Introduction
In the upstream oil and gas industry, fluids produced from wells usually contain a mixture of crude oil, natural gas, produced water, and other impurities. Before these fluids can be transported to storage, export facilities, refineries, or other downstream systems, they must undergo initial gathering, separation, and handling.
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| GGS vs EPS overview: understand how permanent Group Gathering Stations and modular Early Production Systems handle oil and gas production from well gathering to downstream transfer. |
Although GGS and EPS perform related functions, they differ in their purpose, configuration, processing capability, and role in field development. Understanding these facilities is important for anyone working with or studying upstream oil and gas production operations.
In this guide, we explain what GGS and EPS are, how they work, their major components, the production process flow, and the key differences between them.
GGS and EPS: Meaning and Role in Oil and Gas
What Is a Group Gathering Station (GGS)?
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| Group Gathering Station (GGS) process flow from well production and header routing through heating, primary separation, crude treatment, storage, and transfer to a CTF, pipeline, or other receiving facility. |
A Group Gathering Station (GGS) is a permanent surface production facility that receives production fluids from multiple wells and provides the equipment needed for initial processing and fluid handling. Depending on field design and operating requirements, a GGS may include well headers, bath heaters, separators, storage tanks, heater treaters, pumps, and SCADA-based monitoring and control systems.
The GGS acts as a centralized production hub where crude oil, natural gas, and produced water are gathered and processed before being transferred to storage, transportation, or downstream facilities.
What Is an Early Production System (EPS)?
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| Early Production System (EPS) process flow from well production and temporary gathering through primary separation, production measurement, temporary storage, and transfer to a GGS, CTF, pipeline, or other receiving facility. |
An EPS generally provides basic production handling and primary separation, while more extensive treatment may be carried out at a permanent facility such as a GGS. Depending on the field configuration, crude oil from an EPS may be transferred to a nearby GGS or another processing facility for further treatment.
Major Components of a Group Gathering Station (GGS)
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| Group Gathering Station (GGS) process layout showing major oil and gas production components, from well gathering and separation to crude treatment, storage, gas handling, and downstream transfer. |
Well Headers and Gathering Manifolds
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| Well gathering manifold at a Group Gathering Station (GGS) showing Group Header, Test Header, and Zero Header for well fluid routing |
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Incoming wellhead flowlines entering the GGS manifold, equipped with isolation valves and pressure transmitters before diverting into production headers. |
- Group Header: Receives continuous production from normal producing wells. In the field configuration described in this article, the Group Header operates with a defined backpressure, typically around 3–5 kg/cm², subject to well conditions and overall facility design. This pressure regime allows production to enter the primary separation system under controlled operating conditions.
- Test Header: Routes the production stream from a selected individual well or well group to a dedicated Test Separator. It allows operators to evaluate parameters such as wellhead pressure, liquid production rate, gas production rate, Gas-Oil Ratio (GOR), and water cut without requiring the normal production stream from other wells to pass through the test system.
- Zero Header: Is used for low-pressure, depleted, or marginal wells whose available flowing pressure may not be sufficient to overcome the backpressure of the normal Group Header. In the field configuration described here, the Zero Header is maintained at near-zero gauge pressure or minimum practical backpressure, reducing the downstream pressure constraint on these low-energy wells and allowing them to continue producing where conventional gathering pressure could restrict flow.
Together, these header arrangements provide pressure-based production routing, allowing wells with different flowing pressures and production conditions to be directed through an appropriate gathering path before entering the separation and treatment systems.
Bath Heater
A bath heater, typically an indirect heating system, may be used to increase the temperature of the incoming production stream before separation or treatment. Controlled heating can improve process performance by:
- Reducing viscosity: Lowering crude-oil viscosity can improve fluid flow through gathering lines, piping, and process equipment.
- Supporting emulsion treatment: Heating can help weaken stable oil-water emulsions and improve subsequent phase separation.
- Supporting flow assurance: Under suitable operating conditions, heating may help reduce the risk of wax deposition or hydrate formation. The appropriate flow-assurance strategy depends on fluid properties and facility design.
