- Density and volume
determinations
- Slurry design
- Material BOM and
material job cost
- Squeeze Cementing
- Plug Setting
- Foam Cementing
- Job Design Programs
Introduction:
The fundamentals
for designing a cementing job have been available for many years. Much
of the design process if done manually is very time consuming and tedious.
For this reason, most well job designs use previous well designs or
only a single approach is examined. With the use of the personal computer
and the appropriate computer programs, many variations can be investigated
in the same time and a good record of the design is produced. The first
place to start in improving the cementing process is good recording
keeping. If a job result is not good, the two questions that should
always be asked are: 1) Was the actual job design followed, 2) If the
actual job execution was not per the design, how did it differ. The
question is "Was the job plan in error or was the job execution
the problem?" We should not respond to a bad job by developing
a new approach when the only problem was job execution. On the other
hand, if a job went well, we would like to duplicate the approach in
future wells with similar characteristics. Finally, if a job does go
bad, what is the best remedial approach for correcting the job failure
or is a corrective action necessary? The design programs available
from SERVAgroup help the job planner investigate more options
and provides a good record of the selected "plan" for future
reference.
The programs are
divided into the types of jobs: Primary Cementing, Squeeze Cementing,
Plug Back Cementing and Foam Cementing.
Primary Cementing:
A step-by-step procedure
for job design is provided. The procedure identifies the computer program
spreadsheets that will be used and how to use them. The program also
provides a means to allow for deviated holes. Some of the documentation
and calculations provided are:
- Wellbore definition
- Graphical representation
of pore pressure, frac pressure and slurry pressures as a function
of depth
- Volumes for lead
slurry, tail slurry and mud displacement
- Hole conditioning
recommendations
- Pressure to land
the top plug
- Slurry design
(input of materials, output of density, yield, water requirements)
- Total materials
required for the job
- Cost of materials
for the job
- Rheology of well
muds, slurries and displacement fluids (API calculations)
- Maximum lowering
velocities
Squeeze Cementing:
The squeeze program
provides a variety of calculations that typically would be recommended.
The assumption is that a low-pressure squeeze is desirable and high-pressure
squeeze is not desirable. In addition, the program calculates and graphically
represents the surface and downhole pressures as a function of volume
pumped. Some of the calculations provided are:
- Volumes
- Pressure calculations
- Pressure to reverse
- Pressure on formation
- Maximum squeeze
pressure/ casing collapse
- Fracture and pore
pressures
- Slurry design
- Rheology
Plug Back Cementing:
Balanced plug design
is made easier with the Plug Back Cementing program. The program also
incorporates adjustments for deviated holes. Some of the calculations
provided are:
- Wellbore definition
- Spacer and displacement
volumes
- Job total water
requirements
- Squeeze slurry
pressure on formation
- Pore and frac
pressures
- Balanced plug
design
- Slurry design
- Design recommendations
for density and rheology of slurry and wellbore fluids to obtain
a plug that will stay in place without the aide of mechanical devices
Foam Cementing:
Foam cementing is
the biggest innovation in primary and remedial cementing in the last
50 years. Its use has help solve many of the traditional problems that
have always plagued the cementing process. Some of the problems that
are solved with foam cement (along with the use of standard recommended
practices) are:
- Cementing across
weak formations
- Gas migration
control in high pressure, high temperature wells
- Improved mud displacement
efficiency
- Cementing of geothermal
wells and "huff and puff" steam flood wells
- Remedial cementing
in water flood fields to stop unwanted water flows
The Foam Cementing
program provides the calculations and graphical design aides:
- Wellbore definition
- Graphical representation
of pore pressure, frac pressure and slurry pressures as a function
of depth
- Volumes for mud
cap, cap slurry, foam slurry, tail slurry and mud displacement
- Hole conditioning
recommendations
- Pressure to land
the top plug
- Slurry design
(input of materials, output of density, yield, water requirements)
- Total materials
required for the job
- Cost of materials
for the job
- Rheology of well
muds, slurries and displacement fluids (API calculations)
- N2 volume and
density requirements
- Schedule of N2
required as a function of volume of cement pumped
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