The Sleeping Giant Awakens

From the editors of BARNETT: TECHNOLOGY

The ‘Sleeping Giant’ Awakens For more than 20 years, many scoffed at ‘Mitchell’s Folly’ as the intrepid wildcatter doggedly probed the inhospitable shale in the Fort Worth Basin — not anymore. By Dick Ghiselin Contributing Editor

Dawn lights the ailed as the largest unconventional gas play on challenges to be tackled in the Barnett. But no one Barnett, and the Hthe North American continent, the Barnett likes challenges better than the technology providers silence is shattered Shale was the harbinger of untold energy produc- in the service sector. They have applied their con- by dozens of pump tion that has spread across the US and Canada like siderable experience and learnings gained from the engines as they roar wildfire. Names like Horn River, Haynesville, Mar- activities of Mitchell and other early believers to into life, waking the cellus, and Fayetteville were all but unheard of a develop better technology that improves recovery sleeping giant. decade ago until George Mitchell proved the possi- factors, enhances reservoir contact, and reduces well Photo courtesy of bility of producing commercial volumes of natural construction costs. Schlumberger gas from the giant shale that today spans 21 counties of North Texas. Variable reservoirs present With predicted peak production pegged at 8 variable challenges Bcf/d sometime around 2018, there’s still a lot of gas In shale plays, the traditional fracturing technique to be found and produced, and an equal amount of can be characterized as “perforate, pump, and pray.”

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This reasoning seemed logical as many shale for- lenging tight gas shales. “TRA helps to maximize mations and traditional logs in shales lack charac- recovery through expanded knowledge of vertical ter; however, one thing has become evident — not all and lateral reservoir heterogeneity, reservoir quality, shales are created equal, and not all sections of a lat- completion quality, fracture containment, fluid sen- eral can be treated equally. With the massive geo- sitivity, and retention of fracture conductivity. graphical extent of the Barnett Shale, it is not surprising to see differences in reservoir character- Finding the sweet spots is key istics from one part to another and differences in Like most shale play participants, Schlumberger production from one well to another. In fact, it is recognizes that knowledge is power. Finding the also not surprising to learn that different fracturing gas and understanding how to recover it requires an stages in the same well behave differently. Schlum- integrated well evaluation process that draws on berger has developed the tools and expertise to the experience of the company in gas shale devel- understand this variability. opment and its extensive suite of proven tools. The “Schlumberger has a more than 20-year history ECS* Elemental Capture Spectroscopy tool is a geo- of experience in the Barnett, and there has been chemical tool that is the basis for resource evalua- quite an evolution of technology in that time tion. This tool classifies the types of rock in the period,” said Shane Smith, Schlumberger techni- reservoir and quantifies gas in place. The Sonic cal sales manager for the Dallas-Ft. Worth area. Scanner* tool offers a better understanding of the “The first wells were all vertical, but now by far the distribution of stress and stress anisotropy along a majority of wells are horizontal because of the abil- well bore. Lastly, the FMI* Fullbore Formation ity to contact more of the reservoir. To assist with MicroImager device is used to determine the resis- the interpretation of all the data collected in this 20- tivity and clay content along the well bore as well as year span, we opened a Regional Technology Center classify the natural and drilling induced fractures in Dallas in 2007, which focuses specifically on present. These tools are used to characterize the understanding shale gas. localized stress regime (called “states of stress”) that “Completion technology has kept pace with the governs fracture propagation in shales. This infor- evolution to more horizontal completions. There mation can be used to determine the best places to has been a parallel evolution as well in fracture land new laterals, optimize perforation and staging design. We base our designs on data acquisition strategy to contact more reservoir, and avoid poten- and proper use of the data to impact the formation. tial trouble portions of the reservoir that may lead The key to unlocking the full potential of shales is to undesired fracture results. All of these things reservoir characterization and operating efficiency. help create better fracs and better production. Schlumberger has expertise in both.” Following are a few technologies and services Keeping the frac contained that have significantly improved operators’ ability to As explained in SPE Paper 124147, one of the contact more of the right rock. biggest challenges Barnett operators face when expanding their drilling activity to non-core areas is Understanding goes back to ground truth keeping their frac contained. Excessive height Core analysis performed by the Schlumberger geo- growth can introduce inefficiencies, driving up costs technical team at TerraTEK has been fundamental as well as reducing production and recovery. “You to gaining insights into the Barnett Shale. “We have can place and land your well in the sweet spots, but acquired and analyzed thousands of core samples if you don’t have fracture containment, you still using tight rock analysis (TRA) to develop a clearer may have water production issues,” said John understanding of the geology, petrophysics, and Daniels, hydraulic fracture placement optimization geomechanics affecting the reservoir,” said Smith. product champion for Schlumberger. Predicting TRA provides a detailed core measurement of rock fracture containment, therefore, is a must, and the permeability, porosity, and fluid saturation in chal- company has developed a three-step technique

