Study and Application of a High Temperature Drilling Fluid with Strong Plugging Capacity

A high temperature borehole wall stabilizing agent SMNA-1 was developed to resolve problems encountered in high temperature deep well drilling. SMNA-1 functions at high temperature to above 200℃. It has a rigid molecular structure and is deformable at high temperature. SMNA-1 is able to enhance the strength of mud cake through its deformability and cohesion capacity. SMNA-1, through its hydrophobicity, also forms a sealing membrane on the surface of mud cake to bind free water and enhance the toughness and consistence of the mud cake, thereby reducing HTHP flter loss and enhancing the capacity of drilling fluid to plugging and stabilizing borehole wall. A high temperature polymer flter loss reducer, SMPFL-L, was synthesized with acrylamide, 2-acrylamide long carbon chain sulfonic acid and diene sulfonic acid through free radical polymerization. SMPFL-L has low widely distributed molecular weight. A saturated saltwater drilling fluid treated with 2%SMPFL-L had its HTHP flter loss reduced to 54 mL. The property of SMPFL-L remained stable at 210℃, and had good deflocculating ability. SML-4, a high temperature salt-resistant flter loss reducer, has been developed for use in high density muds weighted with weighting materials that will result in high solids content. SML-4 is able to alter the surface behavior, enhance the dispersity, and thin the hydration flm of weighting material. A high density saltwater drilling fluid treated with 4% SML-4 had its API flter loss reduced from 164 mL to 5.8 mL, without increasing the viscosity of the drilling fluid. A drilling fluid of 2.0 g/cm³ treated with 2% SMJH-1 had its extreme pressure friction coeffcient reduced by 24%. A high temperature drilling fluid with strong plugging capacity has been developed with SMNA-1 as the main additive, SMPFL-L and SML-4 as flter loss reduces, SMJH-1 as high effciency lubricant. This drilling fluid formulation was successfully used in drilling the third interval (1,300 m) of the well Shunbei-1-1H located in Xinjiang, and no downhole troubles were encountered. The average percent hole enlargement was only 6.88%, and good application results were achieved.