Study On Horizontal Well Sand Cleanout In Lower Pressure Formation

When the production tail of a well comes, sand production is very common in sandstone reservoirs. It is necessary to proceed a cleanout service. Sand Cleanout is a method which brings sand particles up to the surface by circulating a liquid. However, owing to lower formation pressure, a normal blasting fluid circulation cannot be built due to heavy loss of circulation. What is worse, sand particles may even flow back into the formation to cause damage.For this reason, a new method of sand cleanout in lower pressure formation should be developed. This thesis studies and applies the sand transportation behavior in the vertical wells and horizontal wells, gives theoretical analysis of well sand cleanout in lower pressure formation. Using dual tubing string, applying the jet pump principle, it reduces the pressure of sand cleanout liquid and loss of circulation. A high pressure working fluid is pumped into the annulus from the surface and divided into two parts. One part is used as the sand carrier fluid to flow downwards to stir the sand particles. The other part is used as power fluid of jet pump to reduce the bottomhole pressure. Under the pressure differences, carrier fluid together with the sands will be sucked into the inner string and lifted to the surface.Sand transportation has been studied, considering the effect of irregularity, concentration, tube wall. There is a correlation between sand setting velocity and carrier fluid velocity. It can be a guide for sand cleanout.Aimimg at the challenges, the sand cleanout operation is completed by the double dual strings for supplying the flow and central string for jetting and carrying sands. Applying the jet pump will reduce the pressure from the circulating fluid, avoiding the heavy leakage of working fluid into the formation. Dual string provides a new fluid circulation way and accelerates the velocity of liquid quickly, improving the efficiency.The parameter calculation method in well sand cleanout in lower pressure formation is given. Based on the basic principle of hydromechanics, the sand cleanout mathematical model has been set up and the computer program together with the simulation calculation is presented.The study on well sand cleanout in lower pressure formation is of important economic value and practical significance.