Study of the well near-bottomhole zone permeability during treatment by process fluids
In the process of drilling-in productive horizons, several irreversible physical and chemical processes take place in the near-wellbore zone of the formation: stress state of the rocks changes, penetration of the filtrate and solid phase, as well as drilling mud into the reservoir, and swelling of clay particles of intergranular cementing material are observed. As a result, permeability of productive horizon is significantly reduced and, consequently, potential inflow of oil or gas from formation is excluded. An equally serious problem exists during well servicing and workover, when the use of irrational fluids of well killing causes negative consequences associated with deterioration of reservoir properties of formations in the wells being repaired. Article presents the results of the experiments on permeability of clayed porous samples after exposure to various compositions of liquids. In order to increase permeability of near-borehole zone of the formation and increase productivity of wells completed by drilling, and after well servicing and workover, a composition of the process fluid containing a 15 % aqueous solution of oxyethylene diphosphonic acid (OEDA) with addition of a surfactant is proposed.