6 - Kuwait Oil Company

the application window and should be used carefully
by trained Engineer. The expert system does not
replace the expert but does aid the engineer in the
decision and speed up the selection process and
minimize the dependence on A/L consultants.
Figure 1. Table of A/L Typical Applications
ALES Concept and Development
An Expert System is a software that uses a knowledge
base of human expertise for problem solving, or to
clarify uncertainties where normally one or more human
experts would need to be consulted [Wikipedia]. The
main challenges that comes up from this concept are
basically how the knowledge of the experts will be
coded, how the system will use this human expertise
database to talk and advise about an specific case and
what inputs and calculations will feed the expert system.
It was decided that the Expert System must be fed
with real well parameters and outputs from internal
calculations as if the design of each Artificial Lift
Method is performed at the same time, regardless of
the capability of a specific method to operate under the
given well conditions. By this way, all limitations, critical
conditions and variables that affect the performance
will be calculated and sent to the expert module.
Usually, most of the required parameters to design and
select an A/L System are available. The first thing an
expert would do with this information is to asses and
questioning each A/L system performing under the
given conditions. As an example, the expert may ask
him/herself: Can a SRP produce 10000 BPD at 10000
feet An Engineer with some expertise in this method
may know that it will be difficult, thus he or she might
start thinking about finding a different solution for this
specific well. This approach reflects that there is a
pre-assessment made by the expert based on his/her
experience only, without executing any calculation and
this is meant to be one of the first functionalities of ALES.
Considering the same case mentioned in the above
paragraph, this Engineer may consider an ESP System
as a good option, however, at this stage there are other
parameters that affects the ESP performance that need
to be calculated such as the fraction of free gas into
pump for the desired production rate. If this value is
two high, the expert may start thinking about a different
solution like Gas Lift for example. In this sense, it is
evident that some design calculations must be executed
to have a better picture of each A/L system performance.
Assuming that the free gas into pump is acceptable
and theoretically an ESP can do this Job for the above
case, still it is necessary to calculate all stresses, torques
and pressures under which this pump will operate
and determine if a pump capable to operate under
these conditions is manufactured and available in
the market. After doing all of this for each Artificial
Lift System, the Engineer will be totally capable to
make the right and most assertive decision.
Typically, to execute all the analysis mentioned
before may take long time and might require
more than one expert, thus ALES had to be
designed to function in such a way that evaluating
one case should take less than 5 minutes.
In ALES, when a parameter is being evaluated, there are
a quantitative complex rules whose output values goes
from -1 (bad ) to +1 (excellent) . Figure 2 shows and
example for production rates evaluation when using an
ESP (at 50 hertz) for two different casings sizes (Red line
the 5 ½” casing and green line 7”casing). As can be
appreciated for rates below 500 BPD the corresponding
rule in ALES gives a negative value because a typical
ESP is going to operate below the recommended range
(down-thrust) which reduces the run life, besides it is
expected to have low ESP efficiencies for small pumps
and the corresponding shafts are fragile. Then for rates
from 500 to 1300 BPD the value is positive but lower
than +1 because the pumps are close to the minimum
(downthrust limit) recommended rate. For rates up to
3200 BPD for both casings is the same and then the rule
decreases for 5 ½’’ casing because it is reaching 5000
BPD the maximum recommended limit (upthrust) until
the maximum feasible limit of 5400 BPD. An equivalent
situation happen for 7” casing but with higher rates
because the pump capacities are higher for bigger
pumps that fit inside 7” casing but they don’t in a 5 ½
“casing. To explain this rule a target rate of 4500 BPD
is assumed. In this sense, if the well has a 5 ½ casing
the evaluation will be +0.7 (good but not excellent) and
for a 7” casing the evaluation will be +1 (excellent).
Figure 2. ALES Rules Example
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