| 摘要 |
<p>A method to clean a wellbore and the near wellbore area adjacent to the wellbore of a hydrocarbon bearing and/or coal bed methane formation adjacent to the production zone of the wellbore is provided. Specifically, a method for removing liquids such as water and/or oil from the near wellbore formation is provided. Furthermore, A method to clean a casing inserted into a wellbore is also disclosed. A method for cleaning a wellbore of fracturing fluid, with or without proppant is also disclosed. Each of the methods includes the steps of injecting either liquid carbon dioxide or a treatment medium comprising liquid carbon dioxide into a wellbore through tubing such that the location at which the treatment medium is administered may be controlled. In some embodiments, pressure within the wellbore is regulated in order to either maintain the treatment medium in the liquid state, or allow at least a portion of the treatment medium to vaporize upon introduction into the wellbore. Once the treatment medium has at least partially vaporized it will loosen and/or entrain undesirable materials from within the wellbore or casing, and may also act to mobilize any water and/or oil present by causing the water to effervesce and/or by dissolving any oil. These processes may act to defeat capillary pressure mobilizing the water and/or oil such that it may be blown or pumped to the surface or, if the present invention is practiced in a coal bed methane formation, may be driven into the coal bed methane formation such that it may no longer impose a barrier to methane production. In certain embodiments, the gaseous portion of the treatment medium is allowed to escape through the wellhead, carrying with it the undesirable materials.</p> |
