Wet Gas Compression in Petroleum Engineering by New Generation Multiphase Pumps

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1 Universal Journal of Aerodynamics 5 (207), -8 Wet Gas Compression in Petroleum Enineerin by New Generation Multiphase Pumps E.G. Ladopoulos Interpaper Research Oranization 8, Dimaki Str. Athens, GR , Greece eladopoulos@interpaper.or Abstract A new Multiphase Compressor Technoloy is introduced and investiated for wet as compression in petroleum & as enineerin. Usually the fluid to be handled by the wells operate under wet as conditions, where the fluid contains a mixture of liquid and aseous phases. Thus, the proposed multiphase pumps have the ability to handle directly the wet as without the need for separation equipment, which is very attractive from an economic view, as it reduces very much the weiht, size and cost of the as compression devices. Hence, the rowin interest in wet as compression in petroleum enineerin leads to a eneral request for accurate performance calculation procedures and proper measurement techniques for multiphase flow meterin in compressors. Accordin to the proposed new technoloy method the well known multiphase pumps used for wet as compression will be extended to modern forms. Moreover, the efficiency and operatin rane of a compressor are constrained by aerodynamic instabilities. Consequently, the aerodynamic behavior of such multiphase pumps is studied and investiated. In such way, by the present paper the different flow phenomena associated with compressor instability are investiated and presented recommendations for suitable instrumentation and measurin techniques. Thus, with the hih demand of wet as compression system, it is necessary to model the performance of twin-screw multiphase pump with wet as conditions and provide solutions to increase both efficiency and reliability. So, a calculation model is studied to evaluate the suitable form of the multiphase compressor and to find the proper parameters for its operation. Consequently, the bi petroleum companies must be ready to face the new challenes of usin the next eneration multiphase pumps for wet as compression. Key Word and Phrases Wet Gas Compression, New Generation Multiphase Pumps, Multiphase Compressors, Petroleum and Gas, Gas Processin, Polytropic Compression.. Introduction Generally, the typical production system of petroleum and as reserves consists of a separator, a liquid pump, a liquid meter, a as meter, a as compressor and buffer tank. Then the produced fluid from the well, which is normally oil and as mixture, is first separated and then boosted by liquid pump and as compressor, respectively and transferred throuh separate pipelines to the processin facility a lon distance away. Additionally, sometimes a test separator is needed for well testin and flow rate measurement. Moreover, different from the conventional production system, the multiphase production system eliminates the use of separator. Thus, the full well stream are boosted directly and transported throuh a sinle pipeline to the processin facility without separation. The multiphase pump replaces both the sinle phase liquid pump and the as compressor. Beyond the above, test separator and manifold are replaced by multiphase meter and multiport valve. The production of each well can be selected by multiport valve throuh multiphase meter for well testin and measurement. Then by eliminatin the above equipments, multiphase production system can save about 0% in investment for equal flow station capability and sinificantly reduce the footprint of flow station, which is a bi advantae for offshore application. Thus, in several cases, the application of multiphase production system can eliminate as flarin and ives zero emission.

