An Approach to Compact, Wet Gas Compression

Author(s):  
Jose´ L. Gilarranz R. ◽  
H. Allan Kidd ◽  
Gocha Chochua ◽  
William C. Maier

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.

Author(s):  
Grant O. Musgrove ◽  
Melissa A. Poerner ◽  
Griffin Beck ◽  
Rainer Kurz ◽  
Gary Bourn

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.


Author(s):  
Steve Ingistov

This Paper describes the on-going efforts of finding the root-cause for the failures of high-energy (over 30,000 HP), high-pitch velocity (over 30,000 FPM) gear elements. These gear elements are presently operating in Oil and Gas Production Facilities. They are installed between the GT drivers and turbo-compressors. Turbo-compressors deliver high-pressure gas into the underground oil fields to enhance the oil production. The oldest Gas Compression Units were commissioned in 1995 and the latest in 1998. Since installation in 1995 at least 6 gear boxes experienced failures of the pinion (high speed gear) teeth. The Mean Time Between Failures (MTBF) of the pinion teeth was estimated around 34,000 operating hours. The costly shutdown of Gas Compression Units forced the management to seek advice within the company. The intent of this Paper is to share some field experiences and to present some corrective actions. The intent of this Paper is also to help Original Equipment Manufacturers (OEMs) in this case gear elements Manufacturers to develop better balance between cost, life and reliability. Sometimes the balance between these three parameters is difficult to maintain. Too often the gear elements Manufacturers are forced to compete on the price basis and as result the quality of the gear elements are sometimes compromised. In addition, several well-known gear elements Manufacturers stopped offering high energy, high-pitch velocity gear elements because they suffered serious failures of the gear elements on the test stand and also in the field.


2021 ◽  
Author(s):  
Giuseppe Vannini ◽  
Alice Innocenti ◽  
Filippo Cangioli ◽  
Kim Jongsoo

Abstract The current oil and gas market trends lead the compressor OEMs to increase the rotational speed and maximize the efficiency given a target power output. Especially when applied to large process gas centrifugal compressors, characterized by high-flexibility ratio, the achievement of these targets pushes the rotordynamic design towards its limit in terms of API requirements. Tiling pad journal bearings (TPJBs) are commonly adopted in high-speed applications for their inherent stability characteristics that permit to ensure the rotordynamic stability and eliminate self-induced sub-synchronous vibrations. The experimental activities subject of this paper aim to assess, for the first time, the rotordynamic behaviour of a large dummy rotor (6 meter long and total weight of 8 tons) equipped with Flexure Pivot tilting-pad journal bearing and Integral squeeze film damper (ISFD). This system level testing program has been performed in the Authors’ high-speed balancing bunker properly equipped with special instrumentation such as: flow meters and pad temperature probes to monitor journal bearing behaviour, displacement probes to measure rotor vibrations relative to the bearings. The main objective of the experimental activity is the full assessment of the rotordynamic response and the selection of the best configuration to target the design requirements (e.g. FPJB and “Active ISFD” vs. FPJB and “Inactive ISFD”).


Author(s):  
Melissa Poerner ◽  
Grant Musgrove ◽  
Griffin Beck

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.


2018 ◽  
Vol 42 ◽  
pp. 01010 ◽  
Author(s):  
Muhammad L. Hakim ◽  
Balza Achmad ◽  
Juwari P. Sutikno

Gas Compression Package (GCP) is a vital system in the distribution of gas. Pertamina EP, in this regard as a state-owned company managing oil and gas on the upstream, is in the project phase of purchasing and installing compressor facilities. GCPs are used to increase gas pressure hence it can be transferred from gas wells to industrial areas. Dynamic analysis becomes important to observe the performance of the compressor and to ensure safety during operation, in order to avoid surge phenomenon. Surge is an undesirable phenomenon in the form of a backward flow of gas. The surge may damage the internal components of a centrifugal compressor, hence needs to be prevented from happening. The anti-surge controller manipulates anti-surge valve to give actions in the recycle lines when a surge occurred. PID controller is used for controlling and stabilizing the system. PID tuning is determined using Auto Tuning Variation method. This method is based on the process frequency response from relay oscillations. After the dynamic model of the plant had been developed, some simulations were carried out with various scenarios. The scenarios were based on a variety of issues that may occur in a gas compression system. The applied scenarios were a decrease in flow rate on the input side, a pressure drop in gas wells, and changes in gas composition. The control configuration of gas compression system was designed and modified in order to compensate disturbances and avoid surge phenomenon.


Author(s):  
K. Weeber ◽  
C. Stephens ◽  
J. Vandam ◽  
A. Gravame ◽  
J. Yagielski ◽  
...  

Recent years have seen an increase in high-speed electric compression for Oil & Gas applications where high-speed electric motors drive compressors directly without intermediate gears. To date induction machines have been the predominant workhorse of the industry. The permanent-magnet machine technology provides an alternative that promises a highly reliable and robust system design, especially in applications where motor and compressor are fully integrated and share the same process gas environment. This paper provides an update on the recent progress in developing the permanent magnet technology for Oil & Gas applications in which the process gas may contain corrosive elements.


Author(s):  
Sarah Simons ◽  
Ryan Cater ◽  
Klaus Brun ◽  
Grant Musgrove ◽  
Rainer Kurz

Significant work has been performed to qualify and quantify the effects of operating with wet gas in a centrifugal compressor system [1, 2]. Of particular interest is the sharp decrease in the isentropic efficiency of the machine when operating with process gas containing various liquid volume fractions. However, it is unknown how much of the performance losses are due to aerodynamic effects, such as blade profile and flow separation losses, rather than the basic thermodynamic effects of compressing a multiphase gas that has a higher density, integral wet-cooling, and contains small amounts of high-density droplets. Previous studies showed that the overall efficiency losses exceeded those expected from purely thermodynamic effects so aerodynamic effects have been principally blamed for the lower efficiency. However, no test data exists in the public domain that quantifies these losses and it is experimentally difficult to perform this type of testing in centrifugal compressor. Therefore, a series of tests was performed on a reciprocating compressor with power and efficiency recorded through dynamic pressure measurements obtained inside the compression cylinder, torque measured on the shaft, and enthalpy rise measurements obtained outside the cylinders. Using this approach one can eliminate (or differentiate) the aerodynamic effects of wet gas compression, such as valve losses, thus allowing the direct determination of the thermodynamic losses of wet gas compression. Specifically, when there is multi-phase flow entering the machinery, there is the thermodynamic effect of how a mixture of water and air behaves when being compressed [from a process perspective] and the aerodynamic effect of moisture encountering the blades of a centrifugal compressor [performance loss] or the valve passages of a reciprocating compressor [pressure loss]. Directly instrumenting the internals of a reciprocating compressor cylinder allows the evaluation of the thermodynamic performance of multi-phase compression separate from any aerodynamic penalties. This paper describes the tests performed in a reciprocating compressor open test loop operating with varying amounts of liquid volume fractions (LVFs) of water in the process gas (air). The data was reduced using Pressure-Volume card measurements inside and outside the cylinder, enthalpy rise, as well as torque to determine the impact of volume fraction on compression power and efficiency. Additionally, the valve losses, system efficiencies, and peak compression “spike” were evaluated in relations to the LVFs.


Author(s):  
Øyvind Hundseid ◽  
Lars E. Bakken

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.


Author(s):  
Lars Brenne ◽  
Tor Bjo̸rge ◽  
Lars E. Bakken ◽  
O̸yvind Hundseid

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.


Author(s):  
Dagfinn Mæland ◽  
Lars E. Bakken

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.


Sign in / Sign up

Export Citation Format

Share Document