Scale Deposition Issue in Dual ESP System: A Game Changer for Tempa Rossa Field

Scale removal is one of the classical flow assurance issues faced in the majority of the oil fields and multiple solutions can be adopted by operators to solve it, however some steps are mandatory to reach an effective solution. This paper presents the first successful implementation of chemical treatments in Tempa Rossa Dual ESP systems which allowed to recover the TempaRossa production potential highly affected by scales building-up into pumps stages. Tempa Rossa is an oilfield located in the Sauro valley, in the heart of the region of Basilicata, in southern Italy. Discovered in 1989, is part of the Gorgoglione Concession located in the Gallipoli Cognato regional park and the Pollino national park; the concession is in the heart of a very touristic region thanks to the beauty of its landscapes. The area’s elevation ranges between 600 m and 1100 m above "sea level". It is a fractured carbonate reservoir of Apulia Formation (Lower Creataceous – Miocene), spreading over an area of about 200 km2 and reservoir depth over 4,000 meters developed on primary recovery strategy. The oil column is ≈2000 m high, with varying oil properties and a high content of asphaltenes (≈20%). Today the field is jointly operated by Totalenergies (50%), Shell (25%) and Mitsui (25%) Dual ESP was selected as artificial lift method to assure the required head to lift the production from each well. Since production start-up end of 2019, a severe pressure depletion has been observed (~-100 bar vs initial pressure). Initially, the wells were naturally flowing, then a "single ESP" mode was activated. Ultimately, the majority of the wells are operating in "Dual Boost" mode. In 2022, a severe pumps performance degradation was observed in all the ESP installations significantly impacting production performance; ESP performance degradation was estimated to be on average around 52% in comparison with the original pumps design. To establish the root cause of the pumps performance degradation, different hypotheses were evaluated and several actions implemented trying to solve the issue, but initially no positive results were achieved. Only later, thanks to Dismantling Investigation Failure Analysis (DIFA) carried out in all failed ESPs in Tempa Rossa, the main cause of the progressive pump’s performances degradation has been identified; essentially a relevant scales accumulation was detected along pumps stages, especially into pumps impellers, which was preventing the designed production flow path through the pumps, leading to a progressive lift performance degradation. The Lab analysis carried out to characterize the nature of the scales collected from the pump stages had proven 90% mineral, specifically Aragonites (CaCo3) and 10% organic (Tempa Rossa crude oil). Based on these Lab analysis results a chemical agent was selected to attempt the removal of hard scale accumulations into the pump stages. The chemical product was injected via 3/8" chemical injection line below the ESP installation while the pumps were running to create the best dynamic conditions for chemical reaction. Since the first application it was possible to witness an instantaneous improvement of the Delta Pressure created by pump and an associated significant production improvement encouraging the replication of treatment in all the other ESPs with similar results. Globally, at the end of the chemical treatment campaign, pumps performances recovered on average +40% versus the pre-treatment conditions with no degradation observed so far after 6 months and total field production increased by ca +30 % (ca 12 Kbopd).