Servicing Wells With Pump Down Tools Can Reduce Maintenance Costs
Authors: Vernotzy Richard R. 
Published: October 2008

The Pump Down Tool technique of well work has been extensively tested during the past several years and appears to offer a practical method of performing routine maintenance normally performed with wireline. Minor workover operations have also been performed with a high degree of success.

The technique appears to have application on both underwater and conventional platform completions and, in some cases, onshore application may be justified.

As a result of the indicated increased efficiency with the PDT technique, routine maintenance operations should be less expensive and, as an added feature, substantial savings in workover costs and production losses or delays can be realized.

Costs and resultant estimated savings will be discussed for various reserve size fields with wells equipped for pump down tool maintenance.

Introduction

The oil industry has placed an increased emphasis on offshore operations during the past several years. Along with this increase, there have been numerous new techniques which have evolved in all phases of the operations, from initial exploration through producing of the hydrocarbons. 1, 2, 3, 4, 5, 6,7, 8) Among the equipment techniques which have evolved is the use of subsea Xmas trees to complete existing offshore exploratory wells (cased and capped) or well locations which cannot be reached with existing directional mechanics from surface platforms. In line with the subsea completion innovation, a technique was devised to perform routine maintenance operations which would normally be performed by wireline methods. The method employed is called the Pump Down Tool technique.

The Pump Down Tool (PDT) technique utilizes hydraulics as a means of motivating the piston or motor units in and out of the tubing string during downhole operations. Considerable testing of these tools to evaluate their feasibility in performing maintenance operations on actual and simulated underwater completion facilities has been in progress for several years. 9. 10. 11. 12. 13)

During the testing and evaluation of these tools it has become apparent that they have utility not only on subsea completions, but on all wells; especially those deviated wells drilled from offshore platforms. These wells make routine maintenance with wireline cumbersome due to the high angles. For this reason it appears that the use of hydraulics would be more efficient and. in most cases less expensive than wireline operations. In addition, it has been found through testing that minor workover operations using PDT equipment are feasible. This offers the advantage of being able to effect repairs at the time they are required, instead of having to postpone the work until a sufficient amount of wells require repair. This would not only result in a saving in workover costs but would decrease production losses or prevent deferring that production to the end of the field's life.

The purpose of this text will be to discuss the operations which can be performed using the PDT technique of well work, to compare the operations of wireline and pump down tool methods of well maintenance and to show the estimated savings during the life of various size reserve fields.