Research and Application of Metal Complex - Amphoteric Polymer Drilling Fluid

Abstract Amphoteric polymer and MMH drilling fluid systems have been widely applied in oil fields in recent years with good benefits. The applications have shown the advantages and disadvantages of the two drilling fluid systems. Based on the analysis and research of molecular structure and mechanism of the two kinds of additives in drilling fluid, the molecular structures of new polymers, metal complex - amphoteric polymers PMHA, JMHA, are designed and researched. The new products have properties of both amphoteric polymer and MMH, that is, high inhibition, high thixotropic, stable drilling fluid rheological, excellent filtrate control ability and the ability of protecting production formation from damage. Applications in Zhongyuan, Jiangsu and Liaohe oilfields showed that it increased drilling rate, decreased the trouble under well bore and the enlargement rate of well diameter. The metal complex-amphoteric polymer products have good compatibility with other additives. The drilling fluid system formulated by these products has stable rheological properties with low cost. Now the drilling fluid system has been successfully applied in vertical, directional, deep and slim hole wells in China's oil fields. Taking advantage of the metal complex - amphoteric polymers, we have formulated drilling mud systems, such as the fresh water mud, high-density mud with high salinity, slim hole drilling fluid and completion fluid.