The invention relates to a combined type
sieve tube aiming to overcome the defects of easy blockage of
antiparallelogram gaps, poor self-cleaning capability, low pressure-
bearing capacity and easily extruded damage of the traditional sand prevention
sieve tubes. In the invention, the wall of a base tube is provided with an overflowing hole, and
sieve blades are fixedly arranged on the outer circumference of the base tube; one end of an inner hole of each sieve blade is a straight hole, while the other end is a taper hole which is small inside and big outside; the end surface at one end of each sieve blade straight hole is a plane, while the other end surface is uniformly distributed with three or more lug bosses; the wall of the inner hole of each sieve blade is provided with an axial liquid flow trough; the excircle of the base tube is axially provided with a key; the part of the base tube, with a key, is sequentially provided with a gland, a plurality of sieve blades and a gland, and the glands are fixedly connected with the base tube; and the sieve blades are sequentially arrayed in the same direction. The sieve tube has the advantages of reasonable structure, easiness for
processing and manufacturing, large seepage area, high sand blocking precision, good anti-blockage effect,
high pressure bearing strength and long service life and can be used for extracting liquid with a large
discharge quantity and pumping out dust sand to increase the liquidity of liquid, thereby prolonging the extraction life of an
oil well and reducing the production cost of oil extraction.