Scale deposition in completion strings is becoming a threatening problem to produce and safely operate wells completed in the Upper ZAKUM (UZ) oil field. Calcite or Calcium Carbonate (CaCO3) scale mostly found in the upper part of the production string, and Celestite or Strontium Sulphate (SrSO4) mostly found in the lower part of the production string, are the common type of scales encountered in Upper ZAKUM producing wells. Injection seawater (rich in Sulphate) and formation water (rich in Strontium ions) mix in the reservoir and/or wellbore under varying conditions resulting into Strontium Sulfate Scale formation in downhole equipment. While CaCO3 scales are possible to be removed by the use of common acids and wireline tools, Strontium Sulphate scale requires special techniques to remove chemically and/or mechanically, and present the most challenges to achieve complete removal. This work will describe ZADCO scale management strategy to monitor and remove Strontium Sulfate scale in Upper Zakum producing wells. A scale prediction simulator is used to identify wells with high scaling risk. Scale Risk Matrix (SRM) is being developed to classify the scale risk in each well. The Chlorides content, the percentage sea water in the produced water, the production rate, the percentage water cut and scaling index are the main parameters that are used to calculate the overall scaling risk for a certain string. The wells classified as high scaling risk wells, are included on a monitoring list for periodical scale checks by running gauge cutters on slickline. Scale samples are collected and sent to the lab for analysis and scale type identification. The category of strings with a scale thickness less than 0.25″ are treated with a chemical scale dissolver, the wells containing scale thicker than 0.25″ are treated with downhole cleaning tools run on Coiled Tubing. In 2005, ten wells severely scaled with Strontium Sulphate were mechanically treated using Coiled Tubing, Mills and motor, high pressure rotating tool with Sterling Beads* and Polymer as the cleaning fluid. Most of the job objectives were not completely accomplished due to severe hard scaling conditions. Introduction Upper Zakum field (4th largest known field in the world), operated by ZADCO, and located offshore Abu Dhabi. The field was discovered in early sixties. Oil production started in 1982. Seawater injection to support the reservoir pressure started in 1984. Water breakthrough started in 1990. Strontium Sulfate (SrSO4) scale was observed in 1991. Since 1991 there has been an increase in scale related problems such as interference with producing wells wireline operation and minor production losses. With more than 400 producers and more than 350 pressure support water injectors in UZ, a solid Well Integrity Management System (WIMS)1 was put in place by ZADCO that helps to identify, prevent and solve all the problems related to lack of integrity in each well. Scale management system is a major part of ZADCO WIMS. In 2001 ZADCO carried out a scale study to evaluate the scale risk in UZ field. It was found that the the maximum Scaling Index (SI) (need to explain what is scale index) for mixtures of UZ formation water and injected seawater at reservoir conditions is 0.57 for strontium sulfate which is only just above the positive threshold SI of +0.40 for the lowest zone of scale risk to the production problems. This would tend to indicate that UZ field would not have significant production declines due to scale.

Scale deposition in completion strings is becoming a threatening problem to produce and safely operate wells completed in the Upper ZAKUM (UZ) oil field. Calcite or Calcium Carbonate (CaCO3) scale mostly found in the upper part of the production string, and Celestite or Strontium Sulphate (SrSO4) mostly found in the lower part of the production string, are the common type of scales encountered in Upper ZAKUM producing wells. Injection seawater (rich in Sulphate) and formation water (rich in Strontium ions) mix in the reservoir and/or wellbore under varying conditions resulting into Strontium Sulfate Scale formation in downhole equipment. While CaCO3 scales are possible to be removed by the use of common acids and wireline tools, Strontium Sulphate scale requires special techniques to remove chemically and/or mechanically, and present the most challenges to achieve complete removal.This work will describe ZADCO scale management strategy to monitor and remove Strontium Sulfate scale in Upper Zakum producing wells. A scale prediction simulator is used to identify wells with high scaling risk. Scale Risk Matrix (SRM) is being developed to classify the scale risk in each well. The Chlorides content, the percentage sea water in the produced water, the production rate, the percentage water cut and scaling index are the main parameters that are used to calculate the overall scaling risk for a certain string. The wells classified as high scaling risk wells, are included on a monitoring list for periodical scale checks by running gauge cutters on slickline. Scale samples are collected and sent to the lab for analysis and scale type identification.The category of strings with a scale thickness less than 0.25" are treated with a chemical scale dissolver, the wells containing scale thicker than 0.25" are treated with downhole cleaning tools run on Coiled Tubing.In 2005, ten wells severely scaled with Strontium Sulphate were mechanically treated using Coiled Tubing, Mills and motor, high pressure rotating tool with Sterling Beads* and Polymer as the cleaning fluid. Most of the job objectives were not completely accomplished due to severe hard scaling conditions.

