Horizontal well type was selected to optimize drainage of a mature field which had less than 3 years prior concession end. However, the well construction of horizontal well is relatively more challenging compare to other well type which will lead to higher cost. Offset well execution data showing that the challenges of drilling this well type were wellbore instability, drill bit worn out due to gravel zone, uncertainty on marker prognosis and the potential differential sticking on lateral section (inside the depleted reservoir) especially during running pre-perforated liner as completion equipment. It was realized that drilling performance improvement is required to reduce the cost and accelerate the production.

To overcome the challenges, several technologies were introduced. Drilling fluid optimally designed to support borehole stability and real-time adjustment were performed by analyzing the drill cutting. Ridged shape cutter bit utilized to aid during penetrating the gravel zone. To maximize the penetration rate, point-the-bit Rotary Steerable System was utilized for better weight transfer and improved wellbore geometry compare to conventional mud motor system. To manage uncertainty of marker prognosis, the Bottom Hole Assembly (BHA) was designed to achieve maximum dog leg severity capability by minimizing the number of stabilizers. Near bit gamma ray sensor also installed to aid timely formation marker identification. To mitigate risk of differential sticking, the bridging agent sized to fit with the formation permeability through particle size distribution analysis. Centralizers also installed on pre-perforated liner assembly to minimize contact area which might cause differential sticking.

Though these technologies application has been used on many occasions, they were new to this field development which raised concern over their potential risk, especially with limited investment period. Therefore, a series of execution assurance processes were performed. Cross-functional risk assessment sessions were held to review trade-offs of each new technology potential value with the potential cost incurred by considering the possibility of success and potential changes on other aspect of the well construction that need to be adjusted to accommodate the application and mitigate its potential risk. Then a drill-well-on-paper session held with all personnel that would involve by simulating the drilling execution following the procedure which then improved by creating mitigation steps or provide clarity. Artificial intelligence assisted decision support center was also utilized to monitor execution and aid performance improvement recommendation utilizing geomechanics, hydraulic, torque and drag model as well as the field best practices.

These all result to 17% cycle time improvement with 9% lower cost compare to typical well. The production sweet-spot zone exposure also increased by 20%.

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