SPE Recoverability
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  Copyright 1998, Society of Petroleum Engineers, Inc.This paper was prepared for presentation at the 1998 SPE International Conference on Health,Safety and Environment in Oil and Gas Exploration and Production held in Caracas, Venezuela, 7– 10 June 1998.This paper was selected for presentation by an SPE Program Committee following review ofinformation contained in an abstract submitted by the author(s). Contents of the paper, aspresented, have not been reviewed by the Society of Petroleum Engineers and are subject tocorrection by the author(s). The material, as presented, does not necessarily reflect any position ofthe Society of Petroleum Engineers, its officers, or members. Papers presented at SPE meetingsare subject to publication review by Editorial Committees of the Society of Petroleum Engineers.Electronic reproduction, distribution, or storage of any part of this paper for commercial purposeswithout the written consent of the Society of Petroleum Engineers is prohibited. Permission toreproduce in print is restricted to an abstract of not more than 300 words; illustrations may not becopied. The abstract must contain conspicuous acknowledgment of where and by whom the paperwas presented. Write Librarian, SPE, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A., fax01-972-952-9435. Abstract The oil industry activities generate a great amount of wastesresulting from oil spills, tanks cleaning and maintenance, drilling,etc., which are dispossed in pits, creating a negativeenvironmental impact. The recoverable crude oil from these pitsis estimated to be about 2 MMBBLS. This makes its recoverableeconomically attractive.The recovery process is based on fundamental operations likeDilution, Formulation of oil/water Dispersions using SodiumSilicate as natural surfactant active agent present in the oil andStatic Dehydration by Heating and Chemical DemulsificationTreatment.In this work, the different phases of the study, beginning fromthe results obtained on laboratory scale and subsequentlyindustrial application on a pit in the Boscan Field are presented.The oil recovered in this way was later reincorporated into theproduction line. Introduction During the crude oil production process operations, it isimportant to consider the environmental aspects as one of theircomponents.Oil wastes generated during the execution of these processes,should be disposed or storaged for their future treatment anddisposal. Due to the extensive and the complexity of theprocesses, with the lapse of time, significant quantities of theserefuses has been accumulated (great amount of petroleum),beside that, it hasn’t been any available and efficient processes of treatment and recuperation of the fluids, for that reason, it hasbeen imposible the cleaning of the areas destined for the storageof them.The crude oil recuperation processes of pits with theenvironmental cleaning of the affected area is very complicatedand laborious because the characteristics of the fluids insidethem. The high content of solids together with the ageing of thefluids, generate highly stable emulsions.All emulsions to be tried, should be consider like a specificsystem (1), with theirs own characteristics stablishing theconditions for their treatment. This is so, for the case of the oilwastes requiring the combination of processes like dilution,inverted emulsion, heating, chemical treatment, etc, in order toachieve the main objective. That is, getting cleaned crude oil.These requirements are more demanding in the case of Boscanfield, in which the produced crude oil has a gravity around 10°API, which hinderes the separation of the crude oil/waterphases. Theoretical Foundations The selection and application of any chemical additive andphysical processes to obtain crude oil within specifications is nota matter of chance but of systematic work. All processes obey tospecific theoretical foundations. When these theoreticalfoundations are applied in actual practice, they make feasible theapplication of a determined treatment.The selection of the processes for the recovery of the crudeoil from the pits is based on how they could affect the variablesthat are part of the Stokes’ Law. That is, how they can favorablyinfluence in the sedimentation speed or phases separation.It’s known that: µ   = 2g r 2  (d 1 -d 2 ) / 9 η 2 Where,  µ  : sedimentation speed (phases separation) g : acceleration of gravity r : droplet radiusd 1 : density of the fluid that form the droplet (internal phase)d 2 : density of the fluid that contains the droplet (continuous phase) η 2 : viscosity of the continuous fluid phase.Then, any changes, which generate increments in thenumerator of the equation or decreases in the denominator, willfavour the separation process of phases. SPE 46603Crude Oil Recovery in Oiler Residual Pits in Boscan Field A. Zabala, A. de Jongh, and A. Padron. PDVSA E & P  2A. ZABALA, A. DE JONGH, A. PADRONSPE 46603 Considering the fact, that the fluid to be treated is awater/crude emulsion, the following terms are defined: Chemical Treatment  : Consist in the injection of a chemicalproduct (nonil phenol etoxilates family), with two mainobjectives:1.   To afect the interfacial film. This makes it to break andpermit the coalescense of the droplets of water andincreases the droplet size.2.   The demulsifier chemical avoids the waterreemulsification with the crude oil during the latestdispersion process.  Dilution : Addition of an organic solvent to the emulsion willonly affect the crude oil phase, it means that, the density gradientbetween the crude oil and water will increase and also theviscosity of the continuos phases will decrease as well. Bothfactors will improve phases separation.  