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Pipe recovery is a specific wireline operation used in the oil and gas industry, when the drill string becomes stuck downhole. Stuck pipe prevents the drill rig from continuing operations. This results in costly downtime, ranging anywhere from $10,000-1,000,000 per day of downtime, therefore it is critical to resolve the problem as quickly as possible. Pipe recovery is the process by which the location of the stuck pipe is identified, and the free pipe is separated from the stuck pipe. This allows fishing tools to subsequently be run down hole to latch onto and remove the stuck pipe. == Causes of Stuck Pipe== ;Differentially Stuck Pipe The geological formation downhole occasionally has a significantly lower pressure than the drilling fluid being used. When the pipe string comes into contact with the exposed formation the difference in pressure will cause the pipe to be sucked against the formation. If the rig is able to circulate drilling fluid back to the surface that is often a good indication of differentially stuck pipe. One technique for freeing the stuck pipe, or avoiding the issue to begin with, is to rotate the pipe string while pulling out of the hole. ;Key Seated Stuck Pipe Key seating occurs when the drill string becomes off-centered in the wellbore, and the pipe collars become caught on a deviation in the wellbore. If the rig is able to move the drill string freely downhole, but every time the drill string is pulled upward it becomes stuck at the same point, then it is likely that the pipe is caught in a key seat. ;Cave-in Stuck Pipe An unstable formation can result in a cave in. The collapse of the formation can pin the pipe inside the wellbore preventing its movement. ;Mechanically Stuck Pipe: This can be the result of objects, i.e. slips or pipe wrenches, being dropped down the hole lodging against the BHA. ;Communication between Wells In areas with a high concentration of oil wells, it is not unusual for wells to communicate through the formation for distances of up to mile. During a fracing operation thousands of gallons of fluid and sand are pumped down one well to open up the formation surrounding that wellbore. Often large amounts of that proppant and fluid will travel through the formation and into a nearby well. This sand can lodge on top of a packer or coil tubing in the well sticking the pipe. ;Tubing Stuck in Production Wells: Tubing in production wells is often exposed to a number of highly corrosive chemicals, such as H2S.〔EPA Article on H2S Corrosion()〕 This corrosion can deteriorate the tubing to the point that it separates from the wellhead causing the tubing to fall downhole. The impact of several thousands of pounds of tubing on the bottom of the hole can severely damage the tubing, causing kinks or a corkscrew effect in the tubing, making it difficult to retrieve out of the hole. Sand coming in through holes in the casing or a malfunctioning production packer can also cause tubing to become stuck in production wells. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pipe recovery operations」の詳細全文を読む スポンサード リンク
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