When the International Petroleum Technology Conference comes to Saudi Arabia in February, the technical program will include a significant look at both unconventional oil and gas and conventional tight oil in the Middle East.
Those are two different concepts in the region and the distinctions are important, according to Erdal Ozkan, professor of petroleum engineering at the Colorado School of Mines in Golden, Colo.
The Middle East holds a large conventional tight oil resource, now emerging as a serious focus for development. With so much recent attention devoted to unconventional resources, conventional tight oil could be considered an overlooked sibling.
“There are significant differences of conventional tight oil reservoirs than the typical North American unconventional tight oil plays,” Ozkan noted.
While Middle East conventional tight oil reservoirs have low rock permeability, “(they) are typically fractured carbonates with no organic material, lower initial pressures and higher initial mobile water saturations” than unconventionals, he said.
American versus Middle Eastern Tight Oil Reservoirs
Source rock is associated with unconventional shale oil reservoirs but oil in conventional tight formations is sourced from elsewhere, Ozkan explained.
With conventional tight oil, “reservoir is not the source rock – the oil has migrated in. Originally in these formations there was water, so some of the water remains,” he said.
As a result, conventional tight oil reservoirs require additional up-front effort and expense to develop. There’s generally no quick pay-out available, as companies might have with unconventional plays in the United States, Ozkan said.
“If you have lower initial pressure and more water, then you are basically losing that initial financial advantage,” he noted.
In the United States, the tight Mississippi Lime is one conventional, high-water-cut carbonate play that has responded well to unconventional-resource techniques in the past, but with different development requirements.
This year’s IPTC program includes Ozkan’s presentation, “Numerical Investigation for Developing Conventional Tight-Oil Formations in the Middle East,” prepared with graduate student and co-author Mohammed Althani.
Data-based approaches to development can find challenges in the Middle East, where tight oil reservoir data might not be as abundant, detailed or readily shared.
“For our paper, we had to put together a representative data file using published data and as much information as we could find,” Ozkan explained.
He said the researchers devised “synthetic cases” and simulated production scenarios using computer modeling that incorporated geomechanics.
“Our message is that these will give you initial ideas, but you need to work with the actual data,” Ozkan said.
“We looked at well spacing, and of course how natural fractures and fracture corridors affect production from these formations. How hydraulic fracturing works in these reservoirs is important,” he noted.
“When we look at some of these fractures in unconventional reservoirs, you would like to have more fractures. Fractures are your friends,” Ozkan observed.
It’s a different situation in conventional tight oil formations where, he said, natural fractures “might help you but they can cause extra problems. There are significant well-spacing issues,” he said.
“When you go to conventional tight oil you have existing fractures, but these are open fractures. You would want to intersect those fractures. It definitely affects the design,” he added.
“In these conventional tight oil systems, the oil is still in the matrix, pressure is relatively low and your success depends on how much you can displace the oil,” Ozkan said, and “waterflooding in a fractured formation is an issue. You want to know where the water goes. You want it to go into the matrix.”
In general, tight oil development now utilizes hydraulic fracturing combined with horizontal drilling, which has dominated production from U.S. tight oil formations for more than a decade.
“For conventional tight oil, if it’s not too deep you might consider using verticals,” but horizontal wells likely would prove more practical, although they add to the cost, Ozkan noted.
“One other thing we might mention – in technologies needed for conventional tight oil, you can mix and match” with the U.S. experience in developing unconventionals, he said.
Some development lessons would be applicable to Middle East tight oil while others wouldn’t pertain, given the nature of the region’s tight resources. He noted that drilling and fracturing for unconventional and tight plays in the United States have better logistics, widespread applications and lower cost.
“They are not at that level in the Middle East or the rest of the world,” he observed.
Economic Obstacles toResource Development
Several technical sessions at IPTC will consider the complexities of developing unconventional and tight oil reservoirs in the Middle East and will examine the state-of-the-art in geological and engineering work in unconventionals.
Ozkan said, “There is abundant resource in the tight oil set-up in the Middle East,” with significant conventional tight oil resources in the United Arab Emirates and Saudi Arabia, for example.
“In terms of awareness and development, these tight reservoirs were better known in the Middle East and there have been some efforts to develop them,” he said.
However, “having a large resource is one thing, but having an economic resource is another,” Ozkan noted.
“Economically, the incentives may not currently match up. And additional challenges do occur,” he said.
Ozkan believes a future exists for conventional tight oil development in the Middle East, based on the amount of interest currently shown by companies in the region. There’s a growing body of research related to the issue, but that is no substitute for actual work and experience in the field, he said.
“Having all these books and papers in the library does not guarantee success,” he noted.
A period of lower oil prices led to increased financial caution across the industry and an emphasis on the most predictable production outcomes possible. Operators in the Middle East region have been more attuned to conventional, well-understood reservoirs, and less open to experimentation.
“In the Middle East, if you have safer resources to go for you might be a little more conservative,” Ozkan noted
“You have to understand when the right time comes for what we might call a little new adventure,” he said.
Ozkan observed that geologists understood the abundance of shale resources long ago. The oil and gas industry needed to discover a way to produce that resource economically before unconventionals development took off in a big way.
“We will need a little more time for confidence to develop” in conventional tight oil, he said, adding, “It may take a while to look at multiple approaches and learn from field studies.”
If tight oil does have a bigger future outside of unconventional resources and outside the United States, it will come from the new technologies and techniques beginning to be developed and applied today.
“When they become ripe, these technologies may make conventional tight oil resources economic,” Ozkan said.
The 2022 International Petroleum Technology Conference will be held in Riyadh, Saudi Arabia this month.