A Study On Casing Failure Mechanism And Preventive Measures In Steam Injection Well

Now casing failure of oilfields is urgent to solve in the whole world, many oilfields meet the problem of casing failure in the exploitation process. The casing failure's influence factors are extremely complicated which include the inner casing material, stratum mechanical property and impact ingredient from outer environment. Casing of thermal production well bear more complicated stress than common oil well, the particularity is that casing must bear the high temperature problem caused by steam injection. The production of heavy oil mainly through steam huff and puff and steam drive. But the casing will produce large thermal stress for steam injection, and in the process of steam injection cyclic will produce cyclic residual stress, these can make heavy casing failure. It is very important that in the process of steam injecting accurately forecast well bore temperature field and the loads of casing and reduce the failure of casing to the completion and production of the thermal production well.The main causes of casing failure in Xinzhuang Oilfield are summarized as two aspects: one is external squeeze pressure on casing under non-uniform ground stress exceed it's collapse resistance; the other one is casing produces large thermal stress in the process of steam injection. This paper studies systematically on casing failure mechanism and preventive measures in steam injection well by using spot investigation, literature collect and study, theory analysis and numerical simulation. The main content are as followings:â‘ Based on field data of Xinzhuang and Yanglou region in Henan Oilfield and combined with related literature to further understand the factors and types of casing failure;â‘¡Calculating formula of external squeeze pressure on casing under non-uniform ground stress is deduced from the elastic-plastic theory of thick-wall cylinder, then analyze the influence of external squeeze pressure on casing under different stratum and cement elastic modulus, last apply finite element software ADINA to carry out numerical analysis, then get the verification;â‘¢Using finite element software ADINA to carry out transient analysis for temperature field of casing based on thermal transfer theory, through indirect coupling to get thermal stress of casing. Then consider multi-steam injection cyclic to get the distribution disciplinarian of residual stress produced in casing through elastic-plastic analysis for the process of steam injection;â‘£Put forward preventive measures of casing failure based on the studies as foregoing.