Hydraulic fracturing is certainly not a new concept. But within the basic simplicity of using water pressure to crack open rock there are a lot of moving parts. And companies have been experimenting with combinations of those moving parts to gain advantages, particularly in tight plays like shales.
Operators have come to discover that the “perfect frack” is influenced by several factors—perforation spacing, proppant choice, proppant placement, proppant and fluid volume—the list goes on. Within these pages are countless success stories that highlight the industry’s ingenuity when faced with the difficult challenge of prising open stubborn rock to produce the riches contained within.
Making multistage completions more predictable
The NCS Multistage Unlimited frack isolation system enables operators to design and execute multistage completions predictably and consistently. The system combines cemented casing sleeves with coiled-tubing-deployed single-point injection to deliver predictable and verifiable stage spacing and propped volume, allowing operators to optimize completions and achieve more efficient field frack networks. The result is better reservoir connectivity for improved production and higher ultimate recovery. Consistent and repeatable frack placement allows operators to systematically optimize completions from well to well as they strive to improve the overall quality of multistage completions in shale and other unconventional formations.
The Multistage Unlimited system has allowed operators to increase the number of discrete stages in a well far beyond the limits of plug-and-perf and ball-drop sleeves. In 2014 NCS set several consecutive world records for the number of sleeves/stages in a single well, first with 92 in the Eagle Ford, then 93 in the Bakken and finally 104 sleeves/stages in the Bakken. Bakken wells completed with the Multistage Unlimited system are among the best producers in the Williston Basin.
NCS is implementing downhole pressure and temperature data collection during fracturing, both at the stage being stimulated and in the wellbore below. Analysis of these data is useful in the optimization process because it identifies, among other things, inter-stage communication. Operators use the information to determine the optimum stage spacing for developing a given formation.
NCS has tested and is introducing reclosable frack sleeves that provide important new capabilities over the life of multistage wells. During completion, the sleeves can be closed immediately after each frack to prevent proppant flowback while formation stresses stabilize, then reopened to bring the well into production. They also can be closed to allow out-of-sequence fracturing to take advantage of induced rock stresses. During production, selected sleeves can be closed to shut off water production and thief zones. For refracturing or other remedial work, sleeves can be closed to control the wellbore above the target zone(s).
Acquisition of primary stimulation data will become more important as operators strive to better understand the complex dynamics of multistage stimulation to optimize completions. It is likely that operators will continue to move to cemented liners and single-point injection completions with the goal of achieving more efficient field fracture networks that optimize long-term well economics and ultimate recovery.
Technology transports proppant farther, higher into formation
As oil prices decrease with the expected decrease in E&P company capex, better completion design efficiency for enhanced well net present value (NPV) continues to be imperative. Fairmount Santrol is working closely with operators in this tough business climate to develop the optimal stimulation programs.
Its frack sand and resin-coated sand—complemented by Propel SSP proppant transport technology—are part of the company’s extensive proppant portfolio. Proppant is available through Fairmount Santrol’s 50-plus terminal network, located closer to the wellhead for greater transportation efficiency. This product line ensures operators can engineer the right completion for proppant flowback control and increased conductivity to maximize hydrocarbon production.
Propel SSP technology’s hydrogel proppant coating swells upon the simple addition of water, and the technology is improving hydrocarbon production by transporting proppant farther and higher into the formation, often with less water and fluid additives compared with standard frack fluid.
“By distributing proppant to uniformly contact more formation area with more efficient fracturing operations, the technology is increasing NPV and, we’re confident, accelerating the rate of return for oil and gas wells,” said Brian Goldstein, product director, Propel SSP technology.
Wells in most of the major unconventional formations have been completed with multiple designs, ranging from 100% Propel SSP technology to a Propel SSP technology tail-in. The tail-in design following slickwater is driving cost and hydraulic fracturing efficiency.
In the Escondido Formation in Webb County, Texas, the operator optimized an 18-stage frack design for higher IP with 55% more rich gas production after two months. The operator chose a 46% Propel SSP technology tail-in compared with the all-Northern White sand slickwater offset. Higher proppant concentration furthered fracturing efficiency without a fluid sweep or screenout.
In the Mississippi Lime an operator compared one well using 100% Propel SSP technology with one using 100% slickwater. The Propel SSP technology transported proppant without a friction reducer, fluid sweep or screenout. With enhanced producing gas-oil ratio, hydrocarbon production has increased 32%, driving up oil production 26%.