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Modular Dynamic for multistage frac jobs. To prove the point, a Tester (MDT) tool client used this technique to choose a new land- configured for in situ ing point and determine perforations and staging stress testing. Image for a well drilled in an area plagued with fracture courtesy of containment issues and subsequent water pro- Schlumberger duction. StimMAP Live* hydraulic fracture mapping was used to monitor this treatment in real time. Both the microseismic data and production information confirmed that the fracture stayed contained in the Barnett. This level of multi-measurement integration within a 3-D earth model illustrates the opportunity for step changes in shale gas development.

Microseismic to simulation Daniels acknowledged that the Barnett offers lots of stimulation challenges. “Our expertise has been greatly enhanced by our ability to acquire relevant microseismic data and use it to drill and stimulate better wells for our customers,” he said. “The value of having an integrated solution is three-fold. Firstly, microseismic imaging designed to place and orient fracture perforations in has allowed us to optimize our fracture treatments, the best position every time. Key to this claim was literally on-the-fly, based on our real-time interpre- the development of the in situ stress testing tool, tations. With advanced processing algorithms deliv- which is a creative reverse-application of one of the ering results every 15 seconds, we can use this data company’s most reliable services, the MDT* mod- to help us understand when to deploy diverters or ular formation dynamics tester. alter our pumping schedule to achieve the cus- At the core of the technique is the MDT Pump- tomer’s objectives. Secondly, the integration of this Out Module, which is used to initiate a mini-frac data back into an earth model helps us truly under- while acquiring vital pressure measurements and stand the relationship between geomechanical and transmitting them to surface in real time. Here’s geophysical properties of the reservoir and hydraulic how it works: fracture placement. Lastly, the microseismic data The pump-out module is installed between two can be used to simulate production and recovery packer modules creating a very accurate mini-frac from the well using all of the data contained in the tool. The tool is positioned and mini-frac conducted 3-D earth model. At the end of the day, this infor- opposite a zone of interest identified by the ECS, mation improves our ability to manage the asset and Sonic Scanner, and FMI. The stress required to enhance recovery.” break down the formation is measured by the MDT and is used to calibrate the logs’ measurements as Horizontal re-fracs grow in popularity well as core measurements. These calibrated stress Based on information from SPE Paper 119636, measurements can then be fed back into models, Daniels offers the following: “Recently, we’ve seen allowing operators to land their laterals in the right a lot of Barnett Shale production logs that share a place as well as choose where and how to complete common trend. Of the perforation clusters in a their wells for maximum reservoir contact. typical horizontal, less than half are contributing The application of the three-step process takes to production. A few perforation clusters in each the guesswork out of picking perforation zones well deliver a majority of the gas. Both produc-

