Материал: Russian Journal of Building Construction and Architecture

Russian Journal of Building Construction and Architecture

From then on exploration drilling began for contouring the oil fringe in parallel with exploration gas drilling. Exploration oil drilling finished in 1951. By that time the main well stock had been drilled. In 1949 in order to sustain the formational pressure in the gas cap, some of the gas well stopped being explored and in 1952 the exploration of the gas cap was completely cut short [12].

Originally the oil wells were operated as a fountain but gradually as the formational pressure dropped, bottomhole pumping was introduced. The gas cap of the Bobrikovskiy, Kyzelevsk and Cherepetsk horizons was developed by 19 wells, the oil fringe was operated by 67 wells. In order to sustain the formational pressure as well as consider the possibility of designing an underground gas storage in this field, in 1960 and 1961 there was a trial pumping of gas into the wells located within the gas cap. Since 1966 along with the oil mining gas had been routinely pumped followed by its section during the winter season [12].

The operation of the oil fringe continued up until 1985. As of now, in the YelshanoKurduymsk area more than four hundred well have been drilled for various purposes. The Yelshano-Kurduyskaya anticline was established as part of the expansive YelshanoKurduymsk raise and has a distinct representation in the landscape these days. The structure spans 12 km from North to East and 8 km from North to West. The raise amplitude in the Bobrikovsk, Kyzelovsk and Cherepetsk horizons is 100 m.

2. Lithological and stratigraphic characteristics of collecting rocks. In the YeshanoKurdyumsk underground gas storage there are two independent gas storages, i.e. depleted fields of the Bobrikovsk and Kyzelovks horizons which are significantly different in their lithology and petrophysical characteristics. One of the distinct features of designing a reservoir of the Bobrikovsk-Kyzelovsk field is its “two-storeyed” structure. The upper level is a terrigenous one (Bobrikovsk) and the lower one is a carbonate one (Kyzelovsk). The collecting layers of the Bobrikovsk horizon are mutually connected and the areas of the girth between the Bobrikovsk and Kyzelovks horizons is not consistent resulting in a “gap” between them. Therefore these fields can be considered as a single reservoir.

The Bobrikovsk horizon is represented with sand and clay rocks with the thickness from 2 to 13 m. The collectors are sandstone with the thickness of collectors varying from 0 to 9.3 m. The fields of the Kyzelovsk horizon are represented with carbonate rocks with two distinct types of lithological and physical characteristics: the upper (productive) abd lower (unproductive) one with the total thickness from 7.3 to 20.0 m. Тhe thickness of the productive pack ranges from 6.0 to 17.0 m.

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The Tula horizon. The field of the horizon was introduced into gas mining in February, 1948. In 1958 the gas field of the Tula horizon was almost depleted and thus a decision was made to employ it as underground gas storage. The deposits of the Tula horizon are made up of clay containing sublayers of sandy stone and limestone. The total thickness of the Tula horizon ranges from 22 to 41 m.

3. Major technical and economic characteristics of the object. The industrial activities in the Yelshankiy underground gas storage involve continuous operation of technological gaspumping equipment in an underground gas storage, its selection and transportation to consumers. The major parameters of the operation of the Yelshankiy underground gas storage in the horizons are given in Table 1.

Таble 1

Characteristics of the operation of the underground gas storage in the horizons

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Russian Journal of Building Construction and Architecture

4. Description of a technological process and technological schemes. Drying carbohydrate gases is an important part of preparing natural gas for transportation along the pipelines and to consumer [10, 13, 15]. The depth of drying is determined with particular industrial requirements.

In a technological process on a combined setup for gas drying and purification the absorption process using a diglycol solution was used. The absorption as part of a complex preparation of gas involves two phases, i.e. a liquid one (diglycol) and gas one (moist and gas) and the substance is converted from the gaseous into the liquid phase. Absorption is thus a type of mass transfer (mass exchange). The liquid phase consists of an absorber and absorbent. An absorber is a solution (a diglycol solution) of active components, i.e. diglycols taking part in a chemical reaction with an absorbent (gas). Absorption is cost-effective for preparing (drying and purification) of large natural gas flows. The use of liquid absorbents for drying gas compared to solid ones has the following advantages:

––possibility of drying gases that are included in substances that intoxicate solid absorbents;

––continuous process;

––simple automatic management system;

––drying of gas till a lower dew point.

