TECHFOCUS This section vs/as edited byExecutive Editor Harry Hutchinson

Fluid Handling & Fluid Power

Recycling Water for Hydraulic FracturingBY DAVID GROTTENTHALER

ydraulic fracturinghas unlocked a valu-able energy resource:natural gas in theMarcellus shaleformation of theeastern United Statesand other forma-

tions throughout the country are nowreadily accessible. But the fracturingprocess itself creates environmentalconcerns and production challenges.

One concern is what to do with waterthat flows back out of the formationcontaining down-hole constituents.Treating it for reuse is one option.

Hydraulic fracturing involves inject-ing several million gallons of water deepinto horizontal wells at tremendouspressure, which fractures the shaleand releases gas. As the natural gas isextracted, up to 30 percent of the wateralso returns to the surface.

When it goes into formation,fluid used for hydraulic frac-turing is more than 90 percentwater, almost 9 percent sand,and less than half a percentchemical additives that serve asfriction reducers, scale inhibi-tors, iron controls, and biocides.

The flowback fluid that returnsto the surface contains down-hole constituents that includedissolved solids, hydrocarbons,and heavy metals. These constit-uents i^reclude direct dischargeinto streams because of the hazardto human and environmental health.Untreated flowback water cannot bereused because of high concentrations ofbarium and strontium, and the potentialfor calcite precipitation, which couldinhibit permeability of the formationand proppant pack, the sand that keepsthe fractures in the shale from closing.

To resolve these issues, flowback canbe treated to remove potentially harm-

ful constituents, and chemicals can beintroduced to ensure optimal produc-tion values at the next well site.

Marcellus shale stretches 1,000 milesfrom New York to Virginia and is 300miles across at the widest point.

Experts estimate the Marcellus shalecontains enough recoverable naturalgas to fuel the United States for 20years, which makes production in thisformation one of the best options forcreating domestic economic growthand reducing America's dependence onforeign energy.

The largest formation ofMarcellus shale lies withinPennsylvania. And muchlike the processes of the steeland coal industries—whichare fresh in the minds ofPennsylvanians—drilling inthe Marcellus shale is a risk/reward proposition.

an approach for water managementthat will contribute to the long-termsustainability of natural gas develop-ment in the Marcellus shale.

Two companies, Krofl" Well ServicesInc. and Superior Well Services Inc.,have collaborated to engineer a meth-od to treat flowback water for reusein hydraulic fracturing. The processreduces consumption of fresh waterand addresses the need for disposal offlowback.

The technology was successfullydemonstrated at a number of shale-

Because of elevated levels of dis-solved solids and bromides in flowbackwater and production brines, the Penn-sylvania Department of Environmen-tal Protection has ordered a restrictionon flowback disposal to publicly ownedtreatment works. And the industryrealizes that disposal is not a sustain-able water management strategy.

The challenge for exploration com-panies and municipalities is to adopt

O Lab analysis labovel monitors water usedin fracturing. Bacteria monitoring Irightloptimizes biocide selection and reducesformation fouling.

gas production sites in the Marcellusshale, where treated flowback wasthe source water for the fracturingprocess fluid.

The processing strategy addressesconcerns that any operator will havewhen reusing water: scale, iron deposi-tion, suspended solids, microorgan-isms that could form in the proppantpack, and appropriate pH and otherwater attributes needed to achieveadequate friction reduction.

Various laboratory processes, includ-ing inductive coupled plasma analy-

Continued on page 22

DecemberSOIl MECHANICAL ENGINEERING 21

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Patent Watch: The Deep Roots ofFrackingBYKIRKTESKA

n <it.rMiiij IS cj iiniely topjc. The idea is to fracture therock adjacent to a welt to increase the extraction ofoil and natural gas. Advocates see It as a means forthe U.S. to produce more of its own energy. Critics fearit threatens local water supplies.

It's timely, but not new. Fracking has been with us atleast since the 1860s. Patent No. 59,936 dated Nov. 20,1866, names Edward Roberts as an inventor. The patentstates: "In my improved method of increasing the capac-ity of oil-wells, I fracture the rock containing the oil tosome distance around the wells, thus creating artificialseams, and enabling me to connect the well thereby withseams containing the oil that would not have been oth-erwise reached...." The key to the method was to "sink aflask containing gunpowder, or other powerful explosivematerial or gas, down the well." A column of water abovethe charge directed the explosion downward. Explosivefracking later used nitroglycerin.

Roberts obtained a royalty not only on the procedurebut also on the increased flow of oil—a move that madehim wealthy. Infringers worked at night to escapedetection and came to be called "moonlighters." Thevalidity of Roberts's patent was litigated at least twiceand was upheld.

Today, hydraulic fracturing is the common practice.By some accounts, the Stanolind Oil and Gas Co. intro-duced hydrofracking early in the 20th century.

