According to the basic laws of oilfield development and the economic benefits of current development, the calculation models of economic limit initial oil production of new wells, economic limit water cut of old wells and economic limit oil production are established by using the basic principles of reservoir engineering and economics. On this basis, the changing law of oilfield non-economic output is studied, and the percentage of oilfield non-economic output and annual economic output in a certain period in the future is predicted by using this law. The research and application of this method is of great significance to improve the economic benefits of oilfield development.
Economic output benefit, output inefficiency, output inefficiency, economic limit water cut of well
I. Introduction
Under the condition of market economy, one of the important characteristics of enterprises' pursuit of economic benefits is to strive to maximize and rationalize profits. The basic form for oil enterprises to pursue profit maximization should be to develop all recoverable reserves most economically, or to maximize the development profit of recoverable reserves. Therefore, the existence of uneconomical components should be avoided as much as possible in oilfield development.
According to the production situation in Shengli oil region in recent years, the number of wells with daily average oil production less than 1t increased from 4 17 in192 to 1222 in 1999, and the proportion of wells increased from 4.4% to/kloc-. Some of these oil wells are inevitably in a state of inefficient production. Therefore, it is of great significance to analyze inefficient wells and their production changes to improve the economic benefits of oilfield development.
The research methods of economic output at home and abroad are complicated, and there are many parameters to be predicted, so it is difficult to operate in practice [1]. In order to meet the needs of market economy and improve the economic benefits of oilfield development, it is necessary to study a reasonable and easy-to-operate economic output calculation method.
Second, the economic output calculation model
The annual economic oil production of an oilfield is defined as the annual oil production that can be profitable during the economic development period. Under the condition of commodity economy, the annual economic oil production of an oilfield is closely related to the level of oil price and cost, and the increase of oil price and the decrease of cost will be beneficial to the increase of economic oil production; On the contrary, falling oil prices and rising costs will lead to a decrease in economic oil production. Therefore, the essence of studying the economic oil production of an oilfield is to deeply study the influence of oil price and cost changes on economic oil production on the basis of studying the objective change law of oil production (inherent in oil reservoirs), establish relevant mathematical models, and predict the change of economic oil production in the future.
From an average and objective point of view, for an oil field, as long as the current average cost per ton of oil is lower than the after-tax oil price, the oil field can be profitable. The annual oil production of an oilfield can also be said to be economic oil production, which is defined as annual macroeconomic oil production. However, the overall profitability of the oilfield does not mean that the oil production of every oil well in the oilfield is economical. In fact, the annual macroeconomic oil production of oil fields often includes the non-economic oil production of some wells with low production and low efficiency. Therefore, for an oilfield, the prediction of annual economic oil production should be based on the prediction of annual macroeconomic oil production of the oilfield, excluding the non-economic oil production of low-yield and inefficient wells. The calculation model is as follows:
Essay on exploration and development in Shengli oil region
Where: qi-annual economic oil production of developed oilfield,104t; ;
Qh-annual macroeconomic oil production of the oilfield,104t; ;
QE—— annual ineffective oil production of the oilfield,104t; ;
E-percentage of invalid production,%.
Three, the annual macro oil production forecast method
Annual macroeconomic oil production is the annual oil production during the economic recovery period. The economic recoverable reserves and the remaining economic recoverable reserves can be obtained by combining the water drive series method with the economic limit water content.
Essay on exploration and development in Shengli oil region
In which: NPJ-remaining economically recoverable reserves,104t; ;
NPO- cumulative oil production,104t; ;
A and b—— water drive curve coefficient of water drive series A;
FW, minimum economic limit water content, decimal (deduced later in this paper);
Cl-cost per ton of liquid, yuan/ton;
P—— crude oil price, RMB/ton;
RT-tax per ton of oil, RMB/ton;
W-crude oil commodity price, decimal;
QL- average single well fluid production, t/d
Arps decline method is usually used to predict the annual oil production. Among the three types of Arps decline curve [2], hyperbolic decline equation is a general formula, while exponential decline equation and harmonic decline equation can be considered as two special cases of hyperbolic decline equation when the decline index is n→∞ and n= 1 respectively. Therefore, the decline index n of hyperbolic decline equation can be calculated by best fitting to judge the decline type.
