EP-3656973-B1 - METHOD OF INCREASING THE OIL RECOVERY OF FORMATIONS

Inventors

• SERGEEV, Vitalii Vyacheslavovich

Dates

Publication Date

20260506

Application Date

20180718

Claims (2)

1. A method for increasing oil recovery from an oil-bearing formation, comprising the following successive stages of treating the formation: - injecting an invert-emulsion in a volume of 3-5 m 3 /m of perforated interval thickness followed by squeezing down an acidic composition in a volume of 2-3 m 3 /m of perforated interval thickness to the formation; - injecting a highly stable direct emulsion containing silicon dioxide nanoparticles in a volume of 3-7 m 3 /m of perforated interval thickness followed by squeezing down a liquid from a reservoir pressure maintenance system to the formation; wherein the invert-emulsion has the following composition : a diesel fuel or a treated oil from an oil preparation and pumping station - 25-35% vol., emulsifier - 1.5-3% vol., a technical water - the rest; the acidic composition for carbonate formations has the following hydrochloric acid-based composition : 30% hydrochloric acid - 50-63% vol., acetic acid - 1-3% vol., diethylene glycol - 6-12% vol., a corrosion inhibitor - 1.5-2% vol., water - the rest; the acidic composition for terrigenous formations has the following hydrofluoric acid- based composition : 30% hydrochloric acid - 48-60% vol., hydrofluoric acid - 1-4% vol., diethylene glycol - 6-12% vol., acetic acid - 1-3% vol., the corrosion inhibitor - 1.5-2% vol., water - the rest; the highly stable direct emulsion has the following composition : a diesel fuel or a treated oil from the oil preparation and pumping station - 10-20% vol., emulsifier - 1-2.5% vol., colloidal solution of silicon dioxide nanoparticles with a particle size from 9 to 100 nanometers - 0.5-1.5% vol., a technical water - the rest.
2. The method according to claim 1, characterized in that the technical water is a solution of calcium chloride or a solution of potassium chloride.

Description

FIELD OF THE INVENTION The invention relates to the oil-producing industry, in particular to technologies for influencing on oil and gas formation (reservoir) in order to enhance the oil recovery factor. BACKGROUND The deterioration of geological and physical conditions for the development of oil and gas fields and the need to maintain oil production at maximum levels lead to the implementation of intensive development systems with the use of reservoir pressure maintenance system by injection water into reservoirs. With an intensive system of producing oil reserves, subsoil users are faced with the problem of breaking the oil displacing agent through more permeable intervals of the reservoir, which leads to a sharp watering of the production wells and a decrease in the economic efficiency of operation of high water-cutted wells. All oil and gas bearing reservoirs are characterized by varying degrees of change in the parameters of micro- and macroinhomogeneities over the area and volume of the formation. Geological and physical microinhomogeneity of oil and gas bearing formations is the main characteristic of the filtration and capacitance properties of rocks, and macroinhomogeneity is one of the main complicating factors in the application of development systems for oil and gas bearing reservoirs. The natural geological and physical heterogeneity of oil and gas bearing formations leads to an uneven distribution of oil-displacing agents injected into the reservoir. As a result, the main volumes of agents injected into the formation are absorbed by reservoir intervals with the highest filtration and capacitance characteristics. Implementation of methods for intensifying of oil production leads to increasing the heterogeneity of the filtration-capacitance properties of rocks. One of the ways to intensify oil production, which most significantly affects the reservoir's filtration-capacitance characteristics, is the method of hydraulic fracturing of the formation. Hydraulic fracturing of the formation leads to an increase in the permeability of natural fractures of the formation, and in some cases to the creation of a new system of highly permeable fractures. Thus, in most cases, hydraulic fracturing of the formation results in short-term intensification of oil production and acceleration of oil-and-gas-bearing formation flooding. The most widely used agent for displacement of oil from oil and gas saturated layers is water. One of the main causes of water breakthrough to producing wells is the difference in mobility of formation fluids and the displacing agent - water that is injected from the surface. Both in surface and in reservoir conditions, water moves towards less resistance, i.e. in the case of a subsurface reservoir, through the intervals with the highest filtration-capacitive characteristics. Thus, water is distributed unevenly along the thicknesses of oil-saturated layers and involves only a small part of the oil-saturated intervals in the filtration processes. Also, water is a liquid with a low oil wash ability, which is explained by its polarity. During filtration of water in oil-saturated intervals of layers only a small part of oil reserves is extracted, because of the different polarity of water and hydrocarbons, the biggest part of the oil reserves remains uninvolved in the form of films that envelop the walls of the filtration channels. Under such conditions, the final oil recovery factor does not exceed 20%. In this regard, industry experts have developed ways to enhance the oil recovery factor. The main objective of these methods is to influence the oil and gas bearing layers to increase formation coverage and to equalize the front of oil displacement to production wells. The purpose of the methods is to increase the oil recovery factor. The main task of the methods is solved by pumping oil-displacing agent with reduced mobility into the formation. Reducing the mobility of oil-displacing agents leads to a more even distribution of the agents over the area and volume of the formation. A more even distribution of oil- displacing agents over the area and volume of the formation results in a redistribution of the filtration flows and increased formation coverage by exposing the less filtrable formation intervals to the filtration processes. At present, the most widely used method for increasing oil recovery is polymer flooding. Experience in the development of oil and gas fields shows that methods of increasing oil recovery based on aqueous solutions of polymers are not effective enough in the presence of high and medium permeable cracks in the seams. The polymer compositions used in the industry are based on alternately injecting into the formation a low-concentration aqueous polymer solution and a crosslinking agent. Considering the fact that, when creating repression on a reservoir, the mobility of polymer solutions based on water does not provide sufficient resistance to movement of this pack