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tion logs and microseismic Microseismic events data have clearly shown that we while refracturing are not effectively contacting a Barnett Shale the reservoir. horizontal well. MS “We’ve learned that there is a events were detected lot of gas left to be produced before (yellow) and from the Barnett. So much so, after fiber diversion in fact, that we have identified cycles (blue and red). more than 8,000 Barnett wells The aggressive diver- that could benefit from re-treat- sion cycle (red) suc- ment. This has led us to develop cessfully stimulated a rigorous candidate selection new portions of process whereby we classify wells the reservoir. based upon their potential for Image courtesy of improved production as a result Schlumberger of re-fracing. Following candidate selection, we deploy key enabling technologies to identify the low-hanging fruit for our customers. As a result of these efforts, we have been able to lower finding and development costs for some of our clients by as much as image or distributed temperature profile (DTS), 40%. The horizontal re-frac market is one I call a we know where the treatment is going and that ‘sleeping giant’ in our industry, one that is starting governs our actions. Once we stop fracing new to stir.” rock, we divert. No expensive and risky cement squeezing is required,” Daniels explained. Turning data into decisions adds value “We use the data to help our customers make According to Daniels, for Schlumberger to take a better decisions on which wells to re-frac and leading role in the future of the Barnett Shale, the which zones to re-frac within those wells,” he company will be working with this sleeping giant continued. “It allows us to use our ‘measure- over the next few years. “Our goal is to help operators control-optimize’ process to make decision on- to quickly and efficiently add reserves while reducing the-fly that help place the fractures precisely their finding and development costs,” he said. where they can contact the most new reservoir Daniels explained that unless the production rock. To do this we use our StimMore* fiber logs tell them that a perforation cluster is making diversion technology whereby degradable water there is to need to squeeze off old perfora- microfibers are pumped with the treatment to tions before attempting a re-frac treatment. bridge over the fracs and shift the treatment force “When we go in for a re-frac, we add new perfo- to the next point of least resistance. So we break ration clusters in the zones we have picked based new rock. We can observe this in real time using on relevant stress logs like the FMI or Sonic Scan- StimMAP Live or DTS and use the combination ner, production logs, and/or the previous of pumping, observing, and diverting to contact StimMAP image if this data is available. We start more rock — which is the overall objective. The pumping the re-frac, and if any of the old, open fibers bridging the early fractures degrade after a perforations start taking the treatment, we pump few days leaving all fractures open to contribute the diverter to move the treatment over to the to production. Doing this, we have added on aver- new perforations. By observing the StimMAP age 0.7 Bcf per re-fraced horizontal well.”

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Going green benefits the environment According to Chuck Bell, East Region technical In an effort to reduce the carbon footprint and manager, “The Barnett is a variable reservoir, and its impact on the environment, Schlumberger has variations are striking. There is no universal ‘Barnett developed state-of-the-art “green” chemistries, solution’ so we must take the time to develop a which are gaining popularity in the Barnett. The clear understanding of all the factors affecting pro- principle stimulation treatment is the “Slick-water duction in each Barnett area. Essentially our rec- Frac” and friction-reducing chemicals are used to ommendations and designs are driven by the lower the required frac horsepower. North America interplay of those factors. There are frac barriers, is increasingly focused on the environmental aspects pressure changes, and fluid contacts and they all of the chemicals used in hydraulic fracturing of add up. The vertical wells typically produce less gas shale reservoirs. Schlumberger is responding to than the horizontal wells. However, horizontal wells this need by developing new non-hazardous frac- that aren’t drilled and completed in an optimum turing fluids. The new green fluids will include fric- fashion may not be as good as a vertical well. Start- tion reducers, bacteriacides, surfactants, and scale ing every job with our Understand the Reservoir inhibitors. “These new products will enable our First™ process and knowing the principle stress clients to use a wide range of water qualities such as direction helps operators drill the well in the direc- flowback, produced, plant, or mine water. This will tion of minimum stress to set up transverse frac- have a large beneficial effect on the operator’s envi- tures, thus contacting the maximum amount of ronmental impact,” Daniels concluded. reservoir rock,” Bell said. According to Bell, microseismic imaging is criti- BJ Services: ‘Know your reservoir first’ cal to understanding where the fractures are going. BJ Services’ shale team practices what it preaches. “To that end, we recently commercialized the BJ

A BJ Services frac spread operates beside carefully hoarded frac water, which is exceedingly scarce despite the green appearance of the land. Photo courtesy of BJ Services

