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 10 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 Enhanced Oil Recovery (EOR) fluid is in the early stages of broad use 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 Joint Industry Project (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 as a whole. 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% 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:
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:
Phase 2 EOR
A new set of horizontal wells was 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:
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:
All planned work for Phase 1 and 2 has been completed. Phase 3 is ongoing with significant field testing under way.
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