ESP Technology Improvements in Peregrino Field

Although being widely used as an artificial lift method for heavy oil field developments, Electrical Submersible Pump (ESP) performance in high viscous applications is not fully understood. In order to improve knowledge of pump behavior under such conditions, Equinor has developed stage qualification tests as part of the technical requirements for deploying ESPs in Peregrino Field located offshore Brazil and has funded a series of research efforts to better design and operate the system more efficiently. Qualification tests were made mandatory for every stage type prior to field deployment in Peregrino. It is known that the affinity laws don´t hold true for high viscosity applications. Therefore, extensive qualification tests are required to provide actual stage performance in high viscous applications. Test results are used to optimize ESP system design for each well selecting the most efficient stage type considering specific well application challenges. In addition, the actual pump performance improves accuracy in production allocation algorithms. A better understanding of ESP behavior in viscous fluid application helps improving oil production and allows ESP operation with higher efficiency, increasing system run life. Shear forces inside ESP stages generate emulsion that compromises ESP performance. Lab tests in controlled environments have helped Equinor to gather valuable information about emulsion formation and evaluate ESP performance in conditions similar to field application. Equinor has funded studies to better understand two-phase flow (oil-water) which allowed visualization and investigation of oil drops dynamics inside the impeller. In addition, experimental procedures were proposed to investigate the effective viscosity of emulsion at pump discharge and the phase inversion hysteresis in the transition water-oil and oil-water emulsion. In addition to qualification tests and research performed to better understand system behavior, Equinor has developed and improved procedures to operate ESP systems in high viscous applications with emulsion production during 10 years of operation in Peregrino field. Such conditions also impose challenges to ESP system reliability. Over the years, Equinor has peformed failure analysis to enhance ESP system robustness which, combined with upper completion design, have improved system operation and reliability decreasing operating costs in Peregrino field.

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Understanding ESP Performance Under High Viscous Applications and Emulsion Production

Pastre

Biazussi

Verde

et al. 2021

All Days

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Understanding ESP Performance Under High Viscous Applications and Emulsion Production

Pastre

Biazussi

Verde

et al. 2022

Day 3 Wed, May 04, 2022

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Although being widely used as an artificial lift method for heavy oil field developments, Electrical Submersible Pump (ESP) system performance in high viscous applications is not fully understood. A miscomprehension of challenges and equipment performance in such conditions might lead to operation inefficiencies and equipment failures. This paper presents results of single-phase and multiphase tests performed by University of Campinas (UNICAMP). It also presents operation data, lessons learnt, and failure examples gathered over 10 years of ESP operation in Peregrino field which is a heavy oil, high viscous oilfield offshore Brazil operated by Equinor. Affinity laws commonly used for ESP simulations don't hold true for high viscosity applications. Hydraulic performance of centrifugal pumps is affected by fluid parameters like viscosity and density; operation parameters such as flow rate and rotational speed; and specific stage design characteristics. To determine degradation in head and efficiency as well as power requirement increase in viscous applications, Equinor performs one-phase high viscosity flow loop test to qualify each stage type prior to deployment in Peregrino field. For the qualification of ESPs, single phase qualification tests are performed using mineral oil with viscosities specifically chosen to cover the viscosity range of the specific field. Each stage type is qualified using a prototype with reduced number of stages due to flow loop limitations. Qualification tests for the Peregrino field confirmed that affinity laws are not accurate for high viscous applications and provided important insights regarding pump performance that are used in equipment specification and system surveillance. The UNICAMP research team has designed and performed multiphase flow tests to evaluate emulsion formation inside centrifugal pump stages and effective viscosity behavior. Phase inversion phenomenon investigation was also included in studies. Studies performed using a prototype stage allowed visualization and evaluation of oil drops dynamics inside the impeller in different rotational speeds. Two phase flow loop tests investigated the shear forces influence in effective viscosity inside pump stages and downstream pump discharge. Phase inversion phenomenon was also a point of great interest during the studies. Data gathered during lab tests was used to evaluate accuracy of mathematical models existing in the literature when a centrifugal pump is added to the system. Hysteresis effect associated to catastrophic phase inversion (CPI) was confirmed and replicated during flow loop tests. Such behavior can be related with operation parameters instabilities and equipment failures noticed in actual application in Peregrino field which are also presented in this paper.

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Relative Viscosity Model for Water-In-Oil Emulsion in Electrical Submersible Pumps: Comparing the ESP Head in a Real Scenario

Bulgarelli¹,

Silva²,

Biazussi

et al. 2023

Day 4 Thu, May 04, 2023

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Emulsions are common during oil production, and this is the case of the Peregrino field, e.g. . In several fields, oil and reservoir fluids can be produced through Electrical Submersible Pumps (ESP) and the formation of emulsion affects the ESP system, its run life, and the production itself. The viscosity increase due to emulsion formation severely hampers the ESP performance, requiring an increase in energy consumption on the platform to keep the same production rate. This work presents an initial validation of the model proposed by Bulgarelli (2021) to predict the water-in-oil emulsion effective viscosity within the ESP and its impact on lift capacity. The model can aid the design of the ESP system and can be used as a flow rate estimation tool during ESP production. The initial validation was performed using data from water-in-oil emulsion production of the two wells (A and B) in the Peregrino field, which use two different ESP models. The validation was divided into two parts: the first corresponds to Technology Readiness Level (TRL) 3 and the second, TRL 4, according to ISO 20815:2018. Firstly, well tests data were used to calibrate and test the model for initial validation of the TRL 3. Operation data of these two wells were then used for the initial validation of the TRL 4 in the second part. In the first step, measured and predicted ESP head were compared. Mean Absolute Percentage Errors (MAPE) of 3.6% and 0.8% were obtained for Wells A and B, respectively. In the second part, both the measured and predicted ESP dimensionless head and the measured and predicted differential pressure were compared. From these comparisons, promising results were observed for both wells' operations. However, more oil data field is necessary to complete the TRL 3 and TRL 4 validation.

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ESP Technology Improvements in Peregrino Field

Cited by 3 publications

References 5 publications

Understanding ESP Performance Under High Viscous Applications and Emulsion Production

Understanding ESP Performance Under High Viscous Applications and Emulsion Production

Understanding ESP Performance Under High Viscous Applications and Emulsion Production

Relative Viscosity Model for Water-In-Oil Emulsion in Electrical Submersible Pumps: Comparing the ESP Head in a Real Scenario

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