Production Optimization of Oil Wells - Problem of Salt Deposit

Abstract

The field of Hassi R' Mel is a gas condensate reservoir with a rather significant oil rim in the Eastern and Southern peripheries. Producing wells were drilled to develop the oil zone, unfortunately these wells are confronted to a severe salt deposit problem more or less related to exploitation regime perturbing oil rim production or shut in the well totally. The presence of sodium chloride inorganic precipitate is undoubtedly influenced by: -the type and quantity of water influx -operating procedures -reservoir characteristics such as temperature and pressure. A permanent fresh water injection under packer does not give improvement for these wells. A large volume is required for particular wells; the rapid salt deposition needs then a daily Coil tubing intervention. The treatment becomes a cost factor and these wells are then shut in. A study was undertaken in collaboration with the research and development center ( CRD ) to solve the salt deposit problem in the column of production due to temperature change effect. It consists to analyse a sample of the formation water in order to understand the phenomenon of the salt deposit, to test the anti-deposition product efficiency and to optimise its concentration under surface and bottom conditions; keeping in mind the reduction of the amount of the injection water. Laboratory testing was first of all undertaken, in order to assess chemical water injection compatibility with formation water to ensure that the two fluids will not produce precipitates. It has shown that the alkyl amide aqueous solution is used to prevent precipitation of sodium chloride crystals from high chloride brines from bottom of the hole, changing crystals growth from symmetrical cubic orientation to non-symmetrical dentritic type. Independently of the temperature, its efficiency will also depends on the presence of other salts in the brine and the pH. The purpose of this presentation is to show: Problem of sodium chlorite salt deposit which penalizes the good performance of a well. Solutions to adopt to improve the Index of productivity, by using chemicals to reduce deposit of salt.