The modeling and analysis of well log and physical properties data is a fundamental part of the exploration and production process. The physical properties of the subsurface must be well understood for the robust interpretation of seismic data, and for the construction and integration of models upon which complex analysis if based. Fusion offers a comprehensive suite of physical properties modeling and analysis including:

 

Physical Properties Analysis

 

Rock Physics plays a fundamental role in all exploration and production analysis because physical properties data form the basis for interpreting seismic data. Fusion offers the services of some of the world´s top experts in rock physics and physical properties analysis to solve our client´s most difficult challenges. These experts analyze the client´s well log data and use this information to perform physical properties feasibility studies for the area of interest that can be used in all aspects of geophysical work. This physical properties framework is used to drive forward and inverse modeling, to design new seismic acquisition programs, to test processing streams, to assess the feasibility of using certain geophysical tools, and ultimately to improve our understanding of the subsurface.


Calibration of Vp/Vs ratio as a function of effective stress for clean sands.

 

Well Log Analysis

 

Robust well log analysis is essential to most geophysical work. Well logs are the only near-field remote sensing of the formation that is available to the geophysicist. Fusion offers the services of several senior experts in petrophysics in support of our other geophysical services. We can provide our clients with everything from basic log analysis to advanced interpretation of shear-wave logs, formation micro-imager data and anisotropy analysis. These analyses are designed to provide our clients with the highest quality ground truth available from their investment in wire-line data.


 

Well log analysis is a critical part of any integrated project.Fusion provides our clients with detailed QC plots for all petrophysical analysis performed on your well data.

 

Rock Property Modeling

 

Following a robust well log analysis and construction of physical properties relationships for an area, the next step is to build rock properties models that honor the geological setting and stratigraphic patterns and can provide insight into both the post-stack seismic response of the rocks. Fusion offers the expertise of some of the world´s top experts in this field, and we support them with state-of-the-art tools for modeling. A typical rock properties modeling exercise will include the construction of multiple models for the post-stack response of the subsurface. These models are then compared to the actual seismic responses to assess the quality of the match between the model and actual seismic data. The insights gained from this process are then used in the interpretation of the seismic data.

 


Stacked seismic models showing the response of a sand body to shear
wave propagation as a function of effective stress (after Huffman et al., 2000).

 

 

 
 


 

Example of Our Patchy Segregation Model and The Improvement
Achieved Compared To The Patchy Saturation Model From The Literature.

 

AVO Modeling

 

In addition to the construction of stacked seismic models that honor the geological setting and stratigraphic patterns, increased attention is being paid to the response of the pre-stack seismic data, and in particular to the amplitude versus offset response of the data in reservoir intervals. Fusion offers the expertise of some of the world´s top experts in this field, and we support them with state-of-the-art tools for pre-stack and AVO modeling. A typical AVO modeling exercise will include the construction of multi-layer models to develop an understanding of the pre-stack response of the subsurface in the presence of multiple layers that are often below tuning thickness. As with the stacked models, these models are then compared to the actual pre-stack seismic responses to assess the quality of the match between the model and actual seismic data. The insights gained from this process are then used to interpret the seismic data for the presence of specific fluid and lithologic signatures.

 


 
Seismic gather models showing the response of a sand body to
shear wave propagation as a function of effective stress (After Huffman et al, 2000).

 

Fluid Replacement Modeling

 

Fluid substitution is crucial to seismic analysis. Seismic reflection response varies due to many factors such as changes in lithology, matrix composition, layer thickness and depth as well as changes in the fluid from brine to oil to gas. In a true ``bright spot´´ environment the presence of hydrocarbons overwhelms the changes in reflection strength produced by these other parameters. But as targets get more subtle, it becomes increasingly important to understand the nature and magnitude of effects other than a change in pore fluid. Fluid replacement allows us to quantify these changes in reflection response by substituting different fluids while holding all other rock parameters constant. We can alternatively use the same fluid type and vary porosity, clay content, or other parameters. This is particularly import in exploration areas where there are only a small number of wells. Our petrophysical modeling enables a variety of rocks beyond those encountered in the wells to be modeled. We have developed internal tools to perform more precise fluid replacement calculations on a sample by sample basis than are available in most vendor packages. These are particularly important in mixed lithology reservoirs (mixed matrix) or where the fabric varies due to cementation or grain shape changes.

 


Reflectivity Spectra for a modeled reservoir interval in the presence of hydrocarbons (red curve) and the absence of hydrocarbons (blue curve). Note the differences in the spectrum in specific frequency bands.

 

Rock Physics Measurements

 

A critical aspect of many geophysical projects is the development of rock properties models that can be calibrated with laboratory core measurements. Fusion is pleased to offer the services of the Integrated Core Characterization Center (IC3) as part of the service offering to our clients. Fusion has developed a close working relationship with this world-class experimental rock-physics group in the University of Oklahoma including Dr. Carl Sondergeld and Dr. Chandra Rai (web link here). Together, Fusion and IC3 can meet all of our clients needs for integrated core and log analysis studies that are then integrated with physical properties modeling and seismic analysis as part of Fusion´s service to our clients.


Shear wave velocity measurements as a function of effective stress for clean sand packs.

 

Invasion & Dispersion Analysis

 

Fusion has developed methods for handling the myriad problems that exist with sonic and density logs that are so essential to robust integration of logs with seismic data. These methods allow Fusion scientists to perform invasion corrections for velocity and density logs including fluid substitution, velocity dispersion corrections and electron density correction. Lithology, fluid composition, P-wave & S-wave sonic logs and the density log can be used to calibrate parameters for velocity dispersion correction. The method also allows the prediction of P-wave, S-wave velocity logs and density logs where they are missing or to QC measured values. Fusion offers this technology as part of our integrated project services or as a stand-alone service in support of our client's petrophysical needs.

 


 
Raw sonic measurements obtained in hydrocarbon zones are not applicable for amplitude
seismic modeling unless corrected for dispersion and invasion effects (modified after Murphy, 1993).
 

 


 
An example of the effect of performing invasion and dispersion corrections in combination with Gassmann fluid substitution.
The invasion is shown by the purple area in the lithology column on the left. In-situ gas saturation is shown by the red area. The in-situ sonic log (black curve on right panel) is corrected for invasion, dispersion and brine replacement to produce the brine curve (blue curve). Then the brine curve is substituted with gas to produce the fully gas-saturated curve (red curve). Notice the difference between the in-situ curve and the corrected gas curve. These differences are sufficiently large that they will negatively impact the quality of any models that are generated using the uncorrected sonic log. Fusion recommends that all sonic logs be corrected for these effects before any modeling or well-tie work is performed.