Preparation And Properties Of PAAD/modified Nano-silica Copolymer Drilling Fluid Filtrate Reducer

Exploration and development of oil and gas resources continue to develop in deep wells,the current primary problem is to ensure that the drilling fluid can still maintain good performance under high temperature and high pressure environment.Among them,it is especially important to keep the performance of drilling fluid filtrate reducer.On the basis of previous studies,firstly,we make surface modification of nano silica by gamma methyl allyl propyl trimethyl silicone(KH570),and used single factor experiment to optimize the modification conditions.The results showed that the optimum reaction conditions of the modified nano silica are as follows:the KH570 content is 20%,reaction temperature is 70 ?,the reaction time is 2h and pH value is about 4.Infrared spectrum analysis showed that KH570 was successfully grafted onto the surface of nano silica.Then I used the modified nano silica with acrylamide(AM),2-acrylamide-2-methyl propyl sulfonic acid(AMPS),two methyl diallyl ammonium chloride(DMDAAC)as the reaction material,ammonium persulfate and sodium bisulfite as initiator to synthesis the nano silica filtrate reducer by solution polymerization method,and used single factor experiment to optimize the modification conditions.The results showed that the optimization of the reaction conditions are as follows:the molar ratio of AM/AMPS/DMDAAC is 10:1:0.5,the dosage of modified nano silica is 2.4 percent of the total mass of monomer,monomer concentration was 25%,initiator dosage is 0.3 percent of monomer quality,reaction temperature is 50 ?,reaction time is 5h,pH value is 7.Infrared spectral analysis showed the polymerization reaction of the modified nano silica with the monomer.Thermal analysis showed that the nano silica filtration reducing agent has good thermal stability,all kinds of filtrate reducers had no obvious thermal degradation when the temperature is below 195?.In this paper,we carried out drilling fluid performance test of the nano silica filtration reducing agent and the PAAD filtrate reducer.The experimental results showed that the nano silica filter has better filtration performance,heat-resistance,salt-tolerance,calcium-tolerance and lower rheological properties than the PAAD filtrate reducer at the same amount.When the additive amount of two kinds of fluid loss is 2.5%of the base slurry,the API filtration loss of nano silica filtrate reducer and PAAD filtrate loss reducer in fresh water slurry,saturated salt water base slurry and complex bine base were 6.0mL,4.7mL,4.0mL and 7.0mL,6.0mL,4.4mL respectively.After aging at high temperature of 220 oC for 16h,the API filtration loss of the two kinds of filtrate reducers were 15.8mL and 19.2mL respectively.Under normal temperature,the filtrate loss of two kinds of filtrate reducer drilling fluid system showed a decreasing trend with the increase of NaCl and CaCl2,but after the high temperature aging,the filtration rate of the two systems were larger.Then the nano silica filter was used to prepared drilling fluid system compound with other additives.The experimental results show that the compound drilling fluid system has good heat-resistance,salt-tolerance and calcium-tolerance.According to the SEM analysis,two kinds of filtration reducing agent can effectively improve the morphology of filter cake.The results showed that the two kinds of fluid loss agents could effectively improve the morphology of the filter cake.Particle size analysis showed that the distribution of clay particles in the slurry could be significantly improved by the addition of nano silica filtration reducing agent and the size of clay particles decreases with the increase of the amount of filtrate reducer.The comparison of size distribution of nano silica and PAAD filtrate reducing agent system indicated that after high temperature aging,the particle size distribution of nano silica filtrate reducer is more uniform.