This paper discusses the experience and lessons learned during three years of electrical submersible pump (ESP) operation in heavy and viscous oil in the Peregrino field. Artificial lift applications on heavy oil fields have been a challenge for operators, and the Peregrino field is a good example for this type of ESP application.An ESP was designed to enable a wide operation window to fulfill reservoir conditions changes and to focus on the extended run life and overall lifting efficiency. Three different ESP configurations were applied to produce liquid rates from 1500 to 20000 STB/d utilizing 1100-HP and 540-HP motors. Upper completions using a packer and capsule solution were selected to comply with all production conditions. Peregrino field is a Statoil asset located in Campos Basin, approximately 85 km offshore from Cabo Frio/Rio de Janeiro state in Brazil. The oil in Peregrino has viscosity between 129 cp to 364 cp, and the API gravity varies between 13°and 15°API. The first phase of field development comprised two drilling-capable wellhead platforms and a centrally moored FPSO. Currently, there are 27 producer wells, including 3 multilaterals and 6 injectors in operation. The field is currently producing close to 100,000 STB/d of oil and has achieved a production record of 104,292 STB/d in July 2013.The learning and experience developed from the ESP design phase through three years of operation represents a very important set of best practices. This information can be used by the industry as a complete field-proven method of ESP project implementation, particularly when dealing with high flow rates, high horsepower, and viscous oil ESP operations in an offshore environment.
Peregrino is a Brazilian offshore field which has been operated by Equinor since 2011. The fields crude oil viscosity ranges from 129 to 364 cp and the API gravity varies between 13° and 15° API. Electrical Submersible Pumps (ESP's) were selected as the Artificial Lift method to produce the heavy oil from Peregrino. The ESP equipment design has been modified throughout the years to address various failure modes, therefore improve system reliability by adapting customized solutions. This paper describes in detail the ESP application and solutions implemented in the field to overcome those challenges. Every ESP string pulled from Peregrino is dismantled and inspected and this paper will discuss the routines used to conduct failure analysis and continuous improvement. The main challenge with the ESP operations in Peregrino has been asphaltene precipitation in the seal sections and emulsion formation. Emulsion instabilities cause pressure, temperature and electrical current fluctuations, which increase stress in downhole equipment. This paper will discuss how the ESP equipment in Peregrino has been improved to meet the various challenges, an overview of the following equipment changes will be discussed:Packer penetratorPump diffusersESP MotorNew Seal construction An overview of the ESP equipment reliability spanning the lifetime of Peregrino's operations will also be described in this paper.
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.
This paper presents an innovative concept to run Electrical Submersible Pumps (ESP) and upper completion utilizing dual derrick drillship rigs in deep water wells. The availability of a second deck to assemble, test and rack long assemblies brings the possibility to conduct a safer, efficient and reliable operation. The experience in Brazil running complex completions and high horsepower ESPs shows how important is to implement initiatives to reduce rig time. The main objective of the new process is to have every completion tool readily available in the drilling deck, requiring minimum time to connect it to the completion string. In the standard process, the tool sits in the pipe deck until completion string reaches its set position and only then the equipment is brought into the rig floor to be serviced and made up to the completion string. The methodology to assemble ESP and completion tools offline in the auxiliary derrick was developed in partnership with the operator, the service company, and the drilling rig contractor. The offline preparation concept was considered as part of the completion design phase analyzing every step of the upper completion run, looking for efficiency improvement and reduced total rig time. The modern automated pipe handling system was used to manipulate the long and heavy assemblies from the auxiliary deck to the racking system and from the racking system to the main deck without any safety concern, and with minimal human intervention. Eight deep-water operations were completed in Brazil using the new concept and the results brought important rig time reduction in the upper completion running time. The tools that were part of the completion included DHSV, permanent downhole gauges, chemical injection valves, 1600 HP ESP system and tubing test valves. The new process allows the team to service equipment without the usual operation rush reducing installation related failure therefore increasing equipment reliability. The methodology presented on this paper contributes to oil industry as a field-proven reference for offshore ESP and completion deployment technique reducing HSE exposure and total well construction cost. This is particularly important for deep and ultra-deepwater projects which are associated with high intervention costs. Dual derrick rigs were designed with focus to improve drilling operations and after the new process development, the modern robotized machinery empowers ESP and completion activities with improved efficiencies.
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