Unless the Division approves an alternative method of
disposal, all fluids derived from the geothermal resources must be reinjected
into the same reservoir from which the fluids were produced.
5.1 Construction: The owner or operator of a
proposed injection well or series of injection wells shall provide the Division
with information it deems necessary for evaluation of the impact of injection
on the geothermal reservoir and other natural resources. Information shall
include the items listed for a plan of operations as per Section 2.1.2 of this
section (R655-1), existing reservoir conditions, method of injection, source of
injection fluid, estimates of daily amount of material medium to be injected,
zones or formations affected, description of the effects of injection on such
factors as potable water, seismicity, and local tectonic conditions, proposed
downhole and surface injection equipment and metering facilities with capacity,
design capabilities, and design safety factors in sufficient detail to enable
adequate environmental analysis including construction and engineering design
plans, proposed injectivity surveys, seismic surveys, seismic monitoring, and
other means to monitor injection, and analysis of fluid to be injected and of
the fluid from the intended zone of the injection, if available. The bonding
for an injection well is the same as those required for an exploratory well or
production well.
5.2 Convert to
Injection Well: An owner or operator planning to convert an existing well to an
injection well, even if there will be no change to the mechanical condition,
must submit an injection well conversion plan with the Division and the
Division must approve the plan before injection is commenced.
5.3 Surveillance:
5.3.1 When an operator or owner proposes to
drill or modify an injection well or convert a well to an injection well, he
shall be required to demonstrate to the Division by means of internal and
external tests that the casing and annular cement seals have complete
mechanical integrity. These tests shall be conducted in a method approved by
the Division as proposed in the injection well plan of operations. In the case
of the annular cement seal survey for a new or converted injection well, the
owner or operator shall make sufficient surveys within thirty days after
injection is started into a well to prove that all the injected fluid is
confined to the intended zone of injection.
5.3.2 On a continuing basis and in order to
establish that all injected water is confined to the intended zone of
injection, mechanical integrity surveys on the well casing and annular cement
seals shall be made at least every five years or more often if necessary on a
well-to-well basis. The Division must be notified in writing with a testing
plan for each injection well at least three weeks before mechanical integrity
testing commences. Specific internal and external mechanical integrity tests
shall be proposed in the testing plan and must conform to the most current
industry and regulatory standards for geothermal injection well mechanical
integrity testing. The Division shall approve each testing plan and issue a
written notice to proceed with testing approval to the operator prior to
commencing. A mechanical integrity testing plan shall be submitted by the owner
or operator to the Division for approval prior to each testing cycle. The
Division shall be notified 48 hours in advance of surveys in order that a
representative may be present if deemed necessary. If the operator can
substantiate by existing data that these tests are not necessary, then, after
review of the data, the State Engineer may grant a waiver exempting the
operator from the tests.
5.3.3
Injection wells shall be monitored to ensure that there is no escape of
geothermal fluids from the casings or through the annular space between casings
and open hole except in the zone for which injection is permitted. Monitoring
required by the Division may include gauging pressure between casings, periodic
testing for casing leaks, surveys to detect movement of fluid in adjacent rock
formations, cement bond logs, temperature measurements, analysis of water
chemistry, special wellhead equipment or other methods employed by industry to
monitor re-injection operations.
5.3.4 After a well has been placed into
injection, the injection well site will be visited periodically by Division
personnel. The operator or owner will be notified of any necessary remedial
work. Unless modified by the State Engineer, this work must be performed within
ninety days of approval for the injection well, or approval for the injection
well issued by the Division will be rescinded.
5.3.5 Injection pressures shall be recorded
and compared with the pressures reported on the monthly injection reports. Any
discrepancies shall be rectified immediately by the operator. A graph of
pressures and rates versus time shall be maintained by the operator. Reasons
for anomalies shall be promptly ascertained. If these reasons are such that it
appears damage is being done, approval by the Division may be rescinded, and
injection shall cease.
5.3.6 The
pressure for injection at the wellhead of an injection well must not exceed
that which is calculated to initiate new fractures or propagate existing
fractures in the zone for injection or the confining formation between the zone
of injection and underground sources of drinking water. The operator shall
calculate the maximum injection pressure based upon industry standards and
submit those to the Division for approval.
5.3.7 The chemical, physical, and biological
nature of the injected fluid must be analyzed with sufficient frequency to
yield representative data on its characteristics. When requested by the
Division, or at any time the injected fluid is modified, a new analysis shall
be made and the results sent to the Division.
