ODNR: Ohio earthquakes triggered by brine injection into disposal wells

COLUMBUS — Investigators from the Ohio Department of Natural Resources have confirmed that injection well fluid along a weakened geologic fault triggered the 12 earthquakes that occurred in the Youngstown area between March 2011 and January 2012.

After investigating all available geological formation and well activity data, ODNR regulators and geologists found fluid from the Northstar 1 Class II disposal well intersected an unmapped fault in a near-failure state of stress, causing movement along that fault.

Geologists believe induced seismic activity is extremely rare, but it can occur with the confluence of a series of specific circumstances, as seen in the Mahoning Valley. (Download the full report.)

Stricter regs

All of the conditions associated with induced seismic activity are addressed in Ohio’s new well permitting and construction regulations, announced Friday (March 9).

The standards cover the transporting and disposing of brine, a by-product of oil and natural gas hydraulic fracturing. According to state officials, the new framework makes Ohio’s rules for brine monitoring and disposal among the nation’s toughest.

What’s covered

The new safeguards:

— prohibit any new wells to be drilled into the Precambrian basement rock formation;

— mandate operators submit extensive geological data before drilling; and

— implement state-of-the-art pressure and volume monitoring devices, including automatic shut-off switches and electronic data recorders.

In addition, ODNR will require that brine haulers install electronic transponders to ensure “cradle to grave” monitoring of all shipments.

Applies to all wells

The regulations will apply to new Class II disposal well permit applications and to existing disposal wells, if applicable.

Ohio regulates Class II disposal wells on behalf of the U.S. EPA.

More details

The proposed new regulations includes:

— Requires a review of existing geologic data for known faulted areas within the state and a prohibition on locating new Class II disposal wells within these areas;

— Requires a complete suite of geophysical logs (including, at a minimum, gamma ray, compensated density-neutron, and resistivity logs) to be run on newly drilled Class II disposal wells. A copy of the completed log, with analytical interpretation, will be submitted to ODNR;

— Authority for ODNR to require the plugging with cement of wells penetrating into the Precambrian basement rock and prohibiting injection into the Precambrian basement rock;

— Requires the submission, at time of permit application, of any information available concerning the existence of known geological faults within a specified distance of the proposed well location, and submission of a plan for monitoring any seismic activity that may occur;

— Evaluates the potential for conducting seismic surveys;

— Requires a measurement or calculation of original down hole reservoir pressure prior to initial injection;

— Requires conducting a step-rate injection test to establish formation parting pressure and injection rates;

— Requires the installation of a continuous pressure monitoring system, with results being electronically available to ODNR for review;

— Requires the installation of an automatic shut-off system set to operate if the fluid injection pressure exceeds a maximum level to be set by ODNR; and

— Requires the installation of an electronic data recording system for purposes of tracking all fluids brought by a brine transporter for injection.

All of the reforms will be considered during the permitting process for new Class II disposal wells and will be implemented as attached permit conditions until they are either codified in law or written into administrative rule, which carries the weight of law.