STUDYING THE EFFECT OF CALCIUM CARBONATE SCALE DEPOSIT ON CRUDE OIL FLOW CHARACTERISTICS

Transcription

1 STUDYING THE EFFECT OF CALCIUM CARBONATE SCALE DEPOSIT ON CRUDE OIL FLOW CHARACTERISTICS UKPAKA C.P., IMINABO J.T., AND IMINABO, M. ABSTRACT This paper describes detailed study of calcium carbonate scale deposit on crude oil flow lines in the Niger Delta region. The investigation conducted revealed that the crude oil production could come to a half if a major delivery or discharge line, containing a considerable amount of hard effluent or supersaturated produced water, is blocked by precipitated or crystallized inorganic, dissolved or suspended solids component of the formation fluid. Mathematical model was developed to simulate the effect of diameter, radius, velocity distance, time and volume as functional parameters of flow characteristics. The paper contains flowchart for field preliminary identification of scale and of internal pipe diameter drastically reduced by various mineral scale deposit in some flow station terminals of Niger Delta region High deposit of calcium carbonate increases bacteria and fungi concentration as well as reducing crude oil production volume and corrosion in this case was largely attributed to the presence of these species and calcium carbonate scale deposit. Keywords: Calcium carbonate, scale deposit, characteristics, crude oil, model, flow. Introduction Scale is an assemblage or accumulated solid layers of soft of impermeable deposit that cake and clogs a process opening or surface, preventing normal fluid flow or efficient operation of mechanical devices. The scale is formed either by direct precipitation or crystallization from the mineralized water which naturally occurs in the reservoir rocks or produced water becoming supersaturated with ions of dissolved solid compounds as well as when the solubility limit for one or more mineral components are exceeded (Richardson and McSween, 1989). Investigation conducted by various research groups revealed that mineral scale is a connate and produced water associated problem of the oil industry faced on daily bases due to regular, production and displacement of both gaseous and liquid hydrocarbon reserves of the petroleum reservoir, from discrete subsurface trap to the surface handling and treatment facilities, with gradually accompanying formation water, non-hydrocarbon gases and pressure/temperature declines as time increases.(stiff and Davis, 1952., A & M, 2004). Studies have been carried out on the mechanical and chemical treatment or removal of formed scale, catalyst sand deposits and other particulate or visible sediment particles from the affected process facilities, like the first stage; two-phase separators, the subsequent medium, low and atmospheric working pressure, horizontal three-phase process separator train, the 280

2 Studying The Effect Of Calcium Carbonate Scale Deposit On Crude Oil Flow Characteristics hydrostatic; gravity assisted drainage vessels, including the high temperature effluent treatment and disposal loops and spools were thoroughly achieved (John and Folk, 2002). Scale can be deposited all along water paths from the reservoir to the surface equipment. Investigation conducted revealed that scale deposition breeds a complex unproductive effect to mention but few areas of production operations; partial or total and permanent loss of well productivity when the tubing string is blocked or reservoir matrix becomes plugged ( Chen, et al., 2004., Morizot, et al., 2001). Skin damage, when the porosity index is reduced or lost due to carbonate and sulphate scales deposit in the pores of the Rock, thus reducing the efficiency of natural oil recovery (Mc Geffrey et al., 1987). Nucleation can also reduce the injectivity of effluent water back to the reservoir for water flooding pressure management and production. Optimization/enhancement campaigns equally (Rocha, et al., 2001). Studies conducted on environmental impact assessment on some mineral scales revealed that the characteristics are categorized as potential health hazard due to the amount of radiation they are likely to produce since they contain naturally Radioactive materials (NORM) with toxic and corrosive ions which is detrimental to intelligent and passive life forms within the offshore aquatic base-line or operational environment (Harm and Natolic, 1984 and Boris et al., 2001). Similarly, investigation conducted on metal characteristics and properties revealed that corrosion and microbiological activities also accelerates under mineral scale deposit on a favour condition (Ukpaka, 2009 and Potton, 1986). The aim of the study is to evaluate the effect of calcium carbonate scale deposit on the crude oil flowing characteristics upon the influence of internal diameter reduction, radius, velocity, distance, time, biomass as well as other functional parameters as presented on this paper. Faced with this oil production, economic hazard and flow characteristics and precautionary investigation was carried out and an eventual proposal model for monitoring and predicting the effect of calcium carbonate on crude oil flowing characteristics is well studied. Materials and Methods The Model 281

