The overarching purpose of well stimulation is to improve oil and gas recovery by modifying the flow characteristics and behaviors of the rocks surrounding the wellbore.
In the modern oil and gas industry, there are really two main reasons for stimulating a well.
The first is to repair formation damage. Formation damage describes any negative change in the ability of oil and gas to flow from the reservoir rocks into the well. It can occur during any phase of a well’s life from drilling through to abandonment. Stimulation allows operators to repair or remove formation damage near the wellbore region to ensure the efficient operation of a well.
The second use for stimulation is to allow production from rock units that have permeabilities too low for traditional production. As stimulation techniques have matured, these low-permeability, unconventional resources have come to make up a large percentage of total production in the United States and Canada.
Stimulation can take place any time during the completion or production phases of operation. Unconventional resources are usually stimulated during the completion process. Conventional resources may be stimulated during the completion process, but they are also stimulated during production, especially if formation damage is suspected. Wells can be re-stimulated throughout their lives depending on the needs of a given situation.
These days, the vast majority of wells will undergo some type of stimulation during their life cycles.
In this section, we’ll take a closer look at two of the most common stimulation methods: hydraulic fracturing and acidizing.
Before we learn how these methods work, we need to answer a basic question: what is formation damage?
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