RU2105141C1 - Method for development of oil deposit with low-permeable clay-bearing reservoir - Google Patents

Abstract

FIELD: oil and gas production industry. SUBSTANCE: reduced period of developing deposit, increased output of producing wells and uniform recovery of oil in deposit sections can be achieved by differential increase of permeability of down-hole zones of injection and producing wells. Method implies removing clay from producing and injection wells with subsequent displacement of oil from bed by means of polymeric solution. Clay removing is effected by applying various amounts of desedimentation reagent depending on permeability of down-hole zones of wells being treated. Concentration of water solution of polymer is selected between concentration at which fluidity of polymer solution in water in down-hole zone of bed in which clay is removed is equal to fluidity of water in aforesaid zone prior to clay removal and concentration at which specific increase of oil recovery from deposit is maximal. EFFECT: higher efficiency. 2 dwg, 2 tbl

Description

 The invention relates to the oil and gas industry, and can be used in the development of oil fields with low permeability clay-containing reservoirs.

 A known method of developing an oil reservoir with a low-permeability clay-containing reservoir, comprising injecting through at least one injection well an oil-displacing aqueous polymer solution and withdrawing through at least one oil producing well from the reservoir [1]. Injection and production wells communicate with each other through deposits.

 The disadvantage of this method is the long development time of the field and the low efficiency of oil recovery from heterogeneous deposits, manifested in low oil recovery deposits.

 Closest to the invention, the technical essence is a method of developing an oil reservoir with a low-permeability clay-containing reservoir, including wilting treatment of bottom-hole zones in injection wells by injection of a decolming reagent into them, subsequent injection of an aqueous polymer solution through at least one injection well and oil selection through one producing well [2].

 The disadvantages of this method is the long development time of the field, low flow rates in production wells, as well as uneven oil recovery over the deposits.

 The long term development of the field is due to the fact that the method uses an aqueous polymer solution with a mobility less than that of water that is not optimally selected, and also due to the fact that the same clay factor is selected. This extends the development period to 10-15 years. In addition, as a result of the above, the flow rates in production wells are reduced, and uneven oil recovery occurs in the sections of the reservoir.

 The aim of the invention is to reduce the term of field development, increase the production rate of production wells and provide the possibility of uniform oil recovery in the areas of the reservoir due to the differentiated increase in the permeability of bottom-hole zones of injection and production wells.

 This goal is achieved by the fact that in the method of developing an oil reservoir with a low-permeability clay-containing reservoir, including the claying treatment of bottom-hole zones in injection wells by injection of a decolming reagent into them, subsequent injection of an aqueous polymer solution through at least one injection well and the selection of oil through at least one production well, according to the invention, determine the clay clay factor, while simultaneously with the clay mud treatment of the zones of injection wells, claying treatment of bottom-hole zones of production wells is carried out by injection of a decolming reagent into them, while the volume and / or concentration of the decolming reagent is selected proportionally large for wells with a high clay factor and lower for wells with a lower clay factor, and the concentration of the aqueous polymer solution is selected in the range between the concentration at which the mobility of the aqueous polymer solution in the clayed-out bottom-hole formation zone is and the mobility of water in the area to razglinizatsii and the concentration at which a specific increase of oil recovery reservoir is maximal.

 If mobility is greater than that of water, the use of an aqueous polymer solution is ineffective.

 The advantages of the invention are the reduction of the field development time due to the fact that the invention uses an aqueous polymer solution with a mobility of not more than that of water, and also due to the fact that the concentration of the decolming reagent is selected depending on the clay factor for each production and injection well. As a result, the flow rates in production wells increase and oil is evenly extracted over the deposits.

 The method is as follows.

Hydrodynamic studies are carried out at selected injection and production wells. The coefficients of the clay content of the formation, the permeability of the reservoir (K ₁ ), the mobility of the water in the reservoir and the aqueous polymer solution are determined.

 Then, the wells are washed with anhydrous oil and the bottomhole zone of the formation is decolmated. To do this, at the mouths of injection and production wells, the necessary amount of decolming reagent is prepared, which ensures the treatment of the bottomhole zone in the desired radius. At the same time, a proportionally larger amount of decolming reagent is introduced into the wells with a high clay factor, which is ensured either by a large injection volume or a large reagent concentration, and, accordingly, a proportionally smaller amount of decolming reagent is introduced into the wells with a lower clay content. Wells are closed for response (6-48 hours depending on geological conditions).

Then, the collector permeability value (K ₂ ) is determined after decolmatization, and the collector permeability is increased by how many times after decolmation, i.e., the decolmatization coefficient is determined R = K ₂ / K ₁ .

The dependence of the viscosity of the aqueous polymer solution on its concentration is built and its concentration (C ₁ ) is determined according to the schedule, at which the mobility of the aqueous polymer solution in the muddled formation zone is equal to the mobility of water in this zone.

