Overview
A downhole survey is a measurement taken of the wellbore or the hole drilled in the ground for the purpose of extracting oil, gas, or other subsurface resources. The survey is typically conducted using a tool called a downhole survey instrument, which is lowered into the wellbore on a wireline or conveyed on a drilling assembly. The instrument measures various parameters such as inclination, azimuth, and tool face orientation, as well as the location of the wellbore in relation to the surface. The data collected is used to help guide the drilling process, ensure the wellbore stays on target, and to determine the location and orientation of hydrocarbon-bearing formations.
There Are 4 Main Types Of Downhole Surveys;
Caliper logging is a type of downhole survey that is used to measure the diameter of a wellbore. The tool used for caliper logging is called a caliper, which is a device that is lowered into the wellbore on a wireline or conveyed on a drilling assembly. The caliper has arms that can be opened or closed to fit the diameter of the wellbore. The measurement is taken by comparing the distance between the closed arms to the diameter of the wellbore.
What does Caliper logging measure?
Caliper logging measures the diameter of the wellbore. Caliper logging can measure the diameter of the wellbore in several different ways, such as:
Contact method: the arms of the caliper tool make physical contact with the wellbore and measure the diameter by the distance between the arms.
Non-contact method: the tool uses sensors such as ultrasonic or optical to measure the diameter of the wellbore without making physical contact.Caliper logging can also provide information on the condition of the wellbore such as the presence of ledges, washouts, keyseats, and other features that could compromise the good integrity.
Caliper logging data is also used to identify any changes in the wellbore’s diameter caused by factors such as borehole collapse or formation breakouts, and to detect any other wellbore abnormality. This information is used to help guide the drilling process, ensure the wellbore stays on target, and determine the location and orientation of hydrocarbon-bearing formations.
What is Caliper logging used for?
Caliper logging is used for a variety of purposes in the oil and gas industry and in geothermal and mining drilling. Some of the main uses include:
Wellbore mapping: Caliper logging is used to determine the size and shape of the wellbore, which is important for wellbore navigation, drilling optimization and maintaining wellbore stability.
Detecting wellbore abnormalities: Caliper logging can detect various wellbore abnormalities such as ledges, washouts, keyseats, and other features that could compromise good integrity.
Well integrity check: The caliper log data is also used to evaluate the condition of the well and detect any signs of damage or deformation, which can cause well integrity issues.
Formation evaluation: Caliper logging can be used to identify the presence and orientation of hydrocarbon-bearing formations, which can help in the exploration and production of oil and gas.
Drilling optimization: Caliper logging can be used to optimize drilling parameters such as weight on bit, rotary speed, mudflow, and mud properties, to improve the drilling efficiency and reduce the risk of wellbore instability.
Completion design: Caliper logging is used to design the completion string and select the appropriate size of the casing and tubing, in order to ensure a proper fit and avoid wellbore collapse or other issues.
Exploration and mining drilling: Caliper logging can also be used to identify the presence of different formation types and aid in the exploration of mineral deposits in mining drilling.
Full Waveform Sonic Logging (FWS) is a type of downhole survey that uses acoustic waves to measure the properties of the rock and fluid in the wellbore. It is a type of sonic logging, which is a method of measuring the elastic properties of rock formations by analyzing the speed and attenuation of sound waves as they travel through the rock. FWS is a more advanced version of sonic logging, which records the full waveform of the acoustic signal instead of just the amplitude, as in traditional sonic logging.
What does Full Waveform Sonic Logging measure?
Full Waveform Sonic Logging (FWS) measures the elastic properties of the rock and fluid in the wellbore. It measures the full waveform of the acoustic signal generated by the tool as it travels through the rock and fluid in the wellbore. The data is then analyzed to determine various properties such as:
Density: FWS can measure the density of the rock formation, which is important for determining the type of rock and the presence of fluids.
Compressional wave velocity: FWS can measure the speed at which compressional waves travel through the rock formation. This information can be used to determine the elastic properties of the rock, such as Young’s modulus and Poisson’s ratio.
Shear wave velocity: FWS can also measure the speed at which shear waves travel through the rock formation. This information is used to determine the rock’s mechanical properties such as rigidity, strength, and failure criteria.
Lithology Identification: FWS can be used to identify the type of rock formation, which is important for reservoir characterization and exploration.
Fluid identification: FWS can be used to identify the type of fluid present in the rock formation, such as oil, gas, or water.
Porosity and permeability: FWS can measure the porosity and permeability of the rock formation, which are important for the production of oil and gas.
