Page 8 - A Primer of Oilwell Service and Workover Completion

INTRODUCTION 

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Petroleum Extension-The University of Texas at Austin

INTRODUCTION

newly drilled oilwell is not company—has to work over company, or contrac-
A much more than a lined complete it. The operating com- tor, to do well repair and other
hole in the ground. When a drill- pany completes the well by add- remedial work.
ing crew drills a well, they line ing equipment and carrying out Well servicing is maintenance
it with large pipe called casing. certain procedures that will allow work. It usually involves repair-
They also cement the casing in the well to produce fluids (oil, ing equipment, but a servicing
the well (fig. .). At this point gas, and water). contractor may also add new
in the well’s life, it usually cannot To complete a well, a crew equipment to restore the well’s
produce oil and gas (hydrocar- usually installs a string of relatively ability to produce hydrocarbons.
bons). The company that owns the small pipe—tubing—inside the Workover includes any of
well—the operator, or operating well. Near the bottom of the tub- several operations on a well to
ing, crewmembers usually install restore or increase production
a special sealing device called a when a reservoir stops produc-
packer and connect ing at the rate it should. Many
valves and metering devices on workover jobs involve treating
top of the well to control flow. the reservoir rock rather than the
Sometimes, crewmembers add a equipment in the well.
CASING
1 pump or another device to lift Well servicing and workover
the oil out of the ground. are important because oil is the
As wells produce over time, most heavily used energy source
equipment fails and the rocks throughout the world. The U.S.
CASING holding the hydrocarbons—the Geological Survey has estimated
2
reservoir—cause problems. When that  percent of all hydrocar-
problems with equipment and bons on earth have been discov-
the reservoir occur, flow from the ered. Of these,  percent have
well either slows down or stops been produced and consumed.
CASING
3 altogether. When this happens, The undiscovered  percent
the operator also has to repair is most likely in small fields in
and work on the well to bring difficult environments like the
it back to full production. The polar regions and under the seas
industry calls such repair and and oceans. These environments
Figure .. A newly drilled well
lined with cemented casing work well servicing and work over. are extremely expensive to drill in.
The operating company custom-
arily hires a well servicing and

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