Rock Physics Trivia: MCQ Quiz!

The correct answer is "ratio between mass and volume." Density is defined as the mass per unit volume of a substance. It is a measure of how compact or concentrated the matter in an object is. The ratio between mass and volume gives us an indication of how much mass is packed into a given volume, which is the essence of density.

Rock Physics is a branch of science that focuses on understanding the relationship between geophysical measurements and rock properties. This involves studying how different rock properties, such as density, porosity, and elastic properties, affect the way seismic waves propagate through the subsurface. By understanding this relationship, scientists can interpret seismic data to gain insights into the subsurface geology, such as identifying potential hydrocarbon reservoirs or assessing the structural integrity of underground formations. Rock Physics plays a crucial role in various applications, including oil and gas exploration, geothermal energy, and geological hazard assessment.

The correct answer is "above 20%". Reservoir porosity refers to the amount of empty space or voids within a rock formation that can hold fluids such as oil or gas. A porosity value above 20% indicates that the rock has a high amount of empty space, making it very good for reservoir purposes as it can hold a significant amount of fluid.

The velocity responses to rocks are influenced by various factors, including porosity and pore geometry, fluid type and saturation, and mineral composition and distribution. However, the type of acquisition is not directly related to the velocity responses of rocks. The type of acquisition refers to the method or technique used to gather geological data, such as seismic surveys or well logging. While the type of acquisition may indirectly affect the interpretation of velocity responses, it does not directly impact the velocity responses themselves.

Petrophysics is a branch of geophysics that focuses on the study of physical and chemical properties of rocks and fluids within the Earth's subsurface. It primarily uses well logs, which are measurements taken during drilling operations, to analyze and interpret the properties of the rocks and fluids. This includes examining parameters such as porosity, permeability, and saturation. In contrast, rock physics is the study of the relationship between the physical properties of rocks and their seismic response. It heavily relies on interpreting seismic, sonic, and ultrasonic data to understand the elastic properties of rocks and how they interact with seismic waves. Therefore, the main difference between petrophysics and rock physics is that petrophysics emphasizes well logs while often disregarding sonic logs and seismic data.

Zero phase refers to a wavelet phase where the peak of the wavelet is centered at time zero. In seismic interpretation, zero phase wavelets are commonly used because they simplify the analysis and enhance the resolution of seismic data. By aligning the wavelet peak with time zero, it becomes easier to identify and interpret seismic events accurately. This preference for zero phase wavelets is based on the assumption that the wavelet is symmetric and has equal energy at positive and negative time values, which helps in reducing the distortion and improving the quality of seismic interpretation.

Young's modulus is a measure of the stiffness or rigidity of a material. It is defined as the ratio of extensional stress to extensional strain in a uniaxial stress state. This means that it quantifies how much a material will deform under a given amount of stress. A higher Young's modulus indicates a stiffer material, while a lower Young's modulus indicates a more flexible material.

The correct answer is Voigt and Reuss. Voigt and Reuss are not empirical models used in Rock Physics. Castagna’s equation, Wyllie’s equation, and Han’s equation are all empirical models commonly used in Rock Physics to predict various rock properties. Castagna’s equation relates the P-wave velocity to the porosity and lithology of the rock. Wyllie’s equation is used to estimate the water saturation in a reservoir based on the resistivity log. Han’s equation is used to calculate the shear modulus of a rock.

The given answer suggests that Castagna's empirical relations are used to predict the shear velocity from the compressional velocity. These relations provide a way to estimate the shear velocity, which is a measure of how fast seismic waves travel through a rock in a direction perpendicular to the direction of the compressional waves. By using the compressional velocity, which is a measure of how fast seismic waves travel through a rock in the direction of the wave, these relations allow for the estimation of the shear velocity.

The answer is incorrect. The correct statement on Bulk Modulus is that the Bulk Modulus of water is higher than gas. Bulk modulus is a measure of the resistance of a substance to compression under pressure. Water is much less compressible than gas, which means it has a higher bulk modulus compared to gas.