Fairmount Santrol’s Propel SSP technology and the comprehensive curable and precured resin-coated sand products are boosting completion designs so operators can realize continued success in this newest challenging industry cycle.
Sliding sleeves cut frack costs
TEAM Oil Tools
Cemented completions using a new sliding sleeve technology are optimizing hydraulic fracturing pressure and enabling single-point-of-entry stimulation designs. The technology is a key enabler for the application of hydraulic fracturing methods in much longer laterals and with much greater focus and efficiency.
The most immediate result is a change in fracking economics and the flexibility of completion designs. Recent installations of TEAM Oil Tools’ ORIO XL Frac Sleeve in the U.S. Marcellus, Utica Shale and the Permian’s Spraberry have enabled single-point-of-entry stimulations that reduced pump rates and surface horsepower requirements by as much as 50% compared to plug-and-perf completions. Continuous fracturing operations achieved with the frack sleeves and TEAM’s X-Frac ball launcher greatly reduced completion times and contributed to a savings of more than $500,000 per well.
The tool is a ball-activated sliding sleeve that uniquely allows multiple frack sleeves to be opened using the same diameter ball. The innovation significantly increases the total number of sleeves available in the completion design. Up to 90 individual sleeves can be opened without dropping a ball diameter smaller than 4 in. in 5.5-in. casing or a 3-in. ball in 4.5-in. casing completions.
Completion design flexibility is enhanced with the large inside diameter (ID) ball seats over the length of the lateral. A greater number of sleeves can be used to complete the entire lateral or just the lower half of the lateral in extended-reach applications.
The ORIO XL Frac Sleeve has a three-layer design that protects critical moving parts from cement slurry and frack sand to ensure full opening and access to the formation. Drilling rig installation is enhanced by the ability to rotate while running in the hole. The protected sleeve still retains a large, smooth ID that allows a heavy-duty wiper plug to be used for cement displacement, ensuring a cleaner wellbore and a better cement job.
Microseismic services improve understanding of frack, refrack programs
MicroSeismic Inc. recently worked with a client to evaluate lateral and vertical wellbore spacing as well as fracture height on a multiwell stacked completion in the Permian Basin. The stacked wells were landed in three main formations, and treatment effectiveness was analyzed with surface and downhole microseismic data. Lateral propped fracture length was used to determine optimal well spacing, which improves production and optimizes costs by avoiding treatment overlap and gaps. Analysis of vertical coverage of the propped fractures revealed that some formations were not fully propped, so MicroSeismic recommended adjustments to the corresponding well placements or a change in treatment.
In 2014 MicroSeismic entered into the downhole microseismic business with a differentiated and enhanced offering from the traditional downhole processing techniques. Over the last year, it has developed and applied its passive seismic emission tomography (PSET) to downhole microseismic applications. PSET Downhole was developed to overcome the issues faced with traditional compressional (P) and shear (S) wave picking methods to process downhole data. The new technology uses the full waveform of P waves and S waves and Kirchoff imaging principles to more accurately locate events.
MicroSeismic sees the current oil price environment as an opportunity to continue to develop new services that provide operators with a way to cost-effectively improve production. The company is now delivering a service specifically designed for monitoring refracks, the Refrac Performance Package, that allows clients to understand in real time when they have begun to fracture new rock vs. restimulating rock that was fractured during the first completion.
Much has been written lately on the drawbacks of “factory mode” drilling and completion methods in shales. The underlying issue is that different geology needs different treatment to optimize production. MicroSeismic sees this trend continuing to develop as operators use microseismic along with other completions evaluation techniques to eliminate avoidable costs and improve production in real time.
For 70 years proppant technology has primarily consisted of uncoated frack sands, resin-coated proppant and ceramic proppant. These three tiers of proppant have served, and continue to serve, as the workhorse for propping open hydraulic fractures and have allowed for the successful development of many otherwise uneconomic reservoirs.
Recently, CARBO has embarked on a path to use proppant for more than deploying conductivity in the fracture. The company has identified three primary areas of technology development to allow operators to use proppant to increase their production and lower operating costs—production assurance, flow enhancement and evaluation services. All three use the ceramic proppant grains to deploy technology to meet these challenges.
In the area of production assurance, specially manufactured ceramic proppant is infused with production assurance chemicals that are slowly released at engineered rates to inhibit the formation of scales, wax, salts and other downhole issues. In early 2014 SCALEGUARD was deployed in several wells in the Uinta Basin and, after several months of scale-free production, appears to be outperforming other comparable technologies. The scale prevention is currently projected to last multiple years and will provide a significant reduction in lease operating costs. The success of this product is leading to the development of other assurance technologies such as paraffin, salt, hydrogen sulfide and asphaltene.
