Successful HPHT Drilling Through Innovative Practices: Sharing the Subsalt HPHT Well Drilling Case in Tarim Basin

摘要

The Kuche Fold-Thrust Belt located in Tarim Basin is the most challenging geological structure in west Chin. The average drilling peroid is larger than 450 days with an average MD of about 21000ft, which is far to meet the economic requirements of oil company, due to its unique drilling challenges caused by the high-steep structure (maximum dip angle 80°) and the thick gravel layer (maximum thickness 17933ft, maximum buried depth 26074ft) with high abrasiveness in upper formations, the complicated thick gypsum salt layer and interbedded unpredictable abnormal high pressure salt water in middle of these formations, as well as the poor drillability and high crustal stress along the lower small-geometry borehole. The drilling technologies have been integrated and extensively applied in the Dabei-Keshen block with a tremendous success includes 1) Automatic vertical drilling technology for upper high-steep layer; 2) A unconventional TaBiao series of casing program to isolate multilayer salt and to guarantee subsequent stimulation operations; 3) High temperature resistant and high density oil-base drilling fluid for safe drilling through salt and hydrocarbon-bearing formations; 4) Enhanced PDC bit and downhole motors for ROP improvement. The ultra-deep well drilling cycle is sharply shortened by half with highly improved drilling speed and dramatically reduced downhole accidents and complexities. The drilling breakthrough delivers strong assurance for more safe and cost-effective production in ultra-deep formations in Tarim. This paper will highlight the drilling challenges, matching drilling technologies respectively for suprasalt layer, salt stratum, and subsalt target layer, as well as the application results of technical integration.