Method for determining density of drilling fluid of extremely-thick rock salt stratum

The invention relates to a method for determining the density of drilling fluid of an extremely-thick rock salt stratum. The method comprises the following steps that (1) a rock core of a certain depth of an extremely-thick rock salt layer is drilled, creep testing is conducted on the rock core, and a creep deformation parameter A, a creep deformation parameter B and a creep deformation parameter Q of the rock core are calculated; (2) mineral composition testing is conducted on the rock core, and the volume fraction VNaCl of NaCl is measured; (3) several other depths are selected, the step (1) and the step (2) are executed again, the creep deformation parameter A, the creep deformation parameter B and the creep deformation parameter Q of the corresponding depth of the extremely-thick rock salt layer are obtained, and the volume fraction VNaCl of the corresponding NaCl in rock salt is also obtained; (4) in accordance with the data obtained in the step (3), the correlation between the creep deformation parameter A, the creep deformation parameter B and the creep deformation parameter Q and the volume fraction VNaCl of the NaCl is established; (5) the volume fraction VNaCl of the NaCl of the extremely-thick rock salt layer with a continuous change depth is calculated through well logging data; (6) the creep deformation parameter A, the creep deformation parameter B and the creep deformation parameter Q of the extremely-thick rock salt with the continuous change depth are calculated through the established correlation of the A, the B and the C and the VNaCl; (7) the density of the drilling fluid for controlling the well hole shrinkage speed in the full well section of the extremely-thick rock salt stratum is determined, and a drawing plate of the drilling fluid density is drawn.