METHOD FOR FREEING OF STUCK STRING Russian patent published in 1994 - IPC

FIELD: drilling of oil and gas wells. SUBSTANCE: during forcing of fluid bath into stuck zone, light fluid is included into combined column of fluid forcing into pipe string. Column height of light fluid depends on conditions for creation of technologically permissible depression in stuck zone. Then, pack of gas is formed in isolated drill string-borehole annulus of required height and compressed to build up maximum permissible pressure at wellhead by injection of fluid into pipe string. When that pressure is attained, internal space of pipe string is communicated with atmosphere and fluid is bled from pipe string to produce required depression in well. After that, fluid bath is washed out of well and pipe string is retrieved. EFFECT: higher efficiency.