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 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.

HPHT wells are typically associated with high complexity, technically challenging, long duration, high risk and high NPT as many things could go wrong especially when any of the critical nitty-gritty details are overlooked. The complexity of this project is amplified with very high level of contaminants compounded by high pressure and high temperature environment. In the conceptual planning phase for the upcoming development of such project where its scale and severity are unprecedented in the country/region, a fit for purpose casing and tubing design is critically important to ensure the well integrity over its design life is assured. At the same time, cost optimization can be achieved utilizing industry practices, testing and qualification of materials and vast learning from incidents and failures occurred in similar HPHT projects over the last three decades scattered around the world. This paper intends to outline the challenges and optimization of casing design philosophy which is drawn upon various perspectives such as long term well integrity, drilling operations, working stress design, effect of compaction and subsidence, probability of failure analysis, multi-well thermal analysis, downhole material corrosion performance, connection performance and a combination of all the above in a holistic manner. A particular focus would be discussing the delicate balancing act between satisfying the working stress design of downhole tubular versus the complexity of downhole material selection work. With the given challenging environmental condition, this points towards exotic type of CRA materials which require certain magnitude of yield strength deration attributed to the given environmental condition and their respective manufacturing processes.

Typical sand-control treatments applied in this field are high-rate water packs (HRWPs) or fracture for placement of proppant (FPP). In many cases, the use of a pad is necessary to maximize the amount of proppant placed into the formation and help reduce (bypass) overall skin using onsite data analysis. The gravel pack carrier fluid is a viscosified system with shear-thinning rheological properties and efficiently suspends sand in static conditions. Additionally, this fluid allows substantial flexibility in sand control design for varying degrees of sand support for gravel packing, fluid-loss control, friction-pressure reduction, and a low-damage fluid system (validated with extensive laboratory testing using reservoir cores with carrier fluid to validate returned permeability values). The objective of the relative permeability modifier (RPM) in sand-control chemical treatments is to prolong hydrocarbon production over time with effective control of water production in one step as a prepad fluid, eliminating the cost and complexity of the water-shutoff treatment stage later as part of well life. Applying the RPM process has not only reduced water production in these areas, but it has also resulted in more gas cumulative production. It is also important to monitor production for several months after the treatment to determine the success or failure of the application. Globally, this is the first successful application of RPM delivery in the same aqueous gravel-packing carrier fluid system using a pad fluid consisting of high-grade xanthan polymer as a gelling agent. Implementation of this process provides the operator an additional tool to increase the possibility of hydrocarbon production from a reservoir that has not been considered viable. Use of RPM technique in sand-control completions provides the option to treat wells and control water production resulting from nearby GWC after sand-control treatments.