The required operating temperature depends on factors such as crude properties, operating pressure, emulsion characteristics, fluid composition, and ambient conditions.
Separators: Two-Phase and Three-Phase
Separators are pressurized process vessels used to separate the phases present in produced well fluids. Depending on the production stream and facility design, a GGS may use two-phase or three-phase separators.
- Two-Phase Separator: Separates the production stream into a gas phase and a liquid phase. The liquid phase may contain both crude oil and produced water.
- Three-Phase Separator: Separates the production stream into natural gas, crude oil, and produced water, using differences in density, residence time, and internal separation devices where required.
The separator is a key primary-processing unit, reducing the multiphase well stream into separate streams that can be handled by downstream treatment, storage, and transfer systems.
Storage Tanks
Storage tanks provide temporary storage and surge capacity for separated or treated liquids within the GGS. Depending on the facility configuration, different tanks may be assigned to group production, test production, low-pressure production, or other operating services.
Storage tanks can provide several important operational functions:
- Stream Segregation: Separate storage arrangements can help manage different production streams and operating conditions.
- Settling: Retention time can allow remaining water and other entrained liquids to separate from crude oil.
- Operational Buffer: Tanks provide flexibility between continuous well production, treatment, measurement, and downstream transfer operations.
Before treated crude oil is transferred to a Central Tank Farm (CTF), pipeline, export system, or another receiving facility, it may need to meet the applicable quality requirements of the receiving system, including requirements for basic sediment and water (BS&W).
Heater Treater
A heater treater is a secondary treatment vessel used to improve the separation of water and gas from crude oil, particularly where additional treatment is required after primary separation.
Its operation may involve:
- Heating and Coalescence: Controlled heating reduces oil viscosity and promotes the coalescence and settling of dispersed water droplets.
- Water Removal and Crude Conditioning: Additional water separation helps improve crude-oil quality before storage or transportation.
- Gas Removal: Depending on vessel design and operating conditions, associated gas can be separated from the treated liquid stream.
In the GGS configuration described in this article, oil from Test and Zero Storage Tanks may be routed back through the heater-treater system for further treatment. This can help recover usable hydrocarbons and minimize avoidable product losses.
Pumps and Gas-Handling Equipment
Pumps and gas-handling equipment provide the flow and pressure management required to move separated liquids and gases between process equipment, storage systems, and downstream facilities. The exact equipment configuration depends on production rates, fluid properties, operating pressure, and downstream requirements.
- Crude Oil Transfer Pumps: Transfer treated or conditioned crude oil from storage tanks toward a Central Tank Farm (CTF), pipeline, export terminal, or other receiving facility. Pump type and capacity depend on the required flow rate and discharge pressure.
- Recycle Pumps: Where provided, recycle pumps can return recoverable crude oil, slop oil, or other designated liquids from storage or collection systems to the appropriate treatment or processing stage.
- Produced-Water Pumps: Where required, pumps can transfer separated produced water to a water-treatment, disposal, injection, or other designated handling system according to the facility configuration.
- Gas-Handling Equipment: Separated natural gas may pass through gas scrubbers, knockout vessels, control valves, metering systems, flare systems, or gathering lines before being routed to its designated destination.
- Gas Compressors: Where installed, compressors increase gas pressure when required for gas gathering, transportation, gas lift, fuel-gas systems, or other downstream applications. Compressors are configuration-dependent and are not a universal component of every GGS.
Together, these systems support the controlled movement of crude oil, produced water, and associated gas between the various processing stages and downstream facilities.
SCADA and Control Systems
A modern SCADA (Supervisory Control and Data Acquisition) system, often integrated with Programmable Logic Controllers (PLCs) and other control systems, provides centralized monitoring and operational control of GGS equipment.
Depending on the facility design, the control system can support:
- Process Monitoring: Monitoring parameters such as pressure, temperature, flow rate, tank level, and equipment status.
- Alarm and Shutdown Functions: Detecting abnormal operating conditions and initiating configured alarms or emergency shutdown actions where required.