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Services/Baker Hughes IntelliFrac™ process, which perforation cluster based on our reservoir model, delivers microseismic interpretations during the job taking into account such features as faults that may for improved fracturing treatment management,” act as frac barriers, and connections to the aquifers Bell said. “From production simulations, we have we want to avoid,” he continued. “We want to build come to believe that it’s much better to have several a fracture network that does not intersect the pre- closely spaced short fractures than widely spaced vious stage fractures, but also doesn’t leave any deep fractures as far as efficient reservoir drainage is untapped reservoir sections. It’s important to concerned. We start with reservoir quality parame- understand the limitations of microseismic imaging ters, followed by the well architecture parameters to because depending on the location of the observa- build our frac model. Then we design the frac to get tion wells, there may be blind spots.” the best results given those over-riding parameters. “The Barnett doesn’t have particularly high clo- Then we develop the perforating scheme, fluid type, sure stress, so we can use typical sand proppants — and, finally, select the proppants.” no ceramics for example. Proppant embedment is Unlike many of the other shale plays around the not much of an issue either. Brinell hardness varies, country, the Barnett has plenty of nearby observa- but the formations are generally hard enough to tion wells to enable more usage of microseismic eliminate embedment as a potential problem. At frac monitoring, and this is increasing, Bell said. “It the same time, proppant flowback is not an issue, so has allowed us to get away from evenly spaced deep we don’t need to run resin-coated proppants. We fractures that are far apart, to numerous optimally pump 100-mesh sand, then follow with 40/70 mesh. spaced shallow fractures. Instead of arbitrarily spac- So far we haven’t employed LiteProp™ proppant to ing fractures evenly along the lateral well section, we fill in the tops of the fracture wings, but we expect can actually pick the optimum location for each there may be opportunities to use it in the future.” Randy LaFollette, BJ Services’ shale gas technology manager, shared his views on the Barnett. “One of the most challenging aspects of the Barnett is its diversity. The play covers a large area of North Cen- tral Texas, and there is considerable variation in the composition of the Barnett itself as well as in the effects of structure, geohazards, and overlying and underlying strata. For example, generally west of Ft. Worth, the Viola Formation that separates the Barnett Shale from the Ellenberger pinches out. The Ellenberger is water-filled, and so it constitutes a major geohazard that must be avoided. To the northwest, the Barnett is oily and has some oil wells. Shale mineralogy varies from well to well and that affects its hardness and the way it fractures. Much of the Barnett Shale was cooked to pretty high tem- peratures so we don’t encounter swelling shales to the extent we find them elsewhere.” Asked about future challenges, LaFollette explained, “Water issues are becoming increasingly important. We have to be smart about our treatment designs to make maximum effective use of frac water, and recover as much of it as possible. In addition, many of these wells may need to be re-frac- tured, and that presents additional challenges for

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the future. The advantage is that now we have pro- fraced. Horizontal re-frac work programs began duction history to add to our models.” early in 2008 and continue today. However, it’s one of those subjects we can mention, but we can not No more ‘pump and pray’ publish details about results yet. We’re still experi- Halliburton’s Bill Grieser has made understand- menting with some techniques. Anything we can do ing the Barnett a major objective in his extensive to an existing well bore probably costs less than the career with the company. “We believe we’re in the alternative — drilling a new well. Operators are inves- late stages of the development phase of the Bar- tigating the use of fiber optic cable which can detect nett. There haven’t been a lot of real high-tech temperature changes during injection or production innovations, but now, thanks to the downturn, through a distributed temperature sensing system. operators are going back and looking at how they This allows us to visualize, locate, and quantify pro- did things and trying to find ways to do them bet- duction or injection path. ter in the future. They are trying to evaluate Can anyone predict how the reservoir will behave whether the minor and major tweaks they’ve before drilling? Operators need a simulator that can implemented have been economically successful handle secondary porosity, absorption gas, and or not. conventional Darcy flow. A solution has been doc- “A lot of the analysis done in the past was only umented in SPE 120271, and it accounts for based on 30-day cumulative production. The real injected fluids. It’s very useful in the Barnett. It meat of the subject is finally coming into vision predicts both gas and water flow. At last, we have a because now we’ve got 5 to 10 years of cumulative simulator that gives reasonable production esti- production on wells we’ve tried experimental stuff mates when input reservoir information is limited on. The requests we’re getting have to do with exam- and isn’t labor intensive. ining our learnings and using the information to What about frac water re-use and recycling? plot a path for the future.” We’re being asked about water and how to get the Grieser enumerated the most frequent customer most mileage out of it. A major cost factor for the questions along with Halliburton’s analysis of the industry is getting, pump- best ways to answer them: ing, and then disposing of Where is production coming from? The assump- water. We’re actively look- tion has been that all the zones perforated and ing at chemicals and chem- treated are producing, but that’s not entirely correct. ical systems that allow us Operators are asking us to determine which perfo- to pump fluids downhole rations are contributing to production and which using water that would not are not—and why. Also, how do they get production have previously been con- from the areas that are not producing? sidered suitable for fractur- This brings up the subject of refracs, and there ing fluid. The most typical are 13,000 wells out there to choose from. Prior to water frac chemical pack- the economic meltdown of last summer, the hot age consists of a friction topic was re-completions. Oil company manage- reducer, usually a polyacry- ment is looking at net drainage of (optimistically) lamide, a biocide and scale only 30 to 40% of the stimulated reservoir volume, inhibitor, and as water gets and saying they want another 30 to 40%. more and more loaded with So how do we go about doing this? Our 2009 dissolved solids like Ca and plan entailed developing technology to access the Mg, we’re trying to identify new rock in existing well bores. Halliburton has a chemicals that will not neg- number of proprietary technologies, and we’re atively interact with that working on different diverting materials hoping to water. We now have more change the direction of fracs in wells previously salt- and calcium-tolerant

