Analysis of recovered scale samples deposited within Electrical Submersible Pumps in offshore wells was carried out. The primary objective includes the identification of root cause of deposition and suggesting remedial measures for removal and prevention. Many wells in an offshore field in ONGC are facing an acute problem of decrease in pump efficiency and ultimate failure of Electrical Submersible Pumps due to deposition of inorganic scale. The methodology for carrying out the study consists of a detailed Compositional Analysis of a sample of scale retrieved from inside the ESP of one of the affected wells. Additionally, X-Ray Diffraction analysis of the debris and compositional analysis of produced water sample from the same well were also carried out. The results of the experiments were corroborated by software simulation in Scale Prediction Software. Experiments were also carried out to identify a suitable inhibitor which could operate at high bottom hole temperatures experienced in the affected wells for preventing any future deposition. Based on the compositional analysis of the scale and simulation runs using the produced water analysis, it was established that deposition of hard, adherent sulphate scale was the primary reason behind the choking and subsequent failure of the ESPs. In-situ conditions leading to deposition of the scale including variations in the operating environments and the effect of pump sizing have also been discussed. The paper analyses the problem of inorganic scale deposition in offshore ESPs of ONGC utilising actual scale samples retrieved while dismantling the pump. An attempt has been made to provide an insight into the driving mechanism behind deposition inside the pump and various factors leading to it. The paper also details extensive lab experiments carried out to identify suitable inhibitors for high temperature application.
Analysis of tubing failure of SRP wells with respect to uniform corrosion, pitting and mechanical abrasion has been carried out. The primary objective includes the identification of root cause of failure and suggesting alternate metallurgy. Many wells in an onshore field in ONGC were facing the acute problem of general corrosion, pitting and rod-tubing wear. The methodology for carrying out the study consists of a Failure Analysis of a retrieved sample of the failed tubing from one of the affected wells. This included a thorough visual inspection, Scanning Electron Microscope analysis and X-Ray Diffraction analysis. The results of these tests were backed up by software simulation in Honeywell Predict. Metallurgy selection involved multiple exhaustive simulation runs in Honeywell Software Socrates which was corroborated by relevant oilfield standards as well as literature available on the subject matter. Based on the failure analysis and simulation runs, it was concluded that besides the issue of uniform corrosion and pitting, many of the affected wells are also facing the problem of tubing failures due to abrasion and mechanical wear. It is pertinent to note that the major contributor of the frequent tubing failures in the candidate wells selected for the study were pitting and corrosion. Nevertheless, Abrasion always remains a key threat to the tubing string integrity in rod-pump wells. Therefore, the existing tubing metallurgy of N-80 grade Carbon Steel was deemed inadequate in the absence of reliable corrosion inhibitor continuous dosing facilities. A tubing metallurgy that takes care of both pitting corrosion as well as abrasion and mechanical wear was sought. UNS 41426/41427 or the modified version of 13 Chrome, commercia lly known as Super Martensitic 13 Chrome, are available in 95 ksi and 110 ksi grades. These grades have a maximum hardness of 28-32 HRC which is substantially high compared to L-80 13 Cr (maximum 23 HRC). Also, as this alloy has 4-6% Nickel, it provides added protection against uniform corrosion as well as pitting and hence was recommended. The paper specifically analyses tubing failure in Sucker rod-pump wells due to corrosion, pitting and abrasion. After exploring various viable options, adequate tubing metallurgy has been recommended that should take care of corrosion, pitting as well as mechanical wear problems.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.