Abstract
Elastic impedance inversion is the latest development in the field of hydrocarbon exploration and production. The present research focuses on the improvement of the use of elastic impedance inversion, easing exploration of hydrocarbons. The seismic velocities change with variation in geological constraints. Constant K, which is S-wave to P-wave ratio of the nth layer and n+1 layer across the interface, it must be changed accordingly. This research focuses on testing the effects of K as a constant in the elastic impedance equation. As using the same value of K for all types of formations can give rise to severe errors in the interpretation of data. The importance of the value of K for particular Amplitude Variation with Offset AVO type (I-IV) is studied using different Elastic Impedance Equations. The Reflection Coefficient (RC) curves for each AVO class are generated using Zoeppritz approximation and Elastic Impedance equations. The comparison of RC curves shows significant variations at far offsets in each AVO type using the Constant value of K. When K Calculated is used, AVO type I and Type II shows a good match at near, mid and far offsets. Type III does not change due to the changing value of K. Type IV gives good agreement at near and intermediate offsets. This variation in curves, with the change in the value of K, indicates that it is a significant factor of interpretation using elastic impedance. The application of findings on well logs has given a satisfactory confirmation of the present results. This research can be helpful to resolve severe errors in the interpretation due to the constant value of K.
Highlights
Seismic velocities play a vital role in the determination of lithology, porosity and fluid content
Elastic impedance inversion is based on the assumption of using S-wave to P-wave ratio of the nth layer, and n+1 layer across the interface which is known as K and its value is 0.25
Reflection Coefficient (RC) curves based on the Zoeppritz equation and Elastic Impedance equations are used for comparison of the results
Summary
Seismic velocities play a vital role in the determination of lithology, porosity and fluid content. Seismic velocities vary horizontally and vertically depending upon the geological constraints, the depositional environment, overburden pressure, lithological variations, and others. As the seismic velocities change with the variation in both the elastic properties and other geological constraints, K changes . Conventional acoustic impedance (AI) inversion, which is the product of P-wave velocity and density, assumes that the P-wave strikes the subsurface interfaces at normal incidence (Lindseth, 1979). This assumption remains valid when the offset range is small, and the reservoir is deep. Elastic impedance inversion is the generalization of acoustic impedance for the variable angle of incidence
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