FIGHTING FRACTURED FLAMINGO—LESSONS FROM RAMBLER-I, TIMOR SEA

Abstract

Exploration well Rambler-1, located in the Timor Sea, presented an unusual set of engineering and evaluation problems when drilling a thick section of Flamingo Group (Jurassic–Cretaceous). The well encountered normally pressured open fractures where drilling mud was lost, and at least two mildly overpressured fractures that flowed small quantities of gassy oil into the well-bore. In these circumstances it was difficult to find the right combination of casing, mud density, cement plugs and lost circulation material to drill the well in a controlled and efficient manner.

Fine grained sandstone in the Flamingo Group gave moderate mud log shows and two cased-hole RFTs recovered oil. However, cased-hole DSTs of the same intervals recovered only small volumes of filtrate. This remarkable behaviour is attributed to the RFTs recovering oil from porous cement that had been impregnated with oil from the lower of the overpressured fractures.

Any future wells drilled near the axis of the Sahul Syncline are likely to encounter similar problems and awareness of the lessons learned in Rambler–1 can improve drilling and evaluation strategies.