TA is an over-pressurized well in the field development project located Offshore Peninsular Malaysia. Although the well was drilled as a development well, it also had an exploration objective as it was the first to penetrate the over pressured zones across a fault in the TA field. An initial attempt to drill conventionally resulted in severe gain and loss scenarios across the first of three sands 80 m below the 7" casing shoe, primarily due to weak coal formations. After many attempts to control losses, it was decided to plug-abandon the 6" open hole and to temporarily suspend the well due to insufficient operating window to drill ahead. After a year of suspension, a new drilling approach using a statically underbalanced mud weight (MW) in combination with an Automated Managed Pressure Drilling (MPD) system was introduced as the best solution for drilling into the well objectives. During the planning stage, different scenarios were analyzed based on the formation fracture gradient (FG) and pore pressure (PP) estimations. MPD plans were designed based on statically underbalanced mud while drilling, running the liner, and during the cementing job. During drilling, Dynamic Flow Checks (DFC) and Dynamic Formation Integrity Tests (DFIT) were performed using the MPD system to identify and confirm operating window. The target total depth was successfully reached with mud weighted within the narrow 0.35 ppg drilling window (17.8–18.1 ppg). Decision was then made to top kill the well at 1200 m-MDDF with 18.30 ppg mud, providing an overbalanced condition of 85 psi. Open hole logging operations were then successfully executed. The well was then displaced to a 16.30 ppg mud prior to performing Managed Pressure Cementing (MPC). This technical paper aims to discuss all of the MPD - MPC challenges faced and best practices developed during both the planning and execution stages of the program.

SDX was an exploration well drilled on a jack-up rig, which was located offshore on the west side of the Malay basin. The well was classified as an ultra high pressure high temperature (HPHT) due to 455°F (235°C) maximum formation temperature and 11,200 psi maximum formation pressure. SDX was a very important well for a major operator in the attempt to explore and evaluate the potential hydrocarbon prospects in the field. SDX field was well known for its drilling challenges due to extreme narrow window and HPHT condition. The pore pressure ramp steeply increased at shallower depth causing narrow drilling operating window between pore pressure and fracture gradient. Thus, the well was considered as conventionally "un-drillable" and managed pressure drilling (MPD) was a necessary enabler to achieve the well objectives.MPD was deployed to drill the last four hole sections, 12 ¼" ϫ 14 ¾", 8 ½" ϫ 12 ¼", 8 ½" ϫ 9 ½" and 5 ¾" ϫ 6 5/8" to mitigate the challenging wellbore issues. The drilling strategy was to use a lower mud weight (MW) in order to walk the pore pressure line and allow the use of optimum drilling flow rates. Two essential MPD procedures were implemented to safely verify drilling window. The pore pressure ramp was established by performing static flow check (SFC) and the losses limit was established by conducting dynamic formation integrity test (DFIT). Furthermore, total depth (TD) criteria for the MPD section was defined by the minimum window required to perform managed pressure cementing (MPC) for the liners.SDX well was successfully drilled to TD after overcoming defying wellbore challenges due to narrow window, pore pressure ramp uncertainty and HPHT condition. MPD was fully utilized to drill four most critical sections. MPC was performed splendidly for 11 ¾" and 9 7/8" liners without influx or loss. The paper will further explain on how proven MPD solutions were planned and executed to drill this exploration HPHT well. MPD and MPC lessons learned were also highlighted in this paper as part of the knowledge sharing.

1 Introduction.

PTTEP in the Gulf of Thailand faced costly challenges while conventionally drilling several narrow operating window ultra high temperature (ultraHT) wells with formation temperature up to 220°C (428°F). In the ultraHT sections, the operator encountered serious ballooning issues that resulted in severe non-productive time (NPT) and difficulty reaching well total depth (TD). Additionally, formation pressure uncertainty in the steep pressure ramp region posed additional drilling challenges due to high risk of influxes.PTTEP decided to utilize managed pressure drilling (MPD) to overcome the complex ultraHT wells. The strategy involved designing a hydrostatically underbalanced mud weight to prevent ballooning and to enable optimal drilling flowrates. The automated MPD was used to continuously maintain bottomhole pressure (BHP) above pore pressure to avoid influxes. Furthermore, the MPD system was also used to safely identify formation pressures by performing static flow checks (SFC). Dynamic formation integrity tests (DFIT) and dynamic leak-off tests (DLOT) conducted while drilling accurately identified the losses limit and ballooning gradient. At well TD, special rollover procedures were implemented to displace trip mud weight in order to safely control the well prior to pulling out of hole, taking into account extreme thermal effects on bottomhole pressure (BHP) reduction.PTTEP was able to drill through the narrow operating window and avoid problems associated with typical ultraHT condition, including ballooning, loss and influx events. Moreover, MPD allowed the operator to drill efficiently while identifying the actual drilling window to establish wellbore pressure boundaries. Importantly, the operator was able to log the well to obtain the necessary geological data. As a result, the operator cut well costs by 50%, a total of USD 5 million, and saved 20 days of drilling time.The paper will share the success story of MPD application in drilling challenging ultraHT wells in the Gulf of Thailand. The paper will describe the drilling solutions to solve the well problems and the lessons learnt as part of knowledge sharing.

The JST-1 well is an offshore High Pressure and High Temperature (high pressure by gradient which was more than 0.1 psi/ft) exploratory well, located in the block SK 301A.The primary objective was to evaluate the hydrocarbon potential in Cycle VII and Cycle VI, at the depth of 2374 and 2794 mTVDDF respectively with anticipated reservoir pressure of 5476 and 6898 psi with temperatures from 226 to 264°F at well TD 3477mMDDF/TVDDF the pressure and temperature was predicted to be 9276 psi and 302°F.The well was initially planned to be drilled to 2979 mTVDDF in 12 ¼" hole section and 8 ½" hole section until 3477 mTVDDF. The degree of uncertainty in JST-1 pore pressure and fracture gradient estimates are highly uncertain. This was due to the reason that the offset wells, S-1 and L-1 are very far away from JST-1, approximately 33 km away to the North West and 35 km to the North East respectively. In addition, none of the offset wells have been drilled deeper than 2879 mMDDF. Therefore, high case pore pressure and fracture gradient estimates were used for the well design and planning.Based on cementing simulation for the 11 ¾" liner, 9 5 ⁄8" casing cementing jobs, the resultant cement slurry Equivalent Circulating Density (ECD) will fracture the formation while the cement is pumped into the open hole. Hence, the Managed Pressure Drilling (MPD) method was used to drill hole sections lower than 13 3 ⁄8" casing as well during the cementing job and running in hole with 9 5 ⁄8" casing.This paper aims to describe the application of Automated MPD on this specific well from conceptual to planning to finally execution. Moreover, with the intention to share the challenges observed during execution as well as the decisions taken to overcome these challenges and finally the 5 steps strategy to ensure the well was stable. Well ChallengesDuring drilling, Dynamic Flow Checks (DFC) and Dynamic Formation Integrity Tests (DFIT) were performed using the MPD system to identify and confirm operating window. The target total depth for