In order to develop a deepwater shallow gas field, the feasibility of drilling a relief well, to intersect the planned vertical producing wells, had to be proven. The relief well would need to build to at least 90° inclination to achieve the required surface location separation. The relief well would need to reach horizontal far shallower from the seafloor than had ever been achieved worldwide, and high doglegs would be needed in ultra-soft formation.
• Target formation contained laterally variable fluvial deposits consisting of competent sands (pay zone) with unpredictable occurrences of unstable, fissile shales.
• Production lateral section drilled at 89-92° inclination and sub-parallel to bedding dip, increasing the risk of formation breakout, bedding plane instability and stuck pipe events (Figure 1). Typically, to maintain a stable wellbore, higher mud weights must be used and swabbing loads must be minimized, however geomechanical constraints in the area were limiting.
• No onsite personnel trained in identifying and reporting cavings relating to wellbore instability.
• Existing operational practices prioritized fast connections and tripping speeds, as a result previous wells experienced stuck BHAs and unsuccessful casing runs due to instability and poor management practices.
• Low ROP, premature tool failure & excessive bit wear were common issuesexperienced by client
• Interbedded & laterally variable fluvial deposits containing very hard & abrasive sands ranging from 20-30ksi UCS.
• No downhole real-time drilling measurements available for MSE calculation
Drill shallow extended and extreme reach wells sidetracking from existing boreholes in a field after almost 20 years without drilling.
• Eliminate catastrophic incidents mostly related to stuck pipe, hole condition and drill string failures observed in offset wells
• Maintain an adequate drilling performance by maintaining a good weight transfer and directional control in poor consolidated sands