RU2069260C1 - Method for increase of oil recovery from formations - Google Patents

Abstract

FIELD: oil producing industry; applicable in increasing of oil recovery of water-encroached terrigenic and carbonate reservoirs and regulation of their permeability at the middle and late stages of oil deposit development. SUBSTANCE: method for increase of oil recovery from formations is effected by injection of spent alkali or its mixture with fresh water and subsequent forcing by fresh water into formation. For deposits with mineralized water, prefringe of fresh water is used. Used spent alkalis are of medium and large quantities of secondary material resources of petrochemical production. They should contain 6-26 mas.% of alkali components (sodium hydroxide and/or sodium carbonate) and pH > 10. EFFECT: higher efficiency of application of alkali water encroachment. 2 cl, 5 tbl

Description

 The invention relates to the oil industry and can be used to increase oil recovery from flooded terrigenous and carbonate reservoirs and regulate their permeability.

Known methods of displacing oil from the reservoir, including the use of alkaline reagents (usually sodium hydroxide or carbonate [1]
A disadvantage of the known technical solutions is the low efficiency of the method.

The closest in technical essence to the proposed method is a technical solution, including the injection of an alkali rim followed by its sale with water [2]
Its disadvantage is the low efficiency of oil displacement under conditions of high heterogeneity from terrigenous and carbonate reservoirs.

 The aim of the proposed technical solution is to increase the efficiency of alkaline flooding.

 This goal is achieved by the fact that in the known method, which includes the injection of the rim of an alkaline reagent solution (sodium hydroxide or sodium carbonate), the spent alkali of the wet gas purification processes followed by fresh water is used as the alkaline reagent. For deposits with mineralized injected water, a pre-spot of fresh water is used.

 Used alkalis used are medium- and large-capacity secondary material resources of petrochemical industries. They should contain 6-25 weight. alkaline components (sodium hydroxide and (or) sodium carbonate) and pH> 10.

 Spent alkali can change the wettability of the collector surface, which increases the degree of oil displacement. The interaction of spent alkali with acidic components of oil leads to the formation of surfactants that reduce interfacial tension at the oil-water interface. In addition, the reaction of spent alkali with magnesium and calcium ions contained in injected and produced waters leads to the formation of precipitation, which reduces the permeability of washed zones and layers. The latter contributes to the leveling of the waterflooding front and involvement in the development of lower permeable zones and sections of the reservoir, and the reduction of unproductive water injection.

 The method can be applied in the middle and late stages of oil field development.

 The effectiveness of the method is determined experimentally in laboratory conditions by known methods. The research results are shown in tables.

 Example 1

 An important characteristic of an oil displacing agent is the interfacial tension at the oil / water interface. The measurement of equilibrium interfacial tension was carried out as follows. Equal volumes of degassed padun oil and alkaline solution were shaken for 60 minutes to achieve equilibrium. After settling, the oil and water phases were separated. Then, the interfacial tension between the obtained oil and water phases was measured using a stalagmometer (σ 0.2 mN / m) or a spinning rod gauge (σ 0.2 mN / m).). The results of the experiment are given in table. 3. Characteristics of spent alkali and oil are given in table. 2 and 1. As can be seen from the data in Table 3, spent alkali N 3 allows to reduce interfacial tension at the oil / water interface from 14.8 mN / m to 0.14 mN / m, which will contribute to the displacement of oil from the reservoir. Dilution of alkali with water increases the interfacial tension at the Paduna oil / water interface.

 Example 2

The oil displacing effect of spent alkalis in a terrigenous reservoir was tested on composite linear models of the Urshak field reservoir. For this purpose, bound water was created in cylindrical core samples of the field (previously extracted with an alcohol-benzene mixture) by capillary drawing and saturated with kerosene. Then, the cores were laid in a horizontal core holder and, during filtration, kerosene was replaced with an oil model. After that, the oil was displaced by the injected water and the rims of spent alkali were pumped in, alternating with injections of water. Before and after alkali rims, fresh water rims were pumped into the model. The experiments were carried out at 42-44 ^o With a constant filtration rate of 1 m / day. The results of the experiment are given in table. 4, fluid characteristics in the table. 1, spent alkalis in table. 2.

