This paper describes a methodology that can be used to estimate the potential value of implementing digital and automation technologies in the well construction process in the context of a complex deepwater environment during the drilling conceptualization phase. This serves as a guideline for those interested in quantifying the value of applying digitization and automation processes, not only to make informed decisions related to investment in drillship or systems hardware and software but as well as performance improvement.
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.
This paper describes the application of casing drilling technique for the top hole section in conductor sharing wells in a brown field, offshore Malaysia. Its objective is to describe the integration of the casing drilling technique and the conductor sharing design when used in conjunction. It is intended to share the challenges faced during the design and execution phases of the project, the solutions analyzed and applied; as well as the outcome and learnings. In this case study, the conductor sharing design makes it possible to maximize the well capacity of the offshore drilling platforms by accommodating multiple wells per drilling slot. The casing drilling technique is implemented to manage drilling risks related to wellbore stability, losses and shallow gas. The feasibility for combining the two technologies is evaluated during the planning stage by reviewing the documented previous industry experience of the two technologies, combined or separate; while local knowledge is analyzed to ensure all drilling factors are considered. Solutions to challenges such as wells interface inside the shared conductor, directional control, losses, cement design and placement techniques, well control, operational procedures and time and cost efficiency are analyzed. The execution results are analyzed by comparing design estimations and assumptions with field data and actual results. These data is translated then into recommendations and lessons learnt. The conclusions of this case study are presented as a set of design work, drilling practices and risk analyses processes and their results that can be replicated or considered in future wells design where conductor sharing and casing drilling are to be implemented together. While several individual studies of particular conductor sharing wells configurations, casing drilling and well construction techniques are available, the present work discusses one of the few applications to date where conductor sharing and directional casing drilling technologies are combined to address specific offshore challenges. The team considers of paramount importance that the knowledge obtained on this very specific combination of two technologies is documented and shared within industry professionals to provide reference for future applications.
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.
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