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6 Studying The Effect Of Calcium Carbonate Scale Deposit On Crude Oil Flow Characteristics Computational Procedure The following parameters were used in the simulation of the model developed in the process, 2 such as: radius of the diameter is 10 50mm, frequency factor = 0.25, velocity = 2-5m/s, o change in height = m, time = 10 50sec, viscosity of water at 40 C = x 103Ns/m2, viscosity of sodium chloride at 40oC = x 10-6Ns/m2 and viscosity of calcium carbonate (CaCO3) at 40oC = 0.013Ns/m2. The simulated parameters were fitted into the developed mathematical model illustrated in equation (24) and the results obtained is shown below. Results and Discussion The results obtained in this research work was based on mathematical model developed as well as the application of Matlab (Matrix Laboratory) computer language programme to simulate the significance of the variation on height, radius time and velocity on the flow characteristics of crude oil leading to high deposit of calcium carbonate on the internal surface of the pipe. Figure 2: Graph of Flow Rate versus Height 285

7 Nigerian Journal Of Oil And Gas Technology - Vol 3 No. 1 Figure 2 illustrates the behavours of the crude oil flow rate characteristics upon the influence of height and the rate at which the calcium carbonate is deposited in the internal surface of the pipe as well as the variation in sodium chloride concentration in the process. The flow characteristics of water and sodium chloride in the system is very close, indicating that the deposit of calcium carbonate does not influence the characteristics of water and sodium chloride. The variation on the flow characteristics of the water, sodium chloride and calcium carbonate can be attributed to the variation in height as well as other controlling factors. Decrease in the flow rate characteristics of water, sodium chloride and calcium carbonate was observed with increase in height as presented in Figure 2 above. Figure 3: Graph of Flow Rate versus Radius In this case, increase in the flow rate characteristics of water, sodium chloride and calcium carbonate is observed with increase in the radius, which revealed the significance of diameter and radius on the flow system as shown in Figure 3. Figure 3 illustrates the behavours of the crude oil flow rate characteristics upon the influence of time and the rate at which the calcium carbonate is deposited in the internal surface of the pipe as well as the variation in sodium chloride concentration in the process. The flow characteristics of water and sodium chloride in the system is very close, indicating that the deposit of calcium carbonate does not influence the characteristics of water and sodium chloride. The variation on the flow characteristics of the water, sodium chloride and calcium carbonate can be attributed to the variation in radius as well as other controlling factors. Decrease in the flow rate characteristics of water, sodium chloride and calcium carbonate was observed with increase in radius as presented in Figure 3. Figure 4: Graph of Flow Rate versus Time 286

8 Studying The Effect Of Calcium Carbonate Scale Deposit On Crude Oil Flow Characteristics In this case, increase in the flow rate characteristics of water, sodium chloride and calcium carbonate is observed with increase in the time, which revealed the significance of time on the flow system as shown in Figure 4. Figure 4 illustrates the behavours of the crude oil flow rate characteristics upon the influence of time and the rate at which the calcium carbonate is deposited in the internal surface of the pipe as well as the variation in sodium chloride concentration in the process. The flow characteristics of water and sodium chloride in the system is very close, indicating that the deposit of calcium carbonate does not influence the characteristics of water and sodium chloride. The variation on the flow characteristics of the water, sodium chloride and calcium carbonate can be attributed to the variation in time as well as other controlling factors. Decrease in the flow rate characteristics of water, sodium chloride and calcium carbonate was observed with increase in radius as presented in Figure 4. Figure 5: Graph of Flow Rate versus Velocity In this case, increase in the flow rate characteristics of water, sodium chloride and calcium carbonate is observed with increase in the velocity, which revealed the significance of velocity on the flow system as shown in Figure 5. Figure 5 illustrates the behavours of the crude oil flow rate characteristics upon the influence of time and the rate at which the calcium carbonate is deposited in the internal surface of the pipe as well as the variation in sodium chloride concentration in the process. The flow characteristics of water and sodium chloride in the system is very close, indicating that the deposit of calcium carbonate does not influence the characteristics of water and sodium chloride. The variation on the flow characteristics of the water, sodium chloride and calcium carbonate can be attributed to the variation in velocity as well as other controlling factors. Decrease in the flow rate characteristics of water, sodium chloride and calcium carbonate was observed with increase in radius as presented in Figure 5. Conclusion The following conclusion was drawn from the research work, such as: 1. The flow characteristics of water, sodium chloride and calcium carbonate is influence by the pressures, viscosity, diameter of the pipe, density, concentration. 2. The scale formation in the internal structure of the pipe influence the flow 287

