Preparation And Properties Of Weak Gel Water-based Drilling Fluid Gelling Agent AM/AMPS/OA 8

Facing with the problems of wellbore lubricity,cuttings carrying and influence of the drilling speed in the horizontal wells and high-inclination wells during the process of drilling,the low solid phase and no solid phase water-based drilling fluid have been paid more and more attention in recent years.lt is widely used in directional well and horizontal wells in offshore and onshore oil fields because of its good internal strcture and the low solid content.However,due to the poor performance of the weak gel water based drilling fluid,it has limited its wider application.In this article,a kind of weak gel gelling agent(AMAMPSOA8)is successfully synthesized by reasonable design of molecular structure and micellar polymerization.Setting the apparent viscosity of AMAMPSOA8 at the low shear rate as index,orthogonal experiments are designed to determine the optimal reaction conditions which are 4.8:1 molar ratio of acrylamide(AM)and 2-acrylamide-2-methylpro panesulfonic acid(AMPS),the mass fraction of initiator is 0.04%,the chemical reaction time is 9h,the concentration of hydrophobic monomer is 0.75%,the chemical reaction temperature is 70 ?.Under this condition,the apparent viscosity of AMAMPSOA8 at the low shear rate(3r/min)is 23680 m Pa·s.The structure of OA8 and AMAMPSOA8 are characterized by FTIR,NMR.The characterization results proof that the structure of the synthesized product is consistent with the target structure.The performance is studied by the thermal analyzer,High temperature roller furnace and Bruker rheometer.The results show that the polymer solution system has obvious thixotropy,benefit to improve the drilling fluid suspension,dynamic sand carrying capacity and keep the hole clean.Through the single factor experiment,the other kinds of agents were selected and determ ined in which the weak gel gelling agent AMAMPSOA8 was used as the main agent in the wa ter-based drilling fluid.In this paper,a new type of temperature and salt resistant weak-gel wat er based drilling fluid was established:water + 20%NaCl + 0.2%Na2CO3 + 5%CaCl2+ 7%KC l+ 2%AMAMPSOA8+2%SMP-1+2%FA-367+3%emulsified asphalt +10%KCOOH.The res ults of the performance test of the weak gel drilling fluid show that this system has excellent t hixotropy,temperature resistance and salt resistance.The morphology of the weak gel in the fresh water and saline solution were studied by the scanning electron microscope.The weak gel gelling agent can form a network structure in the solution and this structure is mainly conformed with the hydrophobic association of the structurally physical cross-linking of micro regions and hydrogen bonds which is a three-dimensional network structure.The results show that the weak gel drilling fluid has good thermal stability and anti-pollution ability,and it is a new type of water gel drilling fluid.