RU2009313C1 - Method for development of high-viscosity oil field - Google Patents

Abstract

FIELD: oil producing industry. SUBSTANCE: method consists in periodic injection of steam into producing wells, and oil production. Nonheated water is pumped into injection wells during steam injection into producing wells and steam condensation in formation, and is discontinued during extraction of oil from them. EFFECT: higher oil recovery from highly inhomogeneous formations due to forcing heat-transfer agent condensate out of zone of producing wells. 2 cl

Description

 The invention relates to the oil industry, namely to the development of deposits of highly viscous oil with a highly heterogeneous and heterogeneous reservoir.

 The complexity of developing such high-viscosity oil deposits lies in their low oil recovery, low productivity of producing wells, and the high cost of thermal methods used to develop them.

 Known methods for developing deposits of high-viscosity oil using thermal effects on oil-saturated formations (Gimatudinov Sh. K. Reference book on oil production. - M.: Nedra, 1974, S. 128-131, 462-463; Baybakov N.K., Garushev A. R. Thermal methods of developing oil fields. - M.: Nedra, 1977, p. 67). They describe methods for developing highly viscous oil deposits by injecting coolant (steam) through injection wells to create a thermal rim in the formation and heating the formation, or by periodically injecting steam into production wells.

 The disadvantages of these methods are their high cost due to the high energy consumption for heating oil-saturated formations from the side of injection wells (3-5 tons of steam or more are usually pumped per 1 ton of produced oil) and low oil recovery due to the high mobility of the vapor and rapid breakthroughs of condensate to the producing wells. Periodic injection of steam into production wells is usually applied no more than 3 times (3 cycles) and mainly provides cleaning of the bottomhole zone and increased productivity of production wells, oil recovery during their application increases slightly.

 Closest to the proposed method in technical essence is a method for developing highly viscous oil deposits, in which it is proposed that the superheated steam be injected and oil taken alternately throughout the entire development period of the reservoir both in injection and production wells, while it is proposed to carry out the process of injecting steam and pumping liquid in a mode in which a positive pressure difference is maintained from injection wells to production wells.

 The disadvantages of this method is its high cost and low final oil recovery deposits of high viscosity oil, not which it is used. The high cost is associated with high energy consumption for steam injection into injection wells (the volume of steam injection into injection wells is also 3-5 tons or more per 1 ton of produced oil), due to the high mobility of the steam compared to the mobility of highly viscous reservoir oil, its language-like breakthroughs to producing wells, which leads to low oil recovery.

 The aim of the invention is to increase oil recovery of highly heterogeneous formations due to the alignment of the displacement front and increase oil recovery of heterogeneous formations with low reservoir pressure due to the displacement of coolant condensate from the zone of production wells.

 This goal is achieved by the fact that in the described method, which includes periodic injection of steam into production wells, oil production and injection of a displacing agent into injection wells, cold water is used as a displacing agent, and in highly heterogeneous formations, cold water is injected during the period of steam injection into production wells, and during the period of oil extraction from production wells, cold water injection into injection wells is stopped; with heterogeneous formations with low reservoir pressure, cold water is pumped through injection wells continuously.

 The advantages of the proposed method compared to the known one consist in obtaining high oil recovery due to the equalization of the displacement front due to the periodic injection of water into highly heterogeneous reservoirs and due to the reduction in the difference in mobility of the reservoir oil and the displacing agent and due to the displacement of the coolant condensate from the zone of production wells.

 Since the consumption of steam for the production of 1 ton of oil by the proposed method is 7-10 times less than by the known method with higher oil recovery, when applying the proposed method receive greater energy savings.

 The sequence of operations according to the proposed method is as follows: a highly viscous oil deposit is drilled with producing and injection wells, heterogeneity of reservoir layers is studied using geological and hydrodynamic methods, with highly heterogeneous reservoirs cold water is pumped through injection wells simultaneously with steam being injected into production wells and with its condensation formation, then the injection of cold water into the injection wells is stopped and the oil and formation fluids are produced through production wells Vazhiny.

 In heterogeneous formations with low and low reservoir pressure, cold water is injected through injection wells both during the period of steam injection into production wells, and during the production of oil and formation fluids from these production wells. Periodic steam injection into production wells is carried out during the main life of the reservoir.

