FIRST SUB-SEA DST WELL TEST WITH ESP IN INDONESIA

摘要

The application of Electric Submersible Pump Drillstem Testing (ESP DST) in the Ande-Ande Lumut-3X (AAL-3X) well confirmed the AAL Oil Discovery and also resolved uncertainties from the previous wells. An ESP DST system was selected for the AAL-3X tests with prior knowledge from the previous well, i.e. the well would probably not flow naturally due to being heavy (heavy oil with or without water) and lacking solution gas (low gas liquid ratio - GLR).Several other testing options were considered, i.e. conventional Nitrogen Lift via Coil Tubing; Hydraulic Jet Pumping and other artificial lift methods. However, these options were prohibitively challenging from both logistical and pressure transient test aspects. Although ESP DST was finally selected, many challenges remained as this ESP DST would be the first test in Indonesia on a sub-sea environment; i.e. on a floater (semi-submersible rig). With the current tight rig market, the test string design would need to be suited to the rig. These were the underlying challenges.With an ESP at the bottom of the string, annulus pressure changes would have to be minimized to protect the electric cable from damage. A simplified tool string was adopted instead of a conventional DST string. The packer required a feed-thru to pass the ESP cable through it and still maintain the seal between the annulus and the test string. An ESP Hydraulic Packer was chosen for this purpose. Two joints of MeshRite screen underneath the ESP were installed to reduce any sand problems during testing. The ESP pump was equipped with real time sensors to monitor the pump intake pressure.BOP Can for the ESP cable was used. This system would allow unlatching of the DST string from the surface equipment in emergency situations and allow latching back to continue the test or kill the well. The surface equipment was simplified by the omission of the separator and addition of one atmospheric tank. This was done because the gas volume was minor; the liquid rate was expected to be low; and the oil had to be mixed with diesel to achieve efficient burning.The tests were successful. Each test consisted of an initial flow, an initial surface shut-in, a 24 hour main flow and a 36 hour final downhole shut-in. The 1st zone tested 500 BOPD with 0% water cut in the main flow. The 2nd zone flowed 1200 BOPD with 0% water cut in the main flow period. The pressure data were good.