Full Wave Sonic Waveforms Measurement Principle

Explanation
The Full Wave Sonic Tool is capable of recording acoustic waves in freshwater-based mud and oil-based mud, as well as in cased holes. However, it is not capable of recording acoustic waves in air-drilled holes. This is because air-drilled holes do not contain any fluid medium for the acoustic waves to travel through, making it impossible for the tool to record them.

Explanation
The Full Wave Sonic system utilizes a monopole transmitter, which is a device that converts electrical energy into mechanical energy. This means that the system is capable of converting electrical signals into sound waves, allowing for the transmission and reception of sonic waves. Therefore, the statement is true.

Explanation
Offset refers to the distance between the transmitter and the receiver. It represents the spatial difference or displacement between the two points. In the context of communication systems, the offset is used to determine the physical separation between the transmitting and receiving antennas or devices. It is an important parameter to consider when designing and optimizing wireless networks, as it affects the signal strength, quality, and overall performance of the communication link.

Explanation
Each FWS transmitter pulse records 4 waveforms.

Explanation
The first wave to arrive at the receiver is the compressional wave. Compressional waves, also known as P-waves, are a type of seismic wave that travels through the Earth by compressing and expanding the material it passes through. They are the fastest seismic waves and can travel through solids, liquids, and gases. Shear waves, Stoneley waves, and mud waves are all different types of seismic waves, but they arrive at the receiver after the compressional wave.

Explanation
Slots cut into the tool housing can increase travel times of tool mode waves. This is because the slots create additional obstacles or barriers for the waves to pass through, causing them to slow down and take longer to reach their destination. By increasing the travel times, the slots can affect the overall efficiency and speed of the tool's operation.

Explanation
Mud waves are seismic waves that travel through the subsurface and are influenced by the properties of the mud or drilling fluid. One of the characteristics of mud waves is that they have long travel times, meaning it takes them longer to reach a receiver. Another characteristic is that they have low amplitude at a receiver, meaning they are weaker compared to other seismic waves. Additionally, the velocity of mud waves is dependent on the borehole fluid, meaning it can vary based on the properties of the fluid. However, short travel times are not a characteristic of mud waves.

Explanation
Shear waves and compressional waves are both types of body waves. Body waves are seismic waves that travel through the Earth's interior, as opposed to surface waves which only travel along the Earth's surface. Shear waves, also known as S-waves, move particles perpendicular to the direction of wave propagation, causing rocks to shear or twist. Compressional waves, also known as P-waves, move particles in the same direction as the wave propagation, causing rocks to compress and expand. Leaky mode, Stoneley waves, and mud waves are not considered body waves.

Explanation
The given statement is true. Compressional wave velocity refers to the speed at which a compressional wave, also known as a longitudinal or primary wave, travels through a medium. This velocity is influenced by two main factors: the elastic properties and bulk density of the medium. Elastic properties, such as the stiffness or rigidity of the medium, determine how easily it can be compressed and how quickly it can return to its original shape. The bulk density of the medium, which is the mass per unit volume, affects the resistance to compression and therefore the speed of the wave.

Explanation
Shear wave energy causes particle deformation that is perpendicular to the direction of energy propagation. This means that as the shear wave travels through a medium, the particles within the medium move perpendicular to the direction in which the wave is traveling. This is in contrast to longitudinal waves, where particle displacement is parallel to the direction of energy propagation. In shear waves, the particles move in a back-and-forth motion perpendicular to the wave's direction, resulting in a shearing or twisting effect.

Explanation
The minimum travel time from the transmitter to a receiver represents a critically refracted wave. When a wave travels from one medium to another at an angle greater than the critical angle, it undergoes total internal reflection. However, when the angle of incidence is equal to the critical angle, the wave is neither totally reflected nor totally refracted. Instead, it is critically refracted, meaning it follows the boundary between the two mediums without being completely reflected or refracted. The minimum travel time indicates that the wave is following this critical path.

Explanation
In order for a body wave to be critically refracted, the velocity of acoustic energy through the formation must be faster than the velocity of the fluid pressure wave through the borehole. This means that the body wave needs to travel at a higher speed than the fluid pressure wave in order to be refracted at the critical angle.

Explanation
In formations where shear velocity is slower than the velocity of the fluid pressure wave through the borehole, the FWS monopole transmitter will not generate critically refracted shear waves.

Explanation
The correct answer includes Stoneley Waves, Leaky Mode, and Normal Mode. These three options are considered surface waves because they propagate along the interface between two different mediums, such as the boundary between a solid and a fluid. Shear Waves and Compressional Waves, on the other hand, are bulk waves that propagate through the interior of a medium and do not travel along a surface.

Explanation
Leaky mode and normal mode waves are not used to determine formation properties. These terms are typically associated with guided wave testing, which is used for inspecting pipes and other structures for defects. Formation properties are usually determined using methods such as well logging, core analysis, and seismic surveys. Therefore, the statement is false.

Explanation
Stoneley waves are surface waves that are generated when there is flexing or movement at the interface between the borehole fluid and formation fluid. These waves are characterized by their low frequency and high amplitude, and they play a significant role in well logging and formation evaluation.

Explanation
Stoneley wave velocities are not important for the purpose of formation evaluation because Stoneley waves are primarily used for borehole stability analysis rather than formation evaluation. These waves are sensitive to the presence of fractures and can help identify the need for casing or cementing. However, when it comes to evaluating the properties and characteristics of the formation itself, other types of waves such as compressional (P) and shear (S) waves are more commonly used. Therefore, Stoneley wave velocities are not crucial for formation evaluation.

Explanation
Full Wave Sonic (FWS) is a logging tool that measures the travel time of sound waves through the formation. By analyzing the travel time, FWS can provide information about the porosity of the formation, which is the amount of empty space within the rock. It can also help determine the lithology of the formation, which refers to the type of rock present. Additionally, FWS can identify gas-bearing formations by detecting the presence of gas in the pore spaces. It can also provide depth correlation for seismic sections, helping to align the FWS data with seismic data. However, FWS is not directly used to determine permeability or formation resistivity.

Explanation
The statement is true because compressional and shear wave velocities can be used to estimate various rock elastic properties such as Poisson's ratio, Young's modulus, shear modulus, and bulk compressibility. By measuring the velocities of these waves as they travel through rocks, scientists can gather valuable information about the rock's mechanical properties and behavior under stress. This information is crucial in fields like geology, geophysics, and engineering, as it helps in understanding the behavior of rocks and designing structures that can withstand different types of loads and pressures.

Explanation
The FWS, which stands for Formation MicroScanner, is a tool used in the oil and gas industry to analyze the properties of rock formations. It uses electrical imaging to detect the presence of natural fractures in the formation. Therefore, the statement "The FWS can be used to detect the presence of natural fractures" is true.

Explanation
The FWS (Formation While Drilling) can be used in various conditions including saltwater based mud, freshwater based mud, oil based mud, and cased hole. It is a drilling technique that allows for real-time formation evaluation while drilling, providing valuable information about the formation being drilled. This information can help in making decisions regarding drilling parameters, wellbore stability, and reservoir characterization. The FWS can be used in different types of drilling fluids (saltwater, freshwater, oil-based) and in cased holes where the wellbore has been lined with casing.

Explanation
The four receivers employed by the FWS are positioned at distances of 10, 11, 12, and 13 feet from the transmitter.

Explanation
Direct waves refer to the propagation of waves in a straight line from the transmitter to the receiver without any obstacles or reflections. This means that there are no obstructions or interference that would cause the waves to deviate from their path. Therefore, the statement that direct waves travel directly from the transmitter to the receiver is true.