Depressant replaces mechanical method for removing blockage

A viscosity depressant proved effective for replacing the time-consuming mechanical methods for removing heavy oil blockages during the drilling of wells in the Tarim basin of China.The fracture-cavernous Ordovician carbonate reservoir in Lunxi oil field in the Tarim basin is a multilayered structure with well-developed fractures or fissures in each layer, containing a highly viscous crude oil.Penetrating these naturally fissured formations often encounters two major downhole problems:1. Drilling mud loss to the fractured formation leads to a decrease of the fluid column height, thus reducing the pressure exerted on the open formations. This results in the resident fluid in the high-press...

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