Application of dynamic simulation to assess the effectiveness of well clean-up in a horizontal gas well

Abstract

Well clean-up operation involves the removal of drilling and completion fluids from the wellbore before diverting the well to production facilities. Natural flow clean-up is preferred due to its relatively low cost and simplicity. Depending on the weight of the initial contents in the wellbore and the reservoir properties, artificial lift assisted clean-up such as nitrogen injection through coiled tubing may be required for some wells to ensure the well clean-up objectives are achieved. Well clean-up is transient in nature thus necessitating the need for a dynamic simulation approach to assess the effectiveness of different clean-up options and arrive at the optimal procedure before embarking on the actual field operation. In the current study, a comprehensive-multiphase-transient-simulator (OLGA) was used to predict the clean-up of a gas well with relatively short horizontal open-hole section and low reservoir pressure. Dynamic simulations of clean-up operations for different scenarios such as mud cake lift-off pressures and uncertainties in well productivity were conducted to assess the effectiveness of natural clean-up. Well clean-up failure could lead to impaired deliverability and potential for preferential flow hotspots. The study also assessed if coiled tubing-assisted operations would be beneficial in cases of natural clean-up being ineffective. This paper demonstrates the importance of using transient simulations to provide useful insights into flow and pressure dynamics inside the wellbore during clean-up which can help engineers to predict, design and optimise well clean-up operations, thus increasing the probability of a successful clean-up operation.