Achieving Reliable and Cost-Effective Wellbore Cleanout in Depleted and Low-Pressure Wells Using CT Conveyed Fluid Oscillation Tool – Case Histories

Abstract

The production revival process through wellbore cleanout is majorly carried out using conventional jetting and rotating tools. The conventional tools effective distance is few times the diameter of nozzle and impact pressure of jet stream in fluid reduces significantly beyond several inches. Effectiveness of these tool is further reduced as they enter larger sized tubing, casing/open hole or due to standoff and are hence not effective for hard scales like barium sulphate. The wellbore cleanout operations become more challenging in depleted fields due to limitation of limited flow rate and lean nitrogen pumping through jetting tools, requiring extra CT trips to change BHA causing NPTs. Fluid oscillator tools, based on oscillation technology, produces emissions of alternating bursts of fluid that create pulsating pressure waves (300 to 600 Hz) within wellbore and formation fluids. These cyclic pressure waves cause fatigue breaking up wellbore hard scales like barite, paraffin/asphaltene and proppants. Since the FOTs do not have rotating part, it is compatible with high rate and lean nitrogen. The fast cleanout and lean nitrogen compatibility (avoiding extra trips to change BHA) reduces overall intervention time, thus well can be put back on production timely saving upto 50% of overall operations cost. This paper demonstrates the working principle and three practical applications of FOT at four different wells. The cleanout applications range from packed proppant cleanout to establishing clearance in 7" casing and more than 1,600 ft scale in HT well. The wellbore clearance, in these wells was established in less than 50% time compared to conventional jetting tools, saving more than 20% of overall operations cost.