Establishment And Analysis Of The Mathematical Model On Casing Failure In Thermal Recovery Well

Heavy oil thermal recovery technology, which is now used widely in heavy oil reservoir development in China, has become a kind of mature oil production technology. With the increase of thermal recovery wells, more and more production casing failures phenomena are observed. As the reasons are complicated and changeable, good prevention measures haven’t been found yet.Through extensive literature researches, the author in this paper conducts an analysis on the environmental factors, engineering technology and corrosion factors which influence the casing failures in thermal recovery wells; meanwhile the author also gives us a summary on the casing failure mechanisms. By building heat conduction models of wellbore temperature and on the basis of distribution rules of formation temperature, this paper makes a research about wellbore heat transmission and formation temperature. According to the analysis of casing stress in thermal recovery wells and the calculating theory of thermal stress in thick cylindrical shells, impact of those external forces ignored, the author finds out the calculating formula of casing thermal stress in the recovery wells.In the formation, the temperature, formation pressure and so on cause partial geo-stresses to concentrate, this often leads to the casing failures. In order to help us better understand the relationship between geo-stress distribution and temperature and formation stress, this paper carries out an analysis on the distribution rules and calculating methods of geo-stresses, and meanwhile obtains the calculating formula of horizontal geo-stresses under the change of temperature and formation stress. The analysis of the formula shows that external stress of horizontal geo-stress on casing becomes great with the increase of temperature and formation stress change, which provides a reference for the analysis of casing geo-stress in the recovery wells.