Heating : Increasing temperature will produce the same effectthan that of the dilution processes since it affects the samevariables. In addition, heating process helps the dehydrationprocess. However, this should be done under controlled way,because an excessive temperature in systems no pressurized, itcould produced the lost of the most volatile components of thecrude oil and overheating of the water phase that they couldmake explosions for vapors in expansion and liquids in boil. Formulation of Dispersion: This process means to invert thesrcinal emulsion to get a crude in water emulsion with the use of sodium silicate which works like an active agent of the naturalsurfactants present in the crude oil, for example, carboxilic acids,asphaltenes, resins and other natural components that they haveacid properties. At this time, the viscosity of the emulsion andthat of the water are very similar and also, the diameter of the oildroplets grow by a better coalescense process. The variation of these parameters also influences favorably in the separation of the phases. Laboratory Test Being the main objective of this project, to design a chemical andphysical process that allows to treat the fluid which coming fromthe pits, to reach crude oil within specifications, related to watercontent, and incorporate it to the clean crude oil current, it wasdetermined, at laboratory scale, the best conditions of each one of the variables of the process.In this sense, some tests were developed, considering thevariation of the following parameters: ã   Kind of solvent and dilution percentage ã   Demulsifier agent, dosage and application pointOn the other hand, and due to previous experiences, the nextparameters were constants: ã   Crude oil/water ration equal to 60/40, in order to formthe dispersion ã   Sodium silicate concentration: 4000 ppm in base on thecrude oil phaseFront the final results, presented in Table N° 1, the followingconditions were selected: ã   Kind of solvent: Kerosene ã   Dilution percentage: 25 % ã   Demulsifier agent: Q1 ã   Application point: Directly to the crude oil streamcoming from the pits.Later, keeping constants the previous parameters, a chemicaldosage range was evaluated, with the results presented in TableN° 2. From here, a dosage of 800 ppm was selected to get thebest result in the dehydration test. The dosage of 900 ppm onlyproduces a slight increment of the dehydration efficiency, whichdoesn’t justify the additional cost. Field Test Once the laboratory test finished, the operational activity wasdefined, settling like final procedure for the pilot test, thefollowing: the crude oil coming from the pits is treated with 800ppm of Q1, later is sent to the dilution tank where is diluted at 25% with kerosene, mixing them with a recirculation pump. Themixture is passed through a heater and then returned to the sametank. When the dilution has been completed, this is pumpedtoward the resting tank being mixed with the sodium silicate tomake the dispersion or crude oil in water emulsion in a ration of 60/40. In order to achieve the dispersion, a static mixer is located just after the mixing point of both streams.It is worthwhile mention that the temperature of crude oil isabout 40 °C, then it increases until 80 °C at the dilution step justafter the heater, later it decreases until 65-70 °C upon mixingwith the sodium silicate solution.This process was started on flow station Z-9 from BoscanField that has an oil waste pit. The most important characteristicsof the fluid are presented in Table N° 3, and the flow chart of theprocesses is described in Figure N° 1.During the development of the test, 16350 BBLS of crude oilwith 11 % of water and sediment were treated. The dilution wasmade with 5450 BBLS of kerosene and, in order to form thedispersion, 11530 BBLS of sodium silicate solution were used.As a result of this test, 20 MBBLS of cleaned crude oil (less than1 % of water and sediment content) were produced and added tothe Boscan crude oil production. Treatment Costs The treatment costs are showed in Table N° 4 and it is based on1000 BBLS of cleaned crude oil. The cost of the water used forthe preparation of the sodium silicate solution is not included inthese calculations because it was taken from a water well locatedin the area. Conclusion 1.   It is feasible the application of a chemical and physicaltreatment to the fluids storaged in the pits, for the crude oilrecovery and their incorporation to the clean crude oilcurrent. The treatment consists in the combination of theDilution, Chemical Treatment, Heating, Emulsion Invertionand Static Dehydration.2.   The application cost of the treatment, related to clean crudeoil production, was 7.90 $/BBL.  SPE 46603CRUDE OIL RECOVERY IN OILER RESIDUAL PITS IN BOSCAN FIELD3 References 1.   Salager, J.L.: “Emulsiones, Propiedades y Formulación”,ULA (1993)2.   Becher, P.: Emulsions: Theory and Practice, second edition,Reinhold Publishing Corporation, New York (1966) 151. WASTES PIT DILUTIONTANK WATERCLEANED CRUDETO TH EPRODUCTIO NSTREAMSO DIUM SILICATESO LUTIO NRESTINGTANKHEATERSTATIC M IXER KEROSENE DEMULSIFIER Fig. 1-Flow chart of the process designed to recover crude oil from the pit located in the flow station Z-9 in Boscan Field.  4A. ZABALA, A. DE JONGH, A. PADRONSPE 46603 TABLE N° 1-DEHYDRATATION EFFICIENCY BASED ON THE KIND OF SOLVENT,   PERCENTAGE OF DILUTION AND DEMULSIFIER APPLICATION POINT Test Dilution (% ) Demulsifier Agent. (ppm) Application Point Efficiency DehydrationN° Kerosene Dist. Fraction Q1 Q2 Before Disper. After Disper. ( % ) 1 20 - - - 0.00 2 20 - 500 - x 25.00 3 20 - - 100 x 4.17 4 20 - 500 - x 50.00 5 25 - - - 5.60 6 25 - 500 - x 33.33 7 25 - - 100 x 8.16 8 25 - 500 - x 79.17 9 30 - - - 0.0010 30 - 500 - x 27.4511 30 - - 100 x 25.0012 30 - 500 - x 54.1713 - 20 - - 0.0014 - 20 500 - x 5.0015 - 20 500 - x 6.3516 - 25 - - 0.0017 - 25 500 - x 8.6618 - 25 500 - x 23.4619 - 30 - - 0.0020 - 30 500 - x 7.7721 - 30 500 - x 26.67VARIABLES WITHOUT VARIATION: CRUDE OIL / WATER RATION = 60 / 40SODIUM SILICATE CONCENTRATION = 4000 ppm
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