When oil is replaced by rims of spent alkalis N 1 and N 2, 0.3 p. the increase in oil displacement coefficient (β) was 5.1 7.7% (Experiments 1 and 2, Table 4), and the continuous injection of these alkaline reagents increased β by 7.6-11.7%
Characterization of oils and waters used in the testing of the method.

 Example 3

The oil-displacing effect of spent alkali in a carbonate reservoir was tested on a bulk linear model of the Padunsky reservoir. The body of the reservoir model was packed with disintegrated, extracted alcohol-benzene mixture carbonate core of the Padunskoye field. The reservoir model was saturated with reservoir water and an isoviscous oil model, the characteristics of which are given in Table. 1. The experiment was carried out at a temperature of 20-22 ^o C, displacement was carried out at a constant filtration rate of 1.1 m / day from a horizontally located model.

 Additional oil displacement by the rim of spent alkali N 3 in 0.3 p. leads to an increase in oil displacement coefficient by 5.6 and continuous injection of spent alkali N 3 increases by 12.6 (Test 3 in Table 4). The injection of spent alkali is not accompanied by a noticeable change in the filtration resistance of the reservoir model by water, which favors the use of spent alkali in low-permeability carbonate reservoirs.

 Example 4

 The experiment was carried out as described in example 3.

Introduction to the composition of spent alkali N 3 APAW (sodium alkylbenzenesulfonate) reduces the oil-displacing ability of spent alkali by 2.4-2.5 times. (Experience N 3 and 4 in table. 4). When downloading 0.3 bp there is a decrease in Db from 5.6 to 2.2% and with continuous injection, Db decreases from 12.6 to 5.3%
Example 5

В неоднородных пластах образование осадков снижает проницаемость промытых высоководопроницаемых зон и пропластков, что приводит к выравниванию фронта заводнения, роста коэффициента охвата пласта заводнением, уменьшению непроизводительной закачки воды и обводненности продукции. Осадкообразующее действие отработанных щелочей определяли по отношению объема осадка (V_oc) к общему объему смеси щелочи (V_щ) и сточной воды (V_в):

,
где α объемная доля осадка.Spent alkalis, when mixed with mineralized waters in the reservoir, can form sediments according to the following reactions:

In heterogeneous formations, the formation of sediments reduces the permeability of washed high-permeability zones and interlayers, which leads to equalization of the water flooding front, an increase in the coefficient of formation coverage by water flooding, and a decrease in unproductive water injection and water cut. The sludge-forming action of spent alkalis was determined by the ratio of the volume of sediment (V _oc ) to the total volume of the mixture of alkali (V _Щ ) and waste water (V _в ):

,
where α is the volume fraction of sediment.

 The measurement was carried out as follows. The selected volumes of alkalis and wastewater were placed in volumetric tubes, shaken and left alone until the change in precipitation volumes (precipitation aging) ceased, which took 6-10 days.

 The formation of loose precipitation was observed, occupying up to 30-50% of the system volume (Table 5).

Thus, the application of the proposed method of oil displacement in the oil industry allows you to:
to increase the efficiency of oil recovery from medium and low permeability, heterogeneous terrigenous and carbonate reservoirs of fields with fresh and mineralized injected water;
reduce material costs of alkaline flooding;
to regulate the permeability of water supply channels and interlayers in reservoirs of highly mineralized water fields;
to properly utilize spent alkali from petrochemical production wastes;
improve environmental protection.

Claims (2)

 1. A method of increasing oil recovery, including the injection of alkali rims into the reservoir, characterized in that the spent alkali of the wet processes of gas purification of petrochemical plants is used as the alkaline rim, followed by its sale with pumped water.  2. The method according to p. 1, characterized in that when selling rims of spent alkali with mineralized water, a portion of fresh water is pumped in front of the alkaline rim.

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