- Data Logging: Recording production, well-test, process, and equipment data for operational analysis, reporting, and performance monitoring.
By integrating field instrumentation, automation, alarms, and operator supervision, SCADA improves process visibility, operational control, safety, and reliability across the GGS.
How Does a GGS Work?
A Group Gathering Station (GGS) works by collecting production fluids from multiple oil and gas wells, routing the well streams through the appropriate header system, separating the produced phases, treating the crude oil, and transferring the processed fluids to storage or downstream facilities.
The exact process flow varies with field design and facility configuration, but a typical GGS operation follows these systematic stages.
Well Gathering
The process begins at the producing wells. Multiphase production fluids containing crude oil, natural gas, produced water, and, where present, entrained solids travel through individual well flowlines toward the GGS.
Each well may arrive at a different flowing tubing-head pressure (FTHP) depending on reservoir energy, completion design, fluid properties, and artificial-lift conditions. At the station boundary, incoming flowlines enter the gathering manifold and header system.
The manifold and header network provides an important pressure-segregation and flow-routing point, directing each well stream toward the appropriate system based on well pressure, production conditions, and facility operating requirements.
Test Header
When an individual well's production performance or fluid characteristics need to be evaluated, its stream can be diverted from the normal production route into the Test Header, which directs the well to a dedicated Test Separator.
The testing system allows operators to measure and evaluate parameters such as:
- Liquid Production Rate: Gross liquid and, where applicable, net oil production rate.
- Gas Production Rate: Associated natural gas production.
- Gas-Oil Ratio (GOR): The ratio of produced gas to produced oil, useful for monitoring well and reservoir performance.
- Water Cut: The percentage of water in the produced liquid stream.
- BS&W: Basic Sediment and Water content, where measured.
- Wellhead and Flowline Pressure: Operating pressure of the selected well and its flowline.
Well testing provides individual well performance data without requiring the entire field production stream to pass through the test system. After testing, the well can be returned to its normal production header according to the field operating procedure.
Group Header and Zero Header Operations
Normal producing wells with sufficient flowing pressure are routed through the Group Header for continuous bulk production.
- Group Header: In the field configuration described here, the Group Header operates at approximately 3–5 kg/cm², subject to well conditions, separator pressure, production requirements, and facility design. This controlled backpressure provides a defined operating condition for routing the combined production stream toward the primary separation system.
- Zero Header: Low-pressure, depleted, or marginal wells that may not have sufficient flowing pressure to overcome the normal Group Header backpressure can be routed through the Zero Header. In the configuration described here, the Zero Header is maintained at near-zero gauge pressure or minimum practical backpressure. Reducing the downstream pressure constraint can allow these low-pressure wells to continue producing where the normal gathering pressure would otherwise restrict flow.
The Group, Test, and Zero Header arrangements therefore allow wells with different pressure and production conditions to be routed through an appropriate gathering path before entering downstream processing equipment.
Separation
After header routing and, where provided, indirect preheating through bath heaters, the multiphase production stream enters the primary separation system. Heating can reduce crude-oil viscosity and, under certain operating conditions, support flow assurance and improve separation performance.
Depending on the facility configuration, the GGS may use two-phase or three-phase separators:
- Two-Phase Separator: Separates the incoming stream into a gas phase and a liquid phase. The liquid phase may contain crude oil and produced water.
- Three-Phase Separator: Separates the production stream into natural gas, crude oil, and produced water, using density differences, residence time, and internal separation devices where required.
The separated streams are then routed to their designated downstream systems. Gas may be directed to gas-handling equipment, produced water to the designated water-handling or treatment system, and crude oil toward further treatment.
Treatment
Primary separation removes a significant portion of the free gas and water from the production stream, but crude oil may still contain dispersed water and residual associated gas. Where additional treatment is required, the crude is routed to a Heater Treater for further conditioning.
The treatment process may involve:
- Heating and Coalescence: Controlled heating reduces oil viscosity and promotes the coalescence and settling of dispersed water droplets.
