In horizontal wells completed as open holes that areirregularly shaped or badly washed-out, or with slotted or preperforatedliners, mechanical packers can not be used toisolate a water- or gas-producing zone. Consequently, a newmethod using chemical packers has been developed and tested.The method involves: (i) setting two chemical wellbore plugsin the horizontal section to straddle the problem zone, (ii)squeezing gel into the problem zone, and (iii) cleaning out theborehole prior to production. Using coiled tubing, the wholeoperation would be conducted in one roundtrip.The new method was tested using a 60 ft. long horizontalwellapparatus consisting of an outer 12-3/4 in. PVC casingcontaining two concentric metal screens (ID’s 9 in. and 6 in.).Space between the screens was packed with sand, forming a 6-inch wellbore with a 1-1/2 inch thick formation, into which a4-1/2 inch pre-perforated liner was placed. A gel-placementtool was placed inside the liner. The tool consisted of a 1-1/2inch tubing to spot/squeeze the formation gel, an internal ?inch tubing to spot the wellbore plug, and outer rubberelements for focussed gel placement. Model temperature wasset at 110°F by circulating hot water through the apparatus.Two runs were made, each consisting of spotting a 40 ft.long K-MAX wellbore plug, followed by spotting andsqueezing PERMSEAL across 20 ft. of the borehole. (Fromsymmetry, the placements represent a dual wellbore plug each40 ft. long straddling a 40 ft. problem zone). After theformation gel had set, the apparatus was disassembled,showing the chemical plug had completely filled the borehole,strongly adhering to the borehole surface with no slumping.The formation gel penetrated and consolidated the formation.The tests confirmed the viability of the new zone isolationmethod that is planned for field-testing.
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