'New Paradigm Needed' for De-Risking Unconventionals

“As we are in the forefront of the oil boom associated with unconventional reservoirs, we are on a steep learning curve concerning related high-cost drilling and completion operations and we need to be aware of associated risks and do our best to minimize these risks and financial waste.”

That’s Mamdouh A. Shebl, who has more than 34 years’ experience in unconventional reservoir development, and he has seen the protocols industry professionals take to assess the risks of such wells, both from an industry perspective as senior petrophysicist at Chevron’s MidContinent Business Unit, and from an academic one as petrophysics research professor at Texas A&M University.

And he thinks the industry can do better.

“Traditionally, de-risking,” he said, “as it is applied for conventional reservoirs development, is thought out only when there is a problem, or if a problem is anticipated; and is used … to solve or avoid such problem and improve the outcome.”

That seems intuitive, and for conventionals, it is and has been a sound approach. But Shebl, who has also taught at the University of Wyoming and was an exploration geologist at Conoco-Egypt, said that when it comes to unconventional wells, a new paradigm has to be developed and followed.

Compositional Risk Factors

The difficulties in coming up with de-risking strategies for unconventional reservoirs, though, are systemic.

Image Caption

Well placement considerations, about 450-foot lateral

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“As we are in the forefront of the oil boom associated with unconventional reservoirs, we are on a steep learning curve concerning related high-cost drilling and completion operations and we need to be aware of associated risks and do our best to minimize these risks and financial waste.”

That’s Mamdouh A. Shebl, who has more than 34 years’ experience in unconventional reservoir development, and he has seen the protocols industry professionals take to assess the risks of such wells, both from an industry perspective as senior petrophysicist at Chevron’s MidContinent Business Unit, and from an academic one as petrophysics research professor at Texas A&M University.

And he thinks the industry can do better.

“Traditionally, de-risking,” he said, “as it is applied for conventional reservoirs development, is thought out only when there is a problem, or if a problem is anticipated; and is used … to solve or avoid such problem and improve the outcome.”

That seems intuitive, and for conventionals, it is and has been a sound approach. But Shebl, who has also taught at the University of Wyoming and was an exploration geologist at Conoco-Egypt, said that when it comes to unconventional wells, a new paradigm has to be developed and followed.

Compositional Risk Factors

The difficulties in coming up with de-risking strategies for unconventional reservoirs, though, are systemic.

“From the very beginning to the very end, they are more complex than conventional reservoirs with more risks. We shouldn’t approach this as just steps taken to solve problems when they occur,” he said.

To this end, Shebl said unconventional reservoirs have a heterogeneity, which is made up of the compositional risk factors associated with such plays.

“It is based on the amount, distribution, crystallinity and diagenesis of the various components (silica, carbonate, clay and organic matter), the fabric and texture of the unconventional reservoir, including the amounts, and distribution of various types of matrix and organic porosities and their contribution to fluids flow in these reservoirs,” he explained.

Unlike conventional reservoirs, where petrophysical analysis concentrates on well-by-well formation evaluation, unconventional reservoir petrophysics analysis depends on multi-well analysis. Further, unconventional reservoir petrophysics do not depend only on available wireline data, but also on data from other disciplines, such as mudlogs, routine and special core analyses, static rock mechanics and organic content and maturity.

“The detailed unconventional reservoir’s petrophysical results can contribute to the activities of many disciplines, such as well planning, target selection, drilling, geo-steering, completion, frac’ design and reservoir stimulation,” explained Shebl.

When asked whether conventional and unconventional systems are more prone to risk, hence would benefit more from a comprehensive rethinking of de-risking strategies, Shebl said de-risking conventionals have a century and a half head start.

“Due to vast knowledge that oil industry professionals have accumulated in the past 160 years, they obviously have more experience,” he said.

New Paradigms Needed

That experience, according to Shebl, will not work in the new frontier of unconventionals, in part because the clay amount and organic content of the unconventionals makes them more complex than conventional plays.

“Unconventional petrophysical analysis depends extensively on core data from routine and special core analyses, geochemical analyses, and static rock mechanics,” he said.

This analysis, once completed, can be used to guide geophysical well ties, earth modeling, drilling target selection, frac’ design and selection of frac stages location, and stimulation design.

“It’s something for everyone,” he said.

Shebl will hold a short course at this month’s NAPE Summit in Houston, entitled “De-Risking Unconventional Reservoirs,” in which issues concerning de-risking protocols of unconventional petroleum systems will be discussed, successful multidisciplinary collaboration will be illustrated, and new emerging technologies into de-risking unconventional reservoirs will be introduced.

Some of these new technologies will lessen the risk for unconventionals: digital rock physics, nuclear magnetic resonance, dielectric logging and image logging.

As the drilling and development of unconventional reservoirs is expensive and surrounded by many economical and operational problems, Shebl said the solutions to the special challenges with de-risking unconventionals will come – in fact, can only come – collaboratively, when industry is not “consumed” by its past successes.

“Each new well,” he said, “if more than two or three miles away, should be viewed as a brand new play.”

De-Risking the development of unconventional reservoirs should be a continuous and multidisciplinary (engineered, not geometric; fit-for-purpose, not factory mode) workflow among petrophysicists, geologists, geochemists, geophysicists, earth modeling, and rock mechanics, drilling, completion, and frack engineers, instead of just steps taken to solve problems when they occur.

Shebl said, in addition to a more comprehensive, inter-disciplinary model, the following steps will help mitigate the problems associated with de-risking unconventional play:

  • Identify the anticipated problem(s).
  • Explore all possible solutions.
  • Investigate the applicability of these solutions.
  • Consider which one is the most reasonable solution.
  • Apply the chosen solution to resolve the problem, and
  • Evaluate the success and efficiency of applied solution.

“We must be more alert, more open-minded, more flexible, and think outside the box,” said Shebl.

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