Технические науки/13. Охрана труда

Bekturganova G.S., Satymgalyeva A.

Kazakh National Technical University named after K.I. Satpayev

Almaty city, Republic of Kazakhstan

Determination of depth of penetration of oil in soil and establishment of possibility of its hit in ground waters

Summary. With increase in volumes of oil production the number of cases of pollution of terrestrial surface hydrocarbon raw materials continuously increases. Penetration of liquid hydrocarbons into bowels of the earth leads to pollution of soils, soil and underground waters and, finally, to ecological disruption on a terrestrial surface. In this regard in article questions of determination of regularity of pollution of soil and underground waters are considered during emergency pouring of oil when transporting oil and oil products, change of warm and physical, physic mechanical, physical and chemical properties at oil interaction with a soil earth's mantle. Depth of penetration of oil in soil and possibility of its penetration into underground waters is determined.

Despite considerable advantages of pipeline transport of oil and oil products on pipelines pollution of the atmosphere, reservoirs and the soil take place.

It is necessary to refer the following processes to the main reasons for pollution:

- Emissions of light hydrocarbons connections when filling tanks and temperature fluctuations of gas space of tanks and an oil surface;

- Oil evaporation from a surface of the polluted sewage, at leaks and emergency floods therefore the part of oil is carried away by storm thawed snow in reservoirs;

- Products of cleaning of pipelines and tanks from resinous deposits, etc.

The problem of labor and environmental protection, rational use of natural resources has important social and ecological value. With industry development influence of results of human activity on the nature becomes so big that the damage caused to it not always can be restored by a natural way without carrying out nature protection and nature-restoring actions.

At a construction and operation of the main oil pipelines to a problem of environmental protection pay the main attention. Impact on environment of the main oil pipelines is caused by their specifics as linearly extended objects (extent from hundreds to several thousand kilometers), laid in difficult climatic conditions with application of various constructive schemes and technologies which also make harmful effects on environment. Considering a fundamental role of the main pipelines as means of transportation of liquid and gaseous products and involvement in economic activity few of the mastered natural regions, being characterized high sensitivity to technogenic influences, the environmental protection problem at pipeline transport is today very actual.

At an exit of oil and oil products in environment water and the soil become soiled the hydrocarbons entering into its structure. At the same time there are the processes leading to decomposition of oil: distribution, evaporation and dissolution. At operation of linear part and objects of the oil pipeline the main sources of impact on a condition of underground waters are reservoir parks of oil pumping stations, barns for emergency storage of oil, stores of waste, filtration and evaporation fields for dumping of sewage, warehouses of fuels and lubricants, gas stations and places of leak, emergency dumping of oil on the oil pipeline route.

Influence of these sources on a condition of underground waters results from leaks and consists in pollution of the last by nitrates, nitrites, phosphates and the weighed substances in case of dumping on fields of a filtration and evaporation of household waters and oil products in all other cases. At pollution of underground waters by oil products they can be in a type of a single-phase liquid layer, true solutions or small emulsions, a gas phase and as are occluded by breeds. Processes of phase differentiation along with properties of oil products are influenced by properties of breeds and underground waters, temperature, pressure, a saturation of breeds and waters oxygen and microorganisms. Depth of penetration of pollution is defined by security of the water-bearing horizons. The most vulnerable in this regard is the water-bearing horizon of ground waters first from a surface. In the conditions of normal operation of the oil pipeline by a potential long-term source of impact on underground waters oil pumping stations, and especially head, having capacities for storage of oil products and combined with bases of supply, repair and emergency services will be. The various technogenic drains which are forming on platforms can be sources of pollution of underground waters.

In this regard in article at pipeline transport of oil and oil products we decided to reveal regularities of pollution of soil and ground waters at emergency oil spill, regularity of interaction of oil with the soil, changing heat physical and physical-mechanical and physical-chemical properties. At a filtration the condition of water in a time changes as a result of the phenomena described in work [1]. In this work the formula for definition of a specific amount of water is received:

(1)

where W_M - maximum molecular moisture content of disperse particles less than 0,5 mm in size, %; - mass percentage of particles less than 0,5 mm in size, %.

