Computation Section
Project Management
 - Example: Installation of an Oil Field Pumping Unit

The story was contributed by William Lesso, Professor Emeritus of the University of Texas.

The LongHorn Petroleum Company has just brought in a producing oil well. It’s no gusher. In fact, they need to hook up a ‘horse head’ pumping unit and run a line to a nearby set of oil storage tanks. Periodically a tanker truck will come by and take the accumulated crude oil to the refinery.

Based on past experience, we have listed the following tasks, which should be done along with estimates for this particular well of how long each task will take and the number of persons required for the task.

The first three tasks can be started anytime. At the wellhead, the ground must be cleared, forms put in and a concrete mounting slab poured. This should take about 11 hours but might be done in only 9. If there is some difficulty, it could take as long as 19 hours. Usually a crew of 4 is assigned.

The pump unit must be ordered. This should take about 0.25 hours.

A path must be cut through the brush and cactus from the well to the storage tanks. This should take 30 hours. It may only require 20 hours if the brush is not too thick, but it could take as long as 40. A crew of six will be assigned to this task.

Once the concrete slab is poured, it must cure for 24 hours, no more, no less.

After the order is placed, the pumping unit will be delivered to the well site by the supply company in 9 hours. The time will be no more than that, but the unit may arrive in only 3 hours.

After the path is cleared, a crew of six will dig a trench, put in a flow line and cover it. This usually takes at least 10 hours. It could be as long as 14, but the task should be done in 11.

At the same time, three persons will run an electric line along the path. They estimate a likely time of 10 hours, but it may be as long as 12 and as short as 8.

Once the pumping unit has been delivered and the cement slab has cured, it will take a crew of three persons 5 hours to mount the unit but it might be finished in only 4. If things don’t work out well, it could take as long as 12 hours.

With the pump unit in place, two persons will hook up an electric motor. This will take a minimum of 3 hours and as much as 5, but mostly likely 4.

At the same time, three persons will run sucker rods down the well and to the pump. Thus usually takes 8 hours but might only take half as long. If there are problems, it could take 18 hours.

When the electric line has been run and the electric motor is in place, it will be tied in to the electric supply and tested. One person can accomplish this job in 1 hour.

When the flow line has been completed and the sucker rods installed, the well must be tied in and all the valves ‘nippled up.’ It takes two persons an hour to do this. The time can be no less than an hour, and it could be 4 hours if there are problems.

After the electric motor is ready and the well has been tied into the flow line, the final test of the pump unit is made. This usually takes about 4 hours but could be done within 1 hour. However, it has been known to take as much as 10 hours if many adjustments need to be made. A crew of two does this job.

At the same time, one person goes around and makes sure all the values are open. This could take only a few minutes. More likely it could take an hour, but never more that 2.

With these tasks completed, the unit is ready to pump oil.

The situation described is a project that involves a number of activities with different execution times and different crew requirements. The administrator of this project wants to schedule the activities to get the job done as soon as possible. The activities cannot all be scheduled to start at the same time, because some activities cannot be started before others are completed. If the total work force is limited, activities cannot be scheduled simultaneously if the total number of workers required is greater than the work force.

The scheduling of the activities in a complex project is the subject of Project Management. The Project Management add-in can be used to model the problem and answer a variety of relevant questions. Additional discussion on the model can be found in the Design section.



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tree roots

Operations Management / Industrial Engineering
by Paul A. Jensen
Copyright 2004 - All rights reserved