INCREASING THE EFFICIENCY OF WELL SELECTIVE ACID TREATMENT BY APPLYING PRECISION HYDRO-SAND BLASTING

Abstract

The relevance of the study is caused by the need to ensure the point distribution of acid solution during acid treatment of the bottomhole zone of the production well. Using this method, the efficiency of this process increases by deeper dissolution of limestone rock in the bottomhole zone of the well and thereby completely opening channels for the flow of formation fluid from the formation into the well. The aim of the research is to develop and propose a method of point hydrosand-jet perforation during acid treatment of the bottomhole zone of a production well, a methodology for its application, and to create designs for underground and surface equipment of wells for implementing the developed method. Objects: laboratory stand with a device simulating a channel in the rock; hydrosand-jet perforator for hydrosand-jet opening; clamp designed to prevent breakage and relieve tensile stresses in the pipe string during hydrosand-jet opening and for fixing when centering the perforator in a given processing interval; acid solution based on hydrochloric acid with a volume of 3–4 m3; displacement fluid. Methods. The experimental study of the pressure in the channel at point hydrosand-jet perforation was carried out on a stand. In the device, a nozzle and a fitting of certain diameters – d and D – were installed at the required distance between them. The pumping unit was used to pump the liquid at a pressure p1 before the attachment, and the pressure inside the branch pipe p2 was recorded. In the experiments, water and aqueous solution of sulfite-alcohol stillage with a viscosity of 12,65 cPz at 20 °C were used as the working fluid. The selective acidizing consists in the fact that a hydroseed-jet perforator is lowered into the well, set at the level of the selected treatment interval, and hydraulic clamps necessary to strictly hold the perforator. After that 3–4 m3 of acid solution and squeezing fluid are pumped in. Then, air or gas is injected into the tubing and the annular space (up to the maximum pressure in the distribution booth) and in this state the well is left under pressure for 20 hours and at the end the well is drained to extract the reaction products to the surface. Results. From the analysis of the results of multiple (threefold) hydro-acid treatment, it can be seen that the initial injection pressure of the acid solution after the first stage of the well treatment was reduced by 24 %, and after the second – by 55 %. The acidizing method with additional accurate perforation of the bottomhole zone of production wells allows implementing a more efficient treatment. As a result, the volume of formation fluid inflow from the formation into the well increases by 20...30 % in comparison with conventional acidizing.

Keywords

• channel
• filtration
• speed
• reaction
• synthanol
• reagent
• opening