SU1694875A1 - Method for secondary baring of terrygenic collectors with low stratum pressure - Google Patents

Abstract

The invention relates to the oil and gas production industry and can be used for well perforation during the secondary opening of the reservoir after a certain period of well operation. The purpose of the invention is to restore the permeability of the contaminated formation by improving its hydrodynamic connection with the well during the perforation process. To do this, fluid is pumped into the interval of the productive formation for perforation followed by perforation of the well. In this case, a solution of methyl alcohol with the addition of a non-ionic surfactant in the amount of 2-3 wt.% Solution is used as a perforation fluid. Perforation is performed at a pressure below the hydrostatic pressure. Non-ionic surfactants help reduce the interfacial tension of liquids in the wellbore zone of the formation. Methyl alcohol plays the role of a desiccant. (Ls

Description

The invention relates to the oil and gas industry, in particular, to methods for the secondary penetration of a formation by perforation of wells operating terrigenous reservoirs with a low formation pressure, the rocks of which are characterized by a high degree of swelling,

The purpose of the invention is to restore the permeability of a contaminated formation with a low formation pressure by improving its hydrodynamic connection with the well in the perforation process.

The goal is achieved by using a solution of methyl alcohol with a non-ionic surfactant as the perforation fluid, and the perforation is performed at a pressure below the hydrostatic pressure.

As a non-ionic surfactant can be used OP-10, ML, Prevocell

or other nonionic surfactants that do not form sediment with formation waters. Their amount is 2 to 3% by weight of the volume of methyl alcohol.

Nonionic surfactants are selected taking into account the physico-chemical properties of reservoir fluids. Surfactants help reduce the interfacial tension of fluids in the bottomhole formation zone, and methyl alcohol plays the role of a desiccant.

The process technology is as follows.

In the well (the reservoir is represented by terrigenous reservoirs), the well fluid is replaced by a hydrocarbon fluid (oil, diesel condensate) with a density less than methanol but providing back pressure to the reservoir to within

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reservoir by 10-35%. In the perforation interval on the tubing pumped a solution of methanol, treated with non-ionic surfactants, such as OP-10. Perforation fluid is displaced by a hydrocarbon fluid (oil, condensate, diesel fuel). The perforator is lowered into the well to the required perforation depth in the reservoir interval and perforation is performed at a pressure below the hydrostatic one. The wellhead is equipped with a blowout preventer.

Perforation fluid enters the reservoir through the perforation channels and, due to the presence of methyl alcohol, takes water adsorbed by clay particles, while a decrease in their volume (shrinkage) is observed, which increases the permeability of the contaminated reservoir and improves its hydrodynamic connection with the well. The surfactant reduces the interfacial tension at the oil-water interface, which increases the permeability of the reservoir. The surfactant also plays the role of a wetting agent, which facilitates the penetration of methyl alcohol into the reservoir through the perforations, and also reduces the hydraulic losses during the injection of perforation fluid.

 The absence of acid in the perforation fluid prevents the formation of precipitation in the presence of formation water, as well as corrosion of pipes and other equipment of the well. Methyl alcohol contributes to the dehydration of clay particles contained in a fine-grained clay reservoir, reducing the amount of residual water in the formations. All this taken together allows to restore the permeability of the formation by improving its hydrodynamic connection with the well.

The positive effect is to restore the permeability of the contaminated formation by improving its hydrodynamic connection with the well during perforation.

Example. It is necessary to conduct a secondary opening of the reservoir by perforation on one of the wells.

Initial data; Artificial bottom hole, m3665

Perforation interval, m3638-3660 Formation capacity is effective, m22 Formation permeability, md15 Plastova temperature, ° С 80

Reservoir pressure, MPa

Hydrostatic pressure at the depth of perforation, MPa

The 146 mm production string is lowered to a depth of 3,750 m and cemented to the mouth. In the well, the NSV1 - 38 pump is lowered onto tubing with a diameter of 73 mm to a depth of 1800 m. Operational object: The Visean deposits (B26) are composed of fine-grained clayey sandstone. The well was operated for 7 years. For this period

1 acid treatment was performed on the well. Before the secondary perforation, the flow rate was 4.5 tons / day. The initial production rate after commissioning the well was 79.4 tons / day. The reduction in production rate is associated with the swelling of clay particles in the reservoir due to the introduction of formation water and precipitation during acid treatment, which clogged the productive formation.

In order to restore the permeability of the reservoir and improve the hydrodynamic connection of the reservoir with the well, perforations were made on a solution of methyl alcohol with surfactants (OP-10).

The amount of solution (methyl alcohol) at the rate of 0.4 m3 (on average) per 1 m of the effective thickness of the formation is 8.8 m3. The surfactant consumption is 2% of the volume of methyl alcohol and is 0.18 m. The perforation fluid solution is prepared on the surface in a separate container. Preparatory work is carried out in the well to ensure injection of the solution into the formation. The wellhead is supplied with a blowout preventer. The wellbore fluid is replaced by a hydrocarbon fluid with a density less than methanol but providing backpressure to the formation 10 to 35% more than the formation.

Perforation fluid (solution of methyl alcohol with surfactant) is pumped through tubing pipes and pushed to the bottom by hydrocarbon fluid (oil, condensate, diesel fuel). Descend

a perforator into the well to a perforation depth of 3660 m, and a chamber is produced at a pressure of 30.1 MPa, which is lower than the hydrostatic pressure. In the process of perforation, the perforation fluid through the perforation channels enters the formation.

Methyl alcohol plays the role of a desiccant.

Methanol (GOST 2222 - 78) PAV-OP-10 (GOST

8433-81), and oil, which is characterized with the following indicators: a density of 0.825 g / cm3, a viscosity of 5.11 FST, with a wax content of 23.5%.

Using this method allows you to restore the permeability of contaminated reservoirs and, on average, increase oil production by 20% from the initial one, which is 2 tons / day. anhydrous oil, and the method is most effective in wells with low reservoir pressure, at the opening of reservoirs composed of terrigenous reservoirs containing clay particles prone to swelling.

Claims (1)

DETAILED DESCRIPTION OF THE INVENTION A method for the secondary opening of terrigenous reservoirs with a low reservoir pressure, comprising pumping a perforation fluid into the interval of the producing formation, followed by a well perforation, characterized in that. in order to restore the permeability of the contaminated formation by improving its hydrodynamic connection with the well during perforation, a solution of methyl alcohol with the addition of a non-ionic surfactant in an amount of 2-3% by weight of the solution is used as the perforation fluid, and the perforation is carried out at a pressure below the hydrostatic .