LIMITED-STAGE DISCONTINUOUS AND DUAL-SPIRAL STRING FOR MIXTURE OF SAND AND LIQUID AT WELL BOTTOM

摘要

Disclosed is a limited-stage discontinuous and dual-spiral string for a mixture of sand and liquid at a well bottom, the string comprising a first stage oil tube (1) and an nth stage oil tube (9) which are connected in sequence from the well head to the well bottom, wherein a plurality of dual-spiral pup joints and oil tubes are provided between the first stage oil tube (1) and the nth stage oil tube (9), the dual-spiral pup joints and the oil tubes being connected alternately. An upper dual-spiral pup joint (12) and an upper hydraulic ejector (13) are connected in sequence at a lower end of the n-th stage oil tube (9), a lower dual-spiral pup joint (15) and a lower hydraulic ejector (16) are connected in sequence at a lower end of the upper hydraulic ejector (13), an expansion compensator (18) is connected at a lower end of the lower hydraulic ejector (16), and a bottom dragging fracturing packer (19) is connected at a lower end of the expansion compensator (18). By utilizing the string, a large amount of liquid with sand at a high flow rate moves in a spiral flow state along a spiral flow channel and an effective sand concentration is ensured, maintaining the concentration of sand entering the ejectors upstream and downstream of a multi-stage clustering perforation in a stable condition, thus improving the perforation effect.