HOT OILING TREATING DEPTH INVESTIGATION

Field tests were performed to better understand the effectiveness of hot oiling to remove paraffin in downhole tubulars. In particular, the tests were designed to investigate the depth to which paraffin might be melted. The temperature decay following the end of the treatment, pump capacities, and heat loss assumptions were used to estimate the treated depths. The results indicated that annular hot oil treatments might be effective for paraffin wax that is very near the surface but the effective treating depth is very limited. In addition to the field testing, industry surveys of the perceived depth of effective treatment were collected. The results of the field tests compared with the industry survey suggest a dramatic problem of perception compared with reality. This disconnect may result in millions of dollars of expenditures that are ineffective or only partially effective. The field tests for a variety of tubular configurations indicated effective treating depths of less than 200 feet, compared with median perceived depth of 1,000 to 3,000 feet. The study also brought to light the seriousness of heat transfer losses from the hot oil burner to the wellhead before the process begins to start down the hole. In effect, the truck itself and injection line to the well act like giant
radiators that rob heat from the treating process. The results of the study suggest that alternatives to annular hot oiling need to be seriously evaluated if the artificial lift failure history indicates paraffin deeper than 200 to 300 feet. Furthermore, annular hot oiling during colder periods should be avoided altogether or otherwise very carefully designed and supervised.