Adding Value to Oilfield Waste

Abstract: Brine co-produced with oil and gas has no inherent value, but efforts by government and academic groups to purify it could pay off—and soon.

Analysis: By far, the most vexing operating cost shouldered by oil and gas producers is co-production and disposal of water from hundreds of thousands of wells around the world.

Almost every well completed for oil and/or gas produces at least small quantities of water. In some areas, it starts and builds from the very beginning of hydrocarbon production; in others, it happens when hydrocarbon flow begins falling off. Even in the industry's "newest" hydrocarbon production segment—the extraction of methane from coal seams—operators must first produce high volumes of water from wells even before they give up their gas.

In the industry's early days, companies disposed of "produced water," as it's called, by dumping it into streams and rivers, even into dry washes and holding ponds. It's still disposed of overboard on offshore production facilities, after some treatment to remove impurities added by drilling and corrosion protection fluids.

Back on land, when the environmental damage caused by such disposal methods eventually was revealed, companies were obliged to design ways either to re-inject the water harmlessly into brine aquifers downhole or, in the case of oil, reintroduce the water into the producing formations via injection wells to improve and extend oil recovery— until the water once again reaches the producing wells. In most cases, such "waterflooded" fields continue to produce until the cost of water handling exceeds the economic limit, or until some other form of improved recovery technology is introduced. The produced water problem persists, however, since the quantity is most often larger than that required for secondary recovery operations.

In other geographical areas, where reinjection is geologically impractical or simply too expensive, producers pay to have the water hauled or piped to where reinjection can be accomplished.

So, it's plain that in the U.S. and Canada alone, produced water disposal represents an annual outlay that, when combined, spirals into many hundreds of millions of dollars.

Ironically, this abundant oversupply of produced brine—which is flat worthless as such since it contains high doses of naturally occurring dissolved salts, hydrocarbons, trace metals, and other substances—coexists with a much larger problem that's beginning to plague the entire world: The acute shortage of fresh water.

The reasons for the growing scarcity of fresh, drinkable water are many: Global warming, world population expansion, industrial growth—take your pick. The fact is that potable water already has become an expensive commodity. One need only buy a bottle of Ozarka or Perrier at a convenience store to prove it. On a per-gallon basis, it's even more expensive than gasoline, at least in the U.S. And it won't be long before water usage bills in this country, particularly in parched areas, will begin to take on new significance in terms of size.

Desalination? Sure. Man has been trying to make seawater potable for centuries, and with some success. But only on a smallish scale. To desalinate ocean water cost-effectively in worthwhile quantities has always been an elusive goal, even though there are signs that new filtering methods and materials may help provide an answer soon, at least for severely drought-pillaged areas reasonably near the seacoast. In any case, every living creature on earth would benefit from cheaply desalinated seawater, particularly if the other constituents also could be removed. But don't hold your breath. Most experts believe agree that reaching such a point could take pretty near the rest of this century.

But there is some hope for purifying produced oilfield water. Compared with seawater desalination, it's a drop in the bucket, but it could prove tremendously important, particularly if it were purified for use near the oilfields it was extracted from. So, let's examine the industry's produced water problem in terms of making it useful, at the very least as an aid to agriculture and perhaps even further, as a new source of drinking water. Because the demand, if would seem, is growing.

The U.S. government, including units of both the Energy and Interior departments, has promoted several initiatives to this end recently, and a number of independent and allied studies are ongoing under the auspices of both national and university laboratories, with some participation by industry.

Late last month, a team of Texas A&M University (TAMU) scientists announced that a process they're testing, which appears to recover fresh water from produced brine, could have near-future applications that range from crop irrigation to meeting emergency drinking water needs.

During the past two years, TAMU researchers have tested methods for removing salt and other substances from produced water at a cost much lower than previous ones. The most promising method, it appears, is nanofiltration and reverse osmosis.

Reverse osmosis involves applying pressure to brine to force it through special filter membranes. Generally, the pure water passes through these membranes, which were developed relatively recently, while the remaining water with high salt concentrations is left behind. Additionally, activated carbon filters absorb low-molecular-weight organics and reduce the amount of chlorine and other chemicals, while depth cartridge filters made of various materials, including cotton, cellulose, synthetic yarns, or micro fibers like polypropylene, handle the remaining impurities and fines. In the past, such thorough filtration was very expensive and involved large arrays of equipment with huge "footprints."

The TAMU research is being funded by federal and state grants, along with some contributions from private industry, including oil companies. The program is aimed at initiating treatment and reuse of oilfield brines in two regions—Texas, Oklahoma, and New Mexico; and New York, West Virginia, and Pennsylvania. The project is valued at something like $1 million.

David Burnett, TAMU petroleum engineering professor and director of technology at the Global Petroleum Research Institute there, said recently that the program's objectives are to design and test portable treatment units for oilfield operations, to measure and monitor the environmental impact of the treated water, to study the uses of oilfield brine, and to promote the technology to broader markets.

The portability factor is crucial, since in order to make produced water a resource, rather than accepting it as an inevitable environmental or disposal problem, such a conversion system must be applicable to water from individual wells, as well as from whole fields.

Burnett told United Press International that the recovered water has obvious applications such as for irrigation, rangeland restoration, and wildlife habitat enhancement. But there are applications for humans, as well, although currently they are more limited due mainly to the need for more involved, higher-cost treatment. Additionally, the water must have nearby demand, since moving it over long distances would add to costs.

Nevertheless, the TAMU work and other such initiatives are heading in the right direction. Producing companies, however, have to be convinced that value can be added to oil and gas production via produced water purification.

"Ultimately, we've got to show that the water we are creating has some value," Burnett told UPI. "If you're Chevron Texaco in West Texas, you can't get a dime for that water. You can't sell it. So, it's very difficult to convince them to spend an extra $100,000 a year to make fresh water when it's coming out of their operating budget. What we're trying to do is to come up with a use for that water that represents a value to the state, to the citizens."

Currently, West Texas agriculture is rather limited. There is significant dry-land cotton production, which can be conducted with light irrigation using water from fresh water aquifers. But that just about does it, other than the need for water to help keep livestock alive. Nonetheless, if farmers and ranchers could use purified produced water from nearby oil and gas fields, and obtain it at prices below those paid for fresh water, it could stimulate expansion of cotton production, as well as introduction of new crops in that arid part of the country.

The same results would be possible in other arid sections of the country, including the plains and Rocky Mountain area, where fresh water use has always been a bone of contention between agricultural interests and both the mining and petroleum industries.

Burnett said treated produced water already could be used during emergencies in small towns affected by the drought conditions that have plagued the West Texas area for the past few years. The cost is competitive with emergency delivery of fresh water, he said, which normally involves the use of tank trucks.

And, of course, the northeastern U.S. also has undergone a number of droughts during the last decade, even though the oilfields in Ohio, Pennsylvania, New York, and other area states have been producing vast quantities of salt water for more than a century. What's more, produced water disposal there usually involves some treatment before it is emptied into the Atlantic Ocean, or transport to other states for injection into benign subsurface formations.

All this is to say that while it would be difficult to pinpoint the amount of money being spent currently on turning produced water into useful fresh water, it's probably not anywhere near enough. And while oil and gas producers no doubt are working on ways to add value to the water produced from their wells they, too, probably aren't giving the process its full due.

It's safe to observe, then, that perhaps the petroleum industry should think about putting more serious emphasis on efforts to make produced water useful. Contributing more money and resources to current efforts by universities and research groups, at least, might help produce results sooner.

Because the possibility of earning revenue from its largest and, currently, least valuable byproduct probably will take on much more importance during the next few years.