Reservoir Characterization with the Application of Seismic inversion Rockphysics & PetrophysicsBy Rajdeep Buragohain, M.Tech(Exploration Geophysics)

• All the pertinent information that is required to describe a reservoir in terms of its ability to store and produce hydrocarbons.

• The entails knowing the complete reservoir architecture including the

1. Internal and external geometry, 2. Its model with distribution of reservoir properties (static such as porosity, permeability, heterogeneity, net pay thickness, etc.), 3. Understanding the fluid flow within the reservoir (dynamic).

Reservoir Characterization

Reservoir Characterization• Such information helps to 1. improve production rates, 2. rejuvenate oil fields, 3. predict future reservoir performance, 4. minimizes costly expenditure, 5. help managements of oil companies to draw up accurate financial models.

Reservoir CharacterizationDevelopment in Reservoir characterization can be listed as follow:• Innovative visualization packages for interactive interpretation

workstations and visionariums.• The idea of integration of different types of data got firmly

rooted in oil and gas companies in form of asset teams.• Ever since 3D seismic survey became routine in oil and gas

companies in the early 1990s, there have been significant advancement in data acquisition and processing techniques that have led to more accurate imaging of reservoirs and their internal architecture.

Seismic Inversion

• Seismic inversion, in Geophysics (primarily Oil and Gas exploration/development), is the process of transforming seismic reflection data into a quantitative rock-property description of a reservoir.

• The aim of inversion is to improve the interpretability of seismic data. Through wavelet removal and the integration of a low frequency model, seismic inversion produces layer based rock physics properties and thereby helps reveal the underlying geology.

Seismic Inversion

• Seismic inversion may be pre-or post-stack, deterministic, random or geostatistical, and typically includes other reservoir measurements such as well logs and cores.

Petrophysics (Seismic Petrophysics)

• Seismic petrophysics is a term used to describe the conversion of seismic data into meaningful petrophysical or reservoir description information, such as porosity, lithology, or fluid content of the reservoir.

• More quantitative nowadays with advancement in seismic API technology.

Petrophysics

• Calibrating this work to well log - ground truth - can convert the seismic attributes into useful reservoir exploration and development tools. Since there are an infinity of possible inversions, it is pretty important to find the one that most closely matched the final edited logs or the computed results from those logs.

Rock Physics

• Rock Physics address the relationship between measurement of elastic parameters made from surface, well, and lab equipment; and intrinsic properties of rocks, such as mineralogy, porosity, and pore shapes; pore fluids; pore pressures; permeability; viscosity; stresses; and overall architecture such as laminations and fractures.

• Optimize all imaging and characterization solutions based on elastic data.

Rock Physics• An important goal of rock physics is to help us

understanding the physical properties of the reservoir. Usually, at the location of a drilled well, we have measurements that gives us a good idea of the elastic and physical properties of subsurface (Velocity, density, lithology, porosity, confining stress, pore pressure, saturation, fracturing, etc.).

Rock Physics• Rock physics helps us to link these properties to the

seismic data. Rock physics help us to link these properties to the seismic data and infer the variation of reservoir properties in a lateral and vertical sense. Rock physics today from an important component of most reservoir characterization studies.

Why we do Seismic Inversion?• Using amplitude data to estimate rock properties

between wells.• Qualitative Interpretation: Inversion improves the

quality and resolution of the image.• Quantitative Interpretation: Calibration to well

control allows accurate mapping of log characteristics into the inverted seismic data.

Seismic Inversion

Benefits Of Inverted Acoustic Impedance• Compares directly wells.• Easier to interpret horizons, faults, stratigraphic units.• Inversion process attenuates wavelet effects, reduces

side lobes and tuning effects.• Possibility of extending beyond the seismic band.

Seismic Inversion workflow

Inversion

Seismic Data

Wavelet Estimation

Well Seismic TieWell

Data

Low Frequency

ModelHorizon

VolumetricEstimation

Interpretation

• P-impedance identifies the Reservoir 1. P-impedance is often directly related to reservoir property. 2. Establish relationship at wells.• Identify the Reservoir Extent.• Quantify the Reservoir.

Product A• Feature 1• Feature 2• Feature 3

Product B• Feature 1• Feature 2• Feature 3

Petrophysics