For clarification of influence of a superficial tension of liquid and wet ability of soil on its relative humidity, we will present space with a time in a look in water of a cylindrical form. Then extent of filling of a time or relative humidity can be presented as:

(2)

где S_к - критическое сечение, при котором начинает наблюдаться явление капиллярности, м²; S₀ - среднее сечение порового пространства, м².

The phenomenon of capillarity is shown at various radiuses of space with a time. However it is necessary to take its maximum value at which the capillarity phenomenon starts being shown for the size S_k.

For a cylindrical form of space with a time relative humidity can be expressed as

(3)

where r_k - the radius at which the m begins the phenomena of a capillarity or the critical radius of manifestation of a capillarity; r₀ - the average radius of a time of a skeleton of soil, m.

Critical radius of r_k we will express through a superficial tension of liquid:

(4)

where - water surface tension, N/m; g - acceleration of a free fall, m/с²; h - height of a capillary raising of water r_k corresponding to radius, m; - regional corner of wetting of water, hail.

Thus, dependence of relative humidity on a water surface tension to wettability of a skeleton of soil can be presented a formula:

(5)

It should be noted that in a formula (5) the roughness of a piece of a skeleton of soil and an orientation of a form of steam space isn't considered. Finally, all this influences the size of relative humidity and therefore on a specific amount of water in a soil time. To exclude these shortcomings relative humidity of soil it is expedient to determine by a weight method (mass) and, therefore, the formula (5) needs to be expressed not through the relation of volumes, and through the relation of masses. It is reached by that density of water is entered into a formula (5) and soil density. Besides, transition to a weight method of definition allows excluding the approach connected with representation of space with a time in the form of a cylindrical form since the amount of capillary water doesn't depend on a shape of a skeleton of soil of space with a time. As a result we have:

(6)

From here it is possible to draw a conclusion that with reduction of a superficial tension and wet ability of a skeleton of soil relative humidity decreases in proportion to a square of these sizes. When studying a filtration of oil it is necessary to consider interaction it with the water which is present at a time of soil which relative humidity is determined by a formula (6).

Some authors [2,3] claim that the water current with incomplete filling of a time of soil, will submit to the laws similar to laws of hydrodynamics, and liquid movement in other conditions, will submit to other laws following from laws of a superficial tension and evaporation. Besides lack of the bottom limit of applicability of the law of Darci suggests an idea that in incoherent porous environments under certain conditions there is a special view of the current of liquid which has so far no mathematical description depending on a superficial tension of liquid and wet ability.

Other directions of studying of problems of a filtration of liquid in porous environments are researches of the equation of movement and continuity under various boundary conditions [2] and others. Thus the exact solution of these equations is consolidated to special mathematical methods and their practical use for specific objectives not always possibly. For the practical appendix they decide various approximate receptions, as methods of small parameter, final differences, total representations, etc. In works [3,4] the condition of water in the soil, in porous water-permeable rocks, depending on their humidity is described. At the smallest content of liquid it is absorbed in soil grains, and with increase in humidity it starts enveloping soil grains in the form of films and further with increase in humidity fills at first small, and then larger time. When filling all time liquid gets opportunity to move by gravity.

However at a liquid current layer-by-layer with absorption without a pressure filling of a time doesn't reach. The current caused by interaction of liquid of the bottom layer with a skeleton of soil which is defined by a superficial tension of liquid and wet ability of rocks will prevail thus. In this case, the bottom layer is water with disperse firm particles. Then the description of such type of movement corresponds to the equation:

(7)

Here V_в - speed of movement of water at incomplete filling of a time of soil, m/s; q - density of a drain of liquid or specific amount of water which contains in space soil with a time.