The acoustic impedance is calculated by multiplying the velocity of sound in a medium by the density of the medium. In this case, the given velocity is 2500 m/s and the density is 2.0 g/cc. To calculate the acoustic impedance, we need to convert the density from g/cc to kg/m3. Since 1 g/cc is equal to 1000 kg/m3, the density becomes 2000 kg/m3. Multiplying this density by the velocity of 2500 m/s gives us an acoustic impedance of 5 x 10^6 m/s kg/m3.

Poisson's ratio is defined as the ratio of the lateral strain (strain perpendicular to the applied stress) to the axial strain (strain parallel to the applied stress) in a uniaxial stress state. It quantifies the relationship between the deformation in different directions when a material is subjected to an external force. A positive Poisson's ratio indicates that a material tends to contract laterally when stretched longitudinally, while a negative Poisson's ratio indicates the opposite behavior.

The given statement "All of the above" is the correct answer because it encompasses all the previous statements. The first two statements provide specific examples of the density of quartz and calcite minerals, indicating that density can be measured for different substances. The third statement defines density as the ratio between mass and volume, which is a general principle applicable to all substances. Therefore, "All of the above" is the correct statement about density as it includes all the provided information.

The statement suggests that all three options (DHI, AVO Classes, and Depth Trends) can be used to differentiate in the Petrophysical / Geological Model. This means that each of these options provides valuable information or characteristics that can help distinguish between different elements or features within the model.

Quartz minerals have a low Poisson's ratio. Poisson's ratio is a measure of the ratio of lateral strain to axial strain when a material is subjected to stress. A low Poisson's ratio indicates that the material has a low tendency to expand laterally when compressed axially. Quartz is a rigid and brittle mineral, and its atomic structure does not allow for much deformation or expansion in different directions. Therefore, it has a low Poisson's ratio compared to other minerals like clay or calcite.

In a shallow high porosity sand region, all of the given statements are true. The AI (acoustic impedance) of gas sand is lower than shale formation because gas has a lower density and slower velocity compared to shale. The AI of gas sand is also lower than brine sand because gas has a lower density and slower velocity compared to brine. Additionally, the Vp/Vs (compressional wave velocity to shear wave velocity ratio) of gas sand is lower than brine sand due to the lower velocity of gas compared to brine. Therefore, all of the statements are correct in this scenario.

Cementation refers to the process of deposition of dissolved material in the pore spaces of sediment, which helps to bind the sediment grains together and increase the effective porosity. This process occurs when minerals precipitate from a solution and fill in the gaps between sediment particles, forming a solid mass. This deposition of dissolved material helps to stabilize loose sediment and increase its strength and stability. Compaction and overburden, on the other hand, refer to the processes of sediment compression due to the weight of overlying layers, which can decrease porosity.

The correct answer is "The hydrocarbon produced from low porosity formation through secondary porosity." This means that the hydrocarbon is being produced from a reservoir with low porosity, but there is secondary porosity present that allows for the flow of hydrocarbons. Secondary porosity refers to fractures, faults, or other openings in the rock formation that create pathways for the hydrocarbons to flow through.

The correct answer is "All of the above." Vp/Vs, also known as the ratio of compressional wave velocity to shear wave velocity, can be used to separate different rock types and fluids. It can also differentiate between coal and gas sand. Additionally, the response can be created from slowness logs, including shear and primary waves.

The correct answer is "All are correct." This means that all of the options given (Shale overlying Reservoir Gas Sand, Shale overlying soft shale, and Shale overlying coal) will result in a negative amplitude response with SEG polarity and a tertiary period.

The AI (acoustic impedance) is a measure of how resistant a material is to the propagation of sound waves. In low porosity sand regions, the AI of gas sand is expected to be lower than that of brine sand. This is because gas has a lower density and compressibility compared to brine, resulting in a lower AI. Therefore, the given answer is correct as it correctly states that the AI of gas sand is lower than brine sand in low porosity sand regions.