- Water Removal and Crude Conditioning: Additional water separation improves crude quality before storage or transportation.
- Gas Removal: Depending on vessel design and operating conditions, remaining associated or flash gas can be separated from the crude.
In the GGS configuration described in this article, crude collected in designated Test or Zero Storage Tanks may be pumped back through the Heater Treater system for further processing. This allows recoverable hydrocarbons to be returned to the appropriate treatment route and helps minimize avoidable product losses.
Treatment continues until the crude meets the applicable quality requirements of the receiving, storage, or transportation system.
Storage and Transfer
Once treated, crude oil is routed to the appropriate storage tanks, which provide temporary inventory and operational buffer capacity between continuous well production, treatment, measurement, and downstream transfer.
From storage, crude-oil transfer pumps move the treated crude toward a Central Tank Farm (CTF), pipeline network, export facility, refinery, or other designated receiving facility, depending on the field configuration.
At the same time, separated gas and produced water follow their respective handling routes. Throughout the process, SCADA and control systems can monitor parameters such as pressure, temperature, flow rate, tank level, equipment status, alarms, and other operating conditions.
GGS Process Flow in Simple Terms
Well Production → Header Routing (Group/Test/Zero) → Bath Heating, Where Required → Primary Separation → Crude Treatment → Storage → Pump Transfer to CTF, Pipeline, or Other Receiving Facility
How Does an EPS Work?
An Early Production System (EPS) is designed to start hydrocarbon production quickly before permanent production infrastructure is fully constructed. It provides essential, modular equipment for receiving, separating, measuring, storing, and transferring production fluids during the appraisal and early development phases of an oil and gas field.
A typical EPS operation follows these structured stages:
Well Production and Gathering
Multiphase fluids from one or more newly drilled or appraisal wells travel through temporary flowlines to an EPS receiving manifold. The incoming well stream may contain crude oil, natural gas, produced water, and minor formation impurities.
The receiving and gathering arrangement directs the well fluids toward the appropriate separation equipment while allowing operators to monitor the incoming production conditions.
Primary Separation
The multiphase well stream enters a separation unit where the produced phases are separated according to the EPS configuration.
- Two-Phase Separation: Separates associated natural gas from the bulk liquid stream. The liquid phase may contain crude oil and produced water.
- Three-Phase Separation: Separates the production stream into natural gas, crude oil, and produced water using gravity separation, residence time, and internal separation devices where provided.
The separated streams are then routed to their respective measurement, storage, treatment, disposal, or transfer systems.
Measurement and Production Monitoring
Measurement equipment and metering systems record important production and operating data used to evaluate individual wells and early field performance.
Depending on the EPS configuration, monitored parameters may include:
- Gross liquid production and net oil production
- Associated gas production and Gas-Oil Ratio (GOR)
- Water production and water cut
- Flowing tubing-head pressure (FTHP)
- Production temperature and other operating parameters
This production data helps operators and reservoir engineers evaluate well performance, production trends, reservoir behavior, and requirements for future permanent production facilities.
Storage and Transfer
Separated crude oil is directed to temporary storage tanks, which may include bolted steel tanks, mobile tanks, or other suitable storage systems depending on the project design.
Because an EPS is generally designed for early-stage production and basic processing, it may not include all of the secondary treatment equipment found in a permanent GGS. Where additional crude treatment is required, the produced oil may be transferred by pumps, tankers, or other suitable transport systems to a Group Gathering Station (GGS), Central Tank Farm (CTF), export facility, or another receiving facility.
Produced gas and water are routed through their designated gathering, utilization, treatment, reinjection, or disposal systems, depending on the EPS configuration and applicable operating requirements.
Transition to Permanent Facilities
As field development progresses, permanent production infrastructure such as a GGS or Central Processing Facility (CPF) can be commissioned to handle the production from the developed wells.
Once the permanent system is ready, well production can be transferred from the temporary EPS arrangement to the permanent facilities. The modular EPS equipment can then be decommissioned, relocated, or redeployed for another well, field-development phase, or exploration area, depending on project requirements.
