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Valve and Actuator Technology for the Offshore Industry
Published in Karan Sotoodeh, Coating Application for Piping, Valves and Actuators in Offshore Oil and Gas Industry, 2023
A choke valve is another type of control valve that is installed on the production wellhead to control the flow being produced from the well. In addition, a choke valve can be used to stop the production if something goes wrong downstream. Downstream refers to the piping and separator that are located after the choke valve. Figure 5.53a shows a choke valve on the right side of some Christmas tree valves. As explained earlier in this chapter, wellhead valves are all TCG valves. The right side of the picture shows a choke valve that is installed on a Christmas tree. The fluid enters the choke valve from the bottom part inside the vertical line; after a 90-degree rotation inside the valve, the fluid exits the valve to the horizontal line shown on the right-hand side of the choke valve in Figure 5.53. Choke valves are at high risk of operational problems such as erosion and cavitation because of the 90° rotation of the fluid inside the valve and the resulting pressure drop. The choke valve on the right side of Figure 5.53 has a stem and handwheel. The handwheel can be operated to move the stem and connected plug upward or downward to adjust the flow passage. In general, rotating the handwheel counter-clockwise moves the stem and connected plug upward, which increases the opening and allows for more flow to pass through the valve. Clockwise rotation of the handwheel has the opposite effect and closes the valve. Choke valves can be automatically operated by an actuator; in that case, there is no handwheel on the valve.
Strategies for Mitigation and Remediation of Asphaltene Deposition
Published in Francisco M. Vargas, Mohammad Tavakkoli, Asphaltene Deposition, 2018
J. Kuang, A. T. Khaleel, J. Yarbrough, P. Pourreau, M. Tavakkoli, F. M. Vargas
If economically and technically feasible, the manipulation of pressure or pressure change in the wellbore could also mitigate asphaltene deposition. Through the production profile, the system goes from a stable state to another stable state by passing through a region of instability. Within this region, precipitation, aggregation, and aging phenomena occur. Precipitation is controlled by thermodynamics. Aggregation and aging are governed by kinetics. If one can increase the rate of pressure drop between the two stable states, such that it overcomes the rate of aggregation and aging, this may result in less and softer asphaltenes. According to the conceptual mechanism discussed in Section 7.1.2, small liquid-like aggregates can potentially be redissolved at the final stable state. The rate of pressure drop can be increased by using the concept of venturi effect through the installation of a choke valve. The location of the choke valve needs to be designed based on each well. This strategy may not be applicable to every wellbore, and it will highly depend on the reservoir pressure and the pressure drop across the wellbore. It may be best used in cases where the reservoir pressure is very high.
Naphthenate The soap-like solids
Published in Jon Steinar Gudmundsson, Flow Assurance Solids in Oil and Gas Production, 2017
The particle (droplet) size distribution of oil-in-water emulsion has been reported by Sjöblom et al. (2003). Experiments were carried out to investigate the effect of mixing on the particle size distribution. A water-in-oil emulsion containing 30% vol. water, was passed through first one choke valve and immediately downstream, through another choke valve. The total pressure drop across the two consecutive choke valves was 20 bar. The droplet size distributions are shown in Figure 7.16. The droplet size distribution was smaller for two choke valves compared to one choke valve. The greater the number of mixing points (flow restrictions), the smaller the water droplets in an oil-continuous petroleum emulsion (stock-tank oils were used). The vertical axis is cumulative volume; the horizontal axis is droplet size in microns (=μ $ {=} \upmu $ m).
Technical barriers and their solutions for deployment of HCCI engine technologies – a review
Published in International Journal of Ambient Energy, 2021
Swapnil Sureshchandra Bhurat, Shyam Pandey, Venkateswarlu Chintala, P. S Ranjit
HCCI engines prone to weak cold start as it already discussed in earlier Section 4.3. Emissions due to a cold start in HCCI engines has also acquired more attention of the researchers (Bielaczyc, Merkisz, and Pielecha 2001a, 2001b). However, it can be solved by using several approaches. Researchers (Kimura et al. 1999; Sato, Yanagihara, and Mizuta 1996) have used the concept of ‘mixed mode’ to run their engines. In this approach engine was run in control auto ignition (CAI) mode at low and medium engine loads and SI mode at the idle, cold start and high loads. In order to solve the cold start problem in HCCI engine, Shi et al. (2006) used the auxiliary injector which was mounted over the cylinder head in addition to default diesel injector to achieve the pilot injection. Pilot injection of fuel was done to ignite pre-mixed fuel injected by default injector. Once the engine warmed up, it was switched to HCCI mode. Ignition of the first few firing cycles in cold start was obtained by Peng et al. (2008) with the use of choke valve and EGR. Peak in cylinder pressure was achieved with partially closed choke valve and completely open EGR valve was 45% more than that when engine was running under normal conditions without EGR and due to this SOC was achieved much earlier and hence overcome the issue of cold start. The glow plug is another solution to the cold starting barrier in the HCCI engine, as it will assist to heat the A/F mixture during cold starting. Increasing CR at the start of operation is another solution (Manofsky et al. 2011).
Monitoring and control of bottomhole pressure during surge and swab operations using statistical process control
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2018
Mahdi Imanian, Aazam Ghassemi, Mahdi Karbasian
BHP can be controlled using choke line volume flow rate, choke valve opening, main fluid volume flow rate, and fluid density. Nygaard et al. (2007) used two methods and a simple linear controller to control BHP during surge and swab operations. In the first method, only choke line flow rate is a controllable input parameter, while in the second method both choke line volume flow rate and choke valve opening are controllable input parameters used to stabilize BHP at a set point. They implemented their method in a case study in an oil well in North Sea. After the implementation of both methods using EPC, BHP was monitored for common causes (sudden influx of fluid from the formation into the drilling well) and assignable causes (surge and swab operations) using SPC approach (Figure 1). To this end, the above-mentioned five-step approach was implemented on the output data of both methods. In the first step, the output data of both methods was extracted at 10-second time intervals and their normality was determined using the Anderson-Darling test at the confidence interval of 95%. The results indicated that the output data of both EPC methods were non-normal (Figure 2(a) and (b)).
Optimization techniques for petroleum engineering: A brief review
Published in International Journal of Modelling and Simulation, 2021
Anuj Kumar, Mridul Vohra, Sangeeta Pant, Sanjeev Kumar Singh
Optimization prototypes for the designing and working of a well-integrated system related to oil production cover the complete field from the sub-surface structure which will consist of the drainage area, reservoir, and wells, and well-head assembly, complete up to the surface and down facilities. Such enhanced optimization prototypes consist mainly the several component models related to wellbore simulation in the reservoir area, well tubing strings models for fluid flow in the pipelines from source to destination, models related to the choke valve of the well, surface flow line models of the surface pipeline network systems, and various separator models for separation facility.