This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 173928, “Removal of Organic and Inorganic Scale From Electrical Submersible Pumps,” by M. Ramones, R. Rachid, SPE, D. Flor, L. Gutierrez, and A. Milne, SPE, Schlumberger, prepared for the 2015 SPE Artificial Lift Conference— Latin America and Caribbean, Salvador, Brazil, 27–29 May. The paper has not been peer reviewed.
Rigless coiled-tubing-unit (CTU) interventions can be effective in returning to production wells that have lost electrical-submersible-pump (ESP) efficiency because of organic, inorganic, or mixed scale deposits. Such operations extended the average ESP run life from 40 to 140 days and eliminated the need for workover (WO) rigs. A heavy-crude viscosity reducer (HCVR) is recommended as part of these treatments, to improve the cleanup process.
Introduction
Recent work with crude-oil viscosity reducers has shown that both inorganic and organic deposits can be removed by spotting/jetting with coiled tubing without the need of a WO rig. When a treating fluid containing the viscosity reducer is mixed with highly viscous crudes, it creates a water-external pseudoemulsion, which decreases the apparent viscosity of the crude by several orders of magnitude, removing more than 60% of the heavy crude from the surface of the scale and accelerating the dissolution of organic deposits. This enables the chemical treatment to dissolve the inorganic deposits, allowing the pump to be restarted without the need to pull out the completion. The new fluid systems have made it possible to remove organic and inorganic deposits systematically from ESPs, extending the average run life from 40 to 140 days, and to eliminate the requirement for WO rigs, with an average rig-cost saving of 6 days per well and an average saving of USD 1.5 million in deferred production.
Problem Definition
Organic or inorganic deposits can occur in different parts of the petroleum system, including the reservoir, well perforations, artificial-lifting equipment, and production lines. Scales are inorganic deposits that are formed when the saturation of the produced water is affected by changes in temperature and pressure conditions, creating significant reduction in oil-production rates or even plugging the entire production system. On the other hand, viscous oils that are exposed to significant pressure drop are the source of organic-material deposition, the most common being paraffins and asphaltenes. These organic materials can be defined as hydrocarbons with high molecular weights that are hard to dissolve and that can also create sludge when in contact with acid systems.
