Experimental Study On Optimization Of High Temperature And High Density Organic Brine Based Drilling Fluid

Organic salt drilling fluid has the advantages of strong inhibition and fast drilling speed when drilling in complex formations such as deep well,ultra-deep well,large-sized salt-gypsum layer and easily-hydrated dispersed shale.However,the use of barite exacerbated organic salt drilling fluid viscosity and shear at high solids content under the conditions of thickening and high temperature aging viscosity decreases.Therefore,the optimization of high temperature and high density organic salt drilling fluid system is of great significance.Aiming at the technical problems such as the rheological control of high temperature and high density organic salt drilling fluid,the effects of temperature,clay and heavier materials on the rheology,filtration loss and settling stability of high temperature and high density organic salt drilling fluid are discussed in this paper,And put forward the method of solving the difficult problem of rheology control of high temperature and high density organic brine-based drilling fluid.With calcium lignosulfonate as the main raw material,acrylic acid,2-acrylamide-2-methylpropyl sulfonic acid as graft monomer,copper ion as the coordination center ion and solution polymerization method,a rheological modifier for high temperature and high density organic salt drilling fluid,CFP-I,was developed.The molecular structure of CFP-I was characterized by Fourier transform infrared spectroscopy,nuclear magnetic resonance spectroscopy and XPS analysis.It was planar topology and the intrinsic viscosity and viscosity average molecular weight of CFP-I were measured.The molecular weight was about 6285 g/mol.Experiments have shown that CFP-I can be stably adsorbed on the surface of solid particles to form a negatively charged solvate film,disassemble the grid structure in the drilling fluid,and reduce the viscosity;and before the temperature rises to 220°C.The chelating structure in CFP-I is continuously enhanced to increase the viscosity and shear force of the organic salt drilling fluid,so that the rheology of the high density organic salt drilling fluid remains relatively stable before and after the high temperature hot rolling.In addition,CFP-I has a more stable effect of regulating the flow pattern over a wider pH range from 7 to 11.The newly developed flow regulator CFP-I was used to optimize the formulation of organic salt drilling fluid with a temperature of 200?and a density of 2.3 g/cm³.The apparent viscosity,plastic viscosity and shear force of the formula before and after aging at200?are similar,and the final cut-off value is high,and the filtration loss under high temperature and high pressure is 15mL,indicating that it has good temperature resistance and good Sedimentation stability.It also has a better performance in mud shale inhibition,plugging,anti-collapse and anti-pollution,and can resistant to 10%NaCl,1.0%CaCl₂ and8%inferior soil contamination.