 The mechanism of processes occurring in the reservoir is as follows. When steam is injected into production wells and cold water is injected into injection wells in all oil-saturated formations, which differ from each other in permeability, thickness and other hydrodynamic parameters, high pressure is created that significantly exceeds the initial reservoir pressure due to interstratal and interlayer flows during all layers, despite the difference in their permeability, it is leveled. Then, during the period of oil and reservoir fluid production from producing wells, the created high reservoir pressure provides an intensive influx of fluids from all differently permeable layers, and due to the fact that a more intensive inflow from the highly permeable layer occurs, the reservoir pressure decreases faster than in less permeable interlayers In this regard, oil flows from these less permeable layers from less permeable layers, where there is a higher reservoir pressure, and thus the oil recovery is equalized. of layers with different permeability, increasing their degree of development of reserves and hence enhanced oil recovery. Alignment of the front of displacement of high-viscosity oil by cold water also occurs due to a decrease in the difference in mobilities of injected cold water and reservoir oil compared with the difference in mobilities of steam and reservoir oil. So, for example, at a viscosity of reservoir oil of 100 mPa˙s, the difference in mobility in the reservoir conditions of cold water (viscosity 1 mPa˙s) and this oil will be 52, and the difference in mobility of steam (vapor viscosity is 0.1 mPa˙s) and the same oil in reservoir conditions it will be 520. As is known, from the practice of developing oil fields, reducing the difference in mobility of the displacing agent and reservoir oil leads to an increase in the coverage factor, and, therefore, to an increase in oil recovery.

 When steam is periodically injected into production wells, condensate remains in the reservoirs due to a rapid decrease in reservoir pressure, and therefore, the remaining condensate prevents the subsequent portions of injected steam from contacting the reservoir oil and reduces the efficiency of steam cyclic treatments. Constant injection of cold water through injection wells allows increasing reservoir pressure and displacing condensate from the reservoir. This ensures efficient heating of reservoir oil with steam during each steam injection cycle and enhanced oil recovery due to oil production at elevated temperature (and, therefore, low viscosity).

PRI me R. They have a reservoir of high-viscosity oil, its geological oil reserves amount to 10 million tons, and the viscosity of reservoir oil is 300 mPa˙s. Temperature reservoir 20 ^C. The reservoir has high permeability of reservoir heterogeneity: the square of the variation coefficient of permeability is 1.50. 40 wells were drilled in the reservoir along a square grid with a distance between the wells of 300 m. The system for the mutual placement of production and injection wells is five-point. To develop the deposits, the proposed method is used.

In production wells pumped intermittently 500-1000 tons of steam with a temperature of 270 ^{° C,} simultaneously with the injection of steam is injected into the production wells into injection wells cold water. Then, after injecting a predetermined volume of steam into production wells, they are closed for the period of condensation of the coolant (1-3 days) and the cold water pumping is stopped in injection wells. After the condensation of the steam in the reservoir and the termination of the injection of cold water into the injection wells begin to produce oil and associated formation fluids from the production wells. This process of periodically injecting steam into production wells and cold water into injection wells is repeated throughout the entire development period of the reservoir to an economically viable amount of water cut and production of oil reserves.

 Technical and economic effectiveness of the proposed method is as follows. To evaluate it, the proposed method is compared with oil recovery and intensity (the rate of production wells) of the proposed method and the reduction in energy costs for the implementation of the method and the resulting economic effect are evaluated. The calculations are performed for a hypothetical reservoir described in the specific example, under the following additional conditions: coefficient of oil displacement by water 0.60; oil displacement by steam - 0.90; the zone covered by steam accounts for 20% of the total volume of the reservoir, the viscosity of the vapor is 0.1 mPa˙s, the viscosity of unheated water is 1.0 mPa˙s. With unsteady injection of unheated water, the injection time is 10 times less than the selection time. Under these conditions, the heterogeneity that determines the development process, expressed by the square of the coefficient of variation, decreases to 0.40.

 The comparison results are shown in the table.

 The data in the table show that, with the same development intensity of the deposit provided by comparable methods, the proposed one provides a 4-fold reduction in energy consumption: in the known oil, 20% of the total oil is spent on oil production (oil recovery coefficient 0.80), and in the proposed 5%. The final oil recovery coefficient when applying the proposed method increases in comparison with the known 1.15-1.60 times, the effective oil recovery coefficient is 1.38-1.90 times.

 Additional oil production when applying the proposed method is 1.01-2.36 million tons, while saving energy (oil) - (0.610-1.46) million tons (56) US Patent No. 4321966, 166-245, 1982.

Claims (2)

 1. METHOD FOR DEVELOPING A HIGH-VISCOUS OIL DEPOSIT, including periodic injection of steam into production wells, oil production and injection of a displacing agent into injection wells, characterized in that, in order to increase oil recovery of highly heterogeneous formations due to the leveling of the displacement front, a cold displacing agent is used as a displacing water moreover, cold water is injected during the period of steam injection into production wells, and during the period of oil withdrawal from production wells, I stop the injection of cold water into injection wells .  2. The method according to p. 1, characterized in that, in order to increase oil recovery of heterogeneous formations with low reservoir pressure due to the displacement of coolant condensate from the zone of production wells, cold water is pumped through injection wells.

Images