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.

One of PTTEP's joint operating company in MTJDA within the Gulf of Thailand has had the obligation to supply gas at its maximum capacity at all times and exploring the deeper territories is the only approach to acquire new reserves within the confined development area. This results in some complications both in drilling engineering and operation, which generally requires larger rig with higher day rate and more expensive technologies. After the operator successfully drilled and completed Muda-9, one of the deepest exploratory wells in term of vertical depth in Muda field, in 2011 with 7,500 psi rig, the operator intended to drill MDE-13, a development well of the same vertical depth, in reference to Muda-9 with a smaller rig of 5,000 psi capacity, having a long term contract with the operator. MDE-13 having a planned depth of 3,065 mTVD/4,207 mMD became the first 5 casing strings for the operator's development well with the highest pressure of approximately 1.85 SG or 8,200 psi at TD. To prepare for drilling MDE-13, there were several concerns during the well design stage relating to rig pump capacity, narrow margin between pore and fracture pressure, an extremely small hydraulic fracturing target, higher temperature, and strength of tubing cement. With the comprehensive well design and the use of proper equipment, however, the operator lessened the associated risks to the acceptable level and the actual drilling operation went well without any major down time. In fact, the normalized time taken to drill MDE-13 is approximately the same as the time taken to drill Muda-9 despite the utilization of smaller rig and much stringent directional control, resulting in the estimate cost saving of the rig day rate of approximately 1 MMUSD. The main objective of this paper is to present how the operator designed and drilled one of its most difficult wells successfully deep into the proximity of higher pressure and temperature environment with a relatively small rig and equipment limitation while maintaining the acceptable safety standards. The well design and practices of this development well are intended primarily for wells drilled in Gulf of Thailand area.