The disposal of drilling sludge is a pressing issue in the oil and gas industry. The present study investigates the effect of three sludge cleaning methods for the Urengoy oil and gas condensate field (washing with water, washing with gasoline, and calcination at 400 °C) on the physicochemical characteristics and mechanical properties of model proppant samples. The scientific novelty of the present study lies in the description of a direct quantitative correlation between the phase composition of the model samples and their ultimate compressive strength. This correlation had not previously been demonstrated for drilling sludge from the Achimov Formation. The initial sludge was characterized using a combination of methods, including X-ray phase analysis, Fourier transform infrared spectroscopy, gas chromatography-mass spectrometry, and X-ray fluorescence analysis. It was shown that it contains 2.2 wt.% residual hydrocarbons and is a polymineral raw material. It has been established that washing with gasoline most effectively removes hydrocarbons (cleaning degree up to 97 %), while washing with water effectively removes chlorides (reduction to 0.05 %). Calcination at 400 °C does not ensure complete removal of hydrocarbons due to the coking of heavy fractions and leads to the amorphization of clay minerals. Using quantitative X-ray phase analysis of model proppant samples, a relationship between the mullite content and the ultimate compressive strength was established. The maximum strength (125.38 MPa) was achieved for the sample obtained from water-washed sludge, which is due to its high mullite content (23.5 wt.%) and minimal amount of amorphous phase. The lowest strength (74.79 MPa) was obtained for the model proppant sample made from calcined sludge, due to the destruction of clay minerals. The results of this work substantiate the choice of water washing as the optimal method for preparing drilling sludge for the synthesis of strong propping agents.