Through hyperbolic decline equation
Essay on exploration and development in Shengli oil region
free
Essay on exploration and development in Shengli oil region
Rewrite as
Essay on exploration and development in Shengli oil region
Where: Qt-output of decreasing T time,104t; ;
Qi—— When the output starts to decline,104t; ;
Di- initial decline rate, decimal;
N- decreasing index, decimal;
T—— Time calculated with the selected decreasing starting point of zero, a. ..
a = LG(QiCn)；
b = n；
C=n/Di .
Firstly, the lgQt-lg(t+C) curve is drawn, and the value of C is changed to maximize the linear regression correlation coefficient of the selected regular segment data. The decline index n can be obtained by fitting the slope value with the best straight line. N→∞ decreases exponentially; 1 < n
When the cumulative oil production in the decline stage is within the scope of the remaining economically recoverable reserves, the annual macroeconomic oil production at any time in the decline stage can be obtained.
Arps decline method is not the only method to predict the annual macroeconomic output of oil fields. In practical work, some forecasting methods suitable for the production change law of the oilfield are often screened out according to the specific conditions of the oilfield. Research on prediction technology of oilfield development trend. 48660.8886868866 1
For example, constant production liquid method, yield composition method, grey model method, AR model and so on.
IV. Calculation of Annual Economic Output
1. Oil well production cost and expense analysis
Oil well production costs and expenses are the sum of all consumption and expenses incurred by oil and gas field enterprises in production and business activities according to regulations. Including oil and gas product exploitation cost, exploration cost, management cost, sales cost and financial cost, the latter three costs are incurred in the process of oil and gas exploration and exploitation, and are not included in the oil and gas product exploitation cost, but directly deducted from sales income as profits and losses. In the cost analysis, according to the specific conditions of new wells and old wells, the cost is divided into two categories: the lowest cost and the complete cost. Among them, the lowest cost refers to the lowest cost that occurs in the production process of an oil well and is closely related to the oil production of the well, mainly including power cost, material cost, oil and gas treatment cost and oil displacement injection cost; The full cost includes not only the cost of simple reproduction, but also the cost of expanding reproduction, such as updating and replenishing oil and water wells, rolling exploration and development, finding new reserves and increasing new production capacity.
From the perspective of analyzing inefficient wells, the investment of old wells has been recovered. As long as the oil well can produce normally and the after-tax output value of the oil produced can be greater than the minimum cost of the oil well, it shows that the production of the oil well is effective. Therefore, the lowest cost calculation of oil well exploitation is used to judge whether the old well is inefficient; The judgment of new wells adopts full cost calculation.
2. Establishment of discrimination model for inefficient wells.
(1) discriminant model of new inefficient wells
The discrimination model of inefficient new wells is the initial oil production calculation model of economic limit of new wells. The economic limit initial oil production of a new well means that under certain technical and economic conditions, when the cumulative output value of an oil well in the payback period is equal to the sum of total investment, cumulative annual operating expenses and necessary taxes, the corresponding initial oil production of the well is called the economic limit initial oil production of the oil well. In order to improve the overall benefit of the oilfield, we must try our best to avoid the initial oil production of new wells below the economic limit.
During the payback period, the economic benefits of a single well [3]:
Essay on exploration and development in Shengli oil region
When the cumulative economic benefit in the payback period is 0, that is, Pp=0, the formula for calculating the initial oil production of economic limit is obtained:
Essay on exploration and development in Shengli oil region
In which: PP-single well economic benefit, 104 yuan; Cm—— drilling investment per meter, yuan/meter;
SP—— output value of single well, 104 yuan; H—— average well depth, m;
K- investment, 104 yuan; I B- single well surface construction investment, 104 yuan/well;
CD- operating cost, 104 yuan; β-coefficient of oil-water well, decimal;
τ o-oil well opening, decimal; The annual operating cost of a single well, 104 yuan/well;
T—— payback period of investment, a; I-annual growth rate of operating expenses, in decimal;
Qo—— average initial oil production of a single well, t/d; Qmin- economic limit of initial oil production, t/d.
B—— annual comprehensive decreasing residual rate, decimal;
Figure 1 Relationship between Ton Fluid Cost and Average Daily Fluid Production of a Single Well in Shengli Oilfield
(2) Discrimination model between old wells and inefficient wells.
