Study on Causes and Preventive Measures of Concentrated Casing Damage in XI Area

The concentrated casing damage occurred in XI area in 2013, and more than 50 new casing damage wells were added annually. The casing damage was mainly in the top oil layers of the reservoir and the oil shale section at the non-oil layer. The large-scale casing loss resulted in nearly half well shutdown in the block, which have affected the production of the block seriously. In order to control the situation of casing damage and timely treatment, in-depth analysis of the causes of casing damage was implemented. Beginning with the mechanism analysis, according to the contrast of mechanical property parameters, the conclusion drawn is that the casing damage mainly occurred in weak lithologic interface, according to the analysis of ground stress model, and pressure difference between blocks was the main causes of casing damage occurred in the non-oil layer, which originated from the channeling of the injected water. Moreover, the casing damage in the reservoir is mainly caused by the interwell pressure difference, which is aroused from the pressure building created by the high water injection intensity, injection without production, channeling and other reasons. Finally, on the basis of cause analysis, casing damage prevention and control strategy was targeted developed. The main measures of preventing reservoir casing from damage are to control water injection strength and injection pressure, improving injection-production relationship or injection suspension, as to the non-oil layer’s prevention, controlling injection pressure, sealing the channel of water uploading and reducing pressure difference between blocks are quite important. The analysis of causes and the formulation of preventive measures provide technical support and prevention and control system for the subsequent prevention and control of casing damage, which guarantee the normal production of oilfields.