Oil-Gas Well Structure for Facilitating Extracting a Downhole Filter String and Method for Extracting the String

Abstract

An oil-gas well structure for facilitating extracting a downhole filter string and a method for extracting the downhole filter string from the oil-gas well are provided. The oil-gas well structure includes a borehole wall ( 1 ) of the oil-gas well and a downhole filter string ( 2 ) run into the oil-gas well. The end of the downhole filter string ( 2 ) close to a wellhead is fixedly connected with the borehole wall ( 1 ). An annulus is formed between the downhole filter string ( 2 ) and the borehole wall ( 1 ), and the annulus is filled with ultra light particles, wherein, the density of ultra light particles approaches or is equal to the density of the carrier fluid which carries the ultra light particles. The method for extracting the downhole filter string includes the following steps: 1) establishing channels; 2) injecting the carrier fluid for ultra light particles so as to remove the ultra light particles from the annulus completely; 3) extracting the downhole filter string. The structure can conveniently extract the downhole filter string from the oil-gas well, thus facilitating the replacement and maintenance of the downhole filter string and the parameter regulation of a flow-control filter.

1 - 13 . (canceled) 
     
     
         14 . An oil-gas well structure for facilitating extraction of a downhole filter string, the structure comprising:
 a borehole wall of an oil-gas well; and   a downhole filter string installed in the oil-gas well, an upper end of the downhole filter string close to a wellhead being fixedly connected with the borehole wall, and an annulus being formed between the downhole filter string and the borehole wall,   wherein the annulus between the downhole filter string and the borehole wall is filled with ultra-light particles having a density that approaches or is equal to a density of a carrier fluid for carrying the ultra-light particles, the carrier fluid being a liquid for carrying and conveying the ultra-light particles into the annulus or for backwashing and conveying the ultra-light particles out of the annulus.   
     
     
         15 . The oil-gas well structure for facilitating extraction of a downhole filter string according to  claim 14 , wherein the ultra-light particles are particles having an average particle diameter of 0.05-1.2 mm and a real density of 0.7-1.3 g/cm 3 . 
     
     
         16 . The oil-gas well structure for facilitating extraction of a downhole filter string according to  claim 15 , wherein the ultra-light particles are particles having an average particle diameter of 0.05-0.8 mm and a real density of 0.94-1.08 g/cm 3 . 
     
     
         17 . The oil-gas well structure for facilitating extraction of a downhole filter string according to  claim 15 , wherein the ultra-light particles are macromolecule polymer particles. 
     
     
         18 . The oil-gas well structure for facilitating extraction of a downhole filter string according to  claim 15 , wherein the ultra-light particles are high density polyethylene particles having an average particle diameter of 0.05-0.8 mm and a real density of 0.90-0.98 g/cm 3 . 
     
     
         19 . The oil-gas well structure for facilitating extraction of a downhole filter string according to  claim 15 , wherein the ultra-light particles are polypropylene and PVC macromolecule polymer particles having an average particle diameter of 0.05-0.8 mm and a real density of 0.7-1.3 g/cm 3 . 
     
     
         20 . The oil-gas well structure for facilitating extraction of a downhole filter string according to  claim 17 , wherein the ultra-light particles are styrene and divinylbenzene cross-linked copolymer particles having an average particle diameter of 0.05-0.8 mm and a real density of 0.94-1.08 g/cm 3 . 
     
     
         21 . The oil-gas well structure for facilitating extraction of a downhole filter string according to  claim 14 , wherein the ultra-light particles and the carrier fluid have a density difference within a range of from −0.35 to +0.35, the range including endpoint values of −0.35 and +0.35. 
     
     
         22 . The oil-gas well structure for facilitating extracting a downhole filter string according to  claim 21 , wherein the ultra-light particles and the carrier fluid have a density difference within a range of from −0.3 to +0.3, the range including endpoint values of −0.3 and +0.3. 
     
     
         23 . A method for extracting a downhole filter string from an oil-gas well structure for facilitating extraction of a downhole filter string, the structure including: a borehole wall of an oil-gas well, and a downhole filter string installed in the oil-gas well, wherein an upper end of the downhole filter string close to a wellhead is fixedly connected with the borehole wall, wherein an annulus is formed between the downhole filter string and the borehole wall, wherein the annulus between the downhole filter string and the borehole wall is filled with ultra-light particles having a density that approaches or is equal to a density of a carrier fluid for carrying the ultra-light particles, and wherein the carrier fluid is a liquid for carrying and conveying the ultra-light particles into the annulus or for backwashing and conveying the ultra-light particles out of the annulus, the method comprising steps of:
 establishing channels by opening an annulus between an upper end of a downhole filter string and a borehole wall;   removing ultra-light particles from the annulus using a carrier fluid for backwashing, the carrier fluid being injected into the downhole filter string in order to backwash and carry the ultra-light particles away from the annulus; and   extracting the downhole filter string.   
     
     
         24 . The method for extracting a downhole filter string according to  claim 23 ,
 wherein the downhole filter string is a flow-control filter string, and   wherein the step of removing the ultra-light particles includes connecting a fluid injection pipe with the downhole filter string and directly injecting the carrier fluid into the flow-control filter string.   
     
     
         25 . The method for extracting a downhole filter string according to  claim 23 , wherein the step of removing the ultra-light particles includes installing a fluid injection pipe into the downhole filter string to perform fluid injection, a lower portion of the fluid injection pipe having an opening, an upper portion of the fluid injection pipe above the opening being provided with a seal ring having an outside diameter substantially identical to an inside diameter of the downhole filter string, and the fluid injection being performed in a sectional manner. 
     
     
         26 . The method for extracting a downhole filter string according to  claim 23 , wherein the carrier fluid is water or a water solution.