At such current of liquid all directions of distribution of liquid will be equivalent. In this regard the equation (7) can be presented in the form of an one-dimensional task:

(8)

Humidity in a formula (6) generally is function of coordinate by X and t time, that is it is possible to write down . Expression differentiating on time and substituting in (8) will look as:

(9)

The sizes W_m, m don't depend on time and coordinates, and depend on density of rocks composing soil. Grouping and dividing variables on time and coordinate, and also considering that from (9) we will receive for integration the equation:

(10)

Relative change of density of liquid at the expense of interaction processes with oil with disperse particles of soil is much less than relative change of humidity of soil, i.e. it is possible to write down

(11)

On it the right member of equation (11) is equal to zero and the left part can be presented in a look:

(12)

Integration of expression (12) it is made on certain limits. At speed change from initial V₀ up to the size U₀ corresponding to speed of movement of water on a time of soil, its humidity changes from natural to relative which corresponds to steam water. Therefore, a certain integral can be written down as follows:

(13)

After integration for water speed on a time of soil we will have

(14)

Here W_e - natural humidity of soil, %.

Exponentiation expression (14) having substituted value of a formula (6) we will receive expression for the speed of a filtration of water during a soil time

(15)

Apparently from a formula process of a filtration has difficult character from the sizes entering into it. However it should be noted essential dependence on a water surface tension and wet ability of grains of soil.

The received formula allows determining depth of penetration of the water transporting with oil

(16)

The sizes entering into this formula can be defined experimentally in vitro on soil models. During t it is necessary to accept time since the oil spill beginning at accident to a complete elimination of its consequences. To liquidate consequences of ruptures of oil pipelines - very difficult task in the practical relation. Therefore depending on climatic conditions, during t it is necessary to accept everything months of year except winter months. Depending on the size of speed, the location of a rupture of the oil pipeline, and also depending on depth of an arrangement of ground waters with rather bigger accuracy it is possible to determine time during which oil will reach a surface of ground waters by a formula.

It should be noted, at accidents on the oil pipelines connected with a rupture of it, there is a pollution not only soils and ground water, but also atmospheric air. Especially strong pollution of atmospheric air happens when the poured oil appears on a soil surface, at the expense of its intensive evaporation.

In article process of a filtration is considered and is revealed that, process of a filtration of oil becomes complicated presence at steam space of water at various conditions. The oil filtration in soil should be considered as a layer-by-layer current of two liquids relatively each other. And as transport of oil the water being in steam space of soil is. The amount of the liquid being in steam space, decides by physic mechanical characteristics of soil and the physical and chemical sizes, characterizing interaction of liquid on soil minerals.

Dependence of relative humidity on wet ability of soil and superficial tension of liquid which is proportional to squares of these sizes is established. Dependence of speed of a filtration of liquid in soil depending on wet ability of grains of soil and a surface of a tension of liquid is proved. The formula for determination of depth of penetration of oil in the soil, depending on physic mechanical properties of soil and physical and chemical characteristics of interaction of liquid with soil grains is offered.

The list of the used literature:

1. Innovation patent #84229 KZ. Способ определения удельного расхода жидкости для увлажнения навала горной массы. Zharaspayev M., Mirzahmetov M.M., Bekturganova G.S.; 17.06.2011. Bulletin-6. Committee on rights of intellectual ownership of Justice Ministry of the Republic of Kazakhstan.

2. Христианович С.А., Михлин С.Г., Девисон Б.Б. Некоторые новые вопросы механики сплошной среды. -М.-Л.: АН СССР, 1938. - 407 с.

3. Веригин Н.Н., Шерпеуков Б.С. Диффузия и массообмен при фильтрации жидкости в пористых средах // Развитие теории фильтрации в СССР (1917-1967) - М.: Наука, 1969. С. 237-313.

4. Лебедев А.Ф. Почвенные и грунтовые воды. -М.-Л.: АН СССР, 1936.-316 с.