Seismic Wave Attenuation And Dispersion Due To Wave Induced Fluid Flow In Full Frequency Band

The importance of hydraulic and geophysical characterization of subsurface rocks cannot be ignored in the many scientific fields,like the sustainable use of aquifers,optimized production of oil and gas,the secure storage of nuclear waste and for the recovery of geothermal(HDR)energy.In the field of oil and gas exploration,the hydrological and geophysical characterization of subsurface rocks get much increased and a number of theories and experimental procedures are playing a vital role in various scientific applications in the field of exploration geophysics.During the last two decades or so,the development in analytical and numerical techniques has transformed geophysics into a multidisciplinary scientific area.As geophysics provide an indirect access to subsurface hydrocarbon resources and also assist in the optimized production of valuable resources.Among other geophysical methods,Seismic methods get much renowned in hydrocarbon field exploration and exploitation,but seismic interpretation on the basis of lithology and fluid content need some distinguished geophysical techniques.Moreover,discrimination between hydrocarbon and non-hydrocarbon fluids demands some efficient,simple,convenient and economically secure geophysical techniques for precise petroleum prospecting.In geophysical method,usually we construct a relationship between elastic and reservoir parameter which Lay the foundation of quantitative and qualitative seismic interpretation.In literature,much convincing evidences are available which suggest that seismic characteristics are sensitive to variation in rock properties(fracture,porosity,permeability etc.)as well as in fluids properties(fluid type,fluid saturation,fluid modulus,etc.).These variations in rock and fluids properties influence seismic signatures in broad range of frequencies and scales,due to which the conventional reservoir technology has been confronted with a variety of problems.So,precise interpretation of seismic responses is the need of time.In order to better interpret seismic signatures,one of the key task for geophysicists is to find the relationship between hydrocarbon saturation and seismic attributes.Current work encompasses analytical and numerical techniques to assist in estimating the influences on seismic signatures owing to the presences of three phase fluid having different saturation in a deformable porous rock.In foreword section,research status of theoretical,experimental and numerical simulation methods for the computation of wave attenuation and dispersion is briefly summarized.After the forward section,an introduction of basic theories of wave propagation through poro-elastic media and the factor influencing the wave characteristics is given which provide a strong foundation for deep understanding of wave characteristics.The third part concerned about the proposal of a novel and suitable rock physical model,for which an analytical method is suggested to estimate the influences on wave characteristics during its propagation through a deformable porous rock saturated with three immiscible fluids.The analytical approach is further authenticated by comparing it with the outcomes of numerical simulation techniques for the same 1D model.The results thus obtained are in good agreement which confirmed the ethnicity of the proposed method and the novelty of the rock physical model.From results analysis it can be concluded that,this analytical approach can be a potential tool in various time lapse seismic cases like in hydrocarbon production,improved oil recovery by water flooding or by gas injection.It can also be utilized in investigating the low-frequency anomalies in passive seismic data,which can be further correlated with location of hydrocarbon reservoir and also in testing the mechanical behavior of medical instruments at low seismic frequencies.As,numerical forward modeling technique is an effective tool to completely understand the characteristics of seismic wave through a complex and deformable porous media.The fourth part revolves around 1D numerical forward modeling methods to analyze wave propagation characteristics.In numerical forward modeling section,1D quasi-static finite difference modeling method in frequency domain is implemented for the estimation of frequency dependent complex P-wave modulus of porous media having mesoscopic heterogeneity due to saturation of three fluids.Our proposed quasi-static method is simple to be implemented by the computing scheme of parallelization and have potential to extend it for two dimensional case comparatively in a flexible way.Furthermore,a 2D fifth ordered staggered-grid method,is proposed for the solution of poro-elastic wave equations in which a second-order time difference is used for updating.The proposed 2D method provide numerical accuracy and computational efficiency in studying the characteristics of seismic waves in a saturated poro-elastic media.The wave field snapshots and the corresponding synthetic seismogram of a poro-elastic rock saturated with three fluids is obtained.In our 2D numerical forward modeling study,It can be concluded by analyzing the results of Bulk pressure(confining),fluid pressure and fluid and solid horizontal and vertical components that the fast longitudinal and shear waves produced their own reflection and transmission and the energy distribution of the wave is related to the elastic parameter.The obtained analytical results are compared with the results obtained by 1D quasi-static numerical technique.Interestingly,from the comparison,it can be concluded that both analytical and numerical results are identical and the proposed method provide an effective tool to efficiently discriminate fluids of different nature from the analysis of seismic data.Also,the analytical and 1D numerical simulation results were further advocated with wave field snapshots and the corresponding synthetic seismogram.The outcomes of above study provide an analytical tool for the development of rock physical theories with the intention to identify and estimate properties of various fluids saturated porous rocks.The computational procedure of 1D forward modeling technique provided in our study is much easier to implement and flexibly extended to two dimensional case which will enhance our understanding about wave propagation through dual phase poroelastic media.Furthermore,our study will lay the foundation for designing a seismic survey,developing an inversion algorithm and for the interpretation of seismic signature form a deformable saturated poro-elastic media.