Anti Collapse Drilling Fluid Technology for the Second Open Hole Section of Cheng-6 Well
The design depth of Cheng-6 well is 5 950 meters,and the size of the second open hole is large.The open hole section is as long as 3 100 meters,and there is a significant difference in lithology between the upper and lower formations of the open hole section;The drilling process will pass through hard and brittle mudstone and coal seams developed in the Jurassic,making it difficult to stabilize the wellbore and purify the wellbore during the drilling process.To this end,the technical difficulties of drilling fluid were analyzed,drilling fluid technical measures were determined,and drilling fluid system research was carried out.Finally,by using a composite amine salt lubrication anti collapse drilling fluid system to assist in on-site drilling fluid construction technology,the wellbore wall was stable and the quality of the wellbore was good during the construction of the second open hole section.The average wellbore enlargement rate was 1.97%,achieving good results in fast and optimal drilling.
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