The Effects To The Casing Damage Bye Insitu-stress Changes In Chaoyanggou Oil Field

The type of Chaoyanggou block the damaged well casing is major deformation, off the main fault. Casing water damage mainly concentrates in the upper and lower layers of mud and rock..Based on the level of stress, condition of sliding and the critical water pressure conditions, the outer casing squeezing force calculation; From the limited element analysis model, analysis methods and theory, combined with a group of blocks C5 well studied, reveale the formation pressure and stress with changes, Casing in order to find the fundamental cause of the damage. The fundamental reason of the water pressure, water pressure exceeds pressure to allow water, mud, rock water page, after the water swelling of the mudstone creep extrusion casing to casing deformation; When the waters of big dip to a certain extent, the nature of strata of rock mechanics and mechanical stratigraphic relations between the change will occur sliding formation, causing the casing off wrong.Mudstone immersion into the water, the rocks of the shear strength significantly decreased, Shale or clay in the mud, shale and the interface of sandstone will gradually form a tensile crack softening characteristics of the secondary structure, In order to break the continuity of the underground rock, which provided for the formation conditions of slip, together with the angle and block form ation pressure so that the sliding occurred stratigraphy, shale to prevent flooding in the area should take the following measures:(1) the need to determine the breakdown of water pressure and the pressure of overlying strata of the precise formation, no pressure and ultra-ultra-rupture overlying water pressure.(2) To improve the quality of cementing, cementing quality, poor water channeling phenomenon will occur to prevent the expansion of shale hydration is to reduce the loss of an important means of sets.(3) The casing damage is between 900 ~ 1100m in Factory 10, so that need special casing of the above design, we consider the process of developing the forces of the casing to casing design to triaxial stress.(4) According to calculations, casing damaged plants should centre on the use of N-80, the casing wall thickness of 9.17mm or more.