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additives. We found that biocides that worked they tend to expand and block, but when gas or oil on the surface got used up quickly at tempera- goes by they tend to shrink. ture. Now we have biocides that will withstand What about Barnett oil wells? The lesser-known the formation heat, are long lasting, and less haz- areas have an oil leg in northern Wise and Montague ardous. We can’t use the dirtiest of waters, but we counties. Surfactant usage has been used experimen- mix brackish returned fluids with freshwater, tally in the gas shales of the Barnett. From our per- which saves a lot of water. The days of pumping spective, those trials have had mixed outcomes. As we huge amounts of potable water downhole are move from gas to oil, all of the things that surfactants gone forever. do get magnified because the hydrocarbon molecules Can we influence or control proppant flow- are bigger. Things like wettability, surface tension and back? The reason these questions are being asked contact angle become very important because instead now is that we’re drawing the wells down harder of moving a methane molecule of say 4 to 5 angstroms now to get back more hydrocarbon. We have aque- you’re trying to move a large oil molecule that may ous tackifiers and on-the-fly resin that we apply to contain a lot of dissolved gas. We believe mobility of proppant. It isn’t particularly a new technology, oil through the matrix and the very narrow cracks in but it is one that’s getting reborn as we draw down the fracture network can be increased with the proper the wells harder. surfactant selection. Can water influx from surrounding strata be Can producing reservoir volume be measured? controlled? We’re pumping relative permeability The fact that the Barnett shatters can be a benefit, modifiers to help reduce water influx. Using this because instead of a typical bi-wing fracture, an material in very low permeability shale is relatively interconnected complex network of fractures is cre- new. We think that putting water control material ated that contact more of the reservoir. One of the in the early proppant stages may be a good idea. We questions we’re being asked is that because of the use little polymer strings that attach themselves to dendritic fracture networks, can we perform reser- the surfaces of quartz and when water goes by them voir volume calculations? If you can imagine the

The shalelog presentation provides an integrated, comprehensive, and correlated view of the reservoir with all the information needed for completion design. Image courtesy of Halliburton.

