This project is to conduct a field-based hydraulic fracturing research program for horizontal shale wells with the objectives of reducing and minimizing potential environmental impacts, demonstrating safe and reliable operations, and improving the efficiency of hydraulic fracturing. The research will advance our understanding of the hydraulic fracturing process in shale reservoirs, and thus, enable the design and execution of effective fracture stages that significantly contribute to production. Improved design and execution of fracture stages will also reduce the number of future infill wells drilled and reduce water volume and energy input. A smaller environment footprint associated with shale drilling will be the result of this work.

Gas Technology Institute, Des Plaines, IL, 60018

Despite the long history of hydraulic fracturing, the optimal number of fracturing stages during multi-stage fracture stimulation in horizontal wells is not known. In addition to the increased expense of multistage fracturing in horizontal wells, increasing the number of fracturing stages does not always correlate with an increase in production. The problem is the application of a uniform fracture stimulation design to all stages with no consideration for geological variations along the wellbore. The result is an inefficient use and costly waste of energy and water.

Optimization of the fracturing process requires an understanding of the cause-and-effect relationship between fracturing parameters and local geological properties at a given location along the wellbore. Realizing that the generalized rock mechanics theories and hypotheses are not truly applicable to fractured and laminated shales, quantifiable impacts of a shale’s geomechanical and depositional features are a prerequisite for design and implementation of optimized hydraulic fractures. The overarching goal of this project is to understand and define the relationships of shale geology and fracture dynamics using detailed field data that includes coring of the fracture domain. Analyses of the data will aid in updating fracture design models and improve the effectiveness of individual hydraulic fracture stages.

Resource recovery from shale formations is currently estimated to be less than ten percent. Research proposed in this project will establish the foundations for investigating enhanced recovery techniques for increased resource recovery in existing fracture treated wells. Natural gas as an EOR fluid is in the early stages of being used broadly in the oil and gas industry and as such, many aspects of the process need to be researched and addressed prior to widespread acceptance. This project will investigate several of those aspects and will also help to accelerate acceptance of the technology due to the number of companies participating in the JIP .

In typical conventional fracture stimulation, a selected fracture design is implemented at all fracture stages of a horizontal well without consideration for reservoir heterogeneity or dynamic stress changes that occur during fracturing. As a result, 50 percent of the total production from the well will come from about one-third of the fracture stages pumped. The intended fracturing optimization through the HFTS program aims to eliminate this inefficiency by creating effective fractures in every treatment. The net effect of such efficiency improvement will increase production from the well with no increase in the amount of water, chemicals, proppants, and energy required. This translates to minimized air emissions and other environmental impacts associated with production of a unit volume of oil and gas.

The shale revolution has enabled the production of significant volumes of oil in some parts of the country, but inadequate infrastructure has been unable to transport the gas produced with the oil out of the field. In such cases, significant volumes of otherwise valuable gas are flared resulting in Greenhouse Gas emissions and lost revenue. The proposed activities will investigate the potential for using flared, or otherwise wasted gas to improve recovery efficiency of oil from shale, by reinjecting the gas back into the reservoir for Enhanced Oil Recovery (EOR) purposes. Not only will this reduce the amount of natural gas being flared, but it will also increase the recovery efficiency of the resource and reduce the number of wells that will be needed to recover it. Another aspect of the overall activity is treatment of the produced water. This is beneficial in two ways. First, water in the Permian Basin is a commodity and if the produced water can be cleaned and used for other purposes, the environment and region benefit. Second, less water will need to be injected down disposal wells, which has been linked to induced seismicity.

Recent advances in understanding of the hydraulic fracturing geometry captured at the HFTS, coupled with advances in expandable liner technologies, have provided an opportunity to significantly increase domestic production and recoveries from existing horizontal wells by strategically contacting previously un-drained portions of the reservoir through in-fill stimulation. Furthermore, recompleting 20 percent of the candidate pool of the existing wells (28,000 wells) would generate substantial economic activity while at the same time minimize the environmental footprint as compared to new well development. Phase 3 of the project, Legacy Well Recompletion – Infill Stimulation, will examine the potential for recompleting existing horizontal wells in a scientific manner which can be replicated across various shale basins with the following specific objectives:

• Answer the key question – Can new, previously undrained reservoir be identified within a produced wellbore, and successfully contacted with new infill stimulation technology to boost production and improve recoveries?
• Understand how new fractures grow in presence of existing stimulated reservoir volume (SRV), and changes in drainage.
• Quantify the economic viability of infill stimulation, potential added resource that could be achieved, environmental benefits by reducing the need for new wells.