EPS Process Flow Summary
Well Production → Temporary Gathering & Receiving → Primary Separation → Production Measurement → Temporary Storage → Transfer to GGS, CTF, or Other Receiving Facility
GGS vs EPS: Key Differences
Although Group Gathering Stations (GGS) and Early Production Systems (EPS) both handle production fluids from oil and gas wells, they serve different roles in the field development lifecycle. A GGS is generally designed as a permanent surface production facility for long-term gathering, separation, treatment, storage, and transfer, while an EPS is typically a temporary or modular production system used to establish early production before permanent infrastructure is fully available.
The exact configuration of either facility can vary depending on field conditions, production rates, fluid properties, well pressures, operator requirements, and downstream infrastructure.
| Parameter | Group Gathering Station (GGS) | Early Production System (EPS) |
|---|---|---|
| Primary Purpose | Long-term gathering, separation, treatment, storage, and transfer of production fluids | Early production, initial fluid handling, and production data collection before permanent facilities are available |
| Development Stage | Long-term field production and ongoing operations | Mainly appraisal, early development, or interim production |
| Facility Type | Generally permanent, fixed surface infrastructure | Typically temporary, modular, or skid-mounted |
| Production Gathering | Collects production from multiple wells through gathering flowlines, headers, and manifolds | Receives production from one or more wells through temporary or modular gathering arrangements |
| Header System | May include Group, Test, and Zero Headers, depending on field configuration | Generally uses a simpler receiving or gathering arrangement suited to the temporary facility |
| Primary Separation | May use two-phase or three-phase separators according to production and process requirements | May use modular two-phase or three-phase separation equipment depending on production requirements |
| Crude Treatment | May include bath heaters, heater treaters, and other treatment equipment depending on crude and facility requirements | Typically focuses on basic production handling and primary separation; additional treatment may be performed at a GGS or another facility |
| Storage | Uses dedicated storage tanks sized and configured for production and operating requirements | Uses temporary or modular storage tanks suited to the EPS configuration |
| Production Testing | May include a Test Header and Test Separator for individual well testing | Typically uses metering and monitoring equipment to evaluate well and early field performance |
| Gas Handling | May include gas scrubbers, flare systems, compressors, metering, or other gas-handling equipment depending on facility design | Gas handling depends on the EPS configuration and may include flaring, fuel-gas use, or connection to a local gathering system |
| Monitoring & Control | Typically includes SCADA, PLC-based controls, instrumentation, alarms, and emergency shutdown systems | Uses instrumentation, metering, and control systems appropriate to the temporary or modular facility |
| Transfer Destination | May transfer treated or conditioned crude to a Central Tank Farm (CTF), pipeline, export facility, or other receiving system | May transfer produced crude to a GGS, CTF, export facility, or other receiving system for further handling or treatment |
| Mobility & Flexibility | Fixed facility designed around long-term field production requirements | Modular and potentially relocatable or redeployable as project requirements change |
| Field Lifecycle Role | Forms part of the permanent surface production infrastructure | Provides an early-production bridge until permanent production facilities become available |
Key Takeaway
The main difference between a GGS and an EPS is their role, permanence, and position within field development.
- GGS: Generally serves as a permanent surface production hub for gathering and processing production from multiple wells before transferring the resulting streams to downstream facilities.
- EPS: Typically provides a temporary or modular production solution that allows operators to start production earlier, monitor well performance, and handle initial production while permanent facilities are being developed or commissioned.
The specific equipment, operating pressure, processing capacity, storage arrangement, treatment requirements, and downstream transfer method can vary significantly with field characteristics, production profile, operator requirements, and facility design.
Applications of GGS and EPS
Group Gathering Stations (GGS) and Early Production Systems (EPS) are used at different stages of an oil and gas field's development lifecycle. Their specific applications depend on the field's production profile, development strategy, well conditions, and available surface infrastructure.
