Effects Of Multi-Factors On The Safety Of Casing String For Thermal Recovery Horizontal Well

Oil field uses steam injection thermal recovery technology effectively to improve heavyoil recovery, but as a result of horizontal Wells in thermal recovery casing load condition ismore complex than traditional vertical Wells, cause the factors and mechanism of casingdamage is more also. Therefore, how to find out the influencing factors and mechanism ofcasing damage in different working conditions, as far as possible when the designconsideration of various factors, avoiding adverse load combination and constraints, forreasonable design of horizontal well completion string provided reference and basis, for thepresent stage to prevent or reduce thermal recovery column horizontal well casing in wellcompletion, operation and damage is of great significance in the process of thermal recovery.In this paper, on the basis of the actual well conditions for thermal recovery Wells, focusedresearch completion casing under different working conditions and mechanism of damage,how to establish scientific and reasonable mechanical computation model of casing,improving thermal horizontal well casing string design and check the accuracy of the safetyproblems. This paper main research content is divided into several parts:(1) Process of steam injection, the casing thermal expansion rate is greater than thethermal expansion rate of the rock leading to deformation, and as a result the casingdeformation is limited by the existence of parts constraint, the thermal stress cannot releasecompletely, and it could cause casing buckling and the strength damage. By studying thecorresponding steam injection temperature and pressure of instability and failure of casing indifferent restraint strength, random constraint conditions cases, giving the safety steaminjection parameters and the corresponding protective measures.(2) In the process of heavy oil thermal recovery, casing damage factors traditionally tendto have couple nature, so under the influence of a single factor the traditional sleeve designideas can not meet the safety needs, which challenge the design of thermal recovery wells casing string. According to the force status of the casing string in the actual process of thermalrecovery wells production, the research on the mechanical behavior and the response of thecasing string under a variety of coupling factors is done. First, failure of critical load value inthe casing string is defined through traditional stress analysis method. Then taking intoaccount the temperature effect on the pipe properties, casing string failure of critical loadvalues are defined using the contingency design methods. By analysis and comparison, failurecritical values through the strain design are much more in accordance with the actualrequirements.(3) During carbon dioxide injection, as a result of the influence of factors such as water,high temperature, and it causes serious casing corrosion. As we all know corrosion willseriously reduce casing residual strength and bearing capacity, bring security hidden danger tothe production of oilfield. Through the study the residual intensity influence law of corrosiondefects and corrosion defects types of casing in thermal recovery horizontal well, providstheoretical reference for oil field safety in production.