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stimulated reservoir volume (SRV) as an ellipse, How does microseismic imaging contribute? The instead of a planar bi-wing fracture, that’s often microseismic images not only help in early phases of what we get. Quantifying gas or oil in place and the shale life cycle, but also in the later phase of estimated ultimate recovery (EUR) in such a regime decline and maintenance as the planning for a re- is extremely difficult, and requires the combination frac program begins. You can go back and look at of microseism mapping, decline curve analysis, and the original microseismic and it gives you a picture volumetric analysis. of what has been stimulated and where to go next to recover more reserves. Halliburton solutions, field Halliburton solution Can we determine the so-called sweet Customer questions development projects (FDP) applied in the Barnett spots in the vertical and horizontal por- in other shale plays or in R&D tions of the well? The reservoir changes Where is production Fiber optics and pressure dramatically from well to well. This is evi- Production logging coming from? transducers on coiled tubing. dent from the large distribution of pro- QuickLook® Reservoir Fluid duction outcome observed in the Barnett. Can you model or Management Services -- 4- Bio-Diverter FDP-903 During the early decline and maintenance predict production? phase simulator. phase, the use of advanced logging and Diverter BioVert®, Pinpoint stim- rock analysis tools become even more How do I access ulation, SurgiFrac™ Fracturing important. Tools like (InSite AFR™) CleanStreamSM new rock (re-frac)? Service, Cobra Frac® H Coiled azimuthal focused resistivity can be used Tubing Fracturing Service to target the drill bit to specific pay sec- Can we reuse frac water? New friction reducer FR-66 tions. Elemental capture spectroscopy Reduce water costs? New biocide BE-9 service (GEM™ Elemental Analysis Tool) and chemostratigraphy on drill cuttings SandWedge® Conductivity Proppant flowback Enhancement System, LaserStrat® Wellsite Chemostratigraphy control as drawdown increases? Expedite™ Fracturing Fluid Service) can provide detailed mineralogy and inorganic geochemical data to help Do you know stimulated Microseismic mapping, classify the shales as we drill through them reservoir volume (SRV)? Production analysis What area am I draining? and identify the sweet spots. How can the thinner areas of the Bar- WaterWeb® Treatment Can you control or nett be exploited? As the Barnett thins, Services, CW-FRac™ reduce water influx? Fracturing Services the expected production outcome and eventual EUR is likely to be less than the Is surfactant chemistry Lab surfactant testing, Surfac- Field surfactant tests. core area. To be commercially viable, these important in oil shale? tant FDP-918 areas require the cost to decrease and the ShaleLog® Logging Services, LaserStrat® Wellsite efficiency to increase. The use of unce- Where are the sweet spots TMDL, WaveSonic® Diagnostic Chemostratigraphy Service, vertical and horizontal? mented mechanical frac stage devices like Service, XMRI InSite AFR™ MRIL™ Swellpacker® Isolation Tool and Delta DatCI™ On site bit design, Stim® Sleeves can make the frac comple- Can we reduce drilling and Swell Packer® Isolation System, tion a continuous single-day event. ® completion days? Delta Stim Sleeves, Can near-wellbore damage be remedi- Cemented DSS ated? As the Barnett is produced, scale for- Pulsonix® Acoustic Stimulation mation becomes a problem. We’re looking Can we detect/remediate DFIT, ShaleFrac RF™ Service, Deep Wave® Stimula- fracture/near wellbore damage? at scale mitigation technology for both ver- tion Service, ShaleClean™ tical and horizontal wells. Our Pulsonix® Can we collect, analyze review, Relational data base analysis, Acoustic Stimulation Tool is a jet pulse and archive what we have Neural Networks. The Digital Asset® tool that actually removes scale with pres- done, and decide what works? sure pulses delivered from the tool. This Source: Halliburton

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tool used in conjunction with shale-specific reactive During the Barnett early decline and mainte- fluids, ShaleFrac-RF™ Treatment Service, has been nance phase, emphasis on technology advancement used to remove wellbore skin. will become more important as engineers attempt to Can we analyze, review, and archive everything extend the decline curve to higher economic ulti- we’ve learned? That’s what we’re doing now. We’re mate recovery. Long-term production results will integrating geology, drilling, and completion in a support or change ideas and theories about the best single package called The Digital Asset® from Hal- drilling and completion methods, as Halliburton liburton. It will take everything into account from better understands the complex mix of Barnett geo- exploration, drilling, completing, and production logic, geochemical, and geomechanical properties. and allow all to visualize the data in real time. The North Texas Barnett will remain the stan- dard by which all other shale plays are compared. Halliburton prescription explained The advantages are time and the talent and dedica- The North Texas Barnett Shale is well into its devel- tion of operators and service providers who have opment phase and perhaps is entering the decline taken this reservoir from a curiosity to a major gas- phase in the shale life cycle. While there are still producing basin. unexplored areas of the 6,000 sq mile extent of the Barnett, the core area (Wise, Denton, Tarrant, Weatherford drills ahead Parker, and Johnson counties) are nearing the end By concentrating on drilling efficiency, Weather- of development mode and are in the early stages of ford aims to reduce total rig costs for its customers. the decline period. Operator needs and challenges It recognizes that the keys to success are speed and are changing as the Barnett Shale lifecycle pro- reliability, and one way to make an impact on these gresses. Areas of the Barnett reservoir that are thin- is to perform detailed pre-job planning. Claiming ner, less bounded, and more oil prone are currently the horizontal drilling speed record, the company being developed. The core dry gas area is reducing pointed out that its success in this area is not a well spacing and is in re-completion/re-frac mode. one-off feat. “We have completed more than 200 During this economic slowdown in activity, cus- bottomhole assembly runs for Quicksilver tomers have the opportunity to stop and ask ques- Resources in the Barnett Alliance Airport Field this tions about what they have done so far, what works, year,” said Dennis Barrett, US drilling manager for what does not work, and what does the future hold? the company. “We’re averaging 10 days from surface The table on page 52 lists customer needs and chal- to total depth,” he said. lenges for the late development/early decline phase After introducing its even-rubber-thickness of the North Texas Barnett. mud motor power sections, the resulting Customers’ questions and challenges have a com- improved drilling efficiency more than compen- mon theme. How can things be done faster, smarter, sated for the equipment’s added cost, even in better? In the current economic environment and tight-margin environments. According to the shale life cycle phase in which the industry is oper- company, one operator drilling from a pad and ating, the emphasis is on efficiency. That is not to using the FrontLine ERT motors was able to say that operators are not concerned about pro- improve its drilling performance from one and a duction results. On the contrary, during this slow- half wells per month to three wells per month. down period, they are taking time to review Typically, Weatherford recommends drilling the production results and are asking hard questions vertical and build sections using FrontLine Plus about the spread of production outcome in this mud lubricated directional drilling motors and “continuous resource play.” They are looking for EMPulse gamma ray sensors for depth correla- technology advances that will increase their ability tion; then it switches to its Revolution rotary to find and produce more hydrocarbon from lesser- steerable systems to drill the lateral section. The quality areas of the Barnett Shale or untapped rock technique has delivered the 10-day surface-to in existing well bores. total depth cycle with 96% to 99% efficiency.

