Pre-Inversion & Inversion
The ground truth is revealed when petrophysical details are tied to seismic data. Sonic and density logs are used to build synthetic seismograms and to tie the logs to the seismic. Various methods for extracting the wavelet are available, including a proprietary patented approach to extract a wavelet in deviated wells. Various spectral imaging attributes are computed at the wells and used to find possible correlations with rock and fluid properties along the wellbore.
SIGMA³ also provides many user-friendly and intuitive tools to transform the interpreted horizons and faults into a consistent structural framework that is geologically meaningful. Using the interpreted or imported faults and horizons, the structural framework is built and adjusted in 3D using an intuitive and rapid process that simultaneously handles 100 or more faults (normal, reverse, thrust, and listric faults) and as many horizons as required. Once a sealed faulted framework is built, a geocellular grid composed of rectangular cells, vertical columns, and multiple zones with different layering schemes could be generated and used for subsequent geophysical and geologic modeling.
Forward and inverse modeling uses models to extract the information contained in the seismic data and predict from the physical properties what the seismic data should look like. Seismic inversion and modeling provides powerful additional information that can be used to lower your risk in exploration, and to quantify your reserves in production. SIGMA³ inversion and modeling offerings driven by the Fusion Product Family, include:
- Velocity & Modeling
- Tomography & Tomostatics
- Inversion (Pre-Stack/Post-Stack)
- Forward Modeling
Velocity Analysis & Tomography
Quality velocity information is critical to robust imaging, pressure prediction, AVO analysis and time-to-depth conversion. SIGMA³ leverage proprietary methods that allow our scientists to determine velocities in a robust and very flexible way. The geophysicist can use a variety of velocity and geologic information separately or in combination to derive velocities. These methods provide a flexible and efficient platform for predicting velocities that can be used to improve the quality of subsequent interpretation and analysis.
The REVEL™ process allows us to perform an initial velocity analysis on a typical spacing of 250 to 500 meters, and then estimate velocities at any finer spacing down to the individual CDP. The REVEL process provides high-resolution velocities for geopressure prediction, AVO analysis and post-stack and pre-stack inversion.
There are several flavors of post-stack inversion of seismic data for acoustic impedance that have become standard technology. Post-stack inversion is routinely used by interpreters to better map extent and thickness of reservoirs and to give a qualitative estimate of reservoir quality. Pre-stack inversion enables us to produce two output volumes including AI and poissons ratio. This information can be parameterized in many ways and it is important to match these displays with the specific exploration challenge. If well data are available, the results of the pre-stack inversion can be calibrated with lithology and a cross-plot of lithology and fluid effects can be produced. In some cases, this method can also be applied for high-resolution geopressure prediction.
SIGMA³ modeling capabilities include conventional stratigraphic and structural modeling, as well as advanced ray-trace modeling techniques, pre-stack wave-equation modeling and borehole seismic modeling. We integrate these modeling techniques with our expertise in rock properties analysis to provide robust well-based predictions and calibrations to seismic data. These predictions and calibrations are an essential component of quantitative seismic studies, and provide the interpreter with ground truth based on well logs that is critical to the evaluation of prospective reservoirs, reservoir delineation, and reservoir simulation.
Clients leveraging CRYSTAL ave gained a competitive advantage by using high-resolution inversion which allows the user to attain a resolution of 1/2 ms (1-3 meters in most reservoirs). This resolution is attained through a careful and unique mix of seismic and well data. Although most of the geophysicists do not believe that such results are possible, these dramatic success stories are happening everyday, and clients have made this inversion technology the standard in their companies.
Clients benefit from various pre- and post-stack inversions, both deterministic and stochastic. These inversion algorithms include the simple methods such as colored inversion and sparse spike as well as our proprietary high resolution deterministic and stochastic methods. The higher resolution is provided by the ability to simulate multiple realizations of the broadband seismic attribute. The algorithm is not calculating in a deterministic manner the values at every 0.5 ms but simply simulating all the possible ranges thus taking into account the uncertainties in the inversion process.
Inversions are able to account for any complex structural framework and are at least one order of magnitude faster than those currently available in the E&P industry. All the inversions algorithms are available in the CRYSTAL new generation geomodeling software.
Pre-Stack Seismic Inversion
Prism CRYSTAL uses multiple seismic offsets and log data to perform a high resolution deterministic and/or a stochastic pre-stack inversion that leads to the extraction of Vp, Vs, Density and subsequent elastic properties that provide detailed imaging of various rock properties, including lithology, facies, and fluid properties.
Post Stack Seismic Inversion
Prism CRYSTAL uses the post stack seismic and log data in several deterministic and/or stochastic high resolution inversion algorithms to provide seismic impedance. All the algorithms are one to two order of magnitude faster than anything available in the E&P industry, and are able to take into account any complex structural framework. The high resolution inversion algorithms provide impedance at a resolution of 0.5ms.