RU2559218C1 - Gas and oil pipeline laying technique - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention is related to oil and gas industry and may be used for construction and repair operations at gas and oil pipelines. According to the gas and oil pipeline laying technique insulated gas and oil pipeline is laid in the trench onto the layer prepared and treated with modifier, backfilling of gas and oil pipeline with cushioning layer treated with modifier with subsequent formation of banking. The modifier is represented by product of decontamination with reagents of oil-contaminated production waste and soil containing calcium hydroxide and carbonate in quantity of 15-45 wt % of soil weight.

EFFECT: reduced corrosion activity of soil for the bed and cushion.

2 cl, 1 tbl

Description

The invention relates to the oil and gas industry and can be used during construction and repair work on gas and oil pipelines.

A known method of laying an underground pipeline, including laying a steel insulated pipeline in a trench on a preparation layer, sprinkling it with a layer of sprinkling followed by backfilling with soil and applying a roll, the preparation and sprinkling layer being treated with a solution of thermal oil cracking residue 50-80% and light gas oil 20- 50% in the amount of 6-8% of the weight of the soil preparation and sprinkling (see ed. Certificate of the USSR No. 93087, F16L 57/00. Bull. No. 20 from 05/30/1982).

The disadvantage of this method is the impossibility of its use in the presence of underlying rock and at the intersection with solonchak soils and swamps. In addition, the binder in the amount of 6-8% of the weight of the preparation and sprinkling soil does not provide an improvement in the operating conditions of the pipeline from the point of view of preventing isolation of the pipeline from mechanical damage, as well as protection from the negative effects of the environment and corrosion.

The closest technical solution to the proposed invention is a method of laying a semi-underground pipeline, including laying a pipeline with insulation in a trench on a preparation layer treated with a modifier — an organic binder in an amount of 3-12% of the weight of the soil, sprinkling it with a dusting layer treated with an organic binder in an amount 3-12% of the weight of the soil. Moreover, BMT (binder of main pipelines) according to TU 38.101960-83, oil and other organic binders with or without additives are used as an organic binder (see RF patent No. 2205316, publ. 27.05.2003. Bull. No. 15). In addition, to ensure longitudinal stability, the formation of deboning is carried out with soil containing 3-12% of an organic binder.

The disadvantage of this method is the relatively high corrosivity of the treated soils for preparation and sprinkling and its low efficiency due to the use of expensive binders.

The objective of the invention is to provide a method of laying a gas pipeline, which reduces the corrosion activity of the soil preparation and sprinkling and increase the efficiency of the processes.

The problem is solved in that in a method for laying a gas and oil pipeline, including laying an insulated gas and oil pipeline in a trench on a preparation layer treated with a modifier, sprinkling it with a sprinkling layer treated with a modifier, with subsequent formation of debris, the secondary product of the reagent neutralization of oil and waste products is used as a modifier containing hydroxide and calcium carbonate, in the amount of 15-45 mass. % by weight of soil.

The claimed method uses the product of the reagent neutralization of oil-contaminated production waste and soil, which is a powdered encapsulated material.

The introduction into the preparation and sprinkling soils of the encapsulated product of the reagent neutralization of oil-contaminated production waste and soil, which is a powdered encapsulated material containing high molecular weight hydrocarbons, calcium hydroxide and mineral soil components, coated with a calcium carbonate crust, provides a fine-grained structure of the preparation and sprinkling soil arrays due to capsules of aggregation of soil particles. The presence of calcium hydroxide and calcium carbonate in the product leads to a decrease in the acidity of the medium, as well as to the formation of limestone crust in the trench at the boundaries of preparation and sprinkling, which impedes water and air exchange with the external environment.

Since in most cases in an alkaline environment the corrosion of steel is reduced, the transition of the medium to a neutral or slightly alkaline zone leads to a decrease in the corrosion rate. In addition, calcium hydroxide partially dissolved in water acts as an inorganic cathodic corrosion inhibitor, forming in the places of gas and oil pipeline insulation breakdown insoluble precipitates of calcium carbonate, which increase the electrical resistance, slow down the cathode process and impede oxygen access. Since the solubility of calcium hydroxide in water is very low, the effect of the drug will manifest itself for a considerable time.