2 Multiphase production system provides further option for subsea production system. The dramatic reduction of development cost and small footprint are the biest advantaes drivin the increasin use of subsea multiphase pumpin system. Besides, multiphase pump can lower the subsea wellhead pressure and improve the hydrocarbon recovery. It also provides additional enery to boost the full well steam throuh lon-distance pipeline, which make the development of remote marinal and deepwater fields more economical. With the multiphase pumpin technoloies bein approved both on-shore and on the topside of platform, subsea is the next bi challene. In eneral, a very bi challene for multiphase pumpin technoloies is wet as compression. Thus, wet as is natural as containin sinificant amounts of liquefiable hydrocarbons. But there is no standard of what percentae liquid phase should be in wet as. Typically, The Gas Volume Fraction (GVF) or as quality is used to define the amount of liquid in wet as. Since most of the pump manufacturers recommend that the averae GVF at the inlet of the pump should be limited to 95% to ensure the pump operability, for the purpose of research, GVF of 95% and above will be considered as wet as compression. Besides, interest in the deployment of wet as compressors is very much increasin as companies seek for economical way to improve recovery of as reservoirs both onshore and offshore. Hih as price is also one of the reasons drivin the application of wet as compression on stranded as reservoir. On the contrary, multiphase flows in compressors have complicated characteristics includin interfacial interactions and relative movement between phases. Determination of actual fluid and thermodynamic properties is a challene in multiphase compressors due to this phase exchane. The instrumentation and measurement techniques employed for sinle-phase compression may have insufficient accuracy due to the liquid introduced in wet as compression. Thus, wet as compression technoloy is of reat importance to the petroleum and as industry for boostin of unprocessed well stream and to reduce investment costs related to equipment and personnel. The rowin interest in wet as compression leads to a eneral request for accurate performance calculation procedures and proper measurement techniques for multiphase flow meterin in compressors. Moreover, the efficiency and operatin rane of a wet as compressor are constrained by aerodynamic instabilities. Thus, different flow phenomena are associated with compressor instability and so recommendations should be presented for suitable instrumentation and measurin techniques. Beyond the above, visualization techniques can be evaluated to determine the suitability for multiphase compressors. Also, the enery demand for petroleum and as will increase up to 200 by 50-60%, as it is increasin worldwide yearly at a pace of.5 to 2.0%. Thus, for the on-shore and off-shore oil and as reserves exploration was proposed by E.G.Ladopoulos []-[5] the new theory of "Non-linear Real-Time Expert Seismoloy". Accordin to the above modern method a non-linear -D elastic waves real - time expert system was proposed for the exploration of petroleum and as resources worldwide, includin the off-shore petroleum reserves, of the seas and oceans in the whole world in deep waters ranin from 00 to 000 m, or even much more. Furthermore, the above technoloy is the best device for searchin the on-shore and off-shore hydrocarbon resources in very deep depths, even approachin 20,000 m or 0,000 m. Over the past years, several studies have been published on wet as compression by usin multiphase pumps [6] []. Hence, for the new and the existin oilfields there is an absolute need for the improvement of the existin methods of wet as compression. For this reason, by the current investiation the Next Generation Multiphase Pumps are proposed and studied. Accordin to the above modern method the well known multiphase pumps used for wet as compression will be extended to next eneration forms. So, an easiest method is proposed for the quicker compression of the wet as in each new oilfield. The new method has many benefits beyond the existin multiphase pumps methods, as the wet as production for each well is increased very much and so there no limits for the oil well production any more. From the above described analysis it is clear the evidence of the applicability of the new method of Wet Gas Compression by New Generation Multiphase Pumps. Also, its novelty, as it is based mostly on a theoretical and very sophisticated model and not to practical tools like the existin methods. The new method will be therefore the best technoloy for wet as compression for a 2

