Acid jobs failures

Reasons why acid jobs fail are discussed in detail in chapter 5. Using a straightforward, systematic approach to sandstone acidizing treatment design—to prevent failure and increase the success rate— is the subject of chapter 6. 

The popular perception is that acid jobs have a high failure rate. That is unfair, as success is very much site specific and largely dependent on practices employed. In any case, acidizing is often considered a hit-or-miss prospect. This reputation is understandable, if based on single-well results alone, ratber than collective multi-well or fieldwide results, and if the factors leading up to—and during—the acid treatment are not considered. 

Nevertheless, the approach to an acid job can be reproduced—and should be. When a systematic approach to acid treatment design is followed, the controllable potential causes of failure can be addressed and eliminated to a great extent. The chance of success is thereby greatly increased. 

Incorporation of quality control measures during all aspects of an acid job can make the difference between success and failure. Quality control monitoring during the actual pumping of the treatment only is not sufficient. In addition, quality control steps must be planned and executed during rig-up of equipment, before pumping, and after pumping. 

Unfortunately, this potential problem was discovered after the acid job, not before. Inspection of tanks after pumping, conducted in the interest of assigning blame, showed that the nearly empty preflush tank contained the material from the prior cement job. This was suspected to be the principal culprit in the stimulation treatment failure. 

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