The adoption of segregated drilling campaigns is commonplace in an effort to harness economies of scale and reduce well construction costs. In an attempt to increase the financial efficiency of drilling campaigns, the division of the well construction and completions operations can be segregated into two distinct phases. A drilling and casing phase leaving a cased well in a Temporary Abandonment (TA) status, followed by a phase consisting of clean-up, completion and stimulation operations resulting in the handover of the well to production to bring hydrocarbon production online. As such an Intervention and Completion Unit (ICU) with the capability to perform perforation, multi-zone completion installation, stimulation, clean-up operations and well testing has significant advantages when deployed in the later phase of a segregated multi-phase drilling campaign. This paper describes the collaborative development of an ICU that facilitates the installation of multi-zone and smart well completions, conveyance for well servicing operations, well bore clean-up (WBC) activities, well testing and stimulation activities. The challenge of undertaking traditional drilling phase activities with a technically capable, yet cost effective ICU is discussed, particularly the core areas where the reduction in specification through it being redundant for the phased operations. The key parameters driving the ICU development and design are presented from the operator's perspective, based on prior campaign experience utilizing this approach with alternative technology. The process identifying the key requirements of the completion and well servicing operations is described with the selection of implementing new technology solutions in the design. The avoidance of Non-Productive Time (NPT) is a core aspiration in making incremental cost efficiencies. The identification of operations not on the critical path that can be performed simultaneously or as an offline activity, have the potential to make high cost impacts. Through innovative design and the implementation of novel and field tested technology, allied to extensive use of offline activities as concurrent operations, the ICU has the potential to make significant cost savings in a segregated well construction project. Collaboration between the operator and service provider drives a design which provides a technically pragmatic and capable ICU and as such attracting project cost savings allied to lower support equipment costs. Further, the deployment flexibility of the ICU allows it to perform operations ranging from well construction activities such as well slot preparation, completions and intervention, to well deconstruction activities such as heavy workover, Permanent Abandonment (PA) phases and slot recovery. The ability to perform multi-phase operations whilst mobilized to a platform brings further cost benefits and operational flexibility.

Free sand movement and fines mobilization during production in Zawtika field is one of the main challenges and can result in failures of production systems leading to SSHE exposure, loss of production or even well suspended. The optimum completion design Cased Hole Gravel Pack (CHGP) allows the well to maintain solid-free gas production with (limiting skin) selectivity, longevity and integrity throughout the life cycle. The Sand Control completion deployment, effectiveness and well productivity is directly related to the cleanliness of cased well bore and completion brine. The Total Solid Suspension (TSS) and Nephelometric Turbidity Units (NTU) or clarity of the fluid is the key indicator of well cleanliness. Zawtika Phase 1A post job review highlighted that Wellbore Cleanout (WBCO) is one of the most time consuming operation. To overcome this challenge and create areas of opportunities for improvement based on efficiencies, several possible solutions identified below. Excessive pipe dope, metal debris and rust from casing can collect within the well bore, bridge in perforation tunnels and ultimately damage reservoir or seriously hinder running completion components. The correct combination of Pipe Dope applying procedure, Chemical Displacement, Mechanical Movement and Hydraulic Displacement are the main key contributing factors to improved operation safety, deployment operational efficiency. Lab scale test conducted to simulate test for pipe dope removal chemical, Mechanical Casing Scraper and casing brush simulate testing in order to remove casing vanishing coating, also applying wellbore cleaning concept from drilling - rotational, pump rate and trip speed Recovery of metal or other debris in a limited number of runs gives several advantages: - Minimize reservoir damage - Reduces risks of screen plugging - Saves rig time. This paper will describe planning process, pipe dope procedure, wellbore clean out chemical / mechanical tool selection based on laboratory testing, displacement techniques, and operation summary. The potential cost saving to project can be more than 5 Million USD. The combination of this improvement in WBCO operation is able to reduce the operation time and cost in Phase 1B more than 71% comparing to Phase 1A performances in 2014-2015

