ERD Drilling Record Achieved in the Gulf of Thailand with an Outstanding Drilling Efficiency
Authors: Naknaka Manchukarn , Phu Trinh Dinh , Siritheerasas Khamawat , Prasongtham Pattarapong , Abu-Jafar Feras , Abbasgolipour Ali , Hieu Pham Nam 
Published: March 2021

The objective of this research is to describe the methodology used to drill the most extended reach well (ERD) in the Gulf of Thailand. The Jasmine field is a mature, sophisticated, oil field with many shallow reservoir targets that require a minimum 10,000ft horizontal displacement. As such, the main challenges faced, and the novel technology applied is described in detail by this research. The research is an example of successfully drilling a challenging well, safely and efficiently.

The Jasmine C – Well X, is a 3-string design structure with an 11-3/4in top hole, an 8-1/2in intermediate section, and a 6-1/8in reservoir horizontal section. Well X was constructed by utilizing an existing platform well slot. The challenge involved drilling from the top hole to the kickoff point and directional drilling away from the casing stump of the existing well to avoid any collision with nearby wells emanating from the Jasmine C platform. The 8-1/2in hole section was the most important segment as it had to reach the landing point precisely in order to start the 6-1/8in section for GeoSteering in the reservoir section. The 8-1/2in section encountered three challenges that could affect drilling efficiency.Directional Drilling – The complexities of the well profile:The method involved making well inclination (INC) lower than 82deg in the tangent interval in order to reduce the well's tortuosity as much as possible.Hole condition – Hole cleaning and fluid losses control:The method involved the use of Low Toxicity Oil Based Mud (LTOBM) CaCO3 system, the chemical elements in the drilling fluid system could help to seal the high permeable zones.Drilling Engineering – Torque and Drag (T&D) control:The method taked into account the 7in casing run to the bottom of the hole, which the casing driven system did not allow for rotation

The well was completed successfully without any additional trips. A Total Depth (TD) was of 13,052ftMD was achieved to reach reservoirs at 3,260ft TVDSS. It was therefore announced in 2019 as a new ERD record for Mubadala Thailand (ERD ratio = 3.26, Directional Difficulty Index (DDI) = 6.95).

The top hole and 9-5/8in casing were set in the right depth. An 8-1/2in section was accomplished on the planned trajectory with an average on bottom Rate of Penetration (ROP) at 319 ft/hr. The 6-1/8in section was drilled by geosteering to achieve sub-surface objectives. A total of 2,143ft intervals inside the reservoir was successfully achieved.

While drilling, lost circulation events occured, but the mud system was conditioned with Lost Circulation Materials (LCM). Therefore, drilling performance was unaffected. Moreover, the Bit's Total Flow Area (TFA) and Rotary steering systems (RSS) flow restrictor was configured to allow directional drilling at a very low Flow rate of 470gpm. Addition, 30 joints of 5-1/2in Heavy Weight Drill Pipe (HWDP) and 39 joints of 4in HWDP were added into the Bottom Hole Assembly (BHA) to transfer string weight to drill bitsand drill to well TD. As complexities of the well profile were fully aware, the casing was runned and minimized the open hole friction until the casing was deployed successfully.

In the Gulf of Thailand, drilling the longest ERD well in a shallow True Vertical Depth (TVD) was clearly groundbreaking and entailed the successful management of the key operational challenges related to identification, job planning, design, technology selection, and implementation. This research illuminates the challenges and technical solutions of long ERD well and serves as an example of what can be achieved in the region and globally.