RU2138626C1 - Method for recovery of residual oil from flooded non-uniform bed - Google Patents

Abstract

FIELD: oil production industry. SUBSTANCE: according to method, injected into bed through injection well is micellar solution containing water-soluble surface-active material and oil-soluble surface-active material, hydrocarbon liquid and water. Additionally, prior to injection into bed or in process of injecting micellar solution into bed, undertaken is isolation of highly permeable zones of bed by means of injecting fine-dispersive solid particles. Application of aforesaid method yields larger oil recovery from beds and reduced flooding of recovered product. EFFECT: higher efficiency. 2 tbl

Description

 The invention relates to the oil industry, in particular to methods for extracting oil from waterlogged formations at a late stage of operation.

 There is a method of developing a watered heterogeneous formation of an oil deposit, which consists in pumping an aqueous suspension of wood flour into the formation / 1 /.

 The disadvantage of this method is its low efficiency due to the fact that after alignment of the injectivity profile, injection of a displacing agent - water slightly increases the oil recovery coefficient.

 Closest to the claimed method is a method of extracting residual oil from the reservoir, including the displacement of oil using a microemulsion (micellar) composition containing an oil-soluble surfactant OP-4, a water-soluble surfactant OP-10, a hydrocarbon liquid and water / 2 / .

 The disadvantage of this method is the low efficiency due to the fact that the emulsion solution will be filtered by the most permeable interlayers having a low filtration resistance.

 The objective of the invention is to increase oil recovery and reduce water cut of produced products by increasing the coverage of the formation by exposure and displacement of residual oil by micellar-emulsion solution.

 The problem is solved in that in a method for extracting residual oil from an irregular flooded reservoir, including injection of a micellar solution containing water-soluble and oil-soluble surfactants, hydrocarbon liquid and water into the injection well, isolation of highly permeable is carried out before injection into the reservoir or directly in the process of injection of micellar solution formation zones by injection of fine particulate matter.

 To prepare the aqueous phase, 5-10% nonionic surfactants with an average molecular weight (OP-10, OP-7, ML-72, ML-80) are used. To prepare the hydrocarbon phase, 2.5-7% sulfonol is used.

 As the dispersed phase, you can use any powdery substance, insoluble in water and having a particle size below the radii of the pore channels (carbon black, clay powder, talc, chalk, milled peat, etc.). The content of the dispersed phase depending on the permeability of the formation varies in the range of 1-10%.

 The essence of the invention lies in the fact that at the final stage of development of an oil field in the reservoir, washed, highly permeable zones are formed. In order that the rim of the injected micellar solution is not filtered into highly permeable zones, the injectivity profile of the formation is leveled.

 The micellar solution is prepared as follows. A nonionic surfactant is dissolved in water and mixed with the dispersed phase, an oil-soluble surfactant (OP-4, sulfonol) in a hydrocarbon. An aqueous solution in the form of a suspension is pumped into the reservoir simultaneously with the hydrocarbon phase through an ejector or tee. Liquids easily mix with each other and spontaneously form a multiple emulsion, and in the presence of mineralized water - a micellar solution. Based on geological conditions, with a high heterogeneity of the formation or the presence of highly permeable washed, as well as with a high viscosity of the micellar solution, the dispersed phase is pre-injected in the form of an aqueous suspension.

 To study the displacement of residual oil from the reservoir model, micellar solutions with various component contents were prepared and their physicochemical properties were determined. The research results shown in table 1 showed that micellar solutions have good results in terms of the main technological parameters. Interfacial tension at the border with water and hydrocarbons has very low values of 0.02 - 0.06 mN / m, viscosity 14 - 80 MPa • s. The increased viscosity of the micellar solution has less mobility and provides greater exposure coverage. The stability of the micellar solution was observed for 10 days and all solutions were stable at surfactant concentrations above 2.5%.

 Studies to determine the effectiveness of the displacement of residual oil were carried out on two interconnected bulk models simulating a flooded reservoir. One of the models was saturated with water, the other with oil. The model is 250 mm long, 30 mm in diameter, and the model is filled with quartz sand. The experiment was carried out according to the following scheme: at the beginning, formation water was injected to determine the initial permeability of the model and the volume of residual oil, then an aqueous suspension of milled peat was pumped into the flooded part of the model and, to determine the degree of isolation, the model permeability was again determined. After that, a microemulsion containing hydrocarbon, water, an oil-soluble and a water-soluble surfactant was pumped. Before injection, the hydrocarbon phase and the aqueous phase were separately prepared, then they were sequentially pumped into the model. When pumping liquids are easily mixed and spontaneously form a microemulsion. The tip of the micellar solution, which is 10% of the pore volume of the model, is pumped with a buffer solution (an aqueous polymer solution having a viscosity higher than the micellar solution) and then three pore volumes of fresh water are pumped.

 The research results are shown in table 2, from which it follows that the proposed method of displacing residual oil from flooded reservoirs is effective compared to the prototype (experiment 5, 8), because pre-isolates highly permeable zones of the formation, increases the coverage of the formation by exposure, provides uniform advancement of the micellar rim throughout the formation and has good oil displacement ability.

Sources of information:
1. RF patent N 2043494, cl. E 21 B 43 / 32.1995 g.

 2. Copyright certificate of the USSR N 1700213, cl. E 21 B 43/22, 1991 PROTOTYPE.

Claims (1)

 A method for extracting residual oil from a flooded heterogeneous formation, comprising displacing oil using a micellar solution containing a water-soluble surfactant, an oil-soluble surfactant, a hydrocarbon liquid and water, characterized in that before the injection into the formation or directly during the injection of the micellar solution, isolation of highly permeable zones of the formation by pumping fine particulate matter.

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