Abstract: Deep fractured tight reservoirs have complex geological conditions and develops natural fractures, with high leakage risk of drilling fluid. In deep fractured tight reservoirs, adding leakage stoppage materials while drilling is an important means to prevent drilling fluid leakage and to control formation damage. In order to systematically study the timing to supplement the leakage stoppage materials consumed during the drilling process, a deep fractured tight gas reservoir in the Tarim Basin was taken as the research object. In the research, the pressure-bearing capacity of the oil-based drilling fluid system under different consumption ratios of the leakage stoppage materials while drilling was evaluated through experiments, and a calculation model for the consumption rate of the leakage stoppage materials while drilling was constructed based on the occurrence of formation fractures. The results show that when the material consumption rate exceeds 15%, the stoppage ability of the oil-based drilling fluid system while drilling is significantly reduced; the width and dip of the formation fractures have a significant impact on the consumption rate of leakage stoppage materials while drilling; the closer of the fractures to 90 °, the wider the fractures and the denser the fracture line, the faster the material consumption rate; after determining the supplement timing and supplement amount of the leakage stoppage materials while drilling, the changes in fracture width and dip should be paid special attention. This calculation model has achieved good application results in field tests, and has a guiding significance for efficient drilling in deep fractured tight reservoirs.

Key words: drilling fluid, leakage stoppage material while drilling, supplement timing, fracture, tight reservoir, fracture dip, fracture width