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Nigerian Journal of Technology

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EXPERIMENTAL STUDY OF HOLE CLEANING PERFORMANCE OF UNDERBALANCED DRILLING AT DOWNHOLE CONDITIONS

YB Adeboye, LO Oyekunle

Abstract


Underbalanced drilling is one of the most widely used drilling technologies while drilling poor permeability, low pressure and depleted reservoirs. Advantages inherent in application of this drilling technique which are major factors affecting cost, time and drilling quality can be significantly hindered due to poor hole cleaning performance. Experimental study of hole cleaning performance in underbalanced drilling at downhole temperatures260C, 400C and 600C   and water influx of  0.25m3/s in a simulated vertical well using gasified mud  was carried out.  Results showed that increasing down-hole temperature by 340C above 260C (ambient temperature) caused 42% and 21.6% increase in annular concentration at flow rates 0.3m3/s and 1.6m3/s respectively. Increasing mud flow rate by 1.3m3/s above 0.3m3/s at  downhole temperatures:260C and 600C and water influx at 0.25m3/s caused 68% and 47.6% decrease in annular cutting concentration. Increase in downhole temperature at constant flow rate resulted in poor hole cleaning performance due to increased in annular cutting concentration. Also, increasing mud circulation rate at a given downhole temperature led to an improved hole cleaning performance due to decrease in annular cutting concentration.  Sensitivity   studies of effect of  mud viscosity, gas/liquid ratio, cutting density and water influx   at  400C  revealed that increasing mud viscosity and gas/liquid ratio  significantly improved the hole cleaning performance while cutting density and water influx cause poor hole cleaning. However, effect of increasing water influx becomes problematic only when the volume is excessively high and miscible with the circulating mud.

 

http://dx.doi.org/10.4314/njt.v35i2.19




http://dx.doi.org/10.4314/njt.v35i2.19
AJOL African Journals Online