An Application Study Of Safety Drilling Technology In Deep Salt Layer

During drilling work in salt layer areas, some complex accidents such as the unsteady of wellbore, the choke of drilling up and down, the drill pipe sticking and casing destroy after cementing will be faced with. If drilling in deep salt layers, the top of the bear wellbore will also be confound with the dangers about well leakiness because of the need of balance salt layer wriggle. Serious safe hidden troubles will be brought to the drilling work.Because of some different between zones, experiences made by drilling in one of the salt layer zones may not be fit for the other zones. So, safety of drilling in the salt layer is concern in the drilling field many years.The applicant technical research on the safety drilling was conducted. In this paper, a super deep well of Tahe oil field by Xinjiang Petroleum bureau was taken as an example. It is located in south Akekule geographical zones, in which the depth and the thickness of salt layer are 5400 and 250 meters respectively. And till now two of the wells cannot be drilled to the aim layer because of the salt layer.The aim layer of no.4well had been reached by the test research, and safety drill technology was formed in this deep salt layer zone.Aimed to the present technical difficulties, this paper put the following technologies in practice.1.improve the technology bearing pressure ability on the top of the long nude wellbore in the salt layer. Through character analysis of lower pressure leakiness layer and mechanism research of the block-off, adaptive materials on prevention were picked out. Bearing pressure ability had been successfully from 1.12g/cm3 to 1.75g/cm3. Above of all will provide safeguard for improving drilling fluid density in deep salt layer drilling.2.Safety operative technology to prevent choke in the salt layer. Through cognition to mechanism and principle of shorting diameter in salt layer, safety operative technologic measures were established. So, frequent choke would be avoided.3.Technology of drilling fluid to prevent salt layer from shorting diameter. Salt-water drilling fluid is a traditional method on dealing with salt layer. Through analysis of investigation and research, under saturation salt-water drilling fluid was brought forward. Through regulation of NaCl thickness, the balance between salt soluble speed in the section of wellbore and short diameter ratio in salt layer can be met by under saturation salt-water drilling fluid. It could achieve the aim of reducing salt layer to short diameter.4.Guarantee special thick wall casing to put down successfully and improve reaming after drilling technology to seal quality of salt layer. Through mechanics mechanism analysis of reaming of enlarger and combination of wriggly principle in salt layer, ream after drilling in salt layer had been finished successfully and been satisfied with demands of both putting casing down and well cementing. A set of technologic technology of reaming after drilling in salt layer had been summarized.The application of results of research in this paper will provide technical support for safe deep salt layer drilling work in the raised south structure of Akekula in the future.