RU2062669C1 - Method of liquidation of soil pollution with hydrocarbons - Google Patents

Abstract

FIELD: oil production. SUBSTANCE: invention relates with use of microorganisms to liquidate oil pollution on soil surface. Method involves aeration of polluted soil and addition of microorganism aqueous suspension and nitrogen and phosphorus mineral salts. Soil aeration method involves trench making parameters of which dependent on soil pollution degree with hydrocarbons. Aqueous suspension draining by trench and containing microorganism and mineral salts is collected and used periodically adding if necessary nitrogen and phosphorus salts. Microorganism source is concortium from water taken off from critical hole zone where soil is polluted with oil. EFFECT: improved method of soil treatment. 3 cl, 1 tbl

Description

 The invention relates to the field of the oil industry, in particular to methods for eliminating oil pollution on the earth's surface using microorganisms.

 Known methods for eliminating oil pollution of the soil, for example, removing fertile as well as contaminated infertile layers, embankment of the contaminated area with mineral soil and installing fences to limit the area of pollution / 1 /. However, these methods do not provide restoration of the fertility of contaminated soil.

 Closest to the proposed one is a method involving loosening the soil by plowing for the purpose of aeration, introducing into it a special culture of bacteria and mineral salts / 2 /. Bacteria introduced into the soil in the presence of oxygen, nitrogen, and phosphorus process hydrocarbons during their life to low-toxic or harmless oxygen-containing compounds up to carbon dioxide, thus eliminating oil pollution.

 However, loosening the soil by plowing does not allow aerating the soil, depending on the degree (depth) of its contamination with hydrocarbons and, if necessary, creating a slope on contaminated soil, which reduces the efficiency of the method.

 The aim of the invention is to increase the effectiveness of the elimination of oil pollution and its cheapening.

 This goal is achieved by the fact that in the method of eliminating hydrocarbon contamination of the soil by aeration and introducing an aqueous suspension of microorganisms and mineral salts of nitrogen and phosphorus for aeration of the soil, trenches are laid in it, the size and frequency of which depend on the degree of soil contamination with hydrocarbons, and flowing down the trenches an aqueous suspension of microorganisms and mineral salts is collected and used cyclically, adding, if necessary, salts of nitrogen and phosphorus.

 Another difference of the method is that as microorganisms use a community of microorganisms present in the water taken from the bottomhole zone of the well, developing the development object, the oil of which is contaminated with soil.

 Thus, the claimed method meets the criteria of the invention of "novelty."

 It is known that hydrocarbon-oxidizing bacteria are aerobic, i.e. a necessary element (condition) of their life is oxygen. The laying of trenches in contaminated soil of a certain depth, width, frequency, depending on the degree of soil contamination with hydrocarbons creates conditions for active aeration of the soil, which contributes to the rapid development of hydrocarbon-oxidizing bacteria and leads to the complete processing of hydrocarbon pollution. In addition, by varying the depth of the trenches along the length, it is possible to create an artificial slope in order to collect an aqueous suspension of microorganisms and nutrient salts for reuse in a batch process. Moreover, in the process of repeated spraying of an aqueous suspension over a contaminated surface, its additional aeration occurs.

 All this increases the efficiency of elimination of hydrocarbon contamination of the soil in comparison with the known method, where the depth and frequency of loosening of the soil by plowing do not allow aerating the entire volume of the contaminated soil layer to a sufficient degree and to a small extent depend on its degree of contamination.

 The known method, unlike the proposed one, does not provide for the collection and cyclic use of an aqueous solution of mineral salts and biomass of bacteria.

 Another difference of the proposed method is the use as microorganisms of hydrocarbon-oxidizing microflora present in water taken from the bottom-hole zone of the well developing the development object, the oil of which is contaminated with soil. This microflora is adapted to the crude oil of the field, and with additional aeration and the addition of nutrients, the active propagation of these microorganisms occurs and, accordingly, a more complete and faster destruction of the spilled oil.

 All of the above features give reason to consider the proposed method in accordance with the criteria of the invention "inventive step".

 In field conditions, the method is as follows.

Measure the area of the contaminated area, the porosity of the soil, the depth of penetration of hydrocarbons into the soil, determine the average molecular weight of hydrocarbons and soil saturation with hydrocarbons. The volume of air required for the oxidation of hydrocarbons to CO _{2 is} calculated, based on this, the size and frequency of the trenches are selected.

 The table shows the parameters of two sites with different degrees of pollution.

As follows from stoichiometric calculations, for the oxidation to CO ₂ 1 m ^{3 of a} hydrocarbon with a molecular weight of 200, 12 thousand m ^{3 of} air are needed.

 When calculating the volume of trenches, one should take into account a multiple increase in aeration due to the cyclical process (i.e., the number of artificial cycles), as well as additional aeration equal to artificial due to the natural air circulation in long trenches (the number of natural cycles). In addition, aeration is also increased due to surface air exchange.

We take the number of artificial cycles n _claim = 100, respectively, the number of natural cycles n _eats = 100. Due to surface air exchange, aeration increases by 2 times.

