In 2012, a redevelopment infill drilling campaign took place in a brown field, offshore Malaysia. Accurate wellbore positioning was critical to place a well within a path that navigates 2200 ft through an antithetic faults panel, separated approximately 900 ft, and with a 120 ft general throw; and to intersect the five target reservoirs of the well. The complex well path also faced the challenges of infill drilling in a brown field, such as collision avoidance in a crowded field, the location of the target reservoirs relative to the available drilling slots; as well as trajectory restrictions due to completions design. This paper presents the well design solutions that include a rigorous anti-collision analysis and a comprehensive survey programme. The survey programme consists of gyro while drilling (GWD) on the upper section of the well until the path is clear of magnetic interference from neighboring wells and the application of in-field referencing (IFR) correction for conventional measurement while drilling (MWD) magnetic survey based on accelerometers and magnetometers. IFR improves survey accuracy with a multi-station analysis that corrects the survey error with the localised crustal effects in the magnetic field of the earth. It was used for well positioning in between faults and for target intersection. It enabled drilling the well with higher confidence while intersecting the target reservoirs. A reduction of 60% on survey uncertainty was observed. The more accurate wellbore survey also optimises collision analysis for future well plans and it gives more reliable control points to update the subsurface static model. The benefits were obtained without compromising the drilling performance given that no extra operational time is required for the survey correction. Introduction Context The well is located in a brown field, offshore Malaysia. Three infill drilling campaigns have been executed since a decade ago to increase oil recovery. To maximise the use of existing assets and to optimise cost, infill drilling has been performed from existing drilling facilities by either accommodating new drilling slots or side-tracking idle wells. The well was planned to target several reservoirs located in crestal position in the southern block of a rollover anticline formed by growth faulting. In the study area, faults show a general east-west trending direction. The reservoirs are entirely related to sealing against faults while within reservoirs the seals are marine flooding surfaces. Well design considerations The well design process consisted of identifying the available surface location -a well with high water cut, idle since 2007- and selecting the subsurface targets. Once drilling targets were identified and preliminary well trajectories were built, an integrated team approach was used to optimise the well paths, usually requiring a compromise between the desired and the practical approach.

PETRONAS Carigali and Schlumberger IPM have formed an alliance to develop a field in offshore Malaysia. Due to space limitations, a platform extension was installed to accommodate three additional conductor sharing wellheads (CSW). Project challenges include limited CSW pass-through, well collision risk, highly unconsolidated formations in the angle building section, directional control and shallow gas zones. To avoid well-to-well collision caused by poor directional control, a pilot hole must be drilled under the conductor to provide good directional control in the unconsolidated sandstone. The pilot hole must also mitigate shallow gas risk. To achieve the reservoir hole size and accommodate dual gravel-pack completions, the pilot hole must be opened from 8–1/2" × 16" to allow subsequent hole section drilling. The project team had to design a BHA that could efficiently deliver the objectives with minimal rig time. To solve the challenges a new hole opening methodology would be required. The pre-drill analysis included studies in: BHA durability/dynamic stability to ensure good hole quality; hydraulics and fluid dynamics to deliver proper cooling and hole cleaning; optimized combination of hole opening technologies. To reduce reaming runs/bit trips, a dynamic modeling system was employed to quantitatively analyze the interaction of various downhole tools and optimize the BHA configuration/drilling parameters. The modeled dual eccentric PDC hole-opening BHA was run and successfully solved the challenges, mitigated risks and met the required drilling objectives for completing the six CSW wells. A post-drill simulation analysis was performed to analyze the dynamic downhole BHA behavior with the actual operating parameters. The authors will explain how the BHA was developed and successfully used in the field to solve the unconsolidated formation challenge. Survey method and challenges of drilling through the conductor sharing wellhead are also discussed.