Phase 1

Laredo Petroleum offered a field site for the project in August 2015. The Laredo site includes 11 horizontal wells (10,000’ horizontal legs) drilled through the Upper and Middle Wolfcamp formation in the Permian Basin. In addition, Laredo has vertical wells nearby, which are being used as observation wells. Significant events and field activities completed to date include:

• Two open-hole logs in horizontal laterals (Image + Quad Combo).
• Vertical pilot hole drilled through Wolfcamp formation.
  • Quad combo log run
  • Image log run
  • 57 rotary side wall cores recovered
  • 50 core vault side wall cores recovered
  • Diagnostic fracture injections tests conducted
• Cross-well seismic surveys completed between three wells on test site prior to and post-hydraulic fracturing operations.
• Two diagnostic fracture injections tests were conducted in multiple wells.
• Website established to share data between project partners.
• Water and air samples collected prior to, during, and post-hydraulic fracturing operations.
• 400+ fracture stages completed in the 11 wells.
• Radioactive and chemical tracers used in stimulations.
• Colored proppant markers used in two wells close to the slant core well to be drilled
• Microseismic monitoring conducted during fracture treatments.
• Core planning workshops held to design slant core well and de-risk operations.
• Slant Core Well drilled at 81 degrees through stimulated rock volume.
• 595 feet of core recovered from Slant Core Well (437 feet of continuous core in the Upper Wolfcamp and 158 feet of continuous core in the Middle Wolfcamp).
• Pressure gauges have been installed in slant core well to monitor pressure during production.
• Core description has been completed by multiple teams, and results have been incorporated into a final core description report.
  • Two main sets of natural opening-mode fractures filled with calcite cement were identified trending broadly NE-SW and WNW-ESE.
  • A total of 11 faults were identified, all within the Upper Wolfcamp formation.
  • More than 700 total fractures (natural and induced) were identified in the core.
• Fracture modeling is ongoing.
• Completed analysis of sludge collected from core barrels. Results provide a detailed subsurface proppant distribution every three feet for the entire cored interval. Proppant size and concentration was quantified as well as the amount of natural fracture cements, providing an indication of natural fractures.
• Proppant scraped from fractures of core is being analyzed to detect proppant quantity and color.
• Final microseismic processing has been completed for each fracture stage.
• A core viewing workshop was held with all participants to showcase fractures and features in entire 595 feet of core.
• Completed multiple-pad systematic pressure interference test on all 11 test wells.
• A second sequential pressure interference test across 13 wells has been completed.
• Slabbed entire slant core
• 3D Laser scanned all hydraulic fractures and many natural fractures before slabbing core
• Geologic description of slabbed core

Phase 2 EOR

A new set of horizontal wells were selected by the project members for the EOR field pilot. The selected wells are approximately one mile to the NW of Phase 1 experiment wells. The EOR wells have an updated completion design to reflect learnings from Phase 1. The site includes a central injector/producer to test cyclic gas injection, offset by horizontal and vertical wells used to monitor gas movement during injection in the reservoir. Significant events and field activities completed to date include:

• Secured multiple vertical wells to restrict vertical gas movement through existing perforations.
• Installed bottomhole pressure gages in five offset wells to monitor gas movement.
• Prepared central injector/producer well for gas injection.
• Drilled and cored a second slant core well next to the injector
  • Recovered 260 feet of through fracture core
  • Logged open hole with quad combo and water-based image log
  • Installed three discrete pressure gages
  • Completed fracture description in slant core
• Performed a flush production test in the injector/producer well.
• Performed a well interference test across the EOR test site to assess interwell communication.
• Completed gas injection using field gas and production test (huff and puff test).
• Collected surface passive seismic surveys during low- and high-pressure portions of gas injection.
• Completed proppant analysis in slant core .
• Completed Pressure Volume Temperature (PVT) analysis on injected gas and reservoir fluids.
• Completed core CT scans for core flow experiments.
• Completed 3D cyclic gas injection reservoir simulations.
• Completed 3D laser scans of all hydraulic fractures captured in the slant core.
• Completed field test to clean up Permian produced water using Membrane Distillation technology with Pitt.