In the area of flow enhancement, chemistry is used to increase the flow of hydrocarbons through the proppant pack. A new relative permeability modification technology has been developed that places a neutral wettability surface on the proppant grain. This virtually eliminates capillary pressures in the proppant pack, allowing for increased fracture fluid cleanup, larger effective drainage area and higher production.
The evaluation services platform uses technology to assist in evaluating the completion. Nonradioactive tracer technology can be used to help visualize the fracture by placing a nonradioactive taggant in each proppant grain that allows detection using a standard neutron log. This information can then be used to help operators optimize their completion strategy through a better understanding of fracture geometry, near-wellbore connectivity and perforation/staging efficiency.
Because each barrel of oil that is produced in today’s unconventional reservoirs must pass through the proppant pack, proppant becomes an ideal way to deliver chemistry and technology to the production stream to solve difficult E&P challenges.
System delivers increased proppant volumes
Calfrac Well Services
Partnering with a manufacturer to develop and implement the SandStorm has resulted in wins for Calfrac’s customers, the environment and the team working at the well site.
With a focus on large-scale unconventional resource development, there was a need for a tool that would better meet the demands of challenging extractions. Properly extracting oil and natural gas from deep complex reservoirs requires injecting a mixture of proppant and fracturing fluid into the subsurface at high rates and volumes. The large volume of materials required creates logistical challenges, especially with proppant delivery.
Calfrac’s implementation of the SandStorm proppant delivery system resulted in a highly calibrated high-volume gravity-fed rapid deployment system engineered specifically for natural resource extraction from shale plays.
An engineered series of storage units, the SandStorm can be easily scaled up or down, depending on the need. With a footprint roughly 30% less than its predecessors, the rig-up and rig-down is significantly improved. The SandStorm uses a simple telescoping belt to quietly and cleanly transport twice the volume of proppant that can be achieved with pneumatic systems. Use of the SandStorm effectively decreases its transport traffic on private and public roadways by 50%.
Development and implementation of innovative tools like the SandStorm are important to the future of responsible extraction and development of natural resources. With the scale and complexity of projects continuing to increase, new fluid systems are being developed that further reduce the use of freshwater. The company expects that developing new technologies and processes that enhance efficiencies will continue to advance the industry.
Technology integration pays off
A significant trend in horizontal unconventional completion design has been greater compartmentalization through reduced zone spacing and increased proppant pumped per foot of lateral. This is providing improved productivity but can lead to deteriorating economics with high completion costs and time associated with conventional mechanical methods required to achieve the isolation needed. Halliburton’s solution has been the integration of completion technologies designed to achieve the highest production output with the most efficient use of stimulation material input while minimizing time on location and well interventions such as plug-and-perf runs and isolation packers.
Over the past 12 months the company’s AccessFrac intracycle stimulation service has delivered more efficient and effective stimulation to a well. Conventional fracturing designs only pump a single injection cycle per zone, which can lead to ineffective zone coverage, increased well interference and diminished returns. The AccessFrac service provides optimized pumping schedules and engineered diversion spacers to segment multiple proppant cycles placed over a zone.
The company’s latest work has been the integration of stimulation and completion systems technology. Its 50+ ball drop RapidSuite openhole sliding sleeve system enables a high degree of reservoir compartmentalization, which is being further enhanced with AccessFrac intracycle stimulation designs.
Halliburton also is aggressively addressing historically steep production decline in shale well completions by meshing AccessFrac stimulation service with patented custom coating chemistry to generate targeted fracture geometries with proppant materials that have been conditioned to achieve the greatest drainage potential from each well through long-term fracture conductivity and maximized hydraulically connected disturbed rock volume. Its custom proppant coating and surface modifying technology modulates the intermolecular forces between proppant grains during the fracturing process to create greater volumization, clustering and adhesion of grains to the fracture face for increased conductivity and propped volume. In the near-wellbore area the cohesive strength between proppant grains can be greatly increased to provide pack flexibility and proppant flowback control.
Better wellbore coverage, proppant delivery
A new sequenced fracturing technique that uses a composite blend of degradable particles and fibers was implemented in 2014 by more than 30 operators in 11 major North American basins to successfully deliver stimulation fluids to understimulated or inaccessible well sections. Better contribution to production from fractures also is attained by incorporating fibers in the fracturing fluids to improve proppant transport and placement. In multiple studies using different applications of the treatment, results showed the methodology can improve production rates, increase reservoir contact and reduce completion times and operational costs.
