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.