Research and Field Application of Key Coring Technology for Unconsolidated Formation in Matured Oilfield

Core is difficult to take in unconsolidated formation,which features high porosity and brittleness.In order to improve the core recovery in this kind of formations,many measures had been taken,as the analysis of the characteristics of the unconsolidated formation,the low water loss of coring drilling fluid,lower WOB,low rotary speed and flow rate,aggressive core head and full closure core catcher,which formed a key technology for coring in unconsolidated formation in old oilfield.Field tests were conducted in 14 wells with coring footage of 311.36 m and average core recovery of 85.40%.The test proved that it is a safe and reliable technique for core protection and improvement of core recovery,and it can meet the need of coring in shallow unconsolidated sand formation.