Hudson's fracture density proportional to Bani demonstration

HTI anisotropy = Vertical inhomogeneities of an isotropic medium Azimuthal Velocity Analysis = Estimation of velocity for different directions based on times of arrival Anisotropic gradient Bani = Measurement of amplitude variations with offset for different azimuthal directions RMS velocity = Integrated seismic parameter obtained from data

Seismic anisotropy = The property that seismic waves travel at different speeds in different directions Geomechanical parameters = Parameters like rock stiffness, stress orientation, and fracture density that can be inferred from seismic data Azimuthal AVO analysis = Study of amplitude variations with offset and azimuthal directions Isotropic medium = A medium where seismic properties are the same in all directions

Normal Moveout correction = Correction for time shifts due to varying velocity along and perpendicular to fractures AVO analysis = Studies amplitude variations with offset for insights into subsurface properties Azimuthal inversion = Estimation of velocities for different directions based on azimuthal data Effective media theories = Inference of information about smaller fractures from seismic data

Variation in wave velocities with direction = Velocities are fastest parallel to fractures and slower perpendicular to them Inconsistencies between isotropic inversion and measured velocity in a well = Well drilled perpendicular to fractures resulting in slower measured velocities Time shifts in reflections within the same offset = Due to varying velocities along and perpendicular to fractures, affecting travel times Anisotropic NMO correction = Correction of gathers based on anisotropic stacking velocities

Direction of Vfast in Azimuthal Velocity Analysis = Defining the direction of the faster stacking velocities Bani represented in color on maps = Displaying anisotropic gradient results visually φiso shown as plates or arrows on maps = Representation of the plane of isotropy direction Integrated RMS velocity parameter = Overall parameter obtained from analyzing seismic data

HTI anisotropy = Vertical inhomogeneities of an isotropic medium VSP data = Used to image relatively large faults Effective media theories = Infer information about smaller fractures with sub-seismic lengths Azimuthal AVO = Technique introduced in advanced QI methods

4D reservoir characterization = Method introduced in the module Broadband seismic data inversion = Inversion technique covered in the module PP-PS joint inversion = Inversion technique discussed in the module Seismic anisotropy study since the 1950s = Important role in industry revision

Impact of anisotropy in production work = Little impact for techniques of the time Attitude towards anisotropy in the industry = Revised due to rapid development of computer technologies Importance of accounting for anisotropy = Reassessed due to technological advancements Description of reservoir using anisotropy = Possibility explored by modern seismic methods

Seismic anisotropy = Vertical fractures represented as vertical inhomogeneities Computer technologies impact = Led to revision of industry's attitude towards anisotropy HTI anisotropy and vertical fractures = Commonly considered in reservoir studies Smaller fractures imaging from seismic data = Inferred using effective media theories

Revision of industry's attitude towards anisotropy = Due to rapid development of computer technologies Importance of accounting for anisotropy = Reassessed due to modern seismic methods Imaging of relatively large faults using seismic data = Achieved with VSP data techniques Inference of information about small fractures from seismic data = Utilizing effective media theories

4D reservoir characterization = Advanced QI method introduced in the module Broadband seismic data inversion = Inversion technique mentioned for reservoir studies PP-PS joint inversion = Method discussed for analyzing seismic data Azimuthal AVO and Inversion Inversion = Techniques covered in advanced QI methods

Full waveform inversion (FWI) = Utilizes ultra-low frequencies in the 0-2 Hz range Tomography = Provides information between 2 and 10 Hz Well logs = Data obtained to address lack of information in the 2-10 Hz range Broadband data = Extends seismic reflectivity to around 2 Hz

Less side lobes in signal = Results in less interference in seismic signal and reduced ambiguity in inversion Improved reservoir geometry definition = Enhances ability to define reservoir's geometry more accurately Reduced uncertainty in reservoir volume calculation = Results from inversion of broadband data Sharper boundaries of reservoir's pay interval = Illustrated by acoustic impedance cross-sections

P-wave = Undergoes mode conversion at a non-zero incident angle S-wave = Generated along with P-wave when hitting an interface at a non-zero incident angle PP wave mode = Provides insights into S-wave velocity through amplitude variations with offsets PS wave mode = Recorded using three-component receivers and provides independent information about S-wave velocity

Effective in studying beneath gas clouds = PS data remains unaffected by gas absorption, unlike conventional PP data More comprehensive Vp/Vs model = Obtained through joint PP-PS tomography Enhanced elastic properties estimation = Achieved by integrating PS data into the inversion process Improved accuracy in reservoir properties analysis = Results from joint PP-PS inversion

Seismic anisotropy = Inferred rock stiffness and fracture density Vertical fractures = Variation in seismic wave velocities Azimuthal inversion = Improved correspondence with measurements 4D seismic = Changes in elastic properties due to reservoir variations

