Tga550

The thermal stability of ANDP was measured with a thermal analyzer (TGA550, Mettler Toledo Co.,) in an N₂ environment. The experimental temperature range was 50.0°C to 1000.0°C, and the heating rate was 10.0°C min⁻¹.

The synthetic product was characterized by the potassium bromide (KBr) tabletting method using an IRTRacer-100 infrared spectrometer (Shimadzu Corporation, Kyoto, Japan). A small amount of sample was mixed well with KBr in a mortar and ground thoroughly, and the ground powder was pressed into a complete and transparent sheet using a tablet press. The scanning wavelength range was from 500 to 4000 cm⁻¹, the resolution ratio was 4 cm⁻¹, and the sample scanning times were 32.
To further characterize the molecular structure of LDMS, its NMR hydrogen spectrum was measured using an Avance NEO 400 MHz NMR spectrometer (Bruker, Berlin, Germany). The signal was collected by dissolving 3 mg of sample in heavy water and cycling 16 times.
The thermal stability of LDMS was measured using a thermal analyzer (TGA550, Mettler Toledo Co. Shanghai, China) in a N₂ environment. The experimental temperature range was 50.0 to 800.0 °C, and the heating rate was 10.0 °C/min.
The relative molecular mass distribution of the filtrate reducer samples LDMS and Driscal was determined by gel chromatography using a Waters 1515 GPC type gel chromatograph (Waters Corporation, Milford, MA, USA). The mobile phase of the test was 0.1 mol/L aqueous sodium nitrate solution, and the standard was polyethylene glycol (PEG).

The drilling fluid samples were prepared by adding different contents of the filtrate reducer to the base fluid. The drilling fluids were cooled and centrifuged after aging at 180 °C for 16 h. The bentonite obtained by centrifugation was rinsed three times with deionized water, dried at 105 °C for 4 h, and ground through a 200 mesh sieve to obtain the bentonite treated with filtrate reducers. The lattice spacing of bentonite was measured by X-ray diffraction (XRD) using an X-ray diffractometer (XPert Powder, PANalytical B.V. Almelo, Netherlands). The experimental test used a Cu target, the test voltage was 40 kV, and the test current was 40 mA. Thermogravimetric analysis of the bentonite was performed using a thermogravimetric analyzer (TGA550, Mettler Toledo Co.) with a nitrogen atmosphere. The heating rate was 10.0 °C/min.