Drilling and coring technologies for polar offshore areas of Russia Far East

Okhotsk Sea is in the Far East of Russia, belonging to sub-polar climate. Reducing coring time and improving coring efficiency during drilling operation has become an urgent topic. The coring formation in this area contains large amount of argillaceous siltstone, hard interbeds and conglomerate interbeds, resulting in poor drillability, low ROP and difficulty in coring. Through optimizing key tools like coring bit, core catcher and coring barrels and by formulating proper coring method, the efficiency of coring operation was improved and the number of drillings was reduced. In its application in three exploration wells, the coring time could be controlled within the designed range, which ensured that the drilling platform could move away from the wellsite within the safe window and also ensured that the core recovery was kept over 90%. The successful application of this technology provides positive guiding significance for coring operations in the similar blocks.