The technological focus of geoscientific interpretation has always shifted with the exploration and production industry’s challenges and opportunities. At the start of the millennium,

Figure 1. RokDoc 2-D Modeling Launcher. RokDoc is launched from inside Petrel so the user only sees the RokDoc functionality he or she wants to use and does not need to launch RokDoc as a separate application. (All figures courtesy of Ikon Science)
visualization of large 3-D seismic data volumes set the pace, and recently the industry has seen a concentration on increasing integration of data into geocellular models to facilitate asset-focused working. The current challenges of high-cost drilling, deep water and increasingly subtle traps have shifted the game once again. Now the main requirement is to get the interpretation right. And with wells costing US $50 million to $100 million, the industry has all the incentive it needs — even with oil prices at $60/bbl.

But what do we mean by “getting the interpretation right?” Obviously it depends on our objectives, but a typical prospect requires not just prediction of “economic” rock and fluid properties but also accurate well planning and pressure prediction. The main new enabling technology for this shift to quantitative use of seismic and other geophysical technologies is rock physics, which helps to make sense of the modern “prospecting mix” of multidimensional seismic datasets (4-C, 4-D, anisotropy), well logs and electromagnetic methods.

Figure 2. In the example, the user needs to validate the choice of the top reservoir pick using rock physics. A single button click launches the RokDoc 2-D modeling utility, which automatically loads the selected portion of seismic, the well data and the interpreted horizons from Petrel.
In the past 2 to 3 years, rock physics has evolved from use almost exclusively by specialist groups of geophysicists based in company headquarters into the mainstream interpretation and asset communities. It has become a vital part of the exploration and development workflow in both exploration risk analysis and reservoir characterization.

This change in work practice is in no small measure due to the requirement for majors and independents to replace reserves and for national oil companies to optimize their key assets. All agree that most of the “easy” oil has been found; after 25 years of good wins through 3-D seismic, the days of simply picking and drilling bumps are over. Companies are now forced to investigate more subtle and difficult prospects.

Each change in methodology requires a new technology or improved technology implementation, and Ikon Science has seized on this need by bringing rock physics to the wider community. With more than 50 oil companies — including all the super majors — using the company’s rock physics and seismic modeling software package, RokDoc, the uptake of this technology has been dramatic.

Despite this success, the real challenge remains to bring rock physics to the entire interpretation community, such that rock physics-led workflows in seismic interpretation and reservoir characterization become an integral part of the interpreter’s daily work routine. To that end, Ikon Science and BG set up a joint project with the assistance of Schlumberger Information Solutions (SIS) to bring together RokDoc and Petrel, using the Ocean framework.

Figure 3. Shown at the left is the original seismic data. On the right is seismic created from the RokDoc model.
The initial design criteria for the project were to ensure the relevant RokDoc functionality was easy for Petrel users to learn and to automate as much of the integration process as possible. This has been accomplished by launching the application from inside Petrel so users only see the RokDoc functionality they want to use and do not need to launch RokDoc as a separate application. Access is via the Petrel user interface.

In the example shown in Figure 1, the user needs to validate the choice of the top reservoir pick using rock physics. A single button click launches the RokDoc 2-D modeling utility, which automatically loads the selected portion of seismic, the well data and the interpreted horizons from Petrel.

Figure 2 shows the 2-D model created from Petrel. Each stratigraphic body has been automatically populated with the well information, so it is a simple matter to convolve this with a wavelet, which can be extracted directly from the 3-D volume using the optimized extraction routine designed by Roy White and built into RokDoc.

Figure 4. Modeling suggests a phase change in the middle of the section due to the presence of hydrocarbons.
The synthetic seismic is then compared with the seismic volume, and it can clearly be seen that there is a mismatch at top reservoir between the data modeled from the well information and the real seismic data. What’s going on? It is very easy and fast to test different scenarios such as different fluid substitutions, porosity, anisotropy, pressure changes, etc., to see how this affects the seismic response, until we get a match with the recorded seismic. In this case the hypothesis was resolved. Modeling suggests there is a phase change in the middle of the section due to the presence of hydrocarbons.

It is important to stress that all the above work has been carried out inside Petrel, so once the interpreter has validated the interpretation, he or she can immediately return to the Petrel session and include any logs, horizons, etc., that have been created in this session. But more importantly interpreters can test insight and share this with their team.
The combination of RokDoc and Petrel allows users to build a combined and validated geological property model in Petrel by checking it against the observed geophysical property model in RokDoc. This delivers a clear speed and quality win — the interpreter can work on a geological model and a geophysical model at the same time. This allows for interactive interpretation: As the user picks horizons in Petrel, RokDoc listens, updates its events and recalculates the synthetic. Ikon Science calls this new capability Modeling While Picking (MWP).

In this way the interpreter can instantly use RokDoc’s technology to investigate change, for example, the impact of varying porosity, tuning, lithology, fluids or pressures. Multiple volumes of seismic can be used interactively with fluid simulation information to explore and give insight into how seismic reservoir properties vary with time and space, for use in real-time field simulations, for example.

The successful first phase of the RokDoc-Petrel Project is nearing completion, and a number of major companies are already showing great interest in building on the initial
concept vision from BG and Ikon and taking the “Modeling while Picking” project to the next stage.

The project provides a bridge between the seismic quantitative interpretation community, who are mostly exploration-focused, and the Petrel world community, who are mostly geological and production asset-focused, with mutual benefits.

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