Wet Gas Compression: Test Conditions and Similitude

2017 ◽  
Author(s):  
Dagfinn Mæland ◽  
Lars E. Bakken
Keyword(s):  
Oil Recovery ◽  
Performance Prediction ◽  
Oil And Gas ◽  
Mechanical Design ◽  
Performance Testing ◽  
Volume Ratio ◽  
Centrifugal Compressors ◽  
Wet Gas ◽  
Gas Compression ◽  
Compressor Design

Wet gas compression of gas/condensate/water provides a business opportunity for oil and gas producers. There are several opportunities of particular note: 1) As well tail-end production commences, the installation of sub-sea compressors will provide enhanced oil recovery and, if the subsea compressor is capable of handling liquids, the subsea process complexity can be dramatically reduced, thus decreasing capital investments and possibly operational costs. 2) Topside and Onshore projects can also be dramatically simplified. This is the case for both new installations and modification projects for which wet gas compression is a suitable solution. However, there are several challenges that need to be addressed before wet gas compression, by means of centrifugal compressors, can be considered as a robust commercial solution for future projects. This relates to the robustness of the mechanical design, effects on electrical systems, and issues related to performance. This paper will focus on challenges related to performance prediction and testing. For conventional dry gas compressor design, performance prediction is usually undertaken by the compressor manufacturer, utilising in-house know-how in impeller design and selection. This specialised knowledge is potentially unsuitable for predicting wet gas performance in the design phase; hence, a wet gas compressor design may not meet design requirements specified by the customer. It is typical that agreements on performance testing of centrifugal compressors state that these are to be conducted according to an international standard such as ASME PTC10 or ISO 5389. These standards require that the compressed gas is dry. However, for wet gas compressors, no such internationally established standards exist for performance evaluation. Several of the requirements stipulated in the standards are challenging to apply to wet conditions and they do not ensure similar conditions. Such parameters including the maximum permissible deviation in the specific volume ratio, Mach number and Reynolds number. It is clear that the path towards a standard for wet gas performance testing will require a substantial amount of effort in order to establish new requirements related to wet gas similarity. Based on wet gas compressor test experience, challenges and requirements related to low pressure inert fluid, compared with full pressure actual fluid tests, are analysed and discussed.

Performance Testing of Centrifugal Compressors: Schultz Compressibility Factors

2015 ◽  
Author(s):  
Matt Taher
Keyword(s):  
Equation Of State ◽  
Natural Gas ◽  
Performance Testing ◽  
Centrifugal Compressors ◽  
Real Gas ◽  
Gas Compression ◽  
Compressibility Factors

ASME PTC-10 [2009] recognizes inaccuracies involved in using the generalized charts to calculate Schultz compressibility factors for real gas compression. However, it neither addresses a method to develop the compressibility factors, nor does it specify when to use calculated compressibility factors rather than using generalized values. Using inaccurate generalized values for Schultz compressibility factors may lead to erroneous calculation of polytropic exponents and polytropic work. This paper employs the LKP equation of state to directly calculate Schultz compressibility factors for a mixture of hydrocarbons typically found in natural gas. The results are compared with the values of compressibility factors from the generalized compressibility charts.

Development of Test Stand for Measuring Aerodynamic, Erosion, and Rotordynamic Performance of a Centrifugal Compressor Under Wet Gas Conditions

2014 ◽  
Author(s):  
Matteo Bertoneri ◽  
Melissa Wilcox ◽  
Lorenzo Toni ◽  
Griffin Beck
Keyword(s):  
Oil And Gas ◽  
Performance Testing ◽  
Oil And Gas Industry ◽  
Test Stand ◽  
Liquid Volume ◽  
Wet Gas ◽  
Liquid Load ◽  
Test Loop ◽  
Gas Environment ◽  
Set Up

As the oil and gas industry addresses technology challenges for accessing gas reserves and enhancing the production of existing installations, wet gas compression becomes an important technology focus. When liquid is introduced into a compressor flow stream, the performance of the compressor is significantly influenced. Therefore, a concentrated effort is required to develop the tools to adequately predict the performance of the compressor when subjected to wet gas conditions. A series of tests were performed on a single stage compressor in a wet gas environment in order to provide empirical data for understanding how to predict wet gas performance. The compressor underwent aerodynamic, erosion, and rotordynamic performance testing. The tests were completed with a mixture of air and water at suction pressures of 10, 15, and 18.5 bar. The compressor was subjected to a multiphase flow with liquid volume fractions ranging from 0 to 3% (corresponding to a mass fraction of 73%) at three Mach numbers. Transient tests with liquid load variation were also done. This paper describes the test stand that was developed and operated for testing of the compressor in a wet gas environment. This includes a review of the overall test set-up, description of key test components and of the instrumentation installed on the compressor and the test loop. An overview of main test results is eventually shown.