Zawtika field, Block M9, Myanmar offshore is one of the gas fields that has been developed and been producing since 2013. Two types of well designs have been selected and drilled from platforms; Monobore (Tubingless completion, Gulf of Thailand technique) and Sand control well (cased hole gravel pack). Over the course of production operation many challenges and difficulties have been encountered; one of which is sand production resulting in excessive corrosion and damages to the surface facility and shorten the well life. Hence, sand control completion has been chosen as the main design for field development. During 2013-2014 Zawtika M9 Phase1A sand control wells were drilled with a drilling rig and later completed completion with a 2nd unit hydraulic workover. Though this strategy could bring a well to production soonest, it comes with additional cost and risks; mobilization, stand by, wait on weather, overheads, etc. Up to now, Zawtika M9 Phase1B for sustainable gas production delivery, previous strategy has been adapted for more cost effective operation during an ongoing oil price crisis starting 2014. "One rig strategy" has been implemented with a tender assist drilling rig (TADR). The strategy is to drill all required wells on the platform, then to convert the drilling rig to completion mode and to run sand control completion. Drilling rig has large deck space, high deck load capacity and capability to accommodate 170 people, and sand control equipment can be installed permanently on drilling rig without major impact to drilling operation. The key completion personnel onboard shall relentlessly prepare and commission equipment to perform completion operation right after drilling operation is completed. Ultimately drilling rig can be converted from drilling to completion mode within 3-5 days, compared with a 15 days move of 2nd unit per platform. With this strategy, risk exposure to heavy lift and marine operation reduce significantly. In fact the unpredicted rig stand by due to bad weather in Zawtika M9 Phase1A becomes manageable due to lesser number of rig moves. Sand control completion has been operated efficiently by using rig equipment, space and experienced crews. Many offline operations and activities can be performed concurrently, e.g. cement bond evaluation, wellbore cleanout, packer installation with wire-line, rack back tubular capability, etc. Likewise the drilling rig performance can be continuously optimized and improved. This also eventually extends to running speed enhancement, non-productive time mitigation by proven equipment and crews. With this strategy, the rig has so far completed 3 platforms in Zawtika M9 Phase1B with significant improvement and remarkable record. The total drilling and completion well duration has significantly decreased from Phase1A 18 days to 10 days in Phase1B. Therefore, millions of cost reduction and saving from "One Rig Strategy" claimed.

Zawtika gas field lies approximately 300 km south of Yangon in the Gulf of Mottama, offshore Myanmar focused on laminated Plio-Pleistocene reservoirs. The formations comprises of mixed deltaic and young shallow marine clastic sediments considered amongst the shallowest unconsolidated, poorly sorted with a high percentage of fine sands on the planet. Phase 1A sand control development wells Basis of Design (BoD) underwent considerable extensive laboratory core testing, equipment & stimulation design verification studies prior to successfully completing Seventeen (17) Wells on three (3) Wellhead Platforms. Four (4) additional Platforms with thirty six (36) wells planned to be completed during Phase 1B and further plans to increase Platforms numbers in subsequent Phases. The optimum Cased Hole Gravel Pack (CHGP) completion design shall allow the well to maintain solid-free gas production with selectivity, longevity and integrity throughout the life cycle. This type of completion design was implemented for the first time in PTTEP during Zawtika development, Phase 1A. Due to its complexity and its criticality to the success of the well, the operational approach implemented in Phase 1A was focused more on conservative approach rather than the performance optimization in order to ensure the success and to prove the design concept. The operation went successful and achieved all objectives; where the average times for completing a single and a dual-zone CHGP well were thirteen (13) and eighteen (18) days respectively. Since the CHGP completion design of the Phase 1A proved to be a great success where most of the wells can produce as per or better than the design expectation solids free, the significant operation efficiency improvement drive is one of the main targets of the Zawtika Phase 1B. PTTEPI reviewed Phase 1A post-completion operations and tendered the work with similar design specifications based on the fact that earlier wells completed with Sand Control continued to produce at expected gas rates solids free. In order to improve operational efficiency, many areas were investigated i.e. operational steps, procedures, lesson learns, equipment designs, rig up diagrams, site layouts and integrated knowledge from the Gulf of Thailand (GOT) drilling practices such as batch operation and offline activities were analyzed for implementation in Phase 1B. Concept of Batch Completion strategy is continued and improved from previous Phase 1A that used a Hydraulic Workover Unit (HWU) deployment method onto Phase 1B utilizing a new generation Tender Assisted Drilling (TAD) Rig with Offline Activity Cantilever (OAC) with further emphasis on batch completion approach. To implement a step change in batch completion strategy, the new concept called "Factory-Batch CHGP Completion Strategy" involving comprehensive detailed job planning, semi-permanent pumping package rig up concept, fit for purpose and robust-design of completion equipment, living Standard Operating Procedure (SOP) documents, full implementation of Simultaneous Operation (SIMOP), effective lessons learnt captured and shared, including cross trainings of all parties on the rig site are the main key factors that contribute to the improved operation safety & efficiency. By incorporating and implementing all these factors, PTTEPI is able to reduce the CHGP completion time and cost of Zawtika Development Phase 1B more than 67% comparing to Phase 1A performances in 2014 – 2015. This paper summarizes the fundamental conceptual approach and detailed features of PTTEPI's "Factory-Batch CHGP Completion Strategy" executed in Zawtika Sand Control Development, Phase 1B.