Applications of a GGS
A Group Gathering Station (GGS) is generally used as a permanent surface production facility for long-term field operations. Common applications include:
- Field Gathering: Collecting production fluids from multiple oil and gas wells through gathering flowlines, headers, and manifolds.
- Primary Separation and Treatment: Separating produced gas, crude oil, and water and, where required, providing additional crude-oil treatment through equipment such as bath heaters and heater treaters.
- Well Testing and Production Monitoring: Providing dedicated test facilities, such as Test Headers and Test Separators, for evaluating individual well performance.
- Storage and Transfer: Storing produced or treated crude oil and transferring it to a Central Tank Farm (CTF), pipeline, export facility, or other receiving system.
- Gas and Water Handling: Routing associated natural gas and produced water to their designated gathering, treatment, utilization, or disposal systems.
- Centralized Operations: Providing centralized instrumentation, SCADA, safety systems, and operational control for ongoing production activities.
Applications of an EPS
An Early Production System (EPS) is typically used as a temporary or modular production solution during appraisal and early field development. Common applications include:
- Early Production Startup: Enabling hydrocarbon production before permanent production facilities are fully constructed and commissioned.
- Field Appraisal: Providing production data that helps evaluate well productivity, fluid characteristics, and early field performance.
- Primary Fluid Handling: Providing basic gathering, separation, measurement, temporary storage, and transfer of produced fluids.
- Temporary Production Infrastructure: Providing a practical production route while permanent surface facilities and export infrastructure are being developed.
- Transition to Permanent Facilities: Continuing early production until a GGS, Central Processing Facility (CPF), or other permanent production system becomes available.
In Simple Terms
- GGS: A generally permanent facility for long-term production gathering, separation, treatment, storage, and transfer.
- EPS: A typically temporary or modular system for early production, basic processing, measurement, and field-development support.
Advantages of GGS and EPS
Both Group Gathering Stations (GGS) and Early Production Systems (EPS) provide important operational benefits, but their advantages are suited to different stages of oil and gas field development.
Advantages of a GGS
A GGS provides several advantages for long-term production operations:
- Centralized Production: Consolidates production from multiple wells into a centralized surface facility, simplifying gathering and process management.
- Integrated Processing: Provides primary separation, crude-oil treatment, storage, and transfer within an integrated production system, depending on facility design.
- Well Performance Monitoring: Dedicated test headers and test separators support individual well testing and monitoring of parameters such as production rate, GOR, and water cut.
- Operational Control and Safety: SCADA, instrumentation, alarms, and emergency shutdown systems provide centralized monitoring and control of production operations.
- Comprehensive Fluid Handling: Provides designated systems for managing crude oil, associated gas, and produced water according to the facility's operating and downstream requirements.
Advantages of an EPS
An EPS provides flexibility during the appraisal and early development stages:
- Earlier Production Startup: Allows hydrocarbon production to begin before permanent production facilities are fully constructed and commissioned.
- Rapid Modular Deployment: Modular equipment can generally be installed and commissioned more quickly than large permanent production facilities.
- Early Production Data: Provides useful information on well productivity, production rates, fluid characteristics, and field performance to support future development planning.
- Operational Flexibility: Modular equipment can be modified, expanded, relocated, or redeployed depending on project requirements.
- Interim Production Solution: Provides a temporary production route between initial well completion and the availability of permanent surface production infrastructure.
In Simple Terms
- GGS: A generally permanent, integrated facility for long-term gathering, separation, treatment, storage, and transfer of production fluids.
- EPS: A typically temporary or modular solution for early production, basic processing, measurement, and field-development support while permanent facilities are being developed.
Frequently Asked Questions (FAQs)
What does GGS stand for in the oil and gas industry?
GGS stands for Group Gathering Station. It is generally a permanent surface production facility used to gather production from multiple oil and gas wells and provide functions such as phase separation, crude-oil treatment, storage, monitoring, and transfer, depending on the facility configuration.
What does EPS stand for in the oil and gas industry?
EPS stands for Early Production System. It is typically a temporary, modular, or skid-mounted surface production facility used to establish early hydrocarbon production, perform initial fluid handling, and collect production data before permanent production infrastructure is fully available.
