METHOD OF ACID TREATMENT OF OIL RESERVOIR Russian patent published in 2015 - IPC E21B43/27 

FIELD: oil and gas industry.

SUBSTANCE: method of acid treatment of the oil reservoir includes geophysical survey in open horizontal wellbore to determine dislocations crossed by the bore in the reservoir, i.e. cracks, fractures, cavities, run in the horizontal wellbore on pipes string the filters with variable perforation density, packers installation, acid injection in horizontal wellbore, acid flush, well washing and commissioning. At that one packer is installed upstream the opened wellbore between the casing string and pipes string, and rest packers (expansing packers) are installed at places where the bore crosses dislocations. For each dislocation packer is selected with length exceeding width of the dislocation determined according to geophysical curves by at least 10 times. In pipes string hydrochloric acid with concentration 10-20% is injected on the basis 5-30 m³ per meter of oil-saturated reservoir thickness under wellhead pressure P_wh=(0.008…0.011)·H, MPa, where H is average depth of the reservoir, m. Perforation holes of filters are made round with diameter 5-10 mm, similar along the wellbore. Density of filters perforation for each section created between the packers, and between packer and bore end is increased linearly from zero at periphery to maximum in centre, in its turn this is determined via the hydrodynamical perfection coefficient as follows: $$\frac{{\text{k}}_{\text{1}}\cdot {\text{h}}_{\text{1}}}{\text{Ln}\frac{{\text{l}}_{\text{1}}}{{\text{r}}_{\text{c}}}+{\text{С}}_{\text{1}}}=\frac{{\text{k}}_{\text{2}}\cdot {\text{h}}_{\text{2}}}{\text{Ln}\frac{{\text{l}}_{\text{2}}}{{\text{r}}_{\text{c}}}+{\text{С}}_{\text{2}}}=\mathrm{...}=\frac{{\text{k}}_{\text{n}}\cdot {\text{h}}_{\text{n}}}{\text{Ln}\frac{{\text{l}}_{\text{n}}}{{\text{r}}_{\text{c}}}+{\text{С}}_{\text{n}}},$$ where C₁, C₂, C_n are hydrodynamical perfection coefficients of the well as per character of opening on each n^th section along the horizontal wellbore; l₁, l₂, l_n are length of n^th section, m; k₁, k₂, k_n are average permeability of n^th section, m²; h₁, h₂, h_n are average oil saturated thickness of n^th section, m; r_c is well radius, m.

EFFECT: increased oil recovery of the reservoir due to increased reservoir coverage by action.

2 dwg, 2 ex