Perspectives and Experience With Wet Gas Compression

2016 ◽  
Author(s):  
Grant O. Musgrove ◽  
Melissa A. Poerner ◽  
Griffin Beck ◽  
Rainer Kurz ◽  
Gary Bourn
Keyword(s):  
Oil And Gas ◽  
Liquid Mixtures ◽  
General Definition ◽  
Limited Information ◽  
Process Gas ◽  
Wet Gas ◽  
Gas Compression ◽  
Process Fluid ◽  
Separation Equipment ◽  
Definition Of

In oil and gas applications, gas-liquid mixtures of a process fluid are commonplace and the phases of the mixtures are separated upstream of pump or compressor machinery. Considering compressors, the separation of phases is important because the liquid causes the compressor to operate significantly different than with dry to affect the range, performance, and durability of the machine. Even with separation equipment, liquid can be ingested in a compressor by liquid carryover from the separator or condensation of the process gas. Additionally, there is no single definition of what is considered a wet gas. In this paper, the definition of wet gas from multiple applications is reviewed and a general definition for wet gas is formulated. The effects of wet gas on reciprocating, screw-type, and centrifugal compressors are reviewed to provide insight into how their operation is affected. The limited information for screw compressors is supplemented with multiphase effects in screw pumps.

Liquid CO2 Formation, Impact, and Mitigation at the Inlet to a Supercritical CO2 Compressor

2016 ◽  
Author(s):  
Melissa Poerner ◽  
Grant Musgrove ◽  
Griffin Beck
Keyword(s):  
Critical Point ◽  
Oil And Gas ◽  
Critical Parameters ◽  
Ambient Conditions ◽  
Performance Impact ◽  
Two Phase ◽  
Power Cycle ◽  
Wet Gas ◽  
Gas Compression ◽  
Liquid Co2

Cycle efficiency is one of the critical parameters linked to the success of implementing a Supercritical Carbon Dioxide (sCO2) power cycle in a Concentrating Solar Power (CSP) plant application. Ambient conditions often change rapidly during operation, making it imperative that the efficiency of the plant cycle be optimized to obtain the maximum power production when sunlight is available. Past analyses have shown that operating the cycle at the critical point provides the optimum efficiency for dry operation. However, operation at this point is challenging due to the dramatic changes in thermophysical properties of CO2 near the critical point and the risk of the fluid having a two-phase, gas-liquid state. As a result, there is a high likelihood that liquid can form upstream of the primary compressor in the sCO2 power cycle. This paper explores the potential for liquid formation when operating near the critical point and looks at the influence of liquid on the compressor performance. The performance impact is based on industry experience with wet gas compression in power generation and oil and gas applications. Options for mitigating liquid effects are also investigated, such as upstream heating, separation, or compressor internal controls (blade surface gas ejection). The conclusions of the paper focus on the risk, estimated impact on performance, and summary of mitigation techniques for liquid CO2 entering a sCO2 compressor.

Fouling Effects on Wet Gas Compressor Performance: An Experimental Investigation

2021 ◽  
Author(s):  
Dagfinn Mæland ◽  
Lars E. Bakken
Keyword(s):  
Oil Recovery ◽  
Failure Modes ◽  
Oil And Gas ◽  
High Reliability ◽  
Oil And Gas Industry ◽  
Successful Implementation ◽  
Gas Industry ◽  
Wet Gas ◽  
Dry Conditions ◽  
Compressor Performance

Abstract Achieving profitability in mature areas such as the Norwegian continental shelf forces the oil and gas industry to apply innovative solutions to increase oil recovery and to reduce both operational and investment costs. Wet gas compressors are promising machines for increasing oil recovery from existing fields and to allow for production from small satellite fields in the proximity of existing infrastructure. A prerequisite for successful implementation of subsea wet gas compressors high reliability. Knowledge of possible failure modes is important. The effect of performance degradation due to fouling has been observed during wet gas compressor testing at K-Lab and has initiated further work to better understand and quantify the effects of fouling in wet conditions compared to dry conditions. A test campaign was conducted at the Norwegian University of Science and Technology (NTNU) to investigate the effect of fouled centrifugal compressor performance in both wet and dry conditions. The results documenting these effects are presented together with a proposed model for correcting the effects of fouling between dry and wet conditions.

