Comprehensive evaluation on drilling mud damage in Ed1 reservoir of NP Oilfield and study on plug removal technique

Acidizing is the main measure to get rid of the reservoir damage and improves the oil & gas well productivity.For each specific type of damage, it is very difficult to achieve the desired stimulation result if using a general acidizing method.Therefore, it is an important issue to acidize specifically according to the reservoir damage mechanisms.Due to the poor understanding about the damage mechanism of drilling mud on Ed1 reservoir of NP Oilfield before this study, unsuitable acidizing fluid has been chosen, which affecting seriously the effect of plug removal.In order to solve this problem, a specific acidizing design method has been put forward.By evaluation on grain size of mud solid phase and infrared spectrum laboratory testing and analysis, the reservoir damage degree and mechanism by drilling mud in Ed1 reservoir have been understood.On this basis, simulation on the generation of mud damage has been done. Through simulation it has been found that permeability of damaged co re will reduce to 0.12 times.Finally, evaluation has been done on the ability to remove this kind of mud damage by using different types of acid systems, and eventually the most effective 4% multi-hydrogen acid system has been chosen to use in reservoir acidizing.