Abstract

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.

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