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Systems for optimizing
production from artificially lifted wells span the spectrum of
sophistication, from multiple-sensor, real-time,
internet-accessible, remote monitoring and control systems to
a simple timer on a rod pump motor. Some would argue that the
latter does not really constitute true production optimization
technology, and many smaller producers might reply: "Maybe
not, but it is affordable." The fact is, many small producers
cannot afford the capital investment required to take
advantage of the benefits that well monitoring and control can
provide, an investment that can total thousands of dollars per
well once the costs of computer hardware and software, data
transmission system installation, power supply enhancements
and training are included. While the per well costs drop
somewhat as larger numbers of wells are added to a system, the
overall economics still can be problematic for stripper wells
producing only a few barrels of oil per day.
On the other hand, the benefits
of even the simplest applications of well monitoring and and
control systems are well established. For example, pump off
controllers (POCs), also called rod pump controllers (RPCs),
are a proven technology that has been operating in fields
worldwide for over three decades. Most POCs are remote
terminal units (RTUs) that monitor conditions, usually by
continuously measuring the load on the pumping unit, and
initiate a pump shut down based on a pre-set condition set by
the operator. By detecting the "pumped off" condition of the
well and shutting down the pump, the controller allows time
for fluid to enter the wellbore before starting the pump once
more.
Over-pumping a well or allowing
it to be pumped after the fluid level has been lowered below
the downhole pump, results in "fluid pound," a condition where
the traveling portion of the pump strikes fluid in the pump
barrel. This action exerts excess stress on the pump, the
rods, the tubing and the pumping unit, contributing to an
increased risk of failure. Of course, the cost of the
electricity running the pump on an over-pumped well is a
wasted investment.
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So, by reducing the amount of
time a pump is run ineffectively, POCs reduce power
consumption. Also, by reducing the number of instances when a
well continues to be pumped without a fluid level, POCs reduce
the number of well remediations due to pump failures, parted
rods or tubing leaks. This in turn reduces down time,
maintenance costs and well workover costs. Reported cost
savings range from 10% to 20% for electrical power and 25% to
40% for rod, pump and tubing repairs. Production increases
from 1% to 7% have also been reported as downtime is reduced
and pump efficiency improved. |
Recognizing a market for
low-cost alternatives that can translate some of these
benefits for low-productivity wells, several companies are
offering controllers that offer a degree of technology at an
affordable price. Two of these are described here.
ChevronTexaco has employed the Pacemaker in a wide variety of well configurations, including: tubing packer completions, open ended tubing, monobore completions (no annulus), and as a replacement for capillary strings and standard plunger lift. These applications have been in sandy environments, in conjunction with single well compression, and even on both sides of a dual completion.
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State-of-the-Art
Summary