Well, a dime just ain't what it used to be, but if it's dollars you're looking for to finance an acquisition, take heed -- the fund-raising tool du jour is a 3-D geologic model.
Rare is the financier who can look at a 2-D map and visualize the pertinent data in three dimensions. But when a 3-D model is available, the folks who deal with capital can better understand complex geological concepts by actually seeing fault closure, stratigraphic traps and such, thereby leaving less to the imagination.
"To buy a property, you must illustrate how you can get more production from the field than the former owner," said Verna Ray, marketing director at Dynamic Graphics. "If you can show why you can operate more efficiently and effectively and that you know where to drill directional wells, to tag multiple pays per well, to get more recovery per dollars spent on the field, it's easier to borrow money."
The models can be invaluable for resource auditing, according to Ron Day, exploitation geologist for the Trinidad East business unit at BP Amoco.
"In our business, external audits are one of the keys to success. When I have to lock up one of those 30-year gas marketing contracts, I have to go to the bank and prove I have three TCF of gas out here that will develop in this time frame and that will go to this market."
Day is a strong proponent of 3-D geologic modeling in the Trinidad gas fields where he focuses his expertise.
The hydrocarbons extend from the surface down to 10,000 feet or more in these fields, but the downside is the presence of a lot of shallow gas that is not vertically stacked and that has very low velocities.
It's complex in a geospatial sense, Day says, so they have to deal with really complex velocity fields.
"One of the main things we use EarthVision® software for is to build robust velocity models," he said, "and this adds a lot of resources. We added a TCF of gas just by doing the velocity model."
The tool is also being used there for intermediate surface mapping to rapidly represent the subsurface and for development and planning.
"With complicated structures like this, it's difficult to know where to put the platforms and where to drill the wells, so we use the models to ID drilling targets in each compartment and assign a resource value to each well," Day continued.
"Knowing where the hydrocarbons are geospatially and knowing the deliverability for each of those compartments is the front end for platform selection and, most importantly, optimization of the development plan."
A Whole New World
Although 3-D data have been used routinely in E&P for a number of years, they have been used for display in the 2-D sense, which precludes visualizing a field in true 3-D representation, according to Karen Hoffman, geological consultant at Dynamic Graphics.
"Using 3-D geologic models, which are a relatively new phenomenon, we're moving the 3-D data into a 3-D world where we can all communicate via a shared earth model," she said.
Indeed, interdisciplinary input and usage by geologists, geophysicists and engineers is a key feature of these models.
For example, the petrophysicist typically will hand off completed work to the geologist, and there will be no more interaction. It then becomes difficult to detect any errors, because everything gets watered down as the interpretation process continues.
Interdisciplinary data are required to build the 3-D geologic model, which forces the team concept.
Because it is a visual representation of the subsurface, the model becomes the focal point for all discussion of how to exploit an asset. For instance, if more gas deliverability is needed, the company engineer, driller, geologist and engineer can sit in front of the model and talk from the same data to build the well path and design the completion.
Seeing Was Believing
An important end result of the modeling exercise at Aera Energy is the impact on engineering, according to Ed Veith, south properties team leader.
"You move away from making blanket assumptions and on to really honoring the reservoir," Veith said, "and it significantly affects the engineering decisions."
The engineering benefits provided by the models are crucial to Aera, where the core focus is on producing and developing principally heavy oil California properties that are undergoing steamflood.
"If you don't take the first leap to build a 3-D model when you go into a big area that's real complex, you're probably going to have a lot of problems optimizing reservoir management," Veith said.
A recent 3-D geologic modeling project using Stratamodel® Geocellular Modeling (SGM) software was conducted with a two-fold purpose, according to Veith.
"It was first used as a descriptive tool for reservoir characterization, volumetrics and calculating pore volumes injected," he said, "but the other reason for building it was to keep using it for pattern management.
"We're now doing 4-D by incorporating new saturation data into the model yearly to get an idea where the steam fronts are."
He noted Area was able to justify the model immediately. They found an additional 10 percent of steam cuts just on the first pass -- and steam is expensive to inject.
"The people we delivered this to said, 'We never would have seen this.'"
