Abstract: Because ofweak pressure conductive ability in high-pressure and low-permeability reservoir, pressure builds up slowly when the oilwell shutdown, and well killing fluid density, according to formation pressure, is higher, resulting in formation damage. In this article, through analyzing pressure build-up speed of the reservoir, thewriterdetermines the appropriate well killing fluid densities which are suitable for different pressure build-up speed and operating cycle. Great effects and economic benefithave been achieved by in-site application, and the reference can be provided for the well killing fluid density optimization in the similar reservoirs.

Key words: high-pressure and low-permeability, pressure conductive ability, pressure build-up, well killing fluid density, operation cycle