Scale deposition in producing well bores is becoming a serious problem to the oil industry. In situations of injected seawater breakthrough, the problem is especially hard, since the growth is often Barium or Strontium Sulfate, both of which almost completely insoluble.
The initial scale growth will change the surface roughness in the production tubing, raising the frictional pressure drop and reducing the production rate. Further growth will decrease the flowing area and hinder the production. Ultimately the scale can restrict the production tubing sufficiently to prevent access for tools into the lower sections of the well and finally it can bridge over completely.
The range of options for scale removal goes from a simple brush run using slick line or basic chemical treatment up to a full rig workover to replace the production string. Very often through-tubing treatments using coiled tubing are used due to the savings compared to the rig cost. This technology can convey tools for mechanical scale removal and also works as a fluid conduit for chemical treatments.
The objective of this paper is to describe the coiled tubing abrasive jet technology used to successfully clean, for the first time, heavy affected Barium Sulfate scale in production tubing in Brazilian offshore operations and its impact on the well economics.