SPE 123201 A Systematic Approach to Well Integrity Management Alex Annandale, Marathon Oil UK; Simon Copping, Expro Copyright 2009, Society of Petroleum Engineers This paper was prepared for presentation at the 2009 SPE Digital Energy Conference & Exhibition held in Houston, Texas, USA, 7 8 April 2009. This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessarily reflect an y position of the Society of Petroleum Engineers, its officers, or members. Electronic reproduction, distribution, or storage of an y part of this paper without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract mus t contain conspicuous acknowledgment of SPE copyright. Abstract Recognising the importance of good well integrity management practices, Marathon Oil UK developed an online database in conjunction with Expro to capture their well integrity data. The database has become a focal point to help facilitate Marathon s well integrity management processes and philosophies. The aim of this paper is to provide an overview of the rational for developing the system and the benefits that are being realised for both the Brae and Alvheim assets. Introduction The Brae Field is a mature asset located in the North Sea and consists of 3 fixed production platforms of around 100 wells, and several subsea tiebacks including Central Brae and West Brae. Due to the age of the asset and the recognition by Marathon of the importance of good well integrity data management, an online database was developed in 2004 in conjunction with Expro to help store well integrity data associated with the asset. The main issue identified by Marathon, was that integrity related well data was commonly located across the organisation by individual departments and would often be time consuming to locate. The ability to analyse information from various data sources was also inefficient and as a result auditing, trending and summary reporting became major tasks. Initially, the system was developed for use on the Brae platforms and a number of further enhancements were made to ensure the system was suitable for the Alvheim subsea development in Norway. Alvheim lies on the Norwegian Continental Shelf, west of Heimdal. The Alvheim development is comprised of the Kneler, Boa and Kameleon fields. The field came online in June 2008 with eight producing wells and two water disposal wells as part of the Phase 1 drilling program. A Phase 2 drilling program is planned in 2010/2011 for further production wells. The development provides for the transportation of produced oil by shuttle tanker, and transportation of produced natural gas to the existing U.K. Scottish Area Gas Evacuation (SAGE) system. Marathon Norway requested that the database was utilised to capture the integrity related data from the initial drilling operations, well handovers and scheduled tree/subsurface safety valve/tubing string testing. The system would supply a regular summary of the integrity status of the well stock. A Systematic Approach A web based system was developed allowing access to the same dataset by both wellsite and office based personnel. The database was designed to address the failings of other methods of data collection that had previously been in place. It provides a real time well integrity management capability and an auditable trail of operations and documentation incorporating wellhead activities, pressure data and part information. To view information on a particular well, the well is selected through a simple series of steps from geographical region to country then field. This allows the user to log into the main tree schematic screen from which a drop down menu allows either the wellhead module or manifold centre to be selected.
2 SPE SPE-123201 The well is selected from the slot diagram (Figure 1). The wells on the platforms are arranged as per their actual slot positions within the wellhead modules, while the subsea wells are positioned relative to their production manifold. Fig. 1 Slot Diagram Both conventional platform and horizontal subsea tree designs are represented within the system (Figure 2 and Figure 3). Each valve is coloured to represent its status from the last applicable activity that was carried out on the well: Green No leak or failure within acceptance criteria. Red Leak above failure criteria. Yellow Scheduled test outstanding. Other important items including subsurface safety valves (SSSVs), tubing string integrity and sustained annulus pressure conditions are also represented. Fig. 2 Surface Tree Example Fig. 3 Subsea Tree Attached Documentation Marathon uses a document management system to archive and control important documents. The database integrates with the external database to access important documentation. The software has several layers at which documentation may be added where it is most relevant. For example a casing design or integrity management document would be linked from a field level while a test certification document would be linked from a specific well. Technical manuals are also added to specific parts to provide necessary information on particular parts such as downhole safety valves, choke valves and tree valves. The primary attached document is the Well Barrier Schematic and can be produced by its own icon within the main tree schematic screen (Figure 4). The Well Barrier Schematic has been presented as promoted by the Norsok Standard D-010 (Aug 04).
