GE MUL­TI­PHASE FLOW ME­TER

Power Watch India - - COVER STORY -

GE is work­ing on de­vel­op­ing tech­nol­ogy ar­chi­tec­ture for a mul­ti­phase flow me­ter to meet the re­quired per­for­mance set by in­dus­try. When a mix­ture of flu­ids such as oil, wa­ter and gas are trans­ported through the pipe, it is ex­tremely chal­leng­ing to make ac­cu­rate vol­u­met­ric flow rate mea­sure­ment of in­di­vid­ual phases with­out sep­a­rat­ing them. The ba­sic re­quire­ment is to mea­sure the phase frac­tion at any in­stant of time in the pipe cross sec­tion and the ve­loc­ity of liq­uid and gas phases. When the pipe is ori­ented ver­ti­cally it is known that the liq­uid and gas travel at dif­fer­ent ve­loc­i­ties as there is slip be­tween the phases pre­dom­i­nantly due to den­sity dif­fer­ences. Phase frac­tion is a mea­sure of the frac­tion of area oc­cu­pied by the gas against the to­tal area of the pipe cross sec­tion. The liq­uid phase is usu­ally a mix­ture of oil and wa­ter. Hence an ad­di­tional mea­sure­ment needs to be made to as­cer­tain the amount of wa­ter and oil in the liq­uid. With the mea­sured phase frac­tion and the phase ve­loc­i­ties, the vol­ume flow rates for each of the phases can be quan­ti­fied. Where nec­es­sary, the mass flow rates of the phases can be com­puted by mea­sur­ing com­po­nent den­si­ties. The mea­sure­ments made through in­di­vid­ual tech­nolo­gies/ sen­sors such as im­ped­ance or mi­crowave needs to be re­lated to the pa­ram­e­ters of in­ter­ests such as gas ve­loc­ity or liq­uid ve­loc­ity. In or­der to find such a re­la­tion­ship and es­tab­lish a re­li­able model for this con­ver­sion, in depth do­main knowl­edge is a crit­i­cal re­quire­ment along with ex­ten­sive ex­per­i­men­ta­tion. De­pend­ing on which phase (oil, wa­ter or gas) dom­i­nates the flow, the per­for­mance of in­di­vid­ual tech­nolo­gies can vary sig­nif­i­cantly. Thus, it is crit­i­cal to iden­tify the flow state in or­der to choose sen­sors that per­form the best and are re­li­able un­der a given con­di­tion. Ad­di­tion­ally over a pe­riod of time, the salt lev­els in the wa­ter and the com­po­si­tion of oil can change. It is crit­i­cal for the sen­sors to es­ti­mate th­ese fluid prop­er­ties real time. GE mul­ti­phase me­ter ad­dresses th­ese chal­lenges in op­er­at­ing en­vi­ron­ments/con­di­tions, through mul­ti­ple dif­fer­en­tia­tors com­pared to other me­ters in the mar­ket. Some of the dif­fer­en­ti­at­ing el­e­ments are the fol­low­ing:

Phase frac­tion es­ti­mate im­mune to prop­erty vari­a­tion: The im­ped­ance sen­sor sys­tem which has 8 elec­trodes dis­trib­uted cir­cum­fer­en­tially can es­ti­mate liq­uid prop­erty real time us­ing novel ex­ci­ta­tion method­olo­gies. Fur­ther­more, mod­els used for es­ti­mat­ing liq­uid to gas ra­tio are con­stantly up­dated when­ever there is change in liq­uid prop­er­ties. This elim­i­nates the need for fre­quent sam­pling of liq­uid/ fluid as is cur­rently be­ing done in the mul­ti­phase me­ters avail­able in the mar­ket.

Im­ped­ance hard­ware that can seam­lessly op­er­ate across the oil and wa­ter con­tin­u­ous flows: In mul­ti­phase flow, the liq­uid ei­ther ex­ists in what are called “oil con­tin­u­ous” or “wa­ter con­tin­u­ous” regimes. When in an oil con­tin­u­ous regime, the di­elec­tric prop­er­ties dom­i­nate whereas in a wa­ter con­tin­u­ous regime, the con­duc­tive prop­er­ties dom­i­nate. The con­ven­tional ap­proach to solv­ing this prob­lem is to use two dif­fer­ent in­stru­ments for mak­ing mea­sure­ments in the two types of flows. GE, on the other hand has built cus­tom hard­ware which has been proven to have a band­width that is wide enough for it to op­er­ate seam­lessly be­tween changes in flow con­di­tions. This en­sures that for a given ap­pli­ca­tion, a wide op­er­at­ing range can be cov­ered us­ing only one in­stru­ment.

Mi­crowave sen­sors that op­er­ate at vary­ing salin­ity while es­ti­mat­ing wa­ter-cut re­li­ably: Mi­crowave sen­sors used in mul­ti­phase me­ters cur­rently avail­able in the mar­ket can­not op­er­ate in liq­uids with high salin­ity. A novel an­tenna sys­tem de­signed by GE of­fers high re­li­a­bil­ity through a pro­tec­tive radome flushed with the in­ner di­am­e­ter of the pipe. While this sen­sor can be used for es­ti­mat­ing wa­ter-cut and gas frac­tion, another mi­crowave sen­sor can track and es­ti­mate the vary­ing salin­ity in ab­so­lute terms.

Ul­tra­sound Dop­pler to pro­file liq­uid ve­loc­ity: A di­rect mea­sure of the liq­uid ve­loc­ity is one of the hard­est mea­sure­ments for a mul­ti­phase me­ter to make. Us­ing Ul­tra­sound Dop­pler tech­nique on mul­ti­phase flow, we can pro­vide in­for­ma­tion that is not ob­tained from other tech­nolo­gies. One of the com­pli­ca­tions in a ver­ti­cal mul­ti­phase flow is that when a large enough gas slug moves up­ward, it can push the liq­uid along the wall to move back­wards mo­men­tar­ily. It has been shown with the Dop­pler tech­nique that th­ese di­rec­tional changes in the liq­uid can be de­tected and quan­ti­fied. With the rich­ness of in­for­ma­tion that GE’s Dop­pler method can pro­vide, the mea­sure­ment ac­cu­racy and re­li­a­bil­ity can be con­sid­er­ably im­proved.

Dual ven­turi & dif­fer­en­tial pres­sure sen­sor de­sign for re­li­able vis­cos­ity in­de­pen­dent mea­sure­ments: With wa­ter-cut vari­a­tion over life of the well, vis­cos­ity of the liq­uid emul­sion is an un­known. The dis­charge co­ef­fi­cient of the ven­turi which is a crit­i­cal pa­ram­e­ter for es­ti­mat­ing the to­tal mass flow rate is strongly re­lated to the vis­cos­ity of the liq­uid. Us­ing a dual ven­turi de­sign with mul­ti­ple dif­fer­en­tial pres­sure mea­sure­ments and us­ing smart es­ti­ma­tion meth­ods, the vis­cos­ity de­pen­dency can be elim­i­nated from the to­tal mass flow rate es­ti­ma­tion.

Novel data an­a­lyt­ics for re­li­able flow rate es­ti­ma­tion: Data han­dling is crit­i­cal in a

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