This paper presents a comprehensive laboratory and field study discussing development, formulation, and application of a new flat rheology drilling fluid system that meets the challenges faced when drilling in an ultradeepwater well environment. The use of this new flat rheology drilling fluid system for the first time in Asia-Pacific Region has created the potential to efficiently drill more challenging deepwater and ultra deepwater wells in offshore Myanmar, Malaysia, and other associated countries. In a deepwater block situated on Myanmar's west coast, conventional synthetic-based drilling fluids (SBM) have been used to drill all the wells to date. During the planning phase of an ultradeepwater well with a water depth of 2,300 m, it was found that the equivalent circulating density (ECD) with a narrow pore pressure and fracture gradient would have increased downhole complications leading to non-productive time (NPT). The main concern was not being able to reach total depth (TD) or successfully setting casing on bottom with the original well design, requiring implementation of a contingency casing and pushing the operational cost over authority of expenditure (AFE). To overcome the challenges, a new flat rheology drilling fluid system was introduced based on ECD challenges and rheology requirements. The initial study of modelled hydraulics showed a significant ECD reduction using a flat rheology drilling fluid system. The first round of laboratory tests exhibited promising results of flat rheology across all temperature ranges and after iterating numerous formulations developed with local seed mud were narrowed down to two final formulations of 1.08 sg and 1.17 sg. The formulation was field trialed with some slight adjustment in chemical concentrations to meet specific field mud properties. The well was drilled successfully with no major variation in ECD or issues related to the large temperature range. Implementing this customized solution combined with precise strategy led to successful results in efficiently completing one of the most challenging wells of the campaign. The paper presents a comprehensive study of the challenges formulating and implementing a new flat rheology drilling fluid system. Additionally, a detailed study on ECD challenges when drilling an ultradeepwater well is also done. The paper also discusses the comprehensive pit management program and required treatment plan for drilling. Finally, the paper aims to compare the existing results with previous drilling techniques, which will assist operators with the future advances in similar fields.

The first PTTEPI deepwater well in 1,003m water was drilled in the Gulf of Martaban, Myanmar in 2013. The tight deepwater rig market and single well program made it difficult to secure a rig, but a newbuild 6th generation drillship was eventually contracted. Non-Productive Time (NPT) is always the major concern when using a newbuild, especially in deepwater where the operational cost was 62,500 USD/hour. This paper explains how NPT was kept to acceptable level, describing the procedures employed.The drillship used was identical to a sister rig which had already started the operations and lessons were learned from that. Start-up NPT from the previous rig was found to be 12.4% in the first 2 wells and the majority of this resulted from drawworks, BOP and Top-drive issues. Sub-sea equipment downtime was especially damaging in deepwater due to the extended time required to pull and re-run the BOP. This area was, therefore, a primary focus.Third party inspection of BOP systems was witnessed by company representatives and a comprehensive testing and inspection program was designed to simulate operations wherever possible. Pre-running and Post-running tests were performed per API standard 53 and all tests were completed successfully. When the rig was in operation, BOP running procedures were strictly enforced. Contractual clauses were also agreed between the contractor and operator to minimise the impact of any start-up NPT.Logistics planning of equipment, bulk, and chemical also played important part of downtime minimization. As the turnaround time from shorebase to well location was 5 days, lots of loadings had been done before rig departed from Singapore.At the end of the well, drilling operations were found to have been performed efficiently. Rig NPT was only 6.9%, but with the majority of this resulting from problems with a new design of diverter system. This level of NPT was impressive for a newbuild high technology drillship, being 70% lower than the figure for start-up of the sister unit.

Myanmar offshore is considered to be a very promising exploration and production (E&P) location for oil and gas but poses significant challenges to drilling and cementing operations. Low temperature at sea bed delays the cement compressive strength development, High pore pressure with steep gradient and low fracture pressure created a very narrow drilling margin, presence of shallow flow in riser-less section further complicated the cementing operation, low density cement with high performance is a must. With the exorbiant cost of Deepwater drilling, much needed fit for purpose cementing technology with efficient logistic support and excellence in execution became crucial. This paper elaborates the cementing challenges at different sections of a recent deep-water well in offshore Mynamar and techniques that were planned and used to address those challenges. This paper will describe in detail the cementing method, how it fit the well situation, how the cement slurry was designed then evaluated and how the logistic support and execution were carried out, resulting in a resounding success.

