Scale inhibitor squeeze treatment efficiency in unfractured and fractured wells

Deployment of scale inhibitor squeeze treatments generally involves injection of aqueous solutions at pressures higher than the formation pressure and at temperatures lower than the formation temperature. If the pressure and temperature differences are great enough, the pumping activity may lead to the development of fractures in the near-well bore area, if the well has not already been fractured and propped. Therefore, attention needs to be paid to the impact of squeezing fractured wells, unfractured wells, or wells that fracture during the scale inhibitor squeeze treatment. This paper presents results of using a simulator to model squeeze treatments for these three scenarios. The simulator has the unique combination of being able to model (i) scale inhibitor propagation and retention in the porous medium, (ii) scale squeeze treatments in unfractured or fractured wells, (iii) the mechanics of fracture propagation during a treatment, (iv) the geochemical reactions that may lead to in situ dissolution or precipitation, and (v) the impact of the injected scale inhibitor on these reactions when they occur within the treatment zone. Parameters considered in this study include locations in the matrix where scaling reactions occur, and fracture geometry and conductivity. If a fracture is created, the timing of this relative to the injection of the main scale inhibitor treatment volume has also been studied and is found to be very important. Inappropriate placement of scale inhibitor during a squeeze treatment may mean that downhole zones at risk of scale damage are not adequately protected, even although the observed inhibitor concentrations at the wellhead are above the level required for protection. In this work, a new approach is presented also in which we define and measure the "efficiency" of the squeeze treatment based on produced water ion compositions. This approach takes account of whether the scaling reactions would take place in the treated zone (and hence should be impacted by the presence of inhibitor), or whether they would take place deep within the reservoir. © 2010, Society of Petroleum Engineers.