NETL and Colorado School of Mines are partnering to advance the use of fiber-optic sensing to monitor fracture growth in the subsurface and optimize the production of natural gas from unconventional reservoirs, an important resource to meet the nation’s growing energy needs.

To increase hydrocarbon flow, natural gas producers employ horizontal drilling techniques coupled with hydraulic fracturing in shale formations, which are known for their low permeability and porosity.

These techniques enable the development of the massive shale reservoirs that exist in abundance in Texas, Pennsylvania and several other key energy-producing states. However, producers must carefully avoid “fracture hits,” one of the most significant challenges encountered in hydraulic fracturing operations.

“Fracture hits occur when the hydraulic fracturing process creates fractures in the rock formation that interfere with nearby wells,” said NETL geoscientist Erich Zorn. “Fracture hits can result in the invasion of fluids and sand into an existing producer (parent well) while a neighboring well (child well) is being hydraulically stimulated, possibly damaging the parent well and its ability to produce hydrocarbons.”

To address this challenge, researchers placed strain-sensitive fiber-optic cable in monitoring wells in the Delaware Basin in west Texas. Monitoring wells are drilled adjacent to production wells to detect rock deformation and locate the active tips of growing fractures in real time. Ideally, there can be more than one monitoring well at the site to provide different “views” of the growing fractures.

“Distributed fiber-optic sensing is a game-changer because it is more sensitive than existing technologies such as geophones and other seismic sensors,” Zorn said. “The fiber-optic cables collect data at a very high resolution to determine a fracture’s dimensions, spatial orientation, growth rate and deformation properties.”

This novel approach utilizes a heart-shaped signal in distributed strain sensing measurements to estimate the hydraulic fracture tip distance before the hydraulic fracture intersects the monitor well, providing an early warning regarding the fracture’s growth and propagation velocity and direction.

Application of this technology may also better prevent drilling hazards if hydraulic fracturing operations pose risks for nearby drilling operations. “Determining the growth, speed and orientation of developing fractures is crucial to planning safe and cost-effective drilling operations,” said NETL geophysicist Colton Kohnke.

Drilling too many wells may unnecessarily waste resources such as water, fuel, steel casing and other infrastructure while adding to emissions issues and the land footprint of the operation. On the other hand, drilling too few wells, from the perspective of well spacing, may leave valuable resources in the ground.

“We expect the research results from this project to have a positive impact on economic, environmental and resource recovery factors,” Kohnke said.

NETL is a U.S. Department of Energy (DOE) national laboratory dedicated to advancing the nation’s energy future by creating innovative solutions that strengthen the security, affordability and reliability of energy systems and natural resources. With laboratories in Albany, Oregon; Morgantown, West Virginia; and Pittsburgh, Pennsylvania, NETL creates advanced energy technologies that support DOE’s mission while fostering collaborations that will lead to a resilient and abundant energy future for the nation.