SPE SPE-123201 3 Fig. 4 Norsok Well Barrier Schematic Other examples of attached documentation include: Drilling and Completion Manuals and Procedures Casing and Tubing Design Documents Cementing Reports Daily Drilling and Completion Reports Well Handover Documents Well Integrity Management and Philosophy Documentation Tubing and Casing String Test Charts Formation Integrity Test and Leak Off Tests Tree Certification Packages Tree and Wellhead Manuals SSSV information Photographs
4 SPE SPE-123201 Reports Electric reports are made up for any type of integrity related activity that is performed on a well. This commonly includes scheduled tree valve, SSSV and tubing string testing. The database allows test activities to be scheduled over any time period and over any number of occurrences. Test activities that have incurred failed tests are represented with a red icon (Figure 5). Fig. 5 Reports The following test activities are currently represented within the system by Marathon for platform and subsea wells:- Well handovers Tree installations Tree valve, SSSV, and tubing string testing Well intervention logging operations such as caliper, BHPs, and production logging leak detection surveys Wellhead testing and maintenance Gauge and hydraulic hose calibration Annulus blowdown and top up operations recognition of sustained annulus pressure conditions Integrity assessments and summaries External well examinations and concessions The test forms can have rules attached to questions regarding inflow pressures and pressure build ups. Failures are automatically determined against preset rules. Other forms have questions that are rated and provide an accumulative score. The resultant score then determines the integrity status of the well. Another important feature of the database is the ability to recreate Marathon s existing paper based forms within the software ensuring that the online system has a familiar look and feel to the old system. Pressure Monitoring The system integrates with the production pressure recording systems utilised in the Brae and Alvheim Fields. Daily pressure readings are imported into the database for each tubing and annulus component. These have maximum pressure service limits configured, which if exceeded issue email alerts to relevant personnel. This feature allows for immediate recognition of a pressure issue within tubing or casing strings, directly to both offshore and onshore personnel. The issue can then be quickly responded to and controlled. The database also allows pressure data to be reproduced as charts over time that can be manipulated by the user (Figure 6). The data can also be reproduced to allow grouping and representation of various queries from the user: Annuli and well pressures in a group set of wells over a set time period (field, platform, module, manifold centre) Annuli and well pressures that have exceeded a pressure limit over a set time Particular annuli pressures (for example all B-Annulus pressures in a field)
SPE SPE-123201 5 Fig. 6 Real Time Pressure Monitoring Data Manipulation One of the strengths of the software is the ability to manipulate and present captured data to a range of queries. The following summary reports are frequently produced as part of day to day integrity management within the Marathon Fields. Well Activity Summaries List well activities carried out over a set time and define as per activity type and/or platform or centre (Figure 7) Fig. 7 Activity Summary
6 SPE SPE-123201 Well Activity Details Answers from within a test form can be reviewed in isolation (Figure 8). For example a pressure build up recorded over a set period covering a series of wells for a selected part, or one well over a set period of time to reveal trending of results. Fig. 8 Activity Details Component Details All well components have a series of part properties assigned and populated containing attributes such as size, type, weight, material and part numbers. This information can be presented per well, platform or field as required to provide a summary table of the details of that particular well component. The system can also export the summary reports into Adobe or Excel formats where further manipulation and presentation of the results can be carried out. Integrity Assessments All of the Brae and Alvheim wells are subjected to (as a minimum) an annual well integrity assessment. However a well will also be assessed following a failure of a barrier during routine testing, or through annulus pressure monitoring and alerts. The questions on the assessment form are based upon the Petroleum Safety Authority Well Integrity Forum and its Well Integrity Categorisation Principles. The questions are focused on a 2 barrier philosophy that should be in place for the well. Depending on the number of failures and their leakage relative to established acceptable criteria, the well is allocated into an Integrity Category as shown in Table 1. Normal Acceptable. Healthy well with minor failure. Barrier failure can be controlled. Example Sustained annulus pressure (non-hydrocarbon) out with the 21 major barrier envelopes. Low Concern Acceptable. Well with integrity anomaly. Barrier failure can be controlled. Example High Annulus Pressure below leak rate criteria and below annulus pressure limit. High Concern Acceptable only if other factors can be controlled / mitigating actions taken. Example Leak into annulus where pressure exceeds pressure limit of the next outer casing, Critical Not acceptable. Failure in one barrier and the secondary is exposed to pressure outside verified design limit. Table 1 Integrity Categories Each of the failure categories have a pre-determined response that must be carried out within a set period of time. This information is available through the database to all parties within the company and provides a consistent means of assessment, classification and reaction to a well integrity issue within a particular field. All parties are therefore aware of the issue and the actions that are expected to be carried out against it. The integrity categories of the wells are presented within the slot diagrams on the main tree schematic screen for each well, providing an overview to the integrity status of that particular location.
SPE SPE-123201 7 Field Integrity Summary An email is issued to all relevant parties on a monthly basis to summarise the integrity status of the field well stock. All of the data within the summary is sourced from and compiled by the system, requiring minimal effort from the database administrator to issue. The summary sheet (Figure 9) lists the number of wells for each field grouped by their integrity category (normal, low concern, high concern, critical). Each field also has further information on its individual wells. This data includes the integrity category, the Well Integrity Forum sub code, a tree image with component results, a list of failed components, the well barrier schematic, a summary and comment of the integrity status of the well and integrity related actions against the well. Tubing and casing pressure chart is also presented for a default time period, with the tubing and annulus pressures service limits listed. Fig. 9 Summary Sheet The Summary Sheet provides a basis for regularly held meetings to discuss the ongoing integrity status of each appropriate field. The document is archived within Marathon s document management system for future reference and auditing. Conclusions The system is a web based database that allows access to the same dataset by both well site and office based personnel, and helps to ensure compliance with Norsok and API standards. Data analysis capabilities are available to analyse results and make informed decisions relating to both policies and procedures, and equipment reliablility. The database provides a real time well integrity management capability in an auditable trail of operations and documentation. This can be performed on a field to well level incorporating wellhead activities, pressure data and part information. Electronic data, such as certification, photographs or scanned pressure charts documentation can be appended to a well or component. Critical data is charted while 'triggers' can be set on each data field to flag abnormalities. This ensures that the relevant personnel are immediately informed of any problems. The systematic approach to well integrity management implemented by Marathon ensures the identification and resolution of issues before they become long term problems. Acknowledgments The authors would like to thank Marathon Oil UK for permission to publish this paper. Operationally sensitive data has been altered from the original values.