An Integrated Sand Cleanout System by Employing Jet Pumps

Sand cleanout is operated by circulating a liquid or a multiphase fluid into the wellbore to bring sand particles to the surface. Although the sand cleanout operations have been applied successfully in most wells with high efficiency and negligible leakage, failure of effective sand removal always occurs in low pressure wells and absorption wells due to heavy loss of circulation. To make the matters worse, solids in the bottomhole may even flow back into the formation to cause further formation damage around the wellbore. In this paper, an integrated sand cleanout system has been developed to effectively remove loose sand particles in low pressure wells and absorption wells by employing a jet pump. More specifically, a high pressure working fluid is pumped through the annulus from the surface and then divided into two parts. One part of the fluid is diverted as the sand carrier fluid to flow downwards, stir up the sand particles via a jetting nozzle at the bottom of a sand cleanout pipe, bring the loose sand particles upwards and then to be boosted by using a jet pump. The other part of the fluid acts as the power fluid of the jet pump to reduce the bottomhole pressure so that the carrier fluid, together with the sand particles, will be sucked into the pump and then lifted to the surface. Detailed structure and principle of the integrated sand cleanout system are described, while a theoretical model is formulated to optimally design the system based on the experimental data and jet pumping theory. It has been shown from field applications that the integrated sand cleanout system makes significant improvements in achieving high efficiency and preventing leakage in low pressure wells and absorption wells.