Synthesis And Evaluation Of High-temperature Resistance And Salt Tolerance Polymer As Fluid Loss Reducer

Nowadays, more and more oil will be used as the development of industry. The oilfield in deep-stratum need to be explored and developed, thus set an even higher demand on the drilling technology. As an important drilling fluid additives, fluid loss reducer for high temperature and high salinity has a direct impact on the performances of water-based drilling fluid. In this paper, based on polymer structure and functional groups,2-acrylamido-2-methylpropane sulfonic acid (AMPS) and other anti-high temperature monomers were be used to synthesized to drilling fluid loss reducer which abbreviated as "P(AMPS/AM/DMAA/NVP)-SA" and "P(AMPS/AM/NVP/DMDAAC)" by adopting free radical water solution polymerization method. As good fluid loss reducer, the synthetic polymers can effectively improve the performance of the drilling fluid with high temperature resistance and salt tolerance.The main contents of the present dissertation are showed as followed:1. Preparation and characterization of AMPS multi-polymersAMPS multi-polymers used as water-based fluid loss reducer abbreviated as "P(AMPS/AM/DMAA/NVP)-SA" and "P(AMPS/AM/NVP/DMDAAC)" were synthesized from2-acrylamido-2-methylpropane sulfonic acid (AMPS), acrylamide(AM), N,N-dimethyl acrylamide (DMAA), N-vinylpyrrolidone (NVP), sodium alginate (SA) and dimethyl diallyl ammonium chloride (DMDAAC). The optimum reaction conditions were determined. Fourier transform infrared spectroscopy (FTIR) and the Element analysis indicated the composition of functional groups and the proportion of each element in the polymers; Intrinsic viscosity method and thermogravimetric-differential scanning calorimetry (TG-DSC) method showed that the average viscosimetric molecular weight of the polymers were2.60×105and5.53×105, respectively, also proved that the polymers had good high temperature resistance properties.2. Evaluation of filtration control properties about AMPS multi-polymers at different mudThe filtration control properties of the polymers were evaluated by the rheological and filtration experiments at room temperature,200℃or240℃aging16h at different muds. The results showed that the synthesized AMPS multi-polymers can effectively reduce the fluid loss of the fresh water mud, salt water mud, compound salt mud and saturated saline-water mud, also can control the rheological properties of the suspensions. Comparing with the early product in our group and the foreign product "Driscal D", AMPS multi-polymers had better performance than the former.3.Aqueous solution properties of AMPS multi-polymers and their interaction with montmorilloniteIn order to explain the high temperature resistance and salt tolerance of the drilling fluid system with the polymers, properties of the polymers aqueous solution and their interaction with montmorillonite were studied by adsorption, calcium ion binding degree and rheological experiments. Adsorption isotherm with the polymers on the montmorillonite conformed to Langmuir type, and the adsorption increased substantially with increasing NaCl; The percentage of calcium ion binding to the polymers was10-25%, which slightly increased after aging treatment; The flow curves of polymer solution and polymer-montmorillonite suspensions could be well described by power law model or Herschel-Bulkely model, which exhibited shear thinning properties, yield value and elastic modulus increased with the increase of polymer concentrations, apparent viscosity, yield value and elastic modulus decreased after aging process, owing to lower intensity of network structure.By the theory of colloidal suspension stability, the mechanisms of AMPS multi-polymers in controlling filtration were shown as followed:(1)to maintain the dispersed montmorillonite particles;(2)viscosifying action;(3)plugging action.