Saturation: FWS can measure the fluid saturation of the rock formation which is important for reservoir characterization and production optimization.
Stress and Strain: FWS can measure the stress and strain on the rock formation which is important for well integrity check and drilling optimization.
Fracture detection: FWS can detect natural fractures in rock formations that can affect the flow of fluids and the production of oil and gas
What is Full Waveform Sonic Logging used for?
Full Waveform Sonic Logging (FWS) is used for a variety of purposes in the oil and gas industry, mining and geothermal drilling. Some of the main uses include:
Reservoir characterization: FWS can be used to identify the presence and orientation of hydrocarbon-bearing formations, which can help in the exploration and production of oil and gas. It can also be used to identify the type of rock formation, which is important for reservoir characterization and exploration.
Completion design: FWS is used to design the completion string and select the appropriate size of the casing and tubing, in order to ensure a proper fit and avoid wellbore collapse or other issues.
Well integrity check: FWS can be used to evaluate the condition of the well and detect any signs of damage or deformation, which can cause well integrity issues. It can also measure the stress and strain on the rock formation which is important for well integrity checks and drilling optimization.
Fracture detection: FWS can detect natural fractures in rock formations that can affect the flow of fluids and the production of oil and gas.
Production optimization: FWS can be used to measure the porosity and permeability of the rock formation, fluid saturation, fluid identification, and other rock and fluid properties, which are important for the production of oil and gas.
Drilling optimization: FWS can be used to optimize drilling parameters such as weight on bit, rotary speed, mudflow, and mud properties, to improve the drilling efficiency and reduce the risk of wellbore instability.
Mining and geothermal drilling: FWS can be used in mining drilling to identify the presence of mineral deposits and in geothermal drilling to identify the presence of hot water or steam.
Reservoir monitoring: FWS can be used to monitor the changes of rock and fluid properties with time, to track the production of oil and gas and to identify the presence of changes in the reservoir that may affect the production.
Optical televiewer Logging (OTV) is a type of downhole survey that uses a camera to capture images of the wellbore walls. It is also known as a borehole televiewer, borehole camera, or borehole imaging. The OTV tool is lowered into the wellbore on a wireline or conveyed on a drilling assembly, and it captures images of the wellbore walls as it is lowered. The images are then analyzed to determine the properties of the rock formation and to identify any abnormalities or features in the wellbore.
OTV can provide detailed images of the wellbore walls, which can be used to identify the type of rock formation, the presence of fractures, vugs, and other features that can affect the good integrity and the production of oil and gas. Additionally, OTV can also detect the presence of drilling mud or cement returns, which can indicate a problem with good integrity.
What does Optical Televiewer Loggingg measure?
Optical televiewer Logging (OTV) measures the features of the wellbore walls by capturing images of the wellbore walls. It does not measure any physical properties of the rock or fluid, instead, it captures images of the wellbore that can be analyzed to identify various features of the wellbore such as:
Rock formation: OTV can be used to identify the type of rock formation, which is important for reservoir characterization and exploration.
Fractures: OTV can detect natural fractures in rock formations that can affect the flow of fluids and the production of oil and gas.
Vugs: OTV can detect the presence of vugs, which are large voids in the rock formation that can affect the good integrity and the production of oil and gas.
Cement and drilling mud returns: OTV can detect the presence of drilling mud or cement returns, which can indicate a problem with good integrity.
Corrosion and erosion: OTV can detect signs of corrosion and erosion on the wellbore walls, which can indicate a problem with good integrity.
Other wellbore abnormalities: OTV can detect other wellbore abnormalities such as ledges, washouts, keyseats, and other features that could compromise good integrity.
What is Optical Televiewer Logging used for?
OTV is used for a variety of purposes in the oil and gas industry, such as:
Reservoir characterization: OTV can be used to identify the presence and orientation of hydrocarbon-bearing formations, which can help in the exploration and production of oil and gas.
Well integrity check: OTV can be used to evaluate the condition of the well and detect any signs of damage or deformation, which can cause well integrity issues.
Completion design: OTV is used to design the completion string and select the appropriate size of the casing and tubing, in order to ensure a proper fit and avoid wellbore collapse or other issues.
Fracture detection: OTV can detect natural fractures in rock formations that can affect the flow of fluids and the production of oil and gas.
Drilling optimization: OTV can be used to optimize drilling parameters such as weight on bit, rotary speed, mudflow, and mud properties, to improve the drilling efficiency and reduce the risk of wellbore instability.
