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' condition of the wed numerous other, less general topi~When these are combined <br />with the problems aSS6ciated with subsidence, plugging beco~fies an always variable and I <br />often formidable task. t <br />Following is the baseline plugging procedure: <br />1) Clean out the wellbore. Field crews occasionally encountered wells with no pipe in the <br />hole, and cleanout consisted of simply circulating debris out of the hole. More often, <br />holes contained one or several strings of uncemented casing and tubing. Tubing ranged <br />in diameter from 1-1/2 inches to 6-5!8 inches. Efforts to pull al{ tubing from the surface <br />were rarely, if ever, successful, and fishing with a variety of tools .vas usually required. <br />Factors that hampered tubing removal included: shears, doglegs, squished or bowed pipe, <br />adhesion of one string of pipe to another, severe pipe corrosion, lack of centralization, and <br />the condition of stubs at depth. In wells without tubing, factors that most commonl}~ <br />limited downhole progress were casing damage, lack of circulation, and junl• in the hole. <br />Even in wells without casing, progress could be inhibited by crumbling of formations and <br />sticking of tools (Yarosz, 1994). Based on downhole conditions, abottom-hole cement <br />or mechanical bridge plug might be set above the salt cavern or at the deepest attainable <br />depth after fishing tubing and otherv;ise cleaning out the wellbore. <br />2) Lo in After cleanout, to assist with decision-making regarding casing recovery <br />methods and cementing, the following logs would be run: <br />Gamma ray -to identify formations and to provide a basis for correlation <br />Caliper -to verify well construction, locate casing damage and provide <br />measurements for computing cement volumes <br />Co!/ar locator -to locate casing, Gazing collars and cuing damage _ <br />Cement bond log -to identify cemented pipe, and in wells with uncemented casing, <br />to explore the potential for casing recovery by providing some <br />indication of debris in the annular space (Yarosz, 1994) <br /> <br />Logging was partially or entirely omitted on wells where sufficient information vas <br />available from other sources or where downhole conditions rendered the work for which <br />a log or logs were needed impracticable. In later stages of the project, logs were not run <br />when cuttings were purely shale and tools behaved as if drilling solid rock in well groups <br />where shearing was known to be likely (Yarosz, 199>). <br />3) Casing removal/oerforatin:;. After cleaning out the wellbore, including open hole below <br />the deepest casing, as near to the top of the salt cavirv as possible and perhaps setting a <br />plug, the goal would be to remove all uncemented pipe. The length of free or recoverable <br />pipe would be estimated from the bond log and a decision would be made regarding the <br />next step. The standard procedure, if do~vnhole conditions allo«ed, would be :o perfe-ate <br />and squeeze cement behind pipe to be left in the hole, if an}', znd then to either cut the <br />pipe or bust a collar at the depth from which casing would be removed. Factors that <br />commonly limited casing removal were similar to these described above which affected <br />removal of tubing. Once all recoverable casing was removed, a bonom-hole cemen: or <br />15 <br />222 ~ <br />J <br />