Then, the dependence of the (experimental) specific oil recovery increase on the concentration of the aqueous polymer solution is built. From this dependence, the concentration (C ₂ ) is found at which the specific increase in oil recovery in the reservoir is maximum.

Next, the concentration of the injected polymer solution between the values of C ₁ and C ₂ is selected, the polymer solution of the selected concentration is pumped in the desired volume.

 The mobility of the polymer solution is determined by the permeability of the reservoir under altered conditions during the passage of the first portion of the polymer solution.

 As the polymer, polyacrylamide, VPK-402 or other low molecular weight polymers can be used. And as decolming reagent used peroxides, soda ash, hydrochloric acid, guamidine salt, etc.

An example is illustrated by drawings, where:
in FIG. 1 shows the dependence of the viscosity of an aqueous polymer solution on its concentration; in FIG. 2 - dependence of the specific increase in oil recovery from the concentration of an aqueous polymer solution.

 An example of the method.

The Jurassic oil reservoir (depth 2950-2956 m) with an average reservoir permeability of 40 X 10 ^-12 m ² (K ₁ ), which corresponds to a water mobility of 73.4 μm ² / mPa with a clay collector, was selected as the object for applying this method average saturated thickness of 6 m, a porosity of 15%, the area of 1050 m the oil-bearing, the proportion of oil 0.88 oil viscosity at reservoir conditions of 0.99 mPa • s, water - 0.545 mPa • c (μ _a), the formation temperature is 80 ^o C. The well location system is in-line with a distance between the wells of 500 m. As a result of the study, 2 agnetatelnyh and 4 production wells selected for approbation this method, the values of the coefficients of clay were as follows (see. Table 1).

 Flush production wells with anhydrous oil.

 At the same time, decolmation of the bottom-hole zone of production and injection wells is carried out, pumping into the wells with a high clay factor a decolming reagent (sodium percarbonate) with a proportionally large value of its concentration (Table 1). Bottom zone treatment is carried out in a radius of 1.5 m for each well.

The volume of injection of decolming reagent into all wells is chosen the same - 4 m ³ . After injection, all selected wells are plugged for 24 hours.

 The solution of the decolming reagent is pumped into wells washed with anhydrous oil and crushed into the reservoir.

Then determine the value of the permeability of the reservoir (K ₂ ) after decolmation and determine the coefficient of decolmation and determine the coefficient of decolmation R = K ₂ / K ₁ (table 2).

Далее, строят зависимость удельного прироста нефтеотдачи от концентрации (фиг.2). Из этой зависимости находим концентрацию (C₂), при которой удельный прирост нефтеотдачи в залежи максимален.Next, determine the concentration of an aqueous polymer solution for each well for further injection. To do this, build the dependence of the viscosity of the aqueous solution of polyacrylamide on the concentration (Fig. 1) and determine the concentration (C ₁ ) from the graph at which the mobility of the polymer solution in the muddled formation zone is equal to the mobility of water in this zone, i.e. with viscosity:

Next, build the dependence of the specific increase in oil recovery from concentration (figure 2). From this dependence we find the concentration (C ₂ ) at which the maximum oil recovery in the reservoir is maximum.

Then, the average concentration between the values (C ₁ ) and (C ₂ ) of the injected polymer solution is selected (C), and the aqueous polymer solution is injected.

 Table 2 presents the results of the wedging treatment of the bottom-hole zones of the wells, expressed in the coefficient of decolmation, water mobility and concentration of polymer solutions, based on which the concentration (C) of the aqueous polymer solution assigned for injection is selected.

 Then, after 24 hours, the wells are put into operation, while the injection wells are pumped with the concentrations (C) of the aqueous polymer solution specified in Table 2, which is used as polyacrylamide with a molecular weight of not higher than 200,000 (to avoid reduced mobility and increase development time )

 Next, the selection of oil through production wells begins.

 As a result of the application of this development method, production rates in production wells increase by 50-70%, the development period decreases.

Sources of information taken into account
1. Pat. USA, 4457372, cl. E 21 B 43/22, 1984.

 2. Pat. USA, 4624314, cl. E 21 B 43/27, 1986 (prototype).

Claims (1)

 A method for developing an oil reservoir with a low-permeability clay-containing reservoir, including clay processing of bottom-hole zones in injection wells by injection of a decolming reagent into them, subsequent injection of an aqueous polymer solution through at least one injection well, oil selection through at least one production well, characterized in that determine the clay clay factor, at the same time as the wedging treatment of bottom-hole zones of injection wells wedging treatment of bottom-hole zones of production wells by injection of decolating reagent into them, while the volume and / or concentration of decolming reagent is selected proportionally large for wells with a high clay coefficient and lower for wells with a lower clay factor, and the concentration of an aqueous polymer solution is selected between the concentration in which the mobility of the aqueous polymer solution in the mudded bottomhole formation zone is equal to the mobility of water in this zone before mudding and the concentration at which the specific increase in oil recovery of the reservoir is maximum.

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