Sandstone acid failures

Sandstone acidizing can be a very successful well stimulation method. However, the risk of failure is moderate to high. Fortunately, there are a limited number of reasons why acid treatments fail in sandstones. Success begins with the selection of a viable acidizing candidate well. Many poorly producing wells are not viable acidizing candidates. Conversely, many relatively prolific producers are the very best acidizing candidates. Once a viable candidate is selected, a systematic approach to the selection of fluids, additives, and acid placement technique must be taken. On-site quality control and posttreatment evaluation help to ensure successful results and improved future treatments. 

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. 

In reality, there are a limited number of reasons, or controllable causes, for sandstone acidizing treatment failure. All can be avoided with proper treatment planning and execution. This is not to say that a success rate of 100% —on a well-by-well basis— is readily attainable. It may be possible in a particular field or with a limited selection of wells. However, stimulation methods are not foolproof, and acidizing is no exception. 

First, one must identify and understand the causes of sandstone acidizing treatment failure that are avoidable. These should always influence the steps taken in the treatment dedsion and design process. 

Understanding that most treatment failures are due to one or more of the preceding reasons simplifies the process. It can also ease the mind when sandstone acidizing treatment design considerations seem hopelessly complicated. 

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