Coring Techniques for Buried Hill Reservoirs in Liaohe Oilfield

In order to enhance the core recovery and coring quality for buried hill reservoirs in Liaohe Oilfield,the coring solutions suitable for the buried hill reservoirs has been studied.Through analyzing the stratigraphic characteristics of buried hill reservoirs in Liaohe Oilfield,the method of exclusion was used to determine the causes of low core recovery and poor coring quality,and counter measures were put forward.First,the coring bit was optimized.Instead of 3-5 cutting teeth originally,the optimized coring bit had 10 cutting teeth made of Z3 diamond compact on cemented carbide base,and port arrangement of low erosion.Next,the coring tool was improved.An implicit basket type core catcher and cited heart shoes,inner barrel centralizer,coring jam indicator and anti-jam coring system were added to the coring tool,and the smooth aluminum alloy inner tube was used.Finally,the technical parameters of WOB,RPM,pumping rate,etc.were optimized.Field test in 9 wells of Liaohe Oilfield indicated the ROP had increased from 0.55 m/h to 2.79 m/h and the core recovery had increased from 51.13% to 89.97%.The results showed that the coring techniques for buried hill reservoirs in Liaohe Oilfield could enhance penetration rate,core recovery and coring quality,and reduce downhole security risks,which could be applied in hard,broken formation coring operation.