RU2085718C1 - Method for increasing coefficient of oil well productive capacity - Google Patents

Abstract

FIELD: oil production industry. SUBSTANCE: this relates to producing oil from drilled wells including that by way of their excitation. Changing of well productive capacity coefficient is recorded, adjustment is effected by reducing bottom-hole pressure in well and pressure reduction is discontinued at intermittent increase of well productive capacity coefficient. EFFECT: high efficiency.

Description

 The invention relates to methods for extracting oil from boreholes, in particular by exciting them.

 A known method of stimulating the productivity of oil wells, which consists in dissolving limestone in the rock by introducing acid (US patent N 3720265, NKI 166-307, MKI E 21 B 43/26, 1973). The disadvantage of this method is its limited application, since the effect can be achieved only in rocks containing limestone. In addition, the use of acids leads to increased corrosion of well equipment.

 There is a method of increasing well productivity by increasing the porosity of the formation by creating shock waves in the well (ed. St. N 1240112, E 21 B 43/25, 1983), the disadvantage of which is the difficulty of implementation.

 Closest to the claimed is a known method of increasing the productivity index of oil wells, including the impact on the bottomhole zone of the well, which is used hydrochloric acid treatment, and registration of changes in the productivity coefficient in the process of research (journal "Oil Industry", 1989, N 3, p. 29-30).

 The disadvantage of this method is the complexity of its implementation.

 The invention is aimed at simplifying the method of increasing the productivity coefficient of oil wells.

 The specified result is achieved by registering a change in the well productivity coefficient during the impact on the bottomhole zone of the well during research, while reducing the pressure on the bottom of the well, which is carried out before the jump-like increase in the productivity index of the oil well, is used as an impact on the bottomhole zone.

 The decrease in pressure at the bottom of the well leads to an increase in mechanical stresses in the soil caused by rock pressure in the borehole area of the reservoir. When the rock pressure is sufficient for a given soil, when a certain value of bottomhole pressure is reached, the stresses that arise lead to the destruction (loosening) of the soil material in a certain area near the well, which accordingly leads to an increase in soil permeability, and, as a result, leads to a sharp ( spasmodic) increase in well productivity coefficient.

 The possibility of carrying out the invention is confirmed by the following example implementation.

 The method is implemented according to the following general scheme. A well was drilled from the surface of the earth to a reservoir. Then it was cased and cemented along its entire length, except for the area located in the productive stratum of the formation (open face). Then the wellhead was equipped with a device that allows you to maintain a constant flow rate from the well and smoothly change it. In this case, a throttle valve was used as such a device.

In addition, a wellhead pressure meter was installed at the wellhead, for which a pressure gauge was used, and a pressure gauge for measuring bottomhole pressure P ₃ at the bottom of the well.

Then a well test was carried out and the dependence of the well flow Q on the bottomhole pressure P _{3 was} determined:
QA (P ₀ P ₃ )
Where
P _{0 is the} initial oil pressure, A is the productivity coefficient.

In the process of testing the well, the pressure P _{3 was} varied within small limits so that the destruction of the soil in the near-well zone did not occur. The limits of change of P _{3 were} determined on the basis of a study of the mechanical properties of the soil extracted from the well. The test itself was carried out in order to determine the nature of the dependence of Q on P ₃ , so that then it would be possible to detect an abrupt increase in the value of Q when pressure P ₃ reaches a value that leads to loosening of the soil in the borehole space.

After testing, the well was stopped (the oil flow rate was brought to zero) and started to enter the operating mode with an increased productivity coefficient. To do this, the pressure P _{3 was} reduced while fixing the dependence of Q on P ₃ until a significant increase in flow rate occurred with a slight change in the bottomhole pressure (jump-like increase), which was evidence that the process of loosening of the soil in the bottom hole, and therefore an increase in soil permeability, occurred.

Claims (1)

 A method of increasing the productivity index of an oil well, including recording its changes during exposure to the bottomhole zone of the well during research, characterized in that the impact on the bottomhole zone of the well is carried out by lowering the pressure on its bottom to an abrupt increase in the productivity of the oil well.