Possible alternatives of locating a gas separating unit in layouts of plants for preparing gas for transporting

and for field booster compressor stations (BCS) are examined. Designs of a gas cleaning unit of the first

separation stage with a built-in lock interceptor based on vertical apparatuses are presented. The dynamics

of development of separating equipment for protecting BCS is discussed. The problem of ambiguities in

current normative-technical documents relating to technical specifications of gas preparing equipment

before the BCS is identified.

Any field gas preparing plant is provided with a separating unit that ensures the desired degree of gas cleaning from

liquid and solid (mechanical) impurities and protects the next equipment.

Usually, the products recovered from the reservoir include:

• liquid (water, methanol, condensate, etc.) and mechanical impurities (in varying degrees in various objects);

• salts dissolved in stratal water; and

• liquid locks whose volume depends on the diameter and length of the gathering line and the ground relief.

Ingress of liquid locks into field objects is common for both gas and gas condensate deposits.

Note that the gas parameters (pressure, throughput, temperature, liquid content, etc.) before the input separation

units vary considerably with time.

In general, at booster compressor stations (BCS), an additional separating unit is not provided past complex gas

preparation plants (CGPP): the technology and equipment of the plants ensure cleaning of the gas. An exception may be dry-

ing with a solid sorbent, in which case a filter may have to be installed after the adsorber.

When a BCS is constructed and installed before a CGPP, the gas pumping unit (GPU) needs to be protected from

liquid and mechanical impurities. The protective unit may be of two versions.

In the first version, a gas separating unit (Fig. 1a) is used before the BCS. The characteristic feature of this version

(Fig. 1b) is that it is necessary to ensure efficient separation throughout the remaining period of development of the field tak-

ing account of ingress of liquid locks, mechanical impurities, salts, hydrate formation inhibitors, and other liquids. Actual

operation conditions cannot always be predicted many years in advance. So, the separating unit, as shown in Fig. 1b, may not

provide reliable protection to GPU in the changed operation conditions. In such a case, a new separating unit (Fig. 1c), which

is designed taking account of the experience of operation of the plant is provided before the BCS and the existing separating

unit remains before the CGPP for protection of the GPU from the condensation moisture.

Liquid Lock Interception. Appearance of liquid locks adversely affects operating efficiency of gas separation units.

To undo (or to reduce to the minimum) this effect, Central Design Bureau of Oil Equipment (TsKBN) has developed hori-

zontal lock interceptors which can be used quite efficiently in various fields [1].

Chemical and Petroleum Engineering, Vol. 49, Nos. 5–6, September, 2013 (Russian Original Nos. 5–6, May–June, 2013)

SEPARATING EQUIPMENT FOR PROTECTING

FIELD BOOSTER COMPRESSOR STATIONS

B. S. Palei, V. A. Tolstov, A. P. Romashov,and E. V. Nemova

Central Design Bureau of Oil Equipment, Subsidiary of Gazprom Company (TsKBN Gazprom), Russia; e-mail: Alexandr.Romashov@ckbn.ru.Translated from Khimicheskoe i Neftegazovoe Mashinostroenie, No. 5, pp. 14–16, May, 2013.

0009-2355/13/0506-0299 ©2013 Springer Science+Business Media New York 299

For economy of space occupied by installations in northern facilities and marine platforms, we designed vertical lock

interceptors (Fig. 2), which, in conjunction with a vertical filter-separator or a filtration section installed in the same housing,

ensure efficient gas cleaning from liquid and mechanical impurities and reliable operation of compressor units.

Dynamics of Development of Separating Equipment for Protecting Field BCS. Dust catchers of linear com-

pressor stations (CS) were used at Medvezhie field during 1980–1985; because of inefficient operation, they were updated

into separators; two-stage protection units, viz., dust catchers and filters-separators, were employed at subsequent BCS.

Two-stage protection units, viz., separators and filter separators were employed at Urengoi oil and gas condensate

field (OGCF), Senomanian stage, during 1990–1995.

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Unstrippedgas

Unstrippedgas

Unstrippedgas

Gasseparating

unit

Gasseparating

unit

Gasseparating

unit

Gasseparating

unit

Complex gaspreparation

plant

Complex gaspreparation

plant

Complex gaspreparation

plant

To pipeline

To pipeline

To pipeline

BCSStage II

BCSStage II

BCSStage I

BCSStage I

a

b

c

Fig. 1. Schematic configuration of gas separating unit in plant for gas preparation for transport and field BCS.

Fig. 2. Schematic design of gas cleaning unit of the first separation stage: a) two-stage unit with built-in lock

interceptor at input stage (Bovanenkovo gas condensate field (GCF)); b) separator of the first stage with a built-in

lock interceptor (Achimgaz, Urengoi oil and gas condensate field (OGCF)).

Separators with a scrubbing unit were employed at Yamsoveiskoe OGCF during 2002–2007; because of increased

withdrawal of gas for ensuring its reliable and efficient cleaning and reduced hydraulic resistance of the piping system,

the project provides for updating of the existing separators (minicyclones and filter elements, Fig. 3a) and construction of an

additional separating unit.

