Research On Automatic Plugging Removal Drilling Fluid

In the process of oil well production,there will be fine particles migration,clay mineral hydration,expansion and dispersion,the solid particles and other organic deposits in the drilling fluid will damage the formation.In order to remove formation damage,We normally use a variety of deplugging techniques,such as chemical deplugging,physical deplugging,complex deplugging and so on.But the conventional deplugging techniques due to its own characteristics and application restrictions,the efficiency is not so high and the process is relatively complex.If the measures taken in the process of deplugging is not appropriate,it will cause new damage to the formation.In this article,a new method is put forward,which is based on the new idea of reducing the damage of the reservoir,simplifying the process of deplugging and increasing the effect of the deplugging.In the drilling process,the sealing material PLA in the drilling fluid play the role of blocking can seal the pore cracks.After well completion,PLA can be degraded gradually under the influence of temperature,and no other process is needed.The permeability of the reservoir is restored,the plugging technology is simplified,and the output of the oil well is improved.Based on the experiments above and through experiments of optimizing tackifiers,fluid loss agents and inhibitors,the study on the automatic degradation of poly lactic acid was carried out,and the optimal ratio of PLA to CaCO₃ was determined.According to the experimental,the formula of the Automatic Plugging Drilling Fluid is determined:Water+0.4%80A-51+0.6%XC+4%No fluorescence filtrate loss reducing agent+2%KCl+1%LYPO+2%HL-8+3%PLA+2%Nano-CaCO₃+2%Buffer.The experimental results show that the drilling fluid system has the advantages of high efficiency,good sealing performance and good rheological property.The drilling fluid system can resist temperature 100,sand bed depth of not more than 4.5cm and anti-pollution up to8%of NaCl,CaCl₂ anti-pollution up to 1%,MgCl₂ anti-pollution up to 0.5%,anti-contaminate drill cuttings capacity of up to 6%,lubrication coefficient of 0.089,24h core linear expansion is not more than 6mm.