Objective Set up of a 2 km coiled tubing in a production well at Bondy. The 1" tubing carbon stainless will permit to inject at the top of dogger reservoir small quantity of poly-acrylates (2-12 mg/l) to avoid iron sulphides formation and to prevent the 7" diameter becoming reduced. Previous workovers to restore wells productivity had proved inefficient, in the long run (one year after). The coiled tubing will allow to test various inhibitors and to select according to controled parameters the appropriate physico-chemical treatment. One of the first applications of downhole inhibitors use in low enthalpy geothermal wells with scaling problems.The injection of scaling inhibitors (polyacrylate with low molecular weight in particular AQUAPROX MD 1030) has proved a good efficiency to prevent sulfides deposits in the geothermal loop. The action of the inhibitor is to lower the sulfides content in the water by reducing the particles size and to spread these particles and avoid them to deposit. The injection without degasing into the coiled tubing has proved operational the surface equipment (dosimetric pump at 25 bars, monitored by the variation of geothermal water flowrate). The metallic nature of the coiled tubing (K55 Steel) is disqualified for this type of operation due to galvanic corrosion which occurred quickly and strongly between cemented casing and remaining sulfides and the tubing itself. The use of composite pipes or coated metallic pipes with inert materials would be more suitable.Initial tests of the two wells of the doublet had been performed in September 1987 to appreciate the state of the wells, the geothermal water physico-chemistry and to restore the initial productivity reduced drastically by sulfides deposition in the production casings. The coiled tubing set into the production well at 7" casing shoe level (1850 m) in October 1987.Surface equipments (pumps, inhibitor storage tank, safety equipment and monitoring) were installed and operating in 1988. During this period, continuous controls and analysis has been done to follow the effectiveness of the injection system and his action to prevent sulfides scaling. Till July 1988, the inhibitors were injected through the coiled tubing. A first diagnostic carried out to understand the troubles at this date have concluded to the destruction of the downhole injection pipes by means of corrosion. The test was stopped and the well abandoned and cemented a few months after. Programme(s) ENG-ENDEMO C - Programme (EEC) of demonstration projects and industrial pilot projects (EEC) in the energy field, 1985-1989 Topic(s) 4.1 - HEATING Call for proposal Data not available Funding Scheme DEM - Demonstration contracts Coordinator GEOPHASE SA EU contribution No data Address B.P. 247 F - 93153 LE BLANC MESNIL CEDEX France See on map Total cost No data
