EP 1110-1-27
27 Jan 00
Chapter 3
Historical Data: Influence on Pumping/Injection and Drawdown Results
3-1. General
a. Purpose. The primary purpose of routine maintenance monitoring data acquisition is to provide
information to chart trends in historical well and system performance. These changes over time indicate
performance change, and trends are used to schedule maintenance activities. A checklist is provided in
Chapter 8 for use in assessing the adequacy of well maintenance actions.
b. Key factors. The key factors in maintenance monitoring analyses are not the absolute numerical
values (e.g., total Fe = 2.6), but the changes over time (total Fe was 2.6, 6 months later it was 0.6). A
significant change in parameters indicates that the well may be in need of attention, or indicates
biogeochemical changes of interest as microorganisms extract Fe, PO4, etc., which may eventually lead to
well performance changes. In any system or activity, data may be collected to fulfill some past directive,
but the purpose for the activity may be lost over time as personnel change. Personnel involved in well
maintenance should be conversant with all of the following sections.
3-2. Pumping Rates
The typical pumps used on HTRW projects are the widespread centrifugal pump designs adapted for well
applications. In centrifugal pumps, output flow is in a dynamic relationship with system head: as system
head is raised and lowered (e.g., due to clogging or other system hydraulic fluctuations), flow lowers or
rises in inverse proportion. Changes in pumping rates over time will result due to changes in pumping
head.
result in lowered pump output, usually as a gradual declining trend. In submersible or lineshaft turbine
well pumps, an abrupt loss of output usually is due to a hole developing in discharge piping. Another
cause may be an inadvertent valve closing or other obstruction.
b. External head changes. If regional or pumping/injection head changes, this change will affect
the pump output of an otherwise properly functioning pump. While direct measurement of water level
(Section 3-4) is a more sensitive parameter, increased drawdown may be reflected in reduced flow. The
size of this effect is specific to the pump.
c. System demand changes. Operational changes may affect the flow and efficiency of a pump.
Restricting flow (e.g., for plume management) may be reflected in a pump operating inefficiently and
having a shortened operating life.
3-3. Wellhead Pressure
Wellhead (system) pressure in the pump discharge significantly affects pump output flow (Section 3-2)
and likewise affects injection acceptance. If system head increases, a centrifugal pump cannot produce as
much output. Reduced flow then also may be a reflection of increased system head. This in turn is most
typically a result of clogging activity. However, other causes, such as inadvertent valve closing or
insufficient power, should also be investigated.
3-1
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