The Caspian offshore is a promising area for hydrocarbon accumulation.Since it is an offshore,it is achallenging area in terms of strict environmental regulations and safety.At the early stage of the project itwas clear,that reservoir properties of the exploration well require artificial lift assistance to produce duringwell testing.Therefore,designing proper DST string with artificial lift was crucial to the success of welltesting.This paper describes the methodology to select the artificial lift solution for well test.It shows the uniquecombination of technologies and techniques that enabled a DST with ESP in combination with the Y tool,that provides capabilities to run thePLT below the pump.Also,one of the main challenges of well testingoperation was to handle heavy oil fluid at surface.Being in environmentally sensitive area,designing asurface well testing equipment in a limited footprint,that enables efficient separation and disposal of heavyoil was very critical.Another challenge was unconsolidated formation with the high risk of sand productionunder drawdown,therefore downhole testing string and ESP pump supposed to withstand large quantity ofsolids during the production.The key technology that enabled testing was a new generation of abrasion resistant ESP pumps,that aredesigned to handle extensive solids production.The heavy oil also posed a number of risks.The surfaceequipment was specifically designed to heat oil in the tanks and if required to mix with diesel before flaringoperations.Local regulation does not permit production during the night time and allows limited number of days forwell testing.Therefore,well testing design must enable to acquire all necessary information within shortperiod of test duration.The real-time data transmission and interpretation was a key to achieve main goalof the testing in exploration well-to accurately characterize the reservoir.This was the first successful ESP-DST in Caspian Sea.Despite of many challenges,the technologies thatwere selected for well testing operation was proven to be reliable.This allowed Operator to untap previouslynot accessible hydrocarbon reserves.
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