With a decrease in the content of modifier in the soil below 15 mass. % increases the corrosion ability of the soil and does not provide water resistance, hydrophobicity and corrosion protection of the gas and oil pipeline in case of violation of the integrity of the insulation in the lower part of the gas and oil pipeline, for example, due to depressurization of the joints between adjacent turns of insulation during longitudinal movements of the structure. The increase in its content above 45 mass. % practically does not affect the corrosion properties of the soil and leads to an increase in reagent consumption.

The essence of the claimed invention is described by the following example.

The product of the reagent neutralization of oil-contaminated production waste and soil is obtained as follows.

First, a reagent for neutralizing oil wastes is obtained, for which quick lime is supplied to the mixer in an amount of 80.6 to 91.5 mass. %, oil waste, in particular bottoms of the primary oil refining at 50-85 ° C, in an amount of from 8.5 to 19.4 mass. %, and mix thoroughly.

Then in the mixer for neutralization serves soil containing 50 mass. % fuel oil, based on 1 kg per 1 kg of reagent. The mixture is stirred with the addition of water until the lime is completely extinguished and a homogeneous mass is obtained.

The obtained encapsulated product of the reagent neutralization of oil-contaminated soil is removed from the mixer, stored and sent to the soil for the layers of the preparation and sprinkling of the gas and oil pipeline as a modifier.

Laying the gas pipeline is as follows.

In accordance with STO Gazprom 2-2.1-249-2008, an insulated gas and oil pipeline is laid in a trench on a preparation layer previously treated with a modifier, and covered with a sprinkling layer treated with a modifier. Then they fill up the trench and form a bunion.

The soil preparation and sprinkling is carried out in the mixer by introducing into it with mixing the soil and a modifier at the rate of 15-45 masses. % by weight of soil.

In order to determine the level of impact on the soil corrosion processes of the proposed method, studies were conducted to determine the corrosion rate by the density of the polarizing current in laboratory conditions and by the method of weight loss in field conditions. For research, samples of 17G1S-U grade steel plate were used.

For laboratory studies, samples of tubular steel with soldered conductors, insulated with bitumen varnish on the outside, which are installed in a container at a distance of 50-60 mm from each other, were used as electrodes. Soil treated with a modifier is loaded into the tank. The soil is compacted and moistened with distilled water until an absorbed moisture appears on its surface. After 24-hour exposure, studies are carried out in accordance with RD 153-39.4-091-01.

Field research was carried out by placing samples of steel plate to a depth of about 0.3 m in pits with soil treated with a modifier. The thickness of the studied soil layer around the samples on all sides was about 0.3 m. After 4 months, the samples were pulled out and, after thorough cleaning, weighed on an analytical balance.

The results of studies of the corrosion properties of soils are given in the table.

The research results show that when using reagent neutralization of oil-contaminated waste and soil as a modifier, the corrosive activity of soils in contact with metal structures located underground is significantly reduced. So, the introduction of the modifier in the amount of 15-45 mass. % of the weight of the soil allows to reduce the corrosion rate of steel in 1.36-1.52 times compared with the prototype. At the same time, the physicomechanical properties of soils increase, which helps to reduce the negative environmental impact on the protective properties of insulation. Improving the properties of the soil, the layers of the preparation and sprinkling of the gas and oil pipeline through the use of a modifier leads to the preservation of the protective properties of the insulation coatings, reduce corrosion of exposed areas in violation of the integrity of the insulation and increase the service life of pipes. In addition, the use of secondary products of reagent neutralization of oil-contaminated production waste and soil, which, in turn, require disposal or disposal, can reduce the cost of modifier purchase and increase the efficiency of gas and oil pipelines.

Claims (2)

1. A method of laying a gas and oil pipeline, including laying an insulated gas and oil pipeline in a trench on a preparation layer treated with a modifier, filling the gas and oil pipeline with a dusting layer treated with a modifier, followed by the formation of a boulder, characterized in that the product is used as a modifier for the reagent treatment of oil-contaminated and contaminated waste products 15-45 masses. % by weight of soil. 2. The method according to claim 1, characterized in that the product of the reagent neutralization of oil-contaminated industrial waste and soil contains hydroxide and calcium carbonate.