I'm not sure that's true. Patent No. 199,488, dated Jan.22,1878, is the flrst I could find for using pressurizedwater to fracture the rock. Packing (a bag filled withseed) is disposed partway down a well. Water above thepacking is pumped out and a ram is placed in the well:"The ram is allowed to fall, striking the seed bag first,thus preventing the water from escaping upward on

account of the great pressure of the ram and causingthe water, under the heavy pressure applied to it, to beforced out through the openings in the well-tubing andthus opening the crevices in the well."

Stanolind's earliest fracking patent—No. 2,667,224,dated June 29,1949—is for a fluid used in hydraulicfracturing. The '224 patent itself admits that varioushydraulic fracturing techniques and fluids precedeStanolind's invention.

Modern fracking techniques include a "proppant,"which must be strong enough to keep the fissures openand also allow the gas or oil to flow. Sand was the prop-pant of choice through the 1950s. Union Oil Co.'s patentofthat era. No. 2,774,431, describes solids that are car-ried by the penetrating fluid and left behind to keep thefissures open. "Ottawa silica sand of about 20-30 meshparticle size is most widely used," the patent reads.

Patents for proppant materials include Nos. 3,399,727(ceramics), 4,068,718 (sintered bauxite), and 3,245,866(vitreous spheres of slag).

But how do you know the process worked? In general,once a crack forms, the pressure of the "frack pump"drops. But there are more sophisticated techniquesfor mapping the fractures to predict yield: ultrasonicsystems, seeding the proppant with radioactive tracersand using gamma ray technology, and using seismichydrophone arrays. Columbia University has a patent.No. 4,832,121, which provides a good overview of thedifferent mapping and monitoring techniques.

Kirk Teska is the author of Patent Project Management(ASME Press) and Patent Savvy for Managers (Nolo), is anadjunct law professor at Suffolk University Law School, andis the managing partner of landiorio Teska & Coleman, anintellectual property law firm in Waltham, Mass.

Recycling Water for Hydraulic FracturingContinued from page 21sis, and spectrophotometric and wetanalytical titration testing, identify thecomposition of process water beforehydro fracturing. A battery of tests pro-vides data for osmotic pressure, chemi-cal oxygen demand, and microbiologicalconcentrations. Analysis at this stageprovides scaling index calculations andfrac fluid design recommendations.

Flowback water samples are col-lected every 500 to 1,000 barrels afterfracturing. These analyses are vital for

anticipating the geochemical impactthroughout the reservoir. Sequentialanalyses provide the basis for flowbackwater reuse strategies, water remedia-tion recommendations, and optimiza-tion in frac fluid design.

A frac fluid calculator incorporatesthe pre-fracturing water analysis andhistoric flowback results from a par-ticular area and provides recommen-dations for component dosages basedon geographic location.

Analysis of fluid design and sequen-

tial flowback data are evaluated usingsophisticated software unique todownhole applications. Assessments,accompanied by 3-D images, confirmthe potential for scale and irondeposition in the proppant pack and inthe formation.

Optimized scale and iron controlchemistry and feed rates are thenapplied for a residue-free formation andimproved well production.

Downhole performance is determinedby advanced friction reduction loops

Continued on page 24

22 MECHANICAL ENGINEERING I December 2011

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Recycling Water for Hydraulic FracturingContinued from page 22to optimize frac water design and todetermine the impact of various waterconditions and fiuid components onperformance. This mode of testingcan screen environmentally respon-sible constituent alternatives that willenhance fiuid performance to developimproved products.

Conducting thermal stability testingon frac fiuid programs allows for maxi-mum performance in cold-weatherapplications or at high-temperature,bottom-hole conditions. These evalua-tions are intended to provide optimizedfluid design, proper product pourpoints and fluid properties, and reliableperformance of frac water under any

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seasonal condition.Adenosine triphosphate testing is

performed to give a rapid analysis formicrobiological concentrations in awater sample.

More extensive testing is then donefor sulfate reducing bacteria, acid-producing bacteria, and total aerobicbacteria counts, to determine the cor-rect microbiocides and application dos-age for frac water. Biocide eflicacy anddeoxyribonucleic acid studies provideadditional insight for biocide selectionand performance assessment.

When put on production, selectedwells were projected to produce athigher rates than traditional wellsusing only fresh water for the fracturingprocess.

With treatment technologies that aresafe, inexpensive, and effective, thosewho profit from natural gas can recon-cile production with the needs of thosewho live among the Marcellus shale.Ultimately, this verifiable approachmakes good business sense, and pro-tects the environment at the same time.

David Grottenthaler is general manager

ofKroff Well Services Inc.

Free TrainingFor Leak-Detection

manufacturer of leak-detectionquipment is offering training ses-ons to engineers at no charge.The Houston-based company, Uson

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Uson, a part of Roper Industries, offersproducts designed to test the seal integ-rity of products ranging from medicaldevices to automotive components.

Rudolph Fuentes, a leak-test specialistin the sales department at Uson, saidthe sessions are open to anyone, butare attended generally by employeesof customers. More information aboutthe training sessions is available on themanufacturer's Web site at http://www.uson.com/Support/Training/.

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