Abstract

Shallow Hazard was detected and prevents this exploration wells to be drilled vertically above the prospects. Thus, a directional well was planned 60m away from the intended surface location. The challenge was to use the same spudding method as the normal vertical well used by the operator in this area. A Casing while Drilling (CwD) level 2 was the norm in this field to spud the surface casing vertically. However, with this shallow hazard, this must be drilled directionally to achieve the intended reservoir. Kicking off deeper will cause the dogleg severity to be high in the subsequent section as the reservoir TVD is as shallow as 1200m.

A feasibility study was done to understand the requirement and the complexity in ensuring the objectives of the wells achieve. Numerous discussions with different expertise from the operator, contractor and drilling engineering to outline the technique, BHA design, drilling parameters, and the risk mitigation in case of any shallow hazard struck. Bit and reamer studies with Dynamic BHA Vibration modeling were performed to define stable drilling parameters and predicting the BHA capability.

With the systematic technical approach, the BHA spudded smoothly until a planned depth before the reamer activated and BHA started to rotate and drill. Kicking off is a challenge with heavy CwD BHA in this soft unconsolidated formation with few stringers observed along the way. 50% of the total meterage was used to slide with WOB ranging from 3-5 klbs to bring the trajectory towards the planned inclination 22 deg and reached TD as per plan depth.

This paper presents the technique and risk evaluation, workflow on offset well data analysis, BHA design process, customized bit/reamer selection and a dynamic vibration analysis to deliver this special Directional CwD Level 3 Technique. The successful of spudding and drilling this surface section had enable the operator to achieve this shallow prospect exploration target.

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