employed in specific situations.

• Micro-SP: Measures SSP at a much finer scale, providing higher resolution data.
• Downhole Resistivity Devices: Some resistivity tools can measure SSP as a secondary parameter.

1.4. Factors Affecting SSP Measurements:

• Borehole Conditions: Borehole diameter, fluid level, and temperature can influence the SSP readings.
• Mud Type and Salinity: The type and salinity of drilling mud can impact the electrical conductivity of the borehole fluid and affect the SSP signal.
• Formation Characteristics: Formation lithology, porosity, permeability, and fluid type significantly impact the SSP measurements.

1.5. Interpretation of SSP Logs:

SSP logs are often interpreted in conjunction with other well logs (e.g., gamma ray, resistivity) to gain a comprehensive understanding of the subsurface. Experienced geophysicists and geologists utilize specialized software and interpretation techniques to analyze SSP data.

1.6. Conclusion:

SSP measurements provide valuable insights into the subsurface geology and fluid content. By understanding the techniques involved and the factors influencing SSP readings, oil and gas professionals can leverage this information for informed decision-making in exploration and production activities.