WATER JET CONFERENCE - Waterjet Technology Association

DISCUSSION
NAME: W. G. Howells
COMPANY: Berkeley Chemical Research
QUESTION: "Mr. Zublin, what methods are used to determine the effectiveness of your
downhole cleaning procedure?"
ANSWER: There were two methods used to determine downhole effectiveness. One
was visual, the other was economic.
Firstly, the relationships between rotational speed and vertical speed that were
used, previously recommended by the orginators of the process, were detailed then, based
on the analysis made, the change in these relationships were detailed and reviewed. Then
both the new and old systems were tried on a liner in-situ.
The liner was retrieved from the hole and visually inspected. It was easy to
establish that the new method, although consuming less time, was 3 to 4 times more
effective than the previously used technique.
The economic method was a bookkeeping job. We kept track of the number of
jobs done throughout a given period and for whom. We then recontacted the clients to
determine what increase in production, if any, and compared the net cost recovery to the
cost of the job. This then gave us an average time to cost recovery. Using the data that
three months cost recovery was effective economics for any oil well, we then divided the
work up between wells with cost recovery of 90 days or less and 90 days or more.
History showed us that when utilizing this approach the older technique showed
58% of the work done to have cost recovery in less than 90 days. With the new technique
the data showed that the cost recovery in less than 90 days was better than 83% of all
wells done.
One of the fallacies in the above technique is that it is entirely possible that the
selection criteria utilized by our customers prior to using our new services improved with
time. Therefore, we were used under conditions in which the service was more effective.
Ignoring that, it would seem that the newer methods were more effective. If I were to
hazard a guess, I would say that the effectiveness would be reduced to somewhere in the
ballpark of 75%, allowing for more efficient selection criteria.
NAME: Mohamed Hashish
COMPANY: Flow Industries
QUESTION: "The impact force of a jet (i.e., quasi-static force) is not kinetic energy per
unit time as equation (5) gives in conjunction with Figure (1). The force is the rate of
change of momentum = WV where W is the fluid flow rate and V is its impact velocity.
This might be reason for the statement you made in the conclusion.
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