Borehole imaging, experts say, is among the fastest and most accurate methods for collecting high-resolution subsurface data – and that’s exceptionally meaningful considering the complex reservoirs that operators face on a routine basis.
So why isn’t it a more prominent tool in the geoscientist’s arsenal?
Maybe it’s all a matter of needing – and having – a recipe for success.
While many geoscientists are willing to incorporate borehole image data into their geological model, they may lack the required expertise to adequately acquire, quality control and process the data into interpretable images, according to AAPG member Michael Pöppelreiter, SRM carbonate team leader at the Qatar Shell Research and Technical Center in Doha.
In other words, there has been no “cookbook” to walk these folks through the important borehole imaging process.
That changed with the recent debut of AAPG Memoir 92: Dipmeter and Borehole Image Log Technology.
The tome, which was three years in the making, was co-edited by Pöppelreiter, AAPG member Carmen García-Carballido (formerly with Shell, now with EnQuest in Aberdeen, Scotland) and Martin Kraaijveld (with Shell Expo Lowestoft, Rijswijk, Netherlands).
“The idea of assembling a borehole image ‘cookbook’ arose from the members of Shell’s borehole imaging team made up of petrophysicists, geologists and data managers,” Pöppelreiter noted.
“The ‘cookbook’ was actively used within Shell,” he said, “and we thought that an ‘upgrade’ into an AAPG Memoir would be beneficial for the worldwide community.
“Some of the experts who participated in Memoir 92 represented service companies and universities,” he added. “The community of borehole image specialists is small, so we had to rely on a select group of authors to contribute to the memoir.”
In all, 19 lead authors contributed, along with co-authors and others.
“The volume provides geoscientists with a practical guide for borehole image log applications along the E&P life cycle, from exploration to field abandonment,” he continued. “This includes planning logging runs, data acquisition, quality control, processing and on to interpretation and application in subsurface models.
“The borehole image logs have evolved from standalone niche applications to a key component of subsurface models used for key decision making,” he emphasized.
Reservoir Modeling Boon
Various borehole imaging tools have been developed during the last five years, but the recent revolution in borehole imaging stems from advances in 3-D modeling software. Modern software enables full integration of image log data in the subsurface model.
Associated interpretation workflows offer the advanced details needed to make operational decisions and enhance the predictability of subsurface models.
The single most important application of borehole image logs is reservoir modeling, especially fractured reservoirs – think shales, for instance.
“It’s the only device that can deliver three dimensional data on fractures, their distribution and nature,” Pöppelreiter noted. “Other applications can detect them, but it is difficult to make a meaningful description of a fractured reservoir without borehole image logs.”
Other than 3-D modeling software, another recent key development has been borehole imaging while drilling, using LWD tools. This provides real time information.
Your Own Back Yard
Want in on a secret?
There’s no need to spend millions of dollars to acquire the data needed for these invaluable subsurface reservoir models – you likely already have them.
“For the specialist in an oil company, the first place to look for such data might be to go to their own tape archives or their own digital data bases,” Pöppelreiter said. “There is so much data in their data bases that can be reprocessed and incorporated into the subsurface models, especially in more mature basins like the U.S. Permian Basin or the UK North Sea, for example.
“Many of these data have been underutilized in the past,” he said. “Now we have the software and a big step forward with reservoir modeling, which enables us to use what we already have.”
If you’re into the unconventional action, pay attention.
“Borehole image data are paramount to unlocking unconventional plays, such as shale gas and coalbed methane,” Pöppelreiter remarked.
He emphasized a couple of the salient aspects of Memoir 92:
♦ It illustrates the value of integrating high resolution dipmeter and borehole image data with seismic, well log and geological knowledge – “in order to construct integrated subsurface models,” he said.
♦ It provides the fundamentals of the technology for novice and specialist geoscientists and petroleum engineers alike.
♦ It introduces state-of-the-art applications.