3 sinle oil well. Moreover, the aerodynamic behavior of such multiphase pumps is studied and investiated. 2. Sinle Phase Gas Analysis A compressor has enerally as primary variables of interest the pressure rise produced, the amount of flow delivered and the required power. Additionally, the thermodynamic evaluation of the centrifual compressors is based on the polytropic procedure. Thus, an accurate method for performance calculations is important to ensure a correct evaluation of the centrifual compressor. Identical compressors operatin at different suction pressures will have variation in isentropic efficiencies due to the deviation in the isobars. The above thermodynamic characteristic is taken into account when assumin a polytropic process. Then, the deduction of the polytropic head is based on the assumption of a constant polytropic exponent alon the compression path. Thus, the polytropic compression process for the centrifual compressors is the best device for handlin a wide rane of ases used in oil & as industry. At hih pressures and temperatures, the ideal as behavior is not valid due to chanes in fluid properties. The ASME PTC 0 [4] has implemented the J.M.Schultz polytropic procedure [5] for thermodynamic performance evaluation of a compressor. Real as behavior therefore is taken into account when utilizin the Schultz procedure. The procedure by J.M. Schultz assumes a polytropic compression path based on averaed as properties of inlet and outlet conditions. Schultz introduced a polytropic volume exponent, to account for chanes in fluid properties. Then, the polytropic volume exponent is defined as a constant in solvin the polytropic head equation due to assumed neliible variation. The polytropic head coefficient is iven by the followin formula: [4] p p 2 u (2.) where (m) denotes the polytropic head and u (m/sec) the tanential velocity. Additionally, in (2.) the tanential velocity u is equal to: DN u (2.2) 60 with D (m) the impeller exit diameter and N (rpm) machine rotational speed. Beyond the above, in (2.) the polytropic head is iven as follows: n ( p2v2 pv ) (2.) n in which n denotes the polytropic volume exponent, p2 (Pa) and v 2 ( m / k) are correspondinly the pressure and the specific volume of the machine dischare, while (Pa) and v ( m / k) are correspondinly the pressure and the specific volume of the machine inlet. In (2.) the polytropic volume exponent n is equal to: p

4 p2 ln p n (2.4) v ln v2 Furthermore, the flow coefficient can be iven by the formula: Q (2.5) N 2 D 60 where Q ( m / sec) is the actual volumetric flow. Head H is referred to the specific work done by a compressor. The compressor actual head, as iven by the followin equation (2.6), describe the total chane in enthalpy h (J/k) for the compression process. The relationship between pressure, temperature and enthalpy are determined by utilizin an appropriate equation of state. The actual head remains constant independently of the iven compression process: H h 2 h (2.6) Moreover, the polytropic efficiency p is defined as the relationship between polytropic and actual head as shown by the followin equation (2.7): p H (2.7) Besides, the power P (in KW) of the compressor is iven by the followin formula: Q P p m (2.8) where γ is the specific ravity of the liquid ( KN / m ) and mechanical power efficiency. m (usually ) is the The above formulas are used for a sinle process as. Consequently, if the compressor inlet contains both as and petroleum, which means wet as, then the above formulas should be properly modified.. Multi-Phase Wet Gas Analysis If the compressor is workin under wet as, then there is no description by standards, as in the case of dry as. However, the previous approach of sinle phase as, can be applied for a multiphase approach. Then, the previous mentioned formulas should be properly be chaned, in order the multi-phase approach to be used. For the case of a multi-phase compressor, the multiphase polytropic volume exponent n is iven as followin: 4

5 wh ere v denotes the multiphase specific volume ( m / k). p2 ln p n (.) v ln v2 Additionally, the multi-phase polytropic head, is iven as follows: H n ( p2v2 pv) (.2) n In (.2) the multi-phase specific volume is base on an homoeneous equation: v GVF ( GVF) (.) w ith the as density ( k / m ), the liquid density ( k / m ) and GVF the as-volume fraction defined as: Q GVF Q (.4) Q m in which Q denotes the as flow ( / sec) and Q the liquid flow. 4. New Generation Multi-Phase Wet Gas Analysis Another approach could be proposed for a new eneration multi-phase pump. Thus, a two-phase fluid model is proposed, where each phase is treated individually. Then, the polytropic head is equal to: H n R x n M 0 W p ZT p 2 n n ( x ) v l ( p 2 p ) (4.) here R denotes the universal as constant, is the molecular weiht (k/kmol), w 0 compressibility factor, T the temperature ( next formula: o K M Z W ) and x is the fluid quality iven by the m x (4.2) m m with m the as mass flow (k/sec) and m the liquid mass flow (k/sec). l l 5

6 Furthermore, the multi-phase head coefficient is equal to: v H GVF (4.) 2 v u and the multi-phase flow coefficient is iven by the followin formula: Q tot (4.4) N GVF 2 D 60 Finally, the power formula: P (in KW) of the multi-phase compressor is iven by the followin P Q tot H m (4.5) in which γ is the specific ravity of the liquid ( KN mechanical power efficiency. / m ) and A description of the multi-phase wet as compression is shown in Fiure. m (usually ) is the Fi. Mult-phase wet as compression. 6

