The giant heterogeneous carbonate field presented here consists of multi-stacked reservoirs and is located in the Arabian Gulf approximately 135 km north-west of Abu Dhabi. The reservoir named "T" measures 9 km by 11.5 km, with large accumulation of 35 °API oil with initial gas oil ratio of about 400 scf/STB. The current reservoir pressure is around 2,700 psi; many of wells are unable to flow naturally against the high sealine pressure, due to low productivity and relatively low GOR. To produce these wells, "artificial lift" or lower sealine pressure are required. A collaborative team of Reservoir Engineers, Petroleum Engineers and Geoscientists was assigned to find a sustainable and cost-effective solution to produce reservoir "T" in order to evaluate its potential. The team conducted a detailed and comprehensive study of the field starting from reservoir "T" and then expanded to the other reservoirs. As a result, the proposal of an "Auto Gas Lift" (AGL) pilot was formulated to use gas from the reservoir "C" (underlying reservoir T) to artificially lift the oil produced from reservoir T. AGL is a cost-effective artificial lift system, directly replacing for conventional gas-lift equipment, gas compression facilities, gas transport pipelines and ancillary equipment. This technique has been identified as the most suitable for such mature offshore field, where existing platforms have limited spare load and space capacity and could not accommodate gas-lift compression facilities or ESP topside equipment. The first pilot completion has been designed. It consists of a perforated downhole high GOR zone from which gas is bled into the tubing at a rate controlled by a downhole gas lift valve. The gas produced from high GOR reservoir C will allow reservoir T to flow by reducing the hydrostatic head of the fluid column in the well. Artificial lift has not been implemented yet in the field. However, several artificial lift techniques, such as Electrical Submersible Pumps or conventional gas lift, are foreseen in long term development plans. "AGL" technique, if successful, could represent a cost-effective solution for further appraisal of this reservoir, without waiting for the implementation of large-scale artificial lift techniques.

Field presented here is located in the southern part of the Arabian Gulf approximately 135 km north-west of Abu Dhabi city. This giant heterogeneous carbonate field consists of multi-stacked reservoirs. The presented reservoir is highly fractured, it measures 9 km by 11.5 km. The reservoir has an original oil in place estimated at 2,240 MMstb of 35°API oil with saturation gas of 400 SCF/bbl. The reservoir pressure is +/− 2,700 psi and the sealine pressure in the field is +/− 1100 psi. The wells completed in T reservoir are unable to flow naturally against the high sealine pressure. Some wells are producing against by-pass line at 600 psi. Crestal gas injection was introduced to maintain the reservoir pressure. To produce the reservoir at its potential, it is required to use some artificial lift techniques. ESP was finalized to install for overcoming the high sea line pressure. As mentioned earlier the T reservoir is naturally fractured and has crestal gas injection, which lead towards 3,500 – 4,000 SCF/bbl and beyond the ESP limit. This requires some solution to handle the gas. A collaborative team of engineers was assigned to design and meet the challenge of such a premier application. The team conducted a detailed and comprehensive analysis of the T reservoir's fracture and fault characterization: the aim was to deliver an optimal well design meeting the requirement of ESP gas handling with minimum cost. A unique, fit-for-purpose dual completion (4-1/2" × 2-3/8") was finalized. The rigless ESP will be run through 4-1/2" tubing and 2-3/8" tubing will be utilized for gas handling and re-injecting gas in the sealine at surface. The dual completion will allow to handle high GOR through short string, which will lead towards the long ESP runlife. Before commencing the full development plan for T reservoir, this will be a pilot for better understanding the reservoir and its behavior. Rigless ESP was selected due to the advantages compared with conventional ESP: POOH and RIH of retrievable ESP parts through a conventional slickline unitPumps can be replaced during the well life without rig workover.Low OPEX cost.