2017 2nd International Conference on Computer Science and Technology (CST 2017) ISBN: 978-1-60595-461-5
Study of Optimization Method of Water Distribution
System in Oil Field
Yan WANG
1,a, Sheng GAO
2,*and Fu-shen REN
31,2,3 Daqing Petroleum Institute, Daqing, China
*Corresponding author
Keywords: Water Flooding System, Distribution, Mathematical Model, Optimization, Calculation Method.
Abstract. According to the present of water flooding system in oil field, the paper sets
up the mathematical model of water flooding pipe system to describe the basic characteristic of water flooding pipe system .Premising no sew age outer row, an objective function that system operating cost is the lowest is set up and the restriction conditions of objective function are defined as an optimizing method of two-stage hierarchical iteration based o n pat tern search method theory is brought forward .The practical application show s that the mathematical model is correct and the algorithm is stable .
Introduction
Water Supply Dispatching System
Composition of the Water Supply System
[image:2.612.170.440.346.508.2]The water supply system is mainly composed of node unit (including dehydration station, sewage Treatment station, water injection station and pipeline junction), pipeline unit and subsidiary units (including valve, three way and elbow) and so on, which covers the area from tens of square kilometers to several hundred square kilometers. Figure 1 shows a simplified oil field water supply system. The water supply pipe network includes two sub pipe net systems. When the system works normally, the dehydration station will produce oil and the sewage is transferred to the sewage station through the raw water network. The sewage and other water sources with the inflow of water through the sewage pipe network water station into the water injection system. Due to the different pressure of sewage flowing through the sewage station, the pressure of the whole water supply system is not continuous. In addition to the annular pipe network structure, there are still many branches of the pipe network structure. So in the raw water pipe network and sewage pipe network, it is divided into a number of independent two level pipe network systems. Each of the two levels of the pipe network subsystem is also affected by the water resources of other primary pipe network system with the impact of household relationship, which together constitute a large complex fluid network system.
Figure 1. Schematic diagram of water supply network.
Scheduling System
of data. Secondly, the dynamic data is used to simulate and optimize the operation of the whole water supply system on the same day. Finally, acquire a certain form results for the guidance of production.
The Establishment and Solutions of Mathematical Model of Water Supply System
Objective Function
The objective function of water supply system is as followed in the absence of oily sewage discharge, the minimum cost of water supply scalar function. The cost of the water supply system includes the purchased water and electricity consumption of water pump in water supply station.
In the formula, X represents a collection of nodes of a dehydration station; Y represents a collection of sewage stations. UJ represents the treatment of water at a certain time interval at the j sewage treatment plant. Volume, m3 /h; UI represents I water station (dehydration station and sewage station) at a time. The inter section of the external water volume, m3 /h; PI represents the exit of the first I water station. Pressure, Mpa; RI represents the cost coefficient of water consumption; VJ water cost coefficient of output water of J sewage treatment station.
Constraint Conditions
Pipe Network Hydraulic Balance Condition. For the water supply pipe network
system with n nodes equation (2)
Pressure Constraint. All incoming water and sewage stations should be more than
the minimum stop pressure.
Traffic Constraints. In the whole water supply system which sewage treatment
Formula, U max SJ I and UMIN SJ I represents the maximum of the I wastewater treatment plant and minimum water treatment, m3 /h; U max YS I and UMIN YS I, respectively, means the I about the maximum and minimum water can be obtained from the sewage pipe network. Volume, m3 /h; U max WS I and UMIN WS I, respectively, said the first I sewage treatment station The maximum and minimum water output to the sewage pipe network, m3/h.
System Quality of Service Constraints
The scheduling of water supply system requires no external discharge of oily wastewater. So, the amount of oil produced by the station is equal to the oily sewage in the sewage pipe network.
Model Solving
In the water supply system, the output of the dehydration station and water diversion are both given factors while only the sewage treatment station quantity is an undetermined factor. The ultimate goal of optimal scheduling of water supply system can be interpreted as follows: ensuring that there is no oily sewage discharge; precisely obtain the amount of water treatment, water purchased and the supply comes from other water resources in order to minimize the consumption of electric energy in the whole system operation. According to the process of water supply, it can be seen that when the water flow rate is constant, the pressure of the outlet pressure is lower. And the energy consumption in the dehydration station and sewage station are equipped with multiple constant speed pump and adjustable speed pump to meet the water supply in a range of continuous change, so it is not necessary to consider the distribution pump.
solution on the trajectory must be stored. Generally speaking, there is only one point K
that exist which makes , and for other points, there will always be
so K is called as the controlling point.
b)If (u, p) satisfies constraint the optimum solution, so, U and
are also satisfied with the same solution.
The mathematical model of water supply scheduling contains hundreds of equality constraints and inequality constraints. According to the characteristics of the model and the water supply system, the iterative method is adopted to solve the two-level hierarchical structure. According to the actual production data, pre-estimate a set of initial data, then, the pattern search method is used to adjust the water treatment capacity of each oil wastewater treatment station. Pattern search method is often used to solve unconstrained problems; Therefore, it is necessary to transform the inequality constraints in the objective function. The flow inequality constraints are handled by formula (9).
Considering the speed of the algorithm and the local minimum solution, during the method searching, variable step size patterns are available. In the second layer of the algorithm, according to the first layer to determine the amount of water, the nonlinear equations of the pipe network system are obtained. Then use the 2 characteristics of the water supply network with the formula (10) to modify the pipe network pressure. Calculate the current objective function and compare it with the previous objective function. Parameters with smaller objective function, and then to the first layer of the algorithm in accordance with the pattern search method to adjust the amount of water, until the end condition is satisfied.
Optimization Calculation Example
Figure 2. Simulation model of water supply system in oil field.
Conclusion
(1) The mathematical model of oil field water supply system operation scheme is built in this paper with the two-level optimization method and develop corresponding calculation software. Practical applications prove that the algorithm is stable and compatible.
(2) With the model mentioned above, the optimized operation of oil field water supply system is achieved by which sewage discharge can be avoided and the production cost can be reduced.
References
[1] Chen suli, Lin li, Ren fushen. Automatism patition and calculation methods of water flooding system. [J]. Oil Field Equipment, 2016, 36(6): 75-78.
[2] Zhou xueyi. Water force calculation[M]. Beijing: Tsinghua University Press, 2015: 188-191.
