Technology of Core Drilling for Investigation of Freshwater Resources in Zhoushan Sea

Abstract:

For DZS1 well of freshwater resources investigation project in Zhoushan sea, the drilling was started at water depth of 15 meters. The full hole coring depth reaches 202.1 meters by drilling in overburden layer mainly with clay and sand layers and 2 meters of weathered bedrock. In the quaternary, 127mm drill pipe was directly used for wire-line hammer collision coring drilling without casing; in bedrock, 50mm drill pipe was used for swivel type double tube coring drilling with 127mm drill pipe as casing. The paper introduces the main construction processes and quality control methods, including anchor of drill ship, consideration of tide impact on drilling pipe，control of drilling procedure, hole cleaning, drill bit replacement，mud technology and so on.