A Brown field, offshore Malaysia, has been in production for over 30 years. The Brown field has low rock strength in shallow reservoirs, while the deeper reservoirs consist of stronger and stiffer formations. As a result, the completion for shallow reservoirs requires gravel pack treatment, whereas the deeper reservoirs can be completed without particular requirements of sand control.Big hole charges followed by mechanical surge are the preferred perforating technique for an optimum gravel pack. For consolidated formations, deep penetration charges, with a dynamic underbalance, are more suitable to maximize inflow. Historically, multi-zone completions in field wells are performed in stages: the deeper zone is perforated and conditioned first; followed by the upper interval, which is perforated, gravel packed, completed and connected to the lower section.This paper presents the combination of the two perforating techniques in one operation. It also discusses the candidate identification process, perforation design, formation damage analysis, execution and results. The gravel packs were performed successfully with a GP factor higher than predicted by simulations, and the initial production behavior suggests no evidence of adverse effect on formation damage even when the mechanical surge required for the big hole charges was done higher than conventionally.Considerable rig time savings were achieved by eliminating a Tubing Conveyed Perforations (TCP) run and clean out operation. The operation was performed in 60.8% of the time observed in a previous similar well. The combined perforating technique is suitable for cases where the reservoir properties are very well known.Based on the result of the world first combination of these techniques, continue supporting the implementation of this optimized solution in future wells is high recommended. Perforating StrategyTubing Conveyed Perforation (TCP) is the technology used for perforation in this field, both Dynamic Underbalanced Perforating (DUP) and Mechanical Surge Technique systems will be utilized on a dependent basis.

A Workover or sidetrack is often performed, in brownfields, to revitalize idle wells or to produce alternate zones. Recently, with a larger number of fields being redeveloped; the proper plug and abandonment (P&A) of donor wells gained relevance. This is a study of the evolution of the P&A methodology in a brownfield, offshore Malaysia, where engineering techniques and risk management strategies have been developed into a consistent approach to well P&A. The methodology has allowed economic access to reserves and has become a process that can be applied across the field based on well configuration, best practices and current technologies. The operations entail not only intervening wells for gravel pack removal, fishing of mechanical obstructions and retrieval of completions, but also isolation of completed reservoirs from surface whilst isolating cross flow between them, which is of paramount importance in a brownfield with plans for future enhanced oil recovery (EOR).Challenges, such as lack of information and the uncertain condition of ageing wells related to corrosion, leaking elements, zonal isolation, annulus pressure and well integrity; as well as inadequate maintenance, mechanical obstructions and failure of existing downhole equipment have been successfully managed in all cases.Key processes include extensive data gathering and upfront well investigation and preparation for contingency planning. The wells sequence has been optimized to minimize the impact of un-foreseen events; and the decision making process has been drafted to cover for a wide range of situations.Results show reserves that have been accessed at 40% the cost of a sidetrack, by retrieving old gravel pack assembly and workover the well; also, sidetrack wells have enabled reaching reserve opportunities in the field without the costly addition of slots to offshore platforms. This consolidates the methodology for its further application in the field with the potential to be implemented on other similar redevelopments.

Workover is the process of performing major maintenance or remedial treatments on an oil or gas well to restore, prolong or enhance its production. The complexity of workover operations is increasing due to the well conditions faced, such as age, environment, mechanical restrictions, completion design, number of completed zones, downhole equipment installed, etc. Well workover can represent up to 49% cost reduction over its sidetrack option, making it economical; but it may require good sand control understanding, and comprehensive procedures, to retrieve existing gravel pack (GP) assemblies, an operation that possess the risk of getting stuck and/or being unable to retrieve the assembly and eventually abandoning the well. For many years the Oil Industry has rejected workover candidates because of risk aversion overriding cost and value added; the actual workover opportunities include new challenges such as retrieving Alternate Path screens. This paper discusses the design, risk management approach and the challenges faced during execution, as well as the lessons learnt, of two workover wells in a brown field; both candidates had several challenges such as: Old completion,Lack of reference data,Length of screens (500 ft of screens)Sand productionDifferences to retrieve Wire Wrap and Alternate Path screens The two successful retrieval of the sandface completion in both wells were the first and second operation of its kind performed by the operator and provide field experience and best practices for future similar operations. Furthermore; the study of the retrieved assembly, after over 20 years of production, helped to understand the sand management system failure mode and the reasons for the sand production issue; knowledge that will impact future well designs in the field.