The economic limit water cut calculation model is used to distinguish old wells from inefficient wells. Economic limit water cut means that when the water cut of an oil field (oil well) reaches a certain development stage, when the water cut rises to a certain value or the oil production drops to a certain value, the input and output are balanced. If the water cut rises again and the oil production drops again, there will be no profit in oilfield development. The water content of an oil field (oil well) at this time is called economic limit water content, and the output corresponding to this water content is called economic limit production. The calculation of economic limit water content and oil production of old wells and the calculation of economic limit initial oil production of new wells all adopt the principle of break-even, but the difference is that the calculation of economic limit initial oil production of new wells refers to the input-output balance in a certain stage (payback period), while the calculation of economic limit water content and oil production of old wells refers to the instantaneous input-output balance (generally one year).
The cost per ton of liquid is a cost form in the process of crude oil exploitation. On the basis of studying the changing law of old well cost and the cost of more than 40 oilfields in Shengli Oilfield, it is found that the cost per ton of liquid is open. Study on the new method of capitalization of the developed oil fields59980.998988888865
It has a good relationship with the average single well fluid production (Figure 1).
The regression relationship is:
Essay on exploration and development in Shengli oil region
Economic benefit of single well:
Essay on exploration and development in Shengli oil region
When the economic benefit is 0, the calculation formula of economic limit water content is obtained:
Essay on exploration and development in Shengli oil region
It can be obtained by substituting the relationship between ton liquid cost and single well liquid production.
Essay on exploration and development in Shengli oil region
3. Calculation and prediction of invalid output
According to the discrimination model of inefficient wells for new and old wells, the wells in Shengli Oilfield since 1994 are tracked respectively, and the percentages of inefficient production and current production at different periods and different oil prices are obtained. Statistics show that the average annual oil production of a single well has a good correlation with time, and the average annual oil production of a single well has a good correlation with the percentage of ineffective production (Figures 2 and 3).
Variation curve of annual average oil production of single well with time.
Fig. 3 Relationship curve between ineffective production percentage and average annual oil production of single well
The relationship between the annual oil production y of a single well and time x is:
Essay on exploration and development in Shengli oil region
The correlation coefficient is 0.9963.
X= 1 is 1994. According to this relationship, the average annual oil production of a single well in the future can be predicted.
Taking the oil price 15 USD/barrel as an example, the relationship between the average annual oil production y of a single well and the percentage of ineffective production x is as follows:
Essay on exploration and development in Shengli oil region
The correlation coefficient is 0.9967.
On the basis of predicting the average annual oil production of a single well, according to the relationship between the average annual oil production of a single well and the percentage of invalid production, the percentage of invalid production under different oil prices in a year after 2000 can be predicted (table 1).
4. Calculation of annual economic output
Calculate the annual macroeconomic output by formula (7); Simultaneous (14) and (15) calculate the percentage of invalid production under different oil prices; Simultaneous (1) and (2) calculation of annual macroeconomic oil production. Table 2 is the calculation results of economic output under different oil prices in Shengli Oilfield during the Tenth Five-Year Plan period.
Table 1 Forecast results of average annual oil production of single well and percentage of ineffective production under different oil prices
Table 2 Calculation results of economic output under different oil prices in Shengli Oilfield
Verb (abbreviation of verb) conclusion
This paper puts forward and realizes the research idea and method of oil field economic output calculation. On the basis of reasonable cost analysis, by introducing the concept of ton liquid cost, the cost analysis process is simplified, and the cost problem of calculating the economic policy boundary for a long time is well solved. The inherent law between the lowest cost per ton of liquid and the average single well production is studied, the identification model of invalid wells is established, the percentage of invalid production is calculated, and the functional relationship between the average single well annual oil production and time, and the functional relationship between the percentage of invalid production and the average single well annual oil production are statistically analyzed. At the same time, it predicts the percentage of invalid output in the next few years, and finally calculates the economic output.
Thanks to Fang Kaipu, chief geologist of Development Management Department, and Fan He, senior engineer of Institute of Geological Sciences, for their support and help.
Main references
Li Liang. Economic output. Dongying: Petroleum University Press, 1997.
Ron Zhao Xin. Fundamentals of reservoir engineering. Dongying: Petroleum University Press, 199 1.
[3] Liu Qingzhi Economics of petroleum technology. Dongying: Petroleum University Press, 1998.