Value -- And Caution
The value of these models for secondary recovery is also evident at Plains Resources. The company has acquired a number of older, complex properties over the last several years that have numerous wells, according to geological manager Bud Simmons.
Their goal is to use the models to better understand the reservoirs.
"We want to integrate all reservoir, production and geological data into one database and let the asset teams then use it and the model generated to maximize capital efficiency," Simmons said. "One of the most effective ways we can use it is to understand where the injected water has affected the reservoir or where it hasn't, so we can better design the waterfloods."
He noted they also use the models to efficiently recognize opportunities such as infill drilling targets and recompletions.
Opportunity knocks loudly when you're using up-to-the-minute technology.
"I wouldn't consider evaluating an acquisition without putting known data in to see if it fits, because if I put data in and see some busts, it's like, 'Hey, wait a minute, there's opportunity here,'" said Tim Altum, geological advisor at Devon Energy.
Indeed, when looking at older properties to see if past interpretations are correct, the 3-D geologic model essentially is unforgiving, according to Dynamic Graphics' Hoffman.
"When mapping multiple pay zones with 2-D maps, the data may appear to be justified for each horizon," she noted. "However, the chance of accurately portraying the fault picture this way is slim to none, particularly in the complexly faulted Gulf Coast fields.
"But plug all of the data into a 3-D geologic model," she continued, "and the misidentified or miscorrelated faults will be obvious because the shape of the fault surface itself will be incorrect."
The model drives the interpretation process, creating contour maps, cross sections and the like from a single data source, so the faults will be properly migrated to the next horizon down because they came from the 3-D model.
When editing the data, according to Ray, the geoscientist can phantom in the seismic information and then visualize the seismic data to see if certain points should be discarded and the seismic data reevaluated.
A caveat: bad data in = bad data out. You can't fudge bad data points, which often are simply the result of too much auto-picking.
"Once you've interpreted a field as the geologist does with tops, picks, surfaces and faults with the addition of petrophysical, engineering and geophysical data and you put this into the 3-D model, the data busts show right away," Altum said.
"It's the single, most powerful QC product to quality control your interpretation as you go."
According to Day at BP Amoco, iterations are a key feature of 3-D geologic model-building.
"The way you create a valid representation of the subsurface is directly proportional to the number of times you can iterate that model," he said. "The more cycles, the better the model."
This, in fact, is one of the many aspects of modeling that is spurring the development of increasingly easier-to-use software products so that the "ordinary citizen" can construct 3-D geologic models instead of having to depend on an outside expert.
Outsourcing not only hinders asset team interaction, but something like the need for additional iterations to, say, try out different velocity fields increases the cost when using external expertise.
One solution, like Plains, is to add such an expert to the company staff.
"We hired a manager of 3-D reservoir visualization applications to expedite the model-building process and make it more efficient," Simmons said. "We can do more things internally, and these people can make a big difference in time and cost."
Time-wise, model building might take days to weeks, according to Tim White, director of earth modeling initiatives at Landmark Graphics.
"A lot depends on the level of rigor a company is willing to put into a particular property -- on the characteristics of the reservoir, such as how complex it is, and how much time they are willing to spend compared to traditional 2-D mapping approach," White said.
Once the data are digitized and in the model appropriately, Altum said this is the place for significant time savings versus the 2-D approach to doing business.
"You can play out what-if scenarios over and over and keep entering new data, and the model keeps living on," Altum said. "It's kind of like a stratigraphic spreadsheet, letting you quickly generate volumetrics and maps -- and management loves it."
White cautioned, however, that while most fields warrant this level of study at some point in their lifetime, 3-D geologic model-building could also be misapplied via use on a field that didn't warrant that level of investigation.
"It can be like dropping an atom bomb on a fly in terms of simple structural models that don't need it," said Chip Story, senior explorationist at CAEX.
"But," he added, "many structural situations demand it, and the process was swept under the rug in the past because there was no computerized procedure to do it."
Indeed, there likely are seemingly endless opportunities to apply 3-D geologic modeling technology.
"We've found the biggies," Altum said, "and most of the stuff now is very complex and smaller targets."