METHOD ACID TREATMENT FOR RESERVOIRS WITH WATER-OIL CONTACT Russian patent published in 2018 - IPC E21B43/27 E21B33/138 E21B7/04 

FIELD: oil and gas industry.

SUBSTANCE: method for acid treatment of reservoirs with water-oil contact includes lowering a flexible pipe string into a horizontal well, injecting gel with density higher than water density, and filling a portion of the horizontal well will with gel and working fluid for treating the reservoir by filling another portion of the horizontal well, successive interval treatment of the formation after the treatment, completion of the well is carried out by swabbing, withdrawal of product from the horizontal well is carried out. In this case, drilling or selection of already drilled horizontal well is carried out in production carbonate reservoir with conventionally open horizontal wellbore, one or several A sections with length of not less than 5 m are selected on the profile located closer to formation cap, as well as corresponding adjacent B sections located closer to water-oil contact. In the middle of the A section which is located closer to the nose of the conventional well, a flexible flush-joint pipe is lowered with hydromonitor nozzle installed at the end of the pipe, through which the solution of surface-active substance is pumped in the volume based on 0.1-1.1 m³ per meter of the length of the sum of the corresponding A section and the adjacent one or two S sections, technological holding is carried out for 0.4-3 h. Then gel selected from the condition of impossibility of its pumping into the reservoir under P_r pressure at which acid will then pumped is injected, the volume of gel is defined as 0.4-0.8 of the volume of the corresponding one or two B sections which are adjacent to A section in which the operation is carried out. Gel is brought to the corresponding A section by pushing flexible pipes with non-dissolving gel liquid, technological holding is carried out for a time required to settle the gel into the bottom part of B sections. Then acid is pumped under P_r pressure in m³ volume equal to (0.02-0.5) h per meter of the corresponding A section length, where h is average thickness of formation along A section in meters, technological holding is carried out for reaction of acid solution with the reservoir, gel solvent is pumped in volume not less than the volume of injected gel. Then the next section A is processed by moving the pipe with the hydraulic giant nozzle towards the toe of conventionally horizontal well. After treatment of all A sections is completed, the conventionally horizontal well is washed and put into operation.

EFFECT: improved efficiency of acid treatment of carbonate oil reservoirs.

1 dwg