Disposal Well
Completion and Maintenance
WELDON M. BAKER,  Division Engineer
Halliburton Company
Evansville, Indiana
INTRODUCTION
Many of the practices and principles that have been developed and used in the
drilling and producing of oil wells over the past years have been adapted for use in
disposal wells of one kind and another. The disposal of large quantities of salt
water or brine which have been produced with the oil is a problem that has plagued
the oil industry for many years. This problem has been solved by injecting the
produced water into a porous strata or formation underground through a well drilled
for this purpose, a former producing well, or one that was drilled to be a producer
but failed. This technique has also teen used to dispose of waste products from industrial plants such as pickle liquor from steel mills. Work has been done on a
method of disposing of radioactive waste by mixing it into a cement slurry and injecting it into a fracture created in a subsurface strata.
The practice of cementing pipe in a drilled well bore, or grouting as it is referred to in the water well industry, was first started around the turn of the century in the oil fields of California. In 1910 the first patent for a plug method of
cementing or grouting was issued. In 1922 a patent was applied for on a method
of mixing cement and water which is still in common use today with many improvements.
CASING CEMENTING
First, let us consider why pipe or casing is cemented (grouted) in a well.
Cementing serves to help protect the pipe from corrosion from salt or sulphur water and electrolysis from the outside. Also it helps to provide segregation of the
fluids contained in the various porous strata behind the pipe. Cementing also reduces the danger of fresh or potable water bearing strata being contaminated by
undesirable fluids from below. Also it serves to reduce the danger of the pipe being collapsed by external pressures. In the last 35 years over 2.5 million cementing jobs of this type have been performed by one leading service company in this
field.
Now let us take a look at some of the mechanics involved in the placement
of a cement slurry behind a pipe or casing in a drilled well bore which is filled
with the fluid used in drilling (Figure 1). After the pipe has been lowered to
the position in which it is to be cemented, a connection is screwed or otherwise
fastened into the top of the pipe. This serves to allow drilling mud, water, or
other fluids to be introduced into the pipe by a pump where desired by the customer, depending upon well conditions known to him. The fluid introduced into
the pipe at the top causes fluid to be displaced from the lower end of the pipe and
returned to the surface through the annular space between the pipe and the well
bore. After circulation has been established in this manner, a cementing slurry
or grout is introduced into the pipe. After mixing and pumping a pre-determined
amount of the cementing material into the pipe, a plug is inserted which serves to
segregate the cementing material and the fluid by which it is followed. This plug
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