In certain oil fields, slim wells are common due to corrosion or erosion in 7-in. casing and sidetracks to evaluate secondary reservoirs. Efforts to produce such wells by electric submersible pumps (ESPs) pose several challenges such as early failures and insufficient pressure to reach target flows due to the limited casing clearance which also limits the pump size. This paper discusses the successful installation and a production test of a bottom intake ESP. In comparison, conventional slim electric submersible pumps had been installed in the same field with limited success in the same type of slim wells.

The slim ESPs have shorter run life compared to standard ESPs, mainly because of equipment damage while running in hole (RIH). The motor lead extensions (MLE) are particularly vulnerable given the tight clearance available, which precludes the use of MLE cable protectors along the ESP. Production is also limited because of the smaller diameters that conventional slim ESPs require to fit into the slim (4.5-in. and 5-in.) casings.

To tackle these challenges, an operator and an energy technology company collaborated to devise a solution using a bottom intake slim ESP architecture. The objective was to modify the conventional slim ESP to maximize clearance thereby improving the reliability of the ESPs and increasing the production rate in slim wells. By combining conventional slim ESP technologies and the inverted architecture used in coiled-tubing-deployed ESP, the challenges described were addressed. The bottom intake slim ESP was designed with MLE to be installed along jointed tubing. Since it is terminated at the top of the ESP string, risk of damage to the MLE while RIH is eliminated, and a larger pump can also be installed. The larger pump outside diameter results in a substantial production increase. The bottom intake slim ESP can operate on higher drawdown compared to conventional ESPs as it can be set deeper. The objective was to prove bottom intake slim ESP technology as a solution to produce 3,500 to 7,000 BPD in 5-in. casing wells, while eliminating the risk of MLE damage during RIH in the operator slim wells. Moreover, based on erosion simulation, the effect of discharge velocity on the casing was negligible, and by utilizing plug-and-play technology, human error and rig time were reduced.

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