7 5. Conclusions By the current paper the new theory of "Next Generation Multiphase Pumps for Wet Gas Compression" has been introduced and investiated for the petroleum well development. Consequently, by usin the proposed new technoloy then it will be possible the production of very bi quantities of oil and as in each well. As is well known, normally the fluid to be handled by the wells operate under wet as conditions, where the fluid contains a mixture of liquid and aseous phases. Hence, by the proposed modern technoloy for enery applications it will be established a stron scientific and technical base for the Science & Technoloy worldwide in the emerin areas of well development in the enery field. Thus, throuh the new technoloy of " Next Generation Multiphase Pumps for Wet Gas Compression ", the production of very bi quantities of oil and as for each well will become possible. Moreover, the petroleum and as markets are multi-billion markets all over the world. So, such a contribution requires an international approach, rather than a local approach, as it is referred to a market all over the world with value of many billions. It is therefore expected in order the international oil companies to keep and to improve their leadin role in the worldwide Science & Technoloy in the petroleum field, to et involved in the new and roundbreakin technoloy in the area of Enery, which is proposed by the present investiation. Finally, as the proposed new method "Next Generation Multiphase Pumps for Wet Gas Compression", is based on a very sophisticated modern method, then it is expected to et the best results. Thus, our proposed hih technoloy method is based on a very sophisticated model by usin multiple net eneration compressors, instead of usin the existin compressors. Consequently, the proposed multiphase pumps have the ability to handle directly the wet as without the need for separation equipment, which is very attractive from an economic view, as it reduces very much the weiht, size and cost of the as compression devices. Beyond the above, efficiency and operatin rane of a compressor are constrained by aerodynamic instabilities. In such way, by the current investiation the different flow phenomena associated with compressor instability are investiated and presented recommendations for suitable instrumentation and measurin techniques. References. Ladopoulos E.G., 'Non-linear sinular interal representation for petroleum reservoir enineerin', Acta Mech., 220 (20), Ladopoulos E.G., 'Petroleum reservoir enineerin by non-linear sinular interal equations', Mech. Enn Res., (20), -0.. Ladopoulos E.G., 'Oil reserves exploration by non-linear real-time expert seismoloy', Oil Asia J., 2 (202), Ladopoulos E.G., Hydrocarbon Reserves Exploration by Real-Time Expert Seismoloy and Non-linear Sinular Interal Equations, Int. J. Oil Gas Coal Tech., 5 (202), Ladopoulos E.G., New Aspects for Petroleum Reservoir Exploration by Real-time Expert Seismoloy, Oil Gas Busin. J., 202 (202), Ladopoulos E.G., Petroleum & Gas Reserves Exploration by Real-Time Expert Seismoloy and Non- in Petroleum Reservoir linear Seismic Wave Motion, Adv. Petrol. Explor. Develop., 4 (202), Ladopoulos E.G., Non-linear Sinular Interal Equations for Multiphase Flows Enineerin, J. Petrol. Enn Tech., 2 (202), Ladopoulos E.G., Real-time Expert Seismoloy by Non-linear Oil Reserves Expert System, J. Petrol. Gas Enn, 4 (20), Ladopoulos E.G., New Sophisticated Model for Exact Petroleum Reserves Exploration by Non-linear Real-Time Expert Seismoloy, Univ. J. Petrol. Scien., (20), Ladopoulos E.G., 'Real-Time Expert Seismoloy and Non-linear Sinular Interal Equations for Oil Reserves Exploration', Univ. J. Nonlin. Mech., (20), -7.. Ladopoulos E.G., Non-linear Real-Time Expert Seismoloy for Petroleum Reservoir Exploration, Univ. J. Nonlin. Mech., (20), Ladopoulos E.G., General Form of Non-linear Real-Time Expert Seismoloy for Oil and Gas Reserves Exploration, Univ. J. Petrol. Scien., (20), -4.. Ladopoulos E.G., Oil and Gas Reserves Exploration by Generalized Form of Non-linear Real-Time 7