During absorption of moist from gas the process will continue till partial pressure of absorbed moist in the gas reaches that over the liquid. The moist absorbed from it as a result of subsequent desorption taking place as an absorber is heated, the pressure in the system drops or blowout gas is supplied. Moisture is released from the solution and enters the gaseous stage as its equilibrium pressure is higher than that in the desorbed absorber (diglycol). Desorption is the most complex stage in a technological scheme of drying of gas that requires considerable amounts of energy.

A combination of absorption and desorption allows an absorber to be multiply used and release a pure absorbed component. For that after the absorber (saturated diglycol) a solution undergoes desorption where a component is extracted and the regenerated solution (a diglycol solution) free from the component returns for absorption into a mass-exchange device, i.e. an absorber. For such a scheme the solution circulates in the system as an “absorber-desorber- absorber” (in circle) with absorber not being used. There are some absorbent losses caused by a mechanical blow of the absorbent in the absorber by a gas flow and thermal decomposition on the surface in the regenerator with possible leaks in the system due to leakage of flanged joints and gland seals. Losses per a unit of time are immeasurably small compared to those in the solution circulating in the system.

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As absorption takes place, there is mass exchange on the surface of phase contiguity (liquid –– gas). Therefore absorption devices have a developed gas-liquid contact surface.

5. Collection of gas selected from underground gas storages. Collection of gas from the Tula and Bobrikovsk-Kyzelovsk horizons takes place according to the X-ray scheme in the following way. The gas coming to the bottom of an operating well under the effect of a pressure drop in the layer goes up the fountain pipes to the mouth of the well. From the wells gas comes into individual overlapping gas pipelines joining the mouths of the wells with the gas collection station through the mouth equipment, fountain reinforcement and pipeline binding.

In gas regulating station 1 gas comes along the overlapping gas pipelines from 28 wells, in gas regulating station 2 from 41 wells, in gas regulating station 3 from 60 wells, gas regulating station “Tula” from 22 wells.

In the input lines from each well there is:

––switching of the wells into the line of pipeline purging into a candle of manual multipurpose reinforcement;

––freeing of the system from gas into a candle of manual multipurpose reinforcement;

––instalment of gas regualting devices, gas consumption control, cutoff multipurpose reinforcement;

––switching of weach well into a separator for measuring gas consumption;

––reverse technological lines;

––dumping the liquid from the separators into the drainage vessel;

––purging of each overlapping pipeline and freeing of the technological system from gas.

In the gas regulating station gas comes into underground gas collectors for complex preparation and then along the input collectors it is transported into the gas collector from where it is distributed along four technological lines for gas distribution and separation and finally it is supplied to the technological lines to be cleaned and dried. Cleaned and dried according to the Gazprom Specifications 089-2010, it is supplied into the main gas pipelines. For automatic maintenance of gas consumption in the technological line there are special devices and crane-controllers at the outlet.

6. Experimental operation. Issues. During experimental operation of the area for preparation of gas from the underground gas storage, a number of issues that affected the technological as well as economic aspects of the process were identified:

–– failure of a fire glycol regenerator due to depressurization and deep failure of a thermosiphon owing to overheating. As a result, large-scale repairs of the fire regenerator had to annually take place;

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Russian Journal of Building Construction and Architecture

––pollution and salinification of diethylene diglycol due to ineffective operation of separators of the first stage purification and diethylene diglycol filters. As a result, it was necessary that the diglycol system is completely replaced at least every other year;

––pollution of internal elements of absorbers, which resulted in the reduction of the efficiency of mass-exchange plates. As a result, this affected the performance of absorbers, which had a negative impact on the technological process;

––clogging of heat-exchange device pipes resulting in the reduction in the efficiency of heat exchange, higher consumption of fuel gas onto the fire glycol regenerator for specified parameters of glycol.

The combination of all of these contributed to an overall reduction in the efficiency of gas preparation, which had a negative effect on the specified parameters of the dew point temperature. Table 2 shows the overall data on economic costs for operating a gas preparation station.

As part of renovation of industrial gas structures, a new station for complex gas preparation was built. Two stages of gas separation (primary gas separators and gas separators with a washing section), complex purification of diethylene diglycol (coal filter, cartridge filter, magnetic processing tool), improved mass-exchange plates of absorbers and fire glycol regenerators allowed the specified temperature of the dew point to be reached while reducing operating costs of gas preparation stations.

During the precommissioning work it was shown that the entire volume of diethylene diglycol going through a pump came into the fire regenerator. As a result, even under a load of one

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