.Given these factors, the volume of air required for the oxidation of 1 m ³ hydrocarbons in one cycle will be

.

Для участка 2

Объем воздуха (V_воз), потребный для окисления углеводородов, соответственно составит:
V^I _возд=0,6x12=7,2 м³
V^II _возд=0,6x100=60 м³
Приняв, что V воздуха V траншей l x h x L, где l, h и L соответственно ширина, глубина и длина траншеи, причем ширина и глубина задаются, можно рассчитать длину траншей и частоту их расположения на загрязненном участке.The volume of hydrocarbons (V _{y / in} ) is calculated by the formula:
For plot 1

For plot 2

The volume of air (V _cart ) required for the oxidation of hydrocarbons, respectively, will be:
V ^I _air = 0.6x12 = 7.2 m ³
V ^II _air = 0.6x100 = 60 m ³
Assuming that V air V trenches lxhx L, where l, h and L are respectively the width, depth and length of the trench, and the width and depth are specified, you can calculate the length of the trenches and their frequency in the contaminated area.

На участке I следует проложить 16 траншей, а на участке II 80 траншей, тогда длина их составит расчетную, при этом расположить их можно так: на участке I 8 вдоль, 8 поперек с частотой 1,25 м; на участке II 40 вдоль, 40 поперек с частотой 0,25 м.In this particular case, the width of the trench is 0.15 m; depth for plot I 0.3 m, for plot II 0.5 m. Hence

In section I, 16 trenches should be laid, and in section II, 80 trenches, then their length will be calculated, while they can be arranged as follows: in section I 8 along, 8 across with a frequency of 1.25 m; on site II 40 along, 40 across with a frequency of 0.25 m.

In addition to the above analyzes, measure the angle of inclination of the contaminated area. If it is equal to zero, then the depth of the furrows along the length of the furrow is increased so as to create a slope of 2-4 ^o .

An aqueous solution of salts in fresh water is prepared in a container, for example, of the following composition: (Na ₂ HPO ₄ x 12H ₂ O + KH ₂ PO ₄ ) 0.1 g / L and NH ₄ Cl 0.5 g / L.

A culture of hydrocarbon-oxidizing bacteria is introduced into this solution in such an amount that their concentration in the solution is at least 10 ⁶ cells / ml.

If the source of soil contamination with hydrocarbons is known (for example, Devonian oil of reservoir N 302), then water is taken from the wellhead located on this reservoir, it is analyzed for the presence of DRR, and when their content in the water is at least 10 ⁶ cells / ml, they are taken into the tank 2 m ^{3 of} water, add the calculated amount of salts of nitrogen and phosphorus there so that their concentration is equal to the original, and the sodium salt of acetic acid to a concentration of 2 g / l. Then the solution is aerated and a hydrocarbon-oxidizing bacteria analysis is carried out every 12 hours. The solution can be used at a concentration of hydrocarbon-oxidizing bacteria of at least 10 ⁶ cells / ml.

Regardless of the method of obtaining a solution of microorganisms, their aqueous solution in a nutrient medium is sprayed over contaminated soil in an amount of at least 1 l / m ² .

 The solution flowing along the furrows is collected in a container or in a special cavity. After analyzing it for the content of mineral salts and adding, if necessary, the missing amount, again spray it over the contaminated area.

 An analysis of the suspension for the content of microorganisms is not performed, since in the process of destruction of hydrocarbons, their number increases.

 The process of spraying the solution is repeated until soil tests from the contaminated area show the absence of hydrocarbons in it.

 The analysis is carried out after 10-15 days, i.e. after undergoing microbiological processes.

 The technical and economic advantage of the proposed method compared to the prototype is a more complete and faster passage of microbiological processes by creating optimal ratios of air and hydrocarbons over the entire volume of pollution, as well as increasing and reusing the culture of hydrocarbon-oxidizing microorganisms and the surface-active substances produced by them in cyclic mode.

Literature:
1) V. D. Kolevatov. Reclamation of land contaminated when drilling wells. Nature protection in the areas of oil production in Tatarstan; Almetyevsk, 1980, p. 52-57.

 2) Reclamation of lands contaminated with oil. EI, ser. Corrosion protection and environmental protection, M. 1991, issue 6, S. 52-56. TTT1

Claims (3)

 1. The method of eliminating hydrocarbon contamination of the soil by aeration and the introduction of an aqueous suspension of microorganisms and mineral salts of nitrogen and phosphorus, characterized in that for aeration of the soil in it lay trenches, the size and frequency of which are calculated based on the degree of soil contamination with hydrocarbons, while the volume of the trenches is equal to the volume of air necessary for the oxidation of hydrocarbons to carbon dioxide, and the aqueous suspension of microorganisms and mineral salts flowing down the trenches is collected and used for next application.  2. The method according to claim 1, characterized in that the collected suspension of microorganisms and mineral salts is used cyclically, adding, if necessary, salts of nitrogen and phosphorus.  3. The method according to PP. 1 and 2, characterized in that as microorganisms use a community of microorganisms present in the water taken from the bottomhole zone of the well, the oil of which is contaminated with soil.

Images