The oil layer protecting drilling fluid without clay consists of inhibitor, coating flocculant, flow form regulator, filtration reducer, temporary shielding and blocking agent, weighting agent and soluble salt, which are compounded into water solution. The oil layer protecting drilling fluid has the various performance indexes meeting well drilling requirement and excellent oil and gas layer protecting effects, including excellent flocculating capacity to eliminate clay in drilling fluid, inhibiting clay to maintain the penetration factor of oil and gas layer, and good acid solubility of temporary shielding and blocking agent for later acidifying elimination to restore the penetration factor of oil and gas layer. |