ZADCO owns more than 500 wells operating in UZ, UA & ST fields to contribute in achieving the production targets as set by the Shareholders. To ensure that wells operate as designed for their assigned life (or greater) with all risks kept as low as reasonably practicable or as mentioned, it is important to insure individual well's integrity. Hence, ZADCO developed an in-house "Well Integrity Management System (WIMS)", which defines & provides the operating standards & guidelines for maintaining the well integrity parameters, ensuring safe well operations and securing well potential availability during its life cycle so that return on investment is maximized without the sacrifice of safety and environment. The implementation of ZADCO's well integrity process follows the cycle assurance testing, preventive measures, monitoring, evaluation / assessment, control & remedy, audit / verification. This paper reviews WIMS in ZADCO. WIMS is structured to include wellhead (surface) equipment, downhole equipment and operational (process control). WIMS places much emphasis on the requirement of barriers for safety and environmental protection. Introduction The objective of developing Well Integrity Management System (WIMS) is to provide standard guidelines to ensure that technical integrity of all the wells is maintained throughout their life cycle, they operate under safe condition and are capable to function continuously to achieve the targeted production/injection requirements. Well integrity is based on the establishment and maintenance of confinement barriers in the particular well. As per WIMS standards, a well is considered integral if at least two separate and sound confinement barriers across each flow path between the potential reservoir and surface are available all the time. WIMS very much emphasis on the problem prevention based approach (endeavour to predict & solve the problem before it happens) that can accommodate several direct advantages and benefits like reduction in operating down time, enhancement in well control and safety aspects, minimized unplanned repair intervention & cost impact etc. Major well issues that would have impact on the technical integrity and operability of a well viz; Surface Completion Components (Wellhead & X-mass tree), Sub-surface Completion Components (downhole safety valve (DHSV), Gas lift valves, electric submersible pump (ESP), Well Construction (Casing & Annulus), Communication Problems, Corrosion, Scaling, Non-hydrocarbon Effluents / Products, Well Operation Suspension, Well Intervention Services (Electric/Slick Line, Stimulation, coiled tubing unit (CTU), Risk Management Process & Auditing System, etc. have been thoroughly discussed in the WIMS manual.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis work will describe the management of scale in a United Arab Emirates offshore carbonate reservoir. Field pressure is sustained by water injection, which contributes to the formation of scale in downhole tubulars. This scaling can cause both safety and production problems, for example, by blocking a subsurface safety valve or chocking flow at downhole nipples.ZADCO has initiated a successful strategy to manage the sulfate-scaling tendency in the completion tubing. Software is used to identify wells early on as potential scale candidates. This software uses real field measurements and analysis of injected and produced water information. The results are used to plan well monitoring and/or treatment. The identified wells are monitored using both slickline gauge measurements to measure actual scale growth and produced water surface analysis to update the software model.Early corrective action is performed using a specialized sulfate scale-dissolving fluid pumped from the surface. More aggressive treatment for larger scale accumulations is performed using a barge, coiled tubing unit, and specialized downhole jetting system.Results have shown that early diagnosis of the scale allows earlier, easier, and far less expensive scale removal treatment. The effect of scale on production decline is also reduced.

Well integrity data is one of the most critical data types in oil production companies. Since this data is a valuable asset, ensuring its availability and reliability must be taken into consideration to avoid unsafe situations and potential catastrophic consequences. ZADCO has recognized this concern and thus makes continuous use of Information Technology to streamline its business processes. This paper outlines the best practices for data management implemented by the Well Integrity Team to boost its business performance. These practices ensure achievement of effective and efficient business processes to cope with today's dynamic, fast-paced business environment. The deployment of Information Technology and its capabilities designed appropriately to serve the business, management and organizational needs result in robust Information Systems that achieve business objectives and save resources, effort and time. Introduction ZADCO Well Integrity Team manages and maintains over 600 wells (producers and injectors) in Upper Zakum field (the 4th largest known field in the world), located offshore Abu Dhabi, UAE. The team's work is crucial in achieving the company's mission: "To build optimal sustainable production". To ensure uninterrupted production, the integrity of wells must be maintained at all times. Therefore, an in-house 'Well Integrity Management System (WIMS)' was prepared in Y2004 to "define and provide the operating standards and guidelines for maintaining the well integrity parameters, ensuring safe well operations and securing well potential availability during its life cycle so that return on investment is maximized without sacrifice of safety and environment." WIMS was reviewed in Y2007 by third party consultants to enhance and optimize the existing standards and procedures. To better manage the system, it was found necessary to acquire an Information System that facilitates and automates the Well Integrity Data Management based on WIMS standards and processes. Zakum Field's Management Being a super giant oil field that is still under development, management of Zakum Field poses a significant challenge to its operator. The constantly increasing number of wells adds to the complexity of the management process. Furthermore, as the wells and facilities age, new obstacles and challenges are encountered. Therefore, it is essential to set and implement robust practices and procedures that maintain the wells and provide guidance for quick and effective mitigation actions in case of well problems. Initial Data Management System Well Integrity (WI) data is very important and affects decisions made by WI Engineers and influences actions taken in the field, consequently determining the fate of wells.