Phase 3 Legacy Well Recompletion – Infill Stimulation Project

A test site was selected in the Eagleford shale operated by Devon Energy to execute the Phase 3 project. The test site comprises nine (9) legacy horizontal wells which were drilled in 2013, of which 2 were re-completed with a cemented liner and will be used for in-fill stimulation testing. In between these two adjacent wells, an observation well will be used to sample the legacy hydraulic fractures by cutting a whole core through the SRV, and then the well will be used to house permanent fiber optic cables and pressure gauges to monitor the infill fracture geometry and the reservoir depletion. Significant events and field activities completed to date include:

• Signed cooperative field data acquisition agreement with Devon Energy to host the Phase 3 field experiment in the Eagleford Shale.
• Removed production equipment, cleaned out, and installed a cemented liner in two legacy Eagleford wells.
• Ran baseline perforation erosion profile log in one re-completed well to identify frac fluid entry points from original frac stimulation.
• Drilled a slant core well between the two re-completed wells and collected 420 ft of whole core through the SRV.
• Collected mud return samples during drilling of slant core well for proppant log analysis, sample analysis ongoing.
• Ran open hole logs and installed permanent fiber optic cables and nine cemented pressure/temperature gauges in the slant core well.
• Completed fracture description of the slant well core.
• Deployed temporary fiber optic cable in adjacent horizontal well to monitor re-frac treatments.
• Performed baseline multi-well production/pressure interference test and monitored with fiber optics (FO).
• Re-fracture stimulated the 2 liner recompleted wells, pumped a total of 68 frac stages.
• Monitored re-fracs in the liner recompleted wells with permanent FO and P/T gauges in adjacent observation wells (slant core well and another horizontal well).
• Ran repeat perforation erosion profile log in the Zgabay 5H once the refrac stimulation operations were completed.
• Drilled out all frac plugs and cleaned out all stimulated wells.
• Placed all wells on production and collected oil samples for time-lapse geochemistry analysis.
• Performed first multi-well production/pressure interference test and monitored with FO.
• Held core workshop in Oklahoma City (Devon facility).
• Completed 3D laser scans of all hydraulic fracture faces from slant core at Corelab.
• Performed second multi-well production/pressure interference test & monitored with FO.
• Held project update meeting in Oklahoma City (Devon Facility).
• All Fiber Optic analysis have been completed and presented.

Performed second multi-well production/pressure interference test and monitored with FO

All field work for Phase 1, 2, and 3 has been completed. All wells are currently on production and pressure data is being collected. Data analysis and integration is underway and preparation of the final report has commenced.

$21,464,101

$22,738,430

NETL – Gary Covatch (gary.covatch@netl.doe.gov or 304-285-4589)
GTI – Jordan Ciezobka (jordan.ciezobka@gastechnology.org or 847-768-0924)

NETL-Backed Field Testing Project Seeks to Improve Efficiency and Safety of Hydraulic Fracturing (Dec 2017)
With a long record of success advancing hydraulic fracturing innovations, NETL teamed with Gas Technology Institute (GTI) of Des Plaines, Ill., to develop and execute a hydraulic fracturing test site program to answer questions, advance the understanding of the hydraulic fracturing processes to attain greater efficiencies, and improve environmental impacts.

Hydraulic Fracturing Test Sites (Aug 2017)
Presented by Jordan Ciezobka, Gas Technology Institute, 2017 Carbon Storage and Oil and Natural Gas Technologies Review Meeting, Pittsburgh, PA

Hydraulic Fracturing Test Sites (Aug 2016)
Presented by Jordan Ciezobka, Institute of Gas Technology, 2016 Carbon Storage and Oil and Natural Gas Technologies Review Meeting, Pittsburgh, PA