GENERAL42099

• Permit No: M1983194
• IBM Index Class Name: General Documents
• Doc Name: COVER SHEET 4 APPENDICES
• Media Type: D
• Archive: No

4.2 APPENDIX B - TECHNICAL EVALUATION OF
WOLF RIDGE CORPORATION'S (WRC) PROPOSED
WELL COMPLETION AND ABANDONMENT PROCEDURES
The following discussion outlines ttie primary points of
technical uncertainty and disagrcemenrt betwcen BLM and
WRC regarding well completion and abandonment as well
as the underlying basis for the application of the mitigating
measures found im the EA and proposed in the EIS. The
discussion a limited to the technical comsideretioms necessary
to ensure a stable well bore for extraction of the subject
resource and adequate isolation of the mining cavity. Any
discrepancies between mitigation measures concerning the
length of the annular cement column (8 i4-inch casing x
bore hole walq that is found in the E.A end proposed for
the EIS are the result of further refinement of the hydrological
analysis subsequent to completion of the EA.
For background information, please refer to the draft EIS
and cortespondence contained in the case file on the proposed
mine plan, geology, and downhole resources. However, it
is important to note that the proposed operation uses new
end emerging technology combined with the adaptation of
existing oil and gas well drilling and completion practices.
The project is further complicated by the unique subsurface
environment found in the Piceance Basin.
The presence of the proper fluid behind the casing
facilitates efficient extraction of the subject resource. WRC
proposed to ensure a stable well bore for nahcohte extraction
by cementing the bottom 100 feet of casing and leaving
a "casing pack" (mud gel), in the annulus betwcen the 8
ye-loch production casing and borehole, from the top of
the cement to surface. Upon abandonrent of the borehole,
the casing cot cemented would be removed end used for
subsequent wells. The mitigating measures proposed in the
EIS expand the length of the cement. column to approx-
imately 250 fcet in total length. This requirement will ensure
isolation of the mine cavity from the annular region behind
the 8 i4-inch casing and the base of the: lower aquifer.
The paragraphs below describe some of BLM's
recommended cementing procedures necessary to ensure an
adequate cement job. The descriptions are brief and are
meant only to identify the considerations that must be
analyzed prior to performing a cementing operadom of this
importance.
Cement selection and desigm mutt satisfy the requirements
of the operation in question. For tha operation, cement
design must include such factors as low frachue gradients,
rock quality, bonding characteri:;tics (pipe-cement-
formation), salt contamination and temperature fluctuations.
Cement strength should be a concern when considerirtg the
horizontal drilling operation that will occur in each well.
However, the cement will not be exposed to the pressures
necessary for formation fracturing and stimulation.
There are many formulations of cements that are
applicable to [his type of operation. WRC identified two
specific types (life and thixotropic) in a meeting at the State
Office on July 30, 1986. Some new developed types of
cements (i.e., foamed, expanding, lighting additives, etc.)
will also satisfy the required design criteria and are lighter
than water.
Poor cement jobs can result because of a number of
reasons, As discussed in the referenced papers (attached),
some of these reasons and cortesponding explanations are
as Follows:
1. Improper pipe cemtralvation
2. Improper mud conditioning prior to cementing
3. Improper removal of mud during cementing]
4. Cement contamination by mud
5. Cement-mud incompatibility (excess viscosity at
interface)
6. Loss of fluid from cement slurry
7. Gas cutting of cement prior to set
S. Lost circulation before or during cementing
9. Breakdown of woes after cementing (fallback)
10. Salt and coal sections
11. Washouts
12. Pipe surface finch
13. Improper flow regime
Consideration must be given to the effects these problem
areas may induce since the well bore mechanics are such
that many of these problems can and will occur in this
operation.
Centralization is responsible for creating a uni[orm Flow
area perpemdicular to the flow direction, increasing
displacement efficiency, preventing mud channels, and
generally ensuring that the cementing operation occurs as
planned and results in a uniform cement sheath around the
casing. During displacement, mud moves much slower in
the region where the casing is closer to the borehole. If
proper centralization is not employed, channeling of cement
will occur.
Lost circulation (LC) will exist in this project's borehole
environment. The leached zone has required even the most
experienced drilling engineer [o rethink the use of common
drilling practices when dealing with LC if cosdy time delays
4,2-1