Acoustic Televiewer Logging (ATV) is a type of downhole survey that uses both acoustic waves and imaging to measure the properties of the wellbore. It combines the capabilities of Full Waveform Sonic Logging (FWS) and Optical Televiewer Logging (OTV) to provide detailed information about the wellbore and the surrounding rock formation.
What does an Acoustic Televiewer Logging measure?
Acoustic Televiewer Logging (ATV) measures both the elastic properties of the rock formation and the features of the wellbore walls. It measures:
Density: ATV can measure the density of the rock formation, which is important for determining the type of rock and the presence of fluids.
Compressional wave velocity: ATV can measure the speed at which compressional waves travel through the rock formation. This information can be used to determine the elastic properties of the rock, such as Young’s modulus and Poisson’s ratio.
Shear wave velocity: ATV can also measure the speed at which shear waves travel through the rock formation. This information is used to determine the rock’s mechanical properties such as rigidity, strength, and failure criteria.
Rock formation: ATV can be used to identify the type of rock formation, which is important for reservoir characterization and exploration.
Fractures: ATV can detect natural fractures in the rock formations that can affect the flow of fluids and production of oil and gas.
Vugs: ATV can detect the presence of vugs, which are large voids in the rock formation that can affect the well integrity and the production of oil and gas.
Cement and drilling mud returns: ATV can detect the presence of drilling mud or cement returns, which can indicate a problem with the well integrity.
Corrosion and erosion: ATV can detect signs of corrosion and erosion on the wellbore walls, which can indicate
What is Acoustic Televiewer Logging used for?
Acoustic Televiewer Logging (ATV) is used for a variety of purposes in the oil and gas industry, mining and geothermal drilling. Some of the main uses include:
Reservoir characterization: ATV can be used to identify the presence, orientation and properties of hydrocarbon-bearing formations, which can help in the exploration and production of oil and gas. It can also be used to identify the type of rock formation, porosity, permeability, saturation, stress and strain, and natural fractures.
Completion design: ATV is used to design the completion string and select the appropriate size of the casing and tubing, in order to ensure a proper fit and avoid wellbore collapse or other issues.
Well integrity check: ATV can be used to evaluate the condition of the well and detect any signs of damage or deformation, which can cause well integrity issues. It can also measure the stress and strain on the rock formation which is important for well integrity check and drilling optimization.
Fracture detection: ATV can detect natural fractures in the rock formations that can affect the flow of fluids and production of oil and gas.
Production optimization: ATV can be used to measure the porosity, permeability, saturation and fluid identification which are important for the production of oil and gas.
Drilling optimization: ATV can be used to optimize drilling parameters such as weight on bit, rotary speed, mud flow and mud properties, to improve the drilling efficiency and reduce the risk of wellbore instability.
Mining and geothermal drilling: ATV can be used in mining drilling to identify the presence of mineral deposits and in geothermal drilling to identify the presence of hot water or steam.
Reservoir monitoring: ATV can be used to monitor the changes of rock and fluid properties with time, to track the production of oil and gas and to identify the presence of changes in the reservoir that may affect the production.
Electrical Resistivity Logging (ERV) is a type of downhole survey that uses electrical currents to measure the resistivity of the rock and fluid in the wellbore. The ERV tool is lowered into the wellbore on a wireline or conveyed on a drilling assembly, and it sends electrical currents into the rock and fluid in the wellbore. The electrical resistivity of the rock and fluid is then measured and recorded.
What does Electrical Resistivity logging measure?
Electrical Resistivity Logging (ERV) measures the electrical resistivity of the rock and fluid in the wellbore.
Electrical resistivity is a measure of the resistance to the flow of an electrical current through the rock and fluid.
Resistivity of rock formation: ERV can measure the electrical resistivity of the rock formation, which can be used to identify the type of rock and to estimate the porosity and fluid saturation of the rock.
Fluid identification: ERV can be used to identify the type of fluid present in the rock formation, such as oil, gas or water, based on the variations of resistivity in the wellbore.
Saturation: ERV can measure the fluid saturation of the rock formation which is important for reservoir characterization and production optimization.
Formation resistivity: ERV can measure the formation resistivity which is a crucial parameter for determining the presence of hydrocarbons, water, and other fluids in the formation.
Well integrity check: ERV can be used to evaluate the condition of the well and detect any signs of fluid influx or fluid leakage, which can cause well integrity issues.
Production optimization: ERV can be used to measure fluid saturation and fluid identification, which are important for the production of oil and gas.
What is the Electrical resistivity log used for?
