Oil explorer Gulf Keystone has begun drilling its Shaikan-5 appraisal well on the Shaikan block, the firm's major oil discovery. The well, in the Kurdistan region of Iraq, is the third deep appraisal well to be drilled in the area with independently audited gross oil-in-place volumes of an average of 7.5bn barrels, with 4.9bn barrels probable and as many as 10.8bn barrels possible. Gulf Keystone is the operator of the Shaikan block, with a working interest of 75%. John Gerstenlauer, the firm's chief operating officer said: "Shaikan-5 is the ninth well to be drilled across the company's four adjacent blocks in the space of 30 months. "Six out of these nine wells have been drilled on the Shaikan and Sheikh Adi blocks which Gulf Keystone operates. With two discoveries on the Shaikan and Akri-Bijeel blocks under our belt, we eagerly anticipate further results from the Sheikh Adi block. "The second exploration well on the Sheikh Adi block will spud in early 2012, when results are also expected from the first exploration well recently spudded on the Ber Bahr block." The share price fell 0.55% to 135.5p by 09:20.NR