The Schlumberger BroadBand Sequence fracturing service represents a significant shift in thinking in the industry that takes a more engineered, cluster-centric approach to well development. By blending degradable fibers and particles of various sizes with stimulation fluid, the service overcomes conventional diversion methods by temporarily isolating zones that have already been stimulated and redirecting the stimulation fluid away from the path of least resistance to understimulated zones. The service is supported by job modeling and measurements to maximize effectiveness.
In one study in the Eagle Ford Shale, three wells of an eight-well, three-pad project were targeted for stimulation, implementing the new sequenced fracturing technique within the existing completion and design strategy to improve the potential for all perforation clusters to be adequately stimulated. The wells were designed with 91.4-m (300-ft) fracturing intervals and six perforation clusters spaced 15 m (50 ft) apart. The proppant volume for each treated interval was divided into two equal ramps pumped with a composite pill in between. Post-fracturing measurements indicated the composite pill did facilitate contact with more than 80% of the clusters showing near-well diversion. After six months, average production per well increased by 22%.
The fracturing service portfolio is being expanded this year with the addition of BroadBand Precision integrated completion service, which improves wellbore coverage by maximizing control of fracture placement, size and conductivity. Cemented sleeves that can be opened or closed at will provide access to develop each fracture, while a retrievable packer conveyed via coiled tubing provides isolation during fracturing operations.
Future focuses on less proppant, water use
Hydraulic fracturing has as many detractors as advocates globally. One of the pressing challenges for service companies and operators alike is to achieve the same or better well productivity while using less water and proppant in the completion process.
Weatherford’s FracAdvisor service is one example of using reservoir and completion qualities to understand how a particular well will behave when hydraulically fractured and how the rock will contribute to hydrocarbon production. This guidance assists operators in making optimal decisions regarding stage and cluster placement. FracAdvisor equips completion teams with data integration that takes geomechanical information, rock properties and anisotropy measurements into consideration.
One of the emerging technologies that potentially lowers both water and proppant use is the latest generation of pillar frack techniques. Pillar fracks are intended to create high-conductivity paths within the fracture, aided by materials capable of synthesizing with the chosen proppant and fluids to withstand closure stresses.
At least three competing pillar frack systems will be available to operators in 2015. Results have been mixed regarding pillar fracks so far, but the elegance of the solution demands additional applications. Pillar fracturing stands out as a viable alternative to high proppant-loading techniques.
Today some service companies mix produced and flowback waters to reduce freshwater consumption. WaterSure is a water treatment product requiring zero freshwater while running 100% produced/flowback water with a range of high salinities, total dissolved solids and ion interference that would typically be rejected for frack fluids.
Waterless fracturing R&D is taking place worldwide on a range of alternatives.
Liquid propane has already been introduced to the industry. Artificially inducing permeability in tight formations could also be accomplished (again in theory) by breakthroughs in CO2 or nitrogen fracks, exothermic explosions, cryogenic processes or gas pulse fracture creation.
CT aids in zonal isolation
Cudd’s Zone Isolation Packer & Perforating system (ZIPP) is a technology designed for hydraulic fracturing that is used in conjunction with coiled tubing (CT) for single-trip multistage jobs. Key features include single-trip perforating and fracturing, proven abrasive perforating technology, no additional cleanout runs, CT or threaded pipe applications, and increased fracture manipulation.
The ZIPP system uses a specially designed perforator and packer to accomplish a multiple-zone completion in a single trip in hole. Once the packer is set at the desired depth, the perforator is activated, allowing abrasive fluids to penetrate the formation in preparation for fracking. While maintaining pressure through the deployed equipment, the fracturing process is initiated through the annulus of the well.
This specialized packer was designed to withstand sand debris associated with abrasive perforating and fracking numerous zones within a wellbore. Large flow-through ports prevent sand buildup on moving parts to ensure reliable operation downhole. This process allows each zone to be isolated, perforated and fracked while all the equipment is still downhole, providing a broad range of adaptability and completely eliminating wireline from the frack process, which potentially saves both time and money.
Additional benefits of running this system include:
- The ability to completely customize the frack;
- The convenience of having CT equipment already on location and rigged up;
- The lack of worry about having explosives on location, mis-runs, losing tools or the premature setting of plugs, which leads to drillouts;
- The ability to make real-time decisions and adjust to the desired depth and reperforate; and
- Less hydraulic horsepower, which means a much smaller footprint.
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