8 Expert Seismoloy, Univ. J. Enn Mech., (20), Ladopoulos E.G., Multiphase Flows in Oil Reservoir Enineerin by Non-linear Sinular Interal Equations, Univ. J. Fluid Mech., (20), Ladopoulos E.G., Non-linear Real-Time Expert Seismoloy for Very Deep Drillins in Petroleum Reserves Exploration, Univ. J. Nonlin. Mech., (20), Hundseid Ø., Bakken L.E., Helde T., A Revised Compressor Polytropic Performance Analysis, ASME GT , Hundseid Ø., Bakken L.E., Wet Gas Performance Analysis, ASME GT , Twu C., Kusch H., Selection of Equations of State Models for Process Simulator, Simsci Inc., Kurz R., Brun K., Lerand D.D, Field Performance Testin of Gas Turbine Driven Compressor Sets, Proceedins 28th Texas A&M Turbomachinery Symposium, Hunziker R., Gyarmathy G., The Operational Stability of a Centrifual Compressor and Its Dependence on the Characteristics of the Subcomponents, ASME J. Turbomach., 6 (994), Gresh M.T., Compressor Performance: Aerodynamic for the User, Newnes, Zieler K.U., Gallus H.E., Niehuis R., A Study on Impeller-Diffuser Interaction Part I: Influence on the Performance, ASME J. Turbomach., 25 (200), Filipenco V.G., Deniz S., Johnston J.M., Greitze E.M., Cumpsty N.A., Effects of Inlet Flow Field Conditions on the Performance of Centrifual Compressor Diffusers: Part - Discrete-Passae Diffuser, ASME J. Turbomach., 22 (2000), Grüner T.G., Bakken L.E., Brenne L., Bjøre T., An Experimental Investiation of Airfoil Performance in Wet Gas Flow, ASME GT , Mizuki S., Oosawa Y., Unsteady Flow within Centrifual Compressor Channels Under Rotatin Stall and Sure, ASME J. Turbomach., 4 (992), Wernet M.P., Briht M.M., Skoch G.J., An Investiation of Sure in a Hih-Speed Centrifual Compressor Usin Diital PIV, ASME J. Turbomach., 2 (200), SchleerM., Son S.J., Abhari R.S., Clearance Effects on the Onset of Instabilityin a Centrifual Compressor, ASME J. Turbomach., 0 (2008). 28. Hayami H., Hojo M., Aramaki S., Flow Measurements in a Transonic Centrifual Impeller Usin a PIV, J. Visualiz., 5 (2002), Ibaraki S., Matsuo T., Yokoyama T., Investiation of Unsteady Flow Field in a Vaned Diffuser of a Transonic Centrifual Compressor, ASME J. Turbomach., 29 (2007), Hayami H., Hojo M., Aramaki S., Flow Measurement in a Transonic Centrifual Impeller Usin a PIV, The Visualization Society of Japan and Ohmsha, LTD, Journal of Visualization, 5 (2002), Albrecht H.E., Borys M., Damaschke N., Tropea C., Laser Doppler and Phase Measurement Techniques, ISBN , , Towers D.P., Towers C.E., Buckberry C.H., Reeves M., A Colour PIV System Employin Fluorescent Particles for Two-Phase Flow Measurements, Meas. Sci. Technol., 0 (999), Navarra K.R., Rabe D.C., Fonov S.D., Goss L.P., Hah C., The Application of Pressure- and Temperature-Sensitive Paints to an Advanced Compressor, ASME J. Turbomach., 2 (200), American Society of Mechanical Enineers, Performance Test Code on Compressors and Exhausters, ASME PTC 0, Schultz J.M., The Polytropic Analysis of Centrifual Compressors, ASME J. Enn Power, 84 (962),

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