GB842302A - Unconsolidated formation core barrel - Google Patents

Abstract

842,302. Core cutting apparatus. JERSEY PRODUCTION RESEARCH CO. Sept. 12, 1958, No. 29267/58. Class 85. Coring apparatus is characterized in that a resilient sleeve is provided to catch the core. The apparatus comprises an outer barrel 2 splined to a pipe string 3 so that it is free to move axially but rotates with the string. An inner barrel 12 is supported inside the outer barrel by a bearing 34 so that relative rotation can occur between the barrels. The inner barrel is double-walled, the inner wall 22 supports one end of a resilient sleeve 17 which is doubled back on itself and secured at its other end to a plug 21 which is suspended by a rod 6 from the pipe string. A bearing 20 permits relative rotation between the plug and the outer barrel. The outer wall 23 of the inner barrel terminates in a shoulder 24 which guides the sleeve 17 and the core 25. Drilling fluid is pumped down the pipe string, passes through the apertures 8 and through the ports 10 in a plate 15. There is a pressure drop in the fluid in passing through these ports and the resultant pressure on the the upper surface of the plate 15 drives the outer barrel downwards. The fluid subsequently passes without pressure drop through a clearance 18 between the rod 6 and the outer barrel 12 and is used to inflate the sleeve 17. The maximum diameter to which the sleeve can be inflated is restricted by a non-extensible external layer of a smaller diameter than the inside of the outer wall 23. A port 19 between the chamber 27 and the annular passageway 35 allows drilling fluid at a pressure P3 which is smaller than P2 to reach the chamber 27. In operation the outer barrel 2 rotates and drives the core cutter 1, the inner barrel 12 and the plug 21 remain stationary and as the inner and outer barrels advance, the sleeve 17 passes under the lower edge of the inner wall 22 of the inner barrel and encloses the core 25.