Separators with a scrubbing unit, which ensure liquid entrainment of up to 20–25 mg/m3 (Fig. 3b), were employed

at the Yamburg OGCF during 2005–2010 to prevent access of salts into the diethylene glycol regeneration system; a GS-1

separator before the BCS, which is provided with a section of oval-cylindrical minicyclones and meshed elements (liquid

entrainment of up to 10 mg/m3), was tested at a UKPG-1V complex gas preparation plant; before this separator, an EP-103

lock interceptor and an S-1 separator of the first stage operate in the system; a separator with a scrubbing section and filter

cartridges, which ensured cleaning of the gas from liquid and mechanical impurities with entrainment of up to 5 mg/m3 was

tested at a UKPG-1 plant. Under conditions of lock ingress of liquid containing mechanical impurities, the input and scrub-

bing sections ensured reliable operation, but the filtration section was unreliable with regard to nonfailure operating time:

hydraulic resistance increased and throughput decreased. Taking this negative factor inherent to any type of filter elements

into account, TsKBN has been working on creating a reliable separator with liquid and mechanical impurity entrainment of

up to 5 mg/m3 without using filter cartridges for both gas and gas condensate fields.

Separators with a scrubbing section (design entrainment up to 20–25 mg/m3, actual up to 40 mg/m3) were employed

at the Zapolyarnyi OGCF during 2005–2010. The scrubbing section was not put into operation; to reduce entrainment to

5 mg/m3, the separator at the UKPG-3S was updated using minicyclones and filter cartridges (the nonfailure operation time

is currently two years).

Separators and filter separators were used at the Komsomolskoe field during 2003–2010. The filter separators failed

frequently because of gas overload of the separators of up to 50% of the rated load, so operation of the equipment will be

analyzed and computational study to ensure reliable operation of the BCS will be carried out.

Quality Requirements of Gas Entering GPU. At present, normative-technical documents are in effect at Gazprom

for designing, constructing, and operating facilities that reflect the specifications for process equipment of gas cleaning plants

at various types of CS (well-head and linear CS of gas fields (GF), BCS, CS of underground gas storage (UGS), etc.).

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Fig. 3. Filter separators: a) Yamsoveiskoe GCF, Zapolyarnyi OGCF; b) South-Russia GCF, Yamburg GCF.

In conformity with VRD 39-1.8-055–2002 “Standard Technical Specifications for Designing CS, BCS, and CS of

UGS” and STO Gazprom 2-3.5-051–2002 “Standards of Technological Designing of Trunk Pipelines,” the amount of solid

and liquid impurities in the gas past the cleaning plant should meet the manufacturer’s specifications for GPUs. Thus, selec-

tion of process equipment of gas cleaning plants for removing solid and liquid impurities depends on the type of GPU and

its protection to the desired extent.

The STO Gazprom 2-3.5-138–2007 “Standard Technical Specifications for Gas-Turbine GPUs and Their Systems”

sets the following requirements and content of impurities entering the centrifugal supercharger along with the gas: mechanical

impurities (dirt particles) not more than 3 mg/m3, of which particles larger than 20 μm must not exceed 0.15 mg/m3; the max-

imum moisture content is the saturation state under suction conditions (short-time content of liquid fractions is allowed),

in which case it is indicated that for BCS and CS of UGS the content of drop moisture is fixed by the specification for gas

compressor design (Author’s note).

The STO Gazprom 1-3.5-230–2008 “Standard Technical Specifications for Gas Preparing Devices at Compressor

Stations” indicates the following:

a) the impurity content in the gas at the dirt catcher outlet must be, mg/m3: solid (mechanical) – up to 1 (briefly, not

more than 100 h/yr – up to 3); liquid – up to 50 (briefly, not more than 100 h/yr – up to 100); cleaning efficiency based on

particles larger than 20 μm – 100%;

b) the impurity content in the gas at the filter-separator outlet must not be more than, mg/m3: solid (mechanical) – 1;

liquid – 5; cleaning efficiency based on particles larger than 10 μm – 100%.

In the referred documents, the impurity content in the gas is divided into solid (mechanical) and liquid. But in the

STO Gazprom 089–2010 “Combustible Natural Gas Supplied and Transported by Trunk Pipelines. Technical Specifications,”

mechanical impurities are defined as dust, resin, and low-volatile liquids in drop form contained in the combustible natural

gas stream. At the same time, in Table 1, point 10 of this STO it is indicated that mass concentration of mechanical impuri-

ties (in the natural gas supplied and transported by trunk pipelines) is not more than 0.001 mg/m3, which agrees with the

referred documents.

Thus, from the referred documents it follows that the requirements for gas cleaning before the superchargers are

ambiguous. This, in turn, injects uncertainty in the following: The requirements of which document are to be complied with

for designing gas cleaning equipment? Is it necessary to assign the cleaned gas quality requirements of a specific document

to a specific object (CS, BCS, BCS of UGS)? If yes, in what way? Because of diversity of quality requirements of the cleaned

gas before the superchargers, questions of methodological nature arise regarding the test of the equipment for confirmation

of their characteristics and of the equipment system (in the gas cleaning industry, no methodology and equipment system are

available for the determination of the diameter and number of particles of liquid impurities in the gas).

In light of the foregoing as well as of the fact that field BCS operates under other, more rigorous conditions compared

to CS of trunk pipelines, it is expedient to conduct R&D work and develop technical specifications of the gas preparation

equipment placed before field BCS.

REFERENCE

1. B. S. Palei and V. A. Tolstov, “Implementing field natural gas preparation processes by modern equipment,” in:

Current Problems and Scientific-Technical Solution to Engineering and Technology of Production, Extraction, and

Preparation of the Hydrocarbon Stock for Transport at Gas Condensate Fields: Materials of the Meeting of the

Committee “Production and Field Preparation of Gas and Gas Condensate” of the Scientific-Technical Council of

Gazprom, IRTs Gazprom, Moscow (2006).

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