Abstract: Based on the study on features of developed faults in Tazhong area, this paper calculated the mudstone smearing coefficient of major faults in Carboniferous within study area according to the definition of mudstone smearing coefficient. The results showed that the mudstone smearing coefficients of F₃, F₄ and F₅ faults are all less than 4, while that of F₂ fault is more than 4, so the distribution continuity of mudstone smearing layers of F₃, F₄ and F₅ faults and their lateral sealing are better than that of F2 fault, thus playing an important role in hydrocarbon accumulation and forming reservoirs of Carboniferous in Tazhong area.

Key words: Tarim basin, Carboniferous, Fault, Mudstone, Coefficient, Lateral, Confining pressure