A NOVEL CORING TOOL FOR IMPROVING CORING OPERATION IN LOOSE FORMATION

Coring in loose and unconsolidated formation is very difficult in Liaohe Oilfield, because of the drilling fluid erosion and interbeded gravel, and the core recovery is only 30%~50%. A new coring tool is designed based on the analysis of factors that influence core recovery. It applies many unique designs, e.g., larger coring diameter to improve core strength, coring barrel made of polyvinyl chloride (PVC) to reduce friction, self-locking design, special bit structure with "U" slots to reduce fluid erosion, and use of centralizing bearings, etc. It has been used in nine wells.The core recovery reaches as high as 80% in this area.