Oil casing damage is always one of the most serious problems in oilfield development.
Main preventive measures for casing construction
1. Reasonable control of water injection pressure
During high-pressure water injection in oil fields, with the continuous increase of water injection pressure, the formation pressure level also rises. When the local layer pressure exceeds the critical pressure, the formation will slip relatively and cause casing deformation, especially in the area of mudstone interlayer development or fault development, casing loss Wells may occur in pieces. In addition, long-term high-pressure water injection will aggravate casing damage speed under long-term high-pressure load. Control the formation pressure within the critical formation pressure or less than 70% of casing extrusion strength to mitigate casing loss.
2. Reasonably control the production pressure difference and maintain the balance of injection and production
Due to the imbalance of injection and production, large range of well network compaction and poor interlayer connectivity, an additional stress is formed from the high pressure area to the low pressure area, which induces formation sliding and produces casing deformation, especially in the high pressure area, casing damage is particularly serious.
3. Optimize the perforation and reservoir modification plan
Any process and quality of acid fracturing and perforation has a significant impact on the life of the casing. Repeated perforation or acid fracturing can greatly reduce the compressive strength of the casing and accelerate casing damage and deformation. The construction pressure should not exceed 80% of the casing compressive strength.
4. Improve downhole tools to avoid grinding the jacking casing
Due to scheme design or construction reasons, underground falling objects, pipe stuck, pipe blocked and other phenomena often occur, so it is necessary to pull out and grind the bushing, which will inevitably cause the wear of casing wall and reduce casing strength. It is suggested that the drilling tool should be improved and the centralizing device should be installed during the drilling and grinding process to reduce the phenomenon of eccentric wear and protect the casing.