9 Nigerian Journal Of Oil And Gas Technology - Vol 3 No. 1 characteristics of the process. 3. The operational procedure of the system influence the high deposit of the scale in the internal surface of pipe, hereby reducing the internal diameter of the pipe. 4. The reservoir contains high deposit of calcium carbonate which is a major agent that leads to internal reduction in pipe diameter. 5. The effect of scale deposit influences the rate of daily production due to reduction in the diameter. 6. Increase in the calcium carbonate deposit lead to increase in microbial growth which influence the pipe characteristics, that is, the action of corrosion may be greatly experienced increase in time. REFERENCES Morizot, A., Neville, A. & Heriot-Wall, U. (2001). Using and Electrochemical Approach for monitoring kinetics of CaCO3 and BaSO4 scale Formation and Inhibition on Metal Surfaces. Society of Petroleum Engineering and SPE -Journal. 7, 1712 Stiff, Jr. H. A. & Davis, L.E. (1952). A method for predicting the tendency of oilfield water to deposit calcium carbonate, pet. Trans-AIME 195, Chen, T., Neville, A & Yuan, M. (2004). Corrosion, New Orleans, LA, USA, 14. Rocha, A.A. Frydaman, M. Da-Fontoura, S.A.B; Rosario, F.F. and Bezerra, M.C.M. (2001). Numerical modeling of salt Precipitation during Produced Water re-injeetion, presented at the 2001 Society of Petroleum Engineers (SPE). Third International SymposIum on Oil Field Scale in Aberdeen, UK, 52. Johnson, D. A. & Folks, K. E. (2002). Computerized Water Modeling in the Design and Operation of Industrial Cooling Systems, international Wt inic1nce, 4f Annual Meeting Piltsburgh, P.A IWC, 80(42): 73. McCaffrey, M.A. Lazar, B & Holland, H. D. (1987). The evaporation path of seawater and the co-precipitation of Br- and IK with halite. Journal of Sedimentary petrology, 57(5): Boris, A., Margarita, A.K. & Alla, Y.F. (2001). Vapour corrosion and scale inhibitors formulation from biodegradable and Renewable raw materials prescribed at the European Symposium on corrosion inhibitors (10 SEIC), 14. A&M. (2004). University System College station, Texas water and Water Quality, Texas Agricultural Extension Service, Texas,

10 Studying The Effect Of Calcium Carbonate Scale Deposit On Crude Oil Flow Characteristics Ukpaka, C. P. (2009). A general overview of scale problems in the oil field and their preventions (produced water management) in Egi land unpublished paper, Patton, C. C Applied water Technology, Campbell Petroleum Series, Norman, Oklahoma, 25. Richardson, S.M & McSween, E. L. Y Geochemistry pathways and process, Englewood Cliffs, New Jersey, USA: prentice-hall, Inc, 80. Harm, W.M. & Natolic, J Acrylic Acid polymers and copolymers as deposit control Agents in alkaline cooling water system, paper presented at the meeting of the national Association of Corrosion Engineers, Houston Texas,