3D seismic survey = Measuring travel times and amplitudes in various directions 4D seismic survey = Monitoring changes in fluid saturation and reservoir properties Baseline survey = Acquired in 1990 for the Draugen Field study Repeat survey = Challenges in maintaining consistency in acquisition parameters

Impermeable shale separation = Lack of accurate lateral extent knowledge Aquifer communication = Flow barriers due to faults Reservoir-simulation scenarios = History-matching to fit available data 4D survey findings = Updating reservoir models and forecasting production extension

Costly repeat surveys = Logistical challenge in conducting multiple surveys Consistency in acquisition parameters = Ensuring data quality between baseline and repeat surveys Noise levels variation = Critical for accurate analysis and interpretation techniques Integrating time-lapse seismic data = Requires understanding complex relationships with reservoir properties

Immediate insight into reservoir situation = Resolve uncertainties and update reservoir models Forecasted production extension = Almost one year plateau production extension Estimated net present value increase = $84 million from accelerated production Snapshot of waterflood situation away from wells = Insight into aquifer connections and faults

Vp/Vs attribute map = Identifying hydrocarbon reservoirs Anisotropic parameters = Detecting fractures Broadband seismic data = Constraining inversion process PP-PS joint inversion data = Integrating information about S-waves

4D seismic reservoir characterization = Monitoring changes in reservoir properties over time Azimuthal seismic data analysis = Estimating anisotropic parameters Joint inversion of PP-PS data = Improving accuracy in elastic properties estimation Broadband seismic analysis = Obtaining accurate impedance estimates

PP waves = Higher dominant frequencies (40 Hz) PS waves = Slower wave velocity when traveling up PP amplitude peak = May correspond to a PS amplitude trough PS seismic alignment = Required for comparison with PP seismic

Successful drilling in northern part of field = Discovery of new deposits Identification of non-structural object in northeastern part = Similar VpVs anomaly observed Primary hydrocarbon reservoir located in southwestern area = Corresponding to low Vp/Vs anomaly Utilizing time-lapse seismic data for reservoir management = Monitoring changes in reservoir properties over time

Wellbore stability analysis = Using anisotropic parameters estimation Hydraulic fracturing operations design = Utilizing azimuthal seismic data Reservoir stimulation activities planning = Considering broadband seismic information Optimizing production strategies = Monitoring fluid movement using time-lapse seismic data

Improved accuracy in elastic properties estimation = Result of integrating PP-PS data Valuable insights into reservoir dynamics = Result of using 4D seismic data Estimation of stress in reservoirs = Role of azimuthal seismic data analysis Accurate impedance estimates without log-derived model = Benefit of using broadband seismic

Frequency range width = Enables capture of finer details in subsurface geology Low frequency bandwidth = Penetrates deeper into the subsurface Inversion algorithms = Better constrained with wider range of frequencies High frequencies attenuation = Primarily result of filtering effect of subsurface

Variable-depth streamer acquisition = Reduces noise from water surface Broadband seismic data = Fills the low-frequency gap Conventional streamer profile = Introduces interference notch pattern Deeper tow depths = Reduces noise and enables full bandwidth access

Fault locations = Shown in white in the background Fracture density = Represented in color Fracture orientation = Illustrated as black lines FMI log interpretation results = Shown in red lines at well locations

Traditional AVO attributes = Characterize layer property Azimuthal AVO analysis = Predicts presence of fractures Anisotropic gradient analysis = Characterizes interface property Inverting angle stacks for different azimuths = Obtains elastic properties and volumes of anisotropy coefficient

Intense sidelobes = Complicates resolution of target horizons High sidelobe amplitude = About 70% of main amplitude Expanding frequency content to higher end = Narrows the signal Extending frequency range at lower end = Minimizes sidelobes

Higher frequency content = Narrows the signal Lower frequency content = Minimizes sidelobes Attenuation of high frequencies = Absorbed and scattered more readily Absence of low frequencies = Constraints in seismic acquisition

Conventional streamer profile = Introduces a particular interference notch pattern Variable-depth streamer acquisition = Reduces noise from water surface Array de-tuned with receiver depth = Varying ghost notch frequency Summing response along cable = Access to full bandwidth

Reduced noise at water surface = Particularly important for low frequencies Array de-tuned with receiver depth = Varying ghost notch frequency Continuous receiver response = No discrete notch Access to full bandwidth = Summing response along cable

Capture of finer details in subsurface geology = Higher-resolution seismic images Penetration into deeper subsurface = Increased low frequency bandwidth Better constrained inversion algorithms = More accurate estimates of reservoir properties Filtering effect of subsurface on high frequencies = Absorption and scattering

Typical low-frequency limit for conventional seismic data is around 10 Hz. = Reliance on well data for constructing low-frequency model Challenges posed by sidelobes in wavelet = Interference with primary reflections Geostatistical approaches in inversion studies = Subjective despite integration of geological information Ability to fill low-frequency gap with broadband seismic data = Addresses constraints in seismic acquisition feasibly