Matching of Gas Turbines and Centrifugal Compressors: Oil and Gas Industry Practice

2012 ◽  
Author(s):  
Matt Taher ◽  
Cyrus Meher-Homji
Keyword(s):  
Gas Turbine ◽  
Centrifugal Compressor ◽  
Gas Turbines ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Site Conditions ◽  
Centrifugal Compressors ◽  
Gas Industry ◽  
Compressor Design ◽  
Selection Of

Gas turbine driven centrifugal compressors are widely used in the oil and gas industry. In evaluating the optimum selection of gas turbine drivers for centrifugal compressors, one of the main objectives should be to verify proper integration and matching of the centrifugal compressor to its gas turbine driver. Gas turbines are of standard designs, while centrifugal compressors are specifically designed to meet customer requirements. The purchaser should clearly specify process requirements and define possible operating scenarios for the entire life of the gas turbine driven centrifugal compressor train. Process requirements defined by the purchaser, will be used by the compressor designer to shape the aero-thermodynamic behavior of the compressor and characterize compressor performance. When designing a centrifugal compressor to be driven by a specific gas turbine, other design requirements are automatically introduced to centrifugal compressor design. Off-design performance, optimum power turbine speeds at site conditions as well as optimum power margin required for a future-oriented design must all be considered. Design and off-design performance of the selected gas turbine at site conditions influences the final selection of a properly matched centrifugal compressor design. In order to evaluate different designs and select the most technically viable solution, the purchaser should have a clear understanding of the factors influencing a proper match for a centrifugal compressor and its gas turbine driver. This paper discusses criteria for evaluating the most efficient combination of a centrifugal compressor and its gas turbine driver as an integral package from a purchaser’s viewpoint. It also addresses API standard requirements on gas turbine driven centrifugal compressors.

Wet Gas Performance Analysis

2006 ◽  
Author(s):  
O̸yvind Hundseid ◽  
Lars E. Bakken
Keyword(s):  
Performance Analysis ◽  
Performance Prediction ◽  
Volumetric Flow Rate ◽  
Phase Changes ◽  
Direct Integration ◽  
Compression Performance ◽  
Wet Gas ◽  
Gas Compression ◽  
Performance Predictions ◽  
Fluid Properties

The growing interest in wet gas compressors calls for accurate methods for performance prediction. Present evaluation methods for compressor and pump performance fail when evaluating the compression of gases containing liquid. Gas compression performance predictions given in ASME PTC-10-97 and ISO 5318 are based on the method John M. Schultz proposed in 1962. This method assumes a polytropic compression path and is based on averaged gas properties of inlet and outlet condition. The polytropic compression path is defined by keeping pvn constant, where n is constant along the compression path. When employing the Schultz method there is a challenge in defining the polytropic constant. This is seen in cases where dry gas compressors are exposed to wet components and compressor efficiency estimates exceed 100%. Today’s computer technology makes a direct integration of the polytropic head (∫vdp) possible where actual fluid properties along the compression path are included. Phase changes along the compression path are included with this method. This enables a detailed prediction to be made of the actual volumetric flow rate for the various compressor stages. This paper reports the implementation of the direct integration procedure for wet gas performance prediction. The procedure enables generic wet gas compression to be studied which forms the foundation for performance analysis with variations in operation at conditions and fluid components and properties.

Integrated Wet Gas Compressor Test Facility

2015 ◽  
Author(s):  
Øyvind Hundseid ◽  
Lars E. Bakken
Keyword(s):  
Oil And Gas ◽  
Volume Fraction ◽  
Operating Conditions ◽  
Torque Control ◽  
Test Facility ◽  
Total System ◽  
Wet Gas ◽  
Gas Compression ◽  
Wide Range ◽  
The Impact

The potential production increase from new and existing oil and gas fields worldwide is huge. In some areas, stringent requirements for field recovery specified in the production licence call for the development and utilisation of novel technology concepts. Enhanced recovery may be achieved with wellhead boosting. For specific systems, the booster is preferably installed subsea, either on a single production well or a cluster of these. Development of rotor-dynamic multiphase pumps for topside and subsea applications was initiated at the mid-1980s. A wide range of these pumps are currently installed and in operation worldwide. They typically cover the gas volume fraction (GVF) range from 0 to 0.70. The ability to increase pressure is limited above GVF 0.9, clearly restricting the area of application. In essence, the development of wet gas compressors covering GVFs from 0.95 to 1.0 has been limited to the centrifugal concept, although an axial contra-rotating concept is available. Two new subsea compression systems will be installed, commissioned and in operation from 2015 for the Gullfaks and Åsgard fields on the Norwegian continental shelf (NCS). Their compressors are based on centrifugal and axial technology respectively. Subsea compression is currently being evaluated for several other field developments. The centrifugal compressor has proved to be a robust concept and dominates in the oil and gas industry. Both inert low-pressure and high-pressure real hydrocarbon fluid tests have shown that understanding of the fundamental wet gas compression mechanisms is limited. Evaluating the ability of the centrifugal stage to handle wet fluids has therefore been of specific interest. A wet gas test rig has been designed and built at the NTNU. Its objectives are to validate a wet gas compression system and to determine capabilities and constraints related to the impact of impellerstage performance: • fluid behaviour and dynamics • corrosion and erosion tolerance • surge suppression and stall avoidance • transient operating conditions, including fluctuations in GVF • novel high-precision shaft torque control (static and dynamic) • electric motor and driver response and interactions • total system control. The article focuses on the ongoing test campaigns and related challenges, including test facility design. Understanding the challenges involved is essential for identifying concept constraints at an early stage and ensuring system reliability and availability.