ERV is used for a variety of purposes in the oil and gas industry, such as:
Reservoir characterization: ERV can be used to identify the presence and orientation of hydrocarbon-bearing formations, which can help in the exploration and production of oil and gas.
Fluid identification: ERV can be used to identify the type of fluid present in the rock formation, such as oil, gas, or water.
Saturation: ERV can measure the fluid saturation of the rock formation which is important for reservoir characterization and production optimization.
Well integrity check: ERV can be used to evaluate the condition of the well and detect any signs of fluid influx or fluid leakage, which can cause well integrity issues.
Production optimization: ERV can be used to measure fluid saturation and fluid identification, which are important for the production of oil and gas.
Drilling optimization: ERV can be used to optimize drilling parameters such as weight on bit, rotary speed, mudflow, and mud properties, to improve the drilling efficiency and reduce the risk of wellbore instability.
FAQs
What difference between each method; Caliper logging, Full Waveform Sonic Logging, Optical Televiewer Logging, Acoustic Televiewer Logging, and Electrical Resistivity logging?
Caliper logging, Full Waveform Sonic Logging (FWS), Optical Televiewer Logging (OTV), Acoustic Televiewer Logging (ATV), and Electrical Resistivity logging (ERV) are all different types of downhole surveys that are used to measure different properties of the wellbore and the surrounding rock formation.
Caliper logging: Caliper logging measures the diameter of the wellbore by measuring the distance between the wellbore wall and the caliper arms. It is used to detect the presence of ledges, washouts, keyseats, and other wellbore abnormalities, which can affect the well integrity.
Full Waveform Sonic Logging (FWS): FWS measures the speed at which compressional and shear waves travel through the rock formation, which can be used to determine the density, elastic properties and mechanical properties of the rock formation. It can be used for reservoir characterization, completion design, well integrity check, fracture detection, and optimization of drilling and production parameters.
Optical Televiewer Logging (OTV): OTV captures images of the wellbore walls, which can be used to identify the type of rock formation, the presence of fractures, vugs, and other features that can affect the well integrity and the production of oil and gas.
Acoustic Televiewer Logging (ATV): ATV combines the capabilities of FWS and OTV, it provides detailed information about the wellbore and the surrounding rock formation, it can be used for reservoir characterization, completion design, well integrity check, fracture detection, and optimization of drilling and production parameters.
Electrical Resistivity logging (ERV): ERV measures the electrical resistivity of the rock and fluid in the wellbore, which can be used to identify the type of rock, fluid and estimate the porosity, fluid saturation, fluid identification and formation resistivity, which are important for reservoir characterization, well integrity check, production optimization and other subsurface exploration and production activities.
Each method measures different properties of the wellbore and the surrounding rock formation, and they are used for different purposes in the oil and gas industry. By combining the information from multiple methods, a more complete picture of the subsurface can be obtained, which can help in the exploration, drilling, completion, production and monitoring of
What limited measures in each method; Caliper logging, Full Waveform Sonic Logging, Optical Televiewer Logging, Acoustic Televiewer Logging, and Electrical Resistivity logging?
Caliper logging, Full Waveform Sonic Logging (FWS), Optical Televiewer Logging (OTV), Acoustic Televiewer Logging (ATV), and Electrical Resistivity logging (ERV) are all different types of downhole surveys that are used to measure different properties of the wellbore and the surrounding rock formation, but each method has its own limitations in terms of what it can measure.
Caliper logging: Caliper logging is limited to measuring the diameter of the wellbore and can’t provide any information about the rock formation or fluid properties. It also can’t detect fractures or other subsurface features that are not visible on the wellbore wall.
Full Waveform Sonic Logging (FWS): FWS measures the speed at which compressional and shear waves travel through the rock formation, but it doesn’t provide any information about the wellbore condition or visual information about the subsurface. It also can’t detect fractures or other subsurface features that are not visible on the wellbore wall.
Optical Televiewer Logging (OTV): OTV captures images of the wellbore walls, but it doesn’t provide any information about the rock formation or fluid properties. It also can’t detect fractures or other subsurface features that are not visible on the wellbore wall.
Acoustic Televiewer Logging (ATV): ATV combines the capabilities of FWS and OTV, but it doesn’t provide any information about the fluid properties and saturation.
Electrical Resistivity logging (ERV): ERV measures the electrical resistivity of the rock and fluid in the wellbore, but it doesn’t provide any information about the wellbore condition, rock formation or visual information about the subsurface.
Each method has its own limitations in terms of what it can measure, and by combining the information from multiple methods, a more complete picture of the subsurface can be obtained, which can help in the exploration
