ADVANCES IN SEALED CORING TECHNOLOGY

The underground of old areas in Shengli oilfield changed a lot after waterflooding for more than 30 years. Ever-increased water cut made the effectiveness of sealed corlng worse and worse, this directly influenced the stipulation of stimulation. The sealed coring technology for extra-high water content, extra -high permeability and extra - unconsolidated formations has been studied since 1995. Combining conformal coring tools with sealed coring tools formed new conformal sealed coring tools. Using coring bits which can prevent cores from drilling fluid, high grade WHC-3 sealant, high grade drilling fluid, balanced pressure drilling technology and so on, 7 wells were experimented. The coring footage was 485. 10m, the core recovery was 93. 77%, 2131 rock samples were analyzed and thecore sealing rate amounted to 85%. This helped to know well about the distribution and principles of residual oil saturation and oil displacement efficiency, the physical properties ofoil reservoir, pore structure and geological features. This provided geological basis for stimulation and improvement of waterflooding effectiveness.