Prospects for Sub Sea Wet Gas Compression

2008 ◽  
Author(s):  
Lars Brenne ◽  
Tor Bjo̸rge ◽  
Lars E. Bakken ◽  
O̸yvind Hundseid
Keyword(s):  
Oil And Gas ◽  
Development Program ◽  
Oil And Gas Industry ◽  
Full Scale ◽  
Gas Field ◽  
Gas Industry ◽  
The North ◽  
Wet Gas ◽  
Gas Compression ◽  
Petroleum Sector

Wet gas compression technology renders possible new opportunities for future gas/condensate fields by means of sub sea boosting and increased recovery for fields in tail-end production. In the paper arguments for the wet gas compression concept are given. At present no commercial wet gas compressor for the petroleum sector is available. StatoilHydro projects are currently investigating the wet gas compressors suitability to be used and integrated in gas field production. The centrifugal compressor is known as a robust concept and the use is dominant in the oil and gas industry. It has therefore been of specific interest to evaluate its capability of handling wet hydrocarbon fluids. Statoil initiated a wet gas test of a 2.8 MW single-stage compressor in 2003. A full load and pressure test was performed using a mixture of hydrocarbon gas and condensate or water. Results from these tests are presented. A reduction in compressor performance is evident as fluid liquid content is increased. The introduction of wet gas and the use of sub sea solutions make more stringent demands for the compressor corrosion and erosion tolerance. The mechanical stress of the impeller increases when handling wet gas fluids due to an increased mass flow rate. Testing of different impeller materials and coatings has been an important part of the Statoil wet gas compressor development program. Testing of full scale (6–8 MW) sub sea integrated motor-compressors (dry gas centrifugal machines) will begin in 2008. Program sponsor is the A˚sgard Licence in the North Sea and the testing takes place at K-lab, Norway. Shallow water testing of a full scale sub sea compressor station (12.5 MW) will begin in 2010 (2 years testing planned). Program sponsor is the Ormen Lange Licence.

An Approach to Compact, Wet Gas Compression

2010 ◽  
Author(s):  
Jose´ L. Gilarranz R. ◽  
H. Allan Kidd ◽  
Gocha Chochua ◽  
William C. Maier
Keyword(s):  
High Speed ◽  
Oil And Gas ◽  
Integrated Approach ◽  
Separation Unit ◽  
Compression System ◽  
Wet Process ◽  
Process Gas ◽  
Wet Gas ◽  
Sea Bed ◽  
Gas Compression

In recent years, several papers have been written regarding the use of centrifugal compression technology to handle applications in which the process gas entering the equipment contains a significant amount of liquids, and can therefore be considered a wet gas. One such application that is currently being considered by many oil and gas operators is the installation of processing and compression equipment on the sea bed, to directly handle the process gas stream in close proximity to the wellhead. Other applications also exist topside, in which the operator would benefit from the installation of additional compression and processing capabilities at brown field facilities. Most of these existing installations have limited space for expansion and have strict size and weight limitations that have to be met by the additional equipment. This, in many cases, hinders the utilization of traditional compression and processing equipment, which is typically arranged using the large and heavy multi deck approach. A novel integrated compression system (ICS) has recently been developed to address the current need for compact compression systems that can handle wet process gas. The ICS makes use of centrifugal compressor stages driven directly by a high-speed, close-coupled electric motor, and incorporates a proprietary integrated centrifugal gas-liquid separation unit within the compressor case. This compact compression unit is packaged with process gas coolers in a single-lift module, providing a complete compression system that can be applied to all markets — upstream, midstream and downstream. With this integrated approach, the total footprint and weight of a conventional module or equipment layout can be greatly reduced. This paper is part of a series of publications that will describe the attributes of the new integrated compression system, and will serve to introduce the ICS and the benefits associated to the integration of the centrifugal separator into the compressor casing. The paper will focus on the OEM’s approach to Wet Gas Compression, with emphasis on the benefits of handling the liquid and vapor phases as separate streams, making the system more efficient and reliable than alternate solutions, including the ones that handle the wet gas directly. Finally the paper will provide a comparison between a traditional compression train and the new ICS to show how the latter system offers significant size and weight advantages.

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