What is the main difference between GGS and EPS?
The main difference is their role and stage of field development:
- GGS: Generally a permanent production facility designed for long-term gathering, separation, treatment, storage, and transfer of production fluids.
- EPS: Typically a temporary or modular production system used for early production, basic processing, measurement, and field-development support.
What is the purpose of a Group Header in a GGS?
The Group Header collects continuous production from normal producing wells and directs the combined stream toward the main production separation system. In the field configuration described in this article, it operates at approximately 3–5 kg/cm², subject to well conditions, separator pressure, and overall facility design.
What is a Zero Header in a GGS?
A Zero Header is used for low-pressure, depleted, or marginal wells that may not have sufficient flowing pressure to overcome the normal Group Header backpressure. In the configuration described here, it is maintained at near-zero gauge pressure or minimum practical backpressure, reducing the downstream pressure constraint on these wells and allowing them to continue producing where higher gathering pressure could restrict flow.
What is the purpose of a Test Header in a GGS?
A Test Header routes the production from a selected individual well to a dedicated Test Separator. This allows operators to evaluate parameters such as liquid production rate, gas production rate, Gas-Oil Ratio (GOR), water cut, BS&W where measured, and operating pressure without requiring the entire field production stream to pass through the test system.
What is the difference between a two-phase and three-phase separator?
- Two-Phase Separator: Separates the production stream into gas and liquid phases. The liquid phase may contain both crude oil and produced water.
- Three-Phase Separator: Separates the production stream into natural gas, crude oil, and produced water using differences in density, residence time, and internal separation devices where provided.
Does an EPS have a Heater Treater?
An EPS typically may not include a Heater Treater, because many EPS configurations are designed primarily for early production, basic separation, measurement, storage, and transfer. Where additional crude treatment is required, the produced oil may be transferred to a GGS or another suitable treatment facility.
Where does crude oil from an EPS go?
Depending on the field configuration, crude oil from an EPS may be directed to temporary storage tanks and then transferred by pumps, road tankers, pipelines, or other suitable transport systems to a Group Gathering Station (GGS), Central Tank Farm (CTF), export facility, pipeline system, or another receiving facility.
Why is an EPS used before a permanent GGS is available?
An EPS allows operators to start hydrocarbon production earlier, evaluate well performance, and collect production data while permanent surface production infrastructure is being designed, constructed, and commissioned.
How does SCADA help in GGS operations?
SCADA (Supervisory Control and Data Acquisition) provides centralized monitoring and control of GGS operations. Depending on the facility architecture, it can monitor parameters such as pressure, temperature, flow rate, tank level, equipment status, alarms, and shutdown conditions, helping operators supervise the production process and respond to abnormal operating conditions.
Can an EPS be relocated?
Yes. Because EPS facilities are commonly designed with modular or skid-mounted equipment, they can potentially be modified, decommissioned, transported, and redeployed when project requirements change. The actual mobility depends on the equipment design, site conditions, and project configuration.
Conclusion
Group Gathering Stations (GGS) and Early Production Systems (EPS) play important roles in upstream oil and gas production, but they serve different purposes within the field development lifecycle.
An EPS is typically a temporary or modular production system used to start hydrocarbon production, perform initial fluid handling, measure production, and evaluate early well performance while permanent infrastructure is being developed.
A GGS, in contrast, is generally a permanent surface production facility designed for long-term gathering, separation, crude-oil treatment, storage, monitoring, and transfer of production fluids from multiple wells. Depending on the field configuration, it may include Group, Test, and Zero Headers, separators, heater treaters, storage tanks, pumps, and SCADA-based monitoring and control systems.
Understanding the working process, major components, applications, and differences between GGS and EPS helps explain how production fluids are gathered and processed from the wellhead through surface production facilities and onward to downstream systems.
The exact configuration, operating pressure, equipment, treatment requirements, and transfer arrangements can vary according to field conditions, production characteristics, operator requirements, and facility design.