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In one Johnson County well, the company demon- ability to achieve transverse fractures with maxi- strated it’s “Turnizontal” drilling technique whereby mum reservoir contact. Then every aspect of the the well is quickly built to 90° deviation, then turned treatment is engineered from pumping schedule to drill the lateral aligned with the principle hori- to fluids to proppant. Specialty chemicals, like zontal stress plane using the minimum number of the company’s ZetaFlow additive, are used to trips. The 10,355-ft 8 ¾-in. diameter borehole was enhance fracture conductivity by changing the completed in 13 days — 15 days less than the opera- way proppants interact to increase porosity and tor’s well plan. Key to this success was elimination of permeability in the proppant pack. costly, time-consuming side tracks, and obtaining excellent wellbore quality throughout. Innovations abound Commenting on Weatherford’s shale play The horizontal completions in the Barnett Shale have approach, Rob Fulks, US projects manager said, seen a transformation from the use of tubing con- “Our capabilities encompass the full shale service veyed perforating, to tractor conveyed perforating sys- sequence of evaluation and planning to well oper- tems, coiled tubing conveyed systems, and now to ations and optimization.” Fulks went on to cite pump down systems. These methods of deployment wireline services, cementing equipment, wellhead are being utilized with cost-savings measures in mind. systems, frac flowback, artificial lift systems for In reality, the “Intelligent Perforating Systems” devel- dewatering, controlled pressure drilling, and mul- oped by Owen Oil Tools, have in large measure been tizone completions as key components of a total major contributors to the enhancement of production service offering. The company believes in risk and reduction of completion costs in the Barnett reduction through increasing its geology and geo- Shale. A marked improvement in breakdown pres- mechanics knowledge prior to drilling. Aug- sures and improved injection rates due to the design menting thorough planning with real-time of the shaped charge perforators have contributed to logging-while-drilling information helps the com- lower breakdown pressures required to frac these tight pany optimize well placement while maximizing formations. Simply put, patented liner technology in drilling efficiency. Importantly, with foreknowl- Owen’s Hero and Super Hero Perforating Systems edge about the formations to be drilled, the com- has made the difference, according to the company. pany can identify zones of inadequate thermal This patented liner material eliminates the debris maturity and organic content to provide eco- normally deposited in the perforation tunnel, there- nomic production. Weatherford’s unique GC- fore reducing the need for acid stimulation and other TRACER surface gas detection service uses measures that raise the cost of the completion. More analysis of formation gas released while drilling perforations open for flow, or treatment, are the result. to identify formation sweet spots, formation per- These “High Efficiency Reservoir Optimization” permeability barriers, reservoir connectivity, and forating charges are providing the same results in all compartmentalization. shale plays in the US and Canada. Recognizing the diversity of the Barnett play, As operators in the Barnett Shale start to develop Barry Ekstrand, vice president, reservoir stimula- programs for re-completions on existing assets, one tion and pressure pumping, said, “We engineer hurdle will come into play — isolating existing per- the well design with an eye on localized charac- foration intervals. teristics. We can integrate data from many A highly efficient and effective casing patch has sources, including logs, cuttings, geomechanics, been introduced by Owen Oil Tools division of and seismic, and apply the results to all phases of CoreLab. Called X-SPAN® the tool consists of an the well’s life cycle, from drilling to evaluation, expandable sealing element at both ends connected completion, production, and intervention.” As an by an almost unlimited number of thin but very example, Ekstrand elaborated on the company’s strong tubular extensions. The tool can be config- ability to align the lateral drainhole with the prin- ured as it is run in the hole simply by adding exten- ciple horizontal stress plane, thus enhancing the sion sections until the patch spans the entire desired