In 2013, PTTEP drilled a deepwater well in the Gulf of Martaban, Myanmar. The water depth was 1003m with riserless drilling over 1000m below seabed. Being exploration well without any reliable offset well, shallow hazards risk was high. Shallow hazards analysis was performed, showing the high risk of shallow water flow. Shallow water flow causes many incidents, including surface casing cement failure. It can happen during cementing, cement phase transitioning, and after the cement has set. Cementing with the shallow water flow presence is, therefore, the critical operation to achieve the well integrity. Using special cement systems, foam or ultra-lightweight, is expensive, logistically challenging, and operationally complicated. After thorough risk analysis and mitigation, conventional class G cement system was selected.Information from 12-1/4Љ pilot hole and actual 26Љ hole were analysed for cementing plan. Shallow water flow occurred at 1819m in pilot hole. Pump and dump was started from 1760m in 26Љ hole to prevent the flow. However, drilling to 2005m encountered another strong flow. So, the critical zone was identified from 2005m downward. For operational success, the critical zone was covered by gas tight tail slurry with API fluid loss control less than 50 mL/30 min, a SGSA transition timer shorter than 30 minutes and a short thickening time to prevent formation fluid migration. Lead slurry was designed for sufficient density and long thickening time to provide enough hydrostatic pressure, preventing fluid migration while tail slurry was setting. Not being ultra-lightweight cement, slurries were pumped with high excess and contain fibrous LCM to mitigate losses risk. Centralisation also contributed to the cementing success.During the cement job, good returns had been observed. No shallow water flow occurred during and after cementing. Operation was continued without subsidence issue.This paper summarises the process of assessing the risks and designing the economical cement operation to mitigate the risks, resulting in safe operation from shallow hazards.

This paper presents a method used in combination with Managed Pressure Drilling (MPD) to determine real time pore pressures while drilling a deepwater exploration well. Not only was the pore pressure accurately determined but additional procedures were implemented to improve efficiency. This deepwater well was the first time MPD used on a semisubmersible rig in Myanmar by both operator and the drilling contractor. MPD was used on all the well sections below the surface casing with the main objectives for MPD listed as follows: Safe and efficient drilling of the well to planned TD. Elimination of contingency casing strings. Enhanced influx detection. Determination of pore and fracture pressure while drilling. The expected pore pressure based on seismic interpretation for the well was provided by the geoscience team. It was presented as minimum and maximum pore pressures. Fracture pressures were provided as sand fracture (minimum) and shale fracture pressures (maximum). A large uncertainty in pore pressures was expected. MPD was combined with real time pore pressure prediction to estimate pore pressures. MPD procedures were reviewed and amended as required to reflect the actual well architecture, actual equipment, and rig capabilities. Most MPD projects are designed to maintain a Constant Bottom Hole Pressure (CBHP) and not to determine pore pressures. Since a significant pore pressure ramp was expected as soon as drilling started below the surface casing a solution had to be found. Methods to make connections and dummy connections were reviewed and discussed to assist the determination of pore pressures using connection and background gas indicators. The devised procedure could be used for all drillstring connections including any dummy connections made throughout the entire well to provide the real time pore pressure team with consistent data. Additional procedures were developed to ensure that bottom hole circulating pressures were maintained using a combination of MPD choke pressures and increasing mud weights while drilling. The paper presents the procedures that were developed and implemented to successfully drill the exploration well to TD. These procedures have now been field tested and proven to be successful not only to accurately determine pore pressures but also to ensure mud weight management. The procedures will be used again on future wells to determine pore pressures and manage BHP to ensure that maximum benefits are derived from MPD operations on deepwater exploration wells.