Performance Evaluation for Gas Production Units Based on ANP

In view of the existing situation of gas field development, one kind of method to evaluate the production performance of gas production units (GPUs) was presented in this paper. Among the commonly used indicators of gas field development, we select 11 indicators from the three aspects of production task, gas reservoir management, and production technology. According to the principle of analytic network process (ANP), this paper introduced one kind of new method to get the weights of indicators. By means of the method of TOPSIS, it is easy to obtain the rankings for all the GPUs through calculating the weighted Euclidean distance between each GPU and the positive or negative ideal point. This evaluation method could constantly improve the management level of gas production units and deepen the delicacy management of gas field development.


Introduction
The oil and gas field companies mostly take the management concept of "Benchmarking" during the process of gas field development [1].According to the dynamic analysis of gas reservoir development, the technical section provides a kind of development scheme and sets some feasible goals that should be achieved.And the gas production units (GPUs) must achieve the production goals in accordance with the development requirements [2].Currently, the development department in the process of gas field development evaluates the production performance of GPUs based on their own statistics data and the assessment results calculated by themselves [3].It means that the evaluation accuracy is not high enough and the crosswise contrast is not enough.In order to make the development department accurate and timely, and grasp the current situation of development and management of GPUs, it needs to establish a relatively perfect evaluation system to really respond to the management level, efficiency, and development effect of GPUs, promoting the delicacy management of gas field development.In this paper, we first present the evaluation indicators and their computing methods.In order to reasonably decide the weight of each indicator, this method of ANP is introduced.Next, we introduce the method of TOPSIS to decide the comprehensive ranking of GPUs and use the Euclidean distance to describe the proximity between two GPUs.

Use Evaluation Indicators and Their Computing Methods
Through the analysis, the production performance evaluation indicators of GPU are divided into three aspects of production task, gas reservoir management, and production technology [1][2][3][4][5] (see Figure 1), including 11 indicators in the following.

Production Task
The production task [4,5], denoted as B 1 , contains the completion rate of gas production (C 11 ) , the completion ate of water injection (C 12 ), and the completion rate of r Measures (C 13 ),.
(1) Completion rate of gas production.
where is the actual gas production, is the planned gas output, unit: m 3 .
where is the actual amount of filling, is the planned amount of filling, unit: "tons".
where is the actual number of measures, is the arranged number of measures, unit: "times".

Gas Reservoir Management
The gas reservoir development [6,7], denoted as B 2 , contains the utilization rate of gas well (C 21 ), the time utilization rate of gas production (C 22 ) and the qualified rate of single well production allocation (C 23 ).
(1) Utilization rate of gas well.
where is the actual time of gas production, is the calendar time of gas production, unit: day.
where is the actual consumption of methanol, is the total annual budget, unit: tons.
(5) Consumption rate of triethylene glycol of gas stations.

100%
where is the consumption of triethylene glycol, unit: kg; is the gas production, unit: m 3 .
V v

Production Performance Evaluation for Gas Reservoir Management Units
Assume that there are GPUs and evaluation indicators, the decision data matrix is denote d by .According to the method of TOPSIS, the comprehensive ranking procedure for GPUs consists of the following steps.(a) When the jth indicator is the benefit type, Step 2: Determine the weights of indicators.The weight vector can be obtained by ANP.Further more, we could calculate the weighted decision matrix , where .
Step 3: Determine the positive ideal vector and the negative ideal vector.Respectively, denoted by and Step 4: Calculate the Euclidean distance from the positive ideal vector and the negative ideal vector.The Euclidean distance between the i-th RMU and the positive ideal vector is denoted by The Euclidean distance between the i-th RMU and the negative ideal vector is denoted by Step 5: Calculate the relative closeness to the positive ideal vector.The relative closeness can be defined as Step 6: Decide the ranking according to the value of * i f .The bigger the closeness shows the better the ranking.

Example Analysis
The statistical data of 7 gas production units (GPUs) of an oilfield in the year of 2012 are listed in Table 1.According to the basic data in Table 1, we could obtain the evaluation results.
Setp 1: Build the network structure of the evaluation indicators (see Figure 2).Setp 2: Calculation the weights of the evaluation indicators.All judgment matrixes are as follows: All calculations are done by the Super Decisions software.From the limit matrix, we can obtain the weights of all the evaluation indicators listed in the following.Step 3: Production performance evaluation for GPUs.

Conclusions
1.A relatively perfect evaluation method is established to really respond to the management level, efficiency, and development effect of GPUs, which can promote the delicacy management of gas field development.
2. Some practically feasible evaluation indicators and their computing methods are firstly presented through analyzing the actual situation in the process of gas field development.
3. We can decide the comprehensive rankings of GPUs through calculating the weighted Euclidean distance between every GPU and the positive or negative ideal RMU by means of the method of TOPSIS.

Figure 1 .
Figure 1.Hierarchical relationship of the evaluation indicators.

0 n( 2 )
is the actual number of open wells, is the total number of gas wells.nTime utilization rate of gas production. 22

Step 1 :
Standardize the decision data matrix.The standardized decision data matrix is denoted by formula are given in the following.

Figure 2 .
Figure 2. The network structure of the evaluation indicaors.t