December 2009 | www.hartenergy.com BARNETT: TECHNOLOGY

interval. Applications include repair of damaged or identified, quantified, and modeled, an effective corroded casing, sealing off unwanted perforations, solution can be developed. The correct biocide, in or water shut-off. But it can also play a valuable role the correct concentration, can then be applied to kill in re-fracturing jobs. the cells and prevent their further proliferation. In Successful fracturing and treatment of new pro- addition to corrosives, dangerous concentrations duction intervals will rely heavily on the ability to of H2S can cumulate in frac tanks or field storage divert the frac fluids and pressures away from the tanks. These, too, can be eliminated. original perforation intervals. Owen Oil Tools’ X- According to the company, in one Barnett proj- SPAN Casing/Tubing Patch Systems provide a ect, 54 frac jobs, including 2,490 frac tanks were heavy-duty seal over perforations and can be used as treated with Baker Petrolite XCide 575 microbio- an effective, inexpensive tool to divert the frac. cide. As a result, gathering system flowline failures According to the company, X-SPAN burst and were reduced 80%. There was a substantial reduction collapse pressure ratings are the highest in the in the number of produced water tanks with bio- industry; therefore, Barnett operators can rest genic H2S production, and a 25% reduction in total assured that frac will go where intended. program treatment costs due to early detection and rapid remediation. Chemistry and drill bit design Additional chemical treatments provided by shines in the Barnett Baker Petrolite to its Barnett Shale customers Baker Petrolite uses its considerable experience in include scale control media, friction reducers, oxy- developing effective oilfield chemistry to advantage gen scavengers, and corrosion inhibitors. Scale con- in the Barnett. The company’s AddFRAC measure- trol media can even be combined with formation ment and control services work to prevent micro- treatments to inject scale inhibitors deep into the bially induced corrosion failures that affect gathering fracture networks where they can prevent scale system flowlines and produced water storage tanks. buildup that can impair fracture conductivity. Even trailer-mounted frac tanks are attacked by Hughes Christensen has developed a bit line that aggressive corrosion media. The combination of these has delivered enviable performance in drilling the corrosion targets can create the risk of negative envi- Barnett. The company’s Q507FX Quantec Force ronmental impact and personal injury. Series, polycrystalline diamond compact (PDC) bits Instead of applying costly and potentially inef- optimize force distribution for added stability. In fective trial and error methods, the AddFRAC team addition, they contain updated PDC cutter tech- works to determine the root cause of potentially nology and feature additional structure design damaging corrosion and develop a permanent solu- methodologies. Compared to eight other bits rec- tion. In one example, Petrolite’s microbiologists ommended for drilling surface and tangent sec- and field technicians performed detailed measure- tions of Barnett Shale horizontal wells, the Q507FX ments and diagnostic services of the fracturing bit beat the average offset well penetration rate by process, tracking every drop of induced and pro- nearly 37%. In one well, 4,315 ft were drilled at 94 duced fluid as it circulated through the system. fph, saving the operator 17 hours of rig time. They looked for potential combinations of fluids that could cause a corrosion cell to evolve. Looking ahead The commonly used technique of re-using frac The Barnett play offers a rich mosaic of opportuni- water may be an excellent way to conserve water, but ties from exploration, to drilling, to completion it may be the mechanism that spreads a biological and production, stimulating innovative minds to agent throughout the system like a virus through create new tools, chemicals and techniques specially the human body. By understanding the actions and designed for the shale as well as adaptations of exist- interactions of all the bio and chemical agents in the ing tools to complement shale applications. system, the bacterial loading of the entire system can be modeled. More importantly, once the agent is * Mark of Schlumberger