Nozzle diameter calculation
The diameter of the wellhead fitting for gas wells is determined by the formula:
Where - the diameter of the fitting, mm;
Consumption coefficient,;
Qg - gas flow rate, m3/day;
Pbur - buffer pressure, according to field data atm.
Calculate the diameter of the wellhead choke hole using formula (2.16) for well No. 1104:
Calculation of the minimum well flow rate that ensures the removal of the liquid phase
During the operation of gas wells, the most common complication is the ingress of the liquid phase (water or condensate). In this case, it is necessary to determine the minimum bottomhole flow rate of a gas well, at which there is still no accumulation of liquid at the bottomhole with the formation of a liquid plug.
The minimum flow rate of a gas well (in m3/day), at which a liquid plug is not formed at the bottomhole, is calculated by the formula:
Where - the minimum gas velocity at which a liquid plug is not formed, m / s;
Temperature under standard conditions, K,
Reservoir temperature, K,
Bottom hole pressure, MPa,
Atmospheric pressure, MPa,
Internal diameter of the tubing, according to the project = 0.062 m,
Coefficient of gas supercompressibility.
The minimum gas velocity at which no water lock is formed:
Minimum gas velocity at which no condensate plug is formed:
During the operation of gas wells, the most common complication is the ingress of the liquid phase (water or condensate). In this case, it is necessary to determine the minimum bottomhole flow rate of a gas well, at which there is no accumulation of liquid at the bottomhole with the formation of a liquid plug.
Using formulas (2.17-2.19), we calculate the minimum flow rates of gas condensate well No. 1104 of the Samburgskoye OGCF, at which condensate will not settle at the bottomhole:
The minimum flow rate at which water is taken out:
Or thousand m3/day.
Minimum gas velocity at which all condensate is brought to the surface:
Minimum flow rate for condensate removal:
Or thousand m3/day.
Comparing the obtained results, it can be noted that, under other unchanged conditions, the complete removal of condensate is possible at higher flow rates of a gas well than the complete removal of water.
Calculation of technological efficiency of sidetracking
The amount of additionally produced gas for the billing period due to drilling of the lateral horizontal wellbore No. 1104 in the productive formation is determined by the formula:
Where - the value of the actual oil produced by the well for the billing period, ;
The value of the theoretical (estimated) oil production from the well for the calculated period in the absence of a horizontal wellbore along the productive formation, .
Where - the flow rate of a well with a horizontal wellbore and a vertical one, ;
The flow rate of a vertical well, .
Correction factor taking into account compliance with additional gas production and depletion of recoverable reserves, n.u. For the first 2 years v=1;
The amount of additionally produced gas condensate is determined by the formula:
Where - the amount of additionally produced gas condensate for the billing period due to the drilling of a side horizontal wellbore, t;
Condensate gas factor, according to field data, kg/m3.
Calculation for 2 years according to the formulas (2.23-2.34):
In this section, the calculation of technological efficiency was made by drilling a horizontal wellbore in a vertical well. Comparison of the "actual" indicators of the development of the site by horizontal wells with the indicators of the base case, once again shows the undeniable advantage of using BGS in the development of low-productive reservoirs of relatively small effective thickness. Over the period of operation in natural mode for two years, when using horizontal wells, additional production will amount to natural gas and tons of gas condensate, which is 9 times higher than these figures over the base case.
Conclusions on the second section
1. Analysis modern methods Intensification of natural gas and gas condensate production showed the promise of using such methods as hydraulic fracturing and sidetracking in vertical and directional wells at the Samburgskoye oil and gas condensate field. Among these production stimulation methods, sidetracking is one of the most effective in the conditions of the Samburgskoye field.
2. The use of sidetracking technology in vertical and directional wells of the Samburgskoye oil and gas condensate field to transfer wells to horizontal wells will not only reduce drilling volumes, increase the flow rate and profitability of wells, but also use reservoir energy more rationally, due to lower drawdowns on the reservoir.
3. Based on the analysis of the production well stock and the density of residual mobile reservoir gas reserves, candidate well No. 1104 was selected for sidetracking. For a larger implementation of this technology, it is recommended to conduct additional studies in order to identify other wells that are promising for sidetracking.
3. Technological calculation of the parameters of a candidate well according to the method of Aliyev Z.S. showed that the flow rate of the design well after sidetracking can increase by more than 10 times from 89.3 thousand m3/day to 903.2 thousand m3/day.
4. Calculations of the profile of well No. 1104 were performed. At the same time, “window cutting” in the EC at a depth of 2650 m was chosen as the technology of the drilling method, with a maximum angle of curvature of 2.0° per 10 m in the range of 2940 - 3103 m vertically and a horizontal section length of 400 m.
5. The calculation of the main parameters of the technological mode of the well operation made it possible to determine the diameter of the wellhead choke, the minimum gas velocities (m/s, m/s) at the bottomhole, ensuring the complete removal of water and gas condensate to the surface, as well as the minimum flow rates at which bottomhole liquid plugs (thousand m3/day, thousand m3/day). Under other constant conditions, the complete removal of condensate is possible at higher flow rates of a gas well than the complete removal of water.
6. The calculation of the technological efficiency of sidetracking shows the undeniable advantage of using this technology in the development of low-productive reservoirs of relatively small effective thickness. Over the period of operation in natural mode for two years, additional production will be natural gas and tons of gas condensate, which is 9 times higher than these indicators over the base option.
7. Thus, the performed calculations for the use of sidetracking at the Samburgskoye oil and gas condensate field have shown their effectiveness, and this technology can be recommended as a method for intensifying the production of natural gas and gas condensate at this field.
This concept refers to the amount of water, oil, or gas that a source can pass off as conventional unit time – in a word, its productivity. This indicator is measured in liters per minute, or in cubic meters per hour.
The calculation of the flow rate is necessary both for the arrangement of domestic aquifers, and in the gas and oil industries - each classification has a certain formula for calculations.
1 Why do you need to calculate the well flow rate?
If you know the flow rate of your well, you can easily select the optimal pumping equipment, since the pump power must exactly match the productivity of the source. In addition, in case of any problems, a correctly completed well passport will greatly help the repair team to choose the appropriate way to restore it.
Based on the flow rates, wells are classified into three groups:
- Low-rate (less than 20 m³/day);
- Average flow rates (from 20 to 85 m³/day);
- High-yield (over 85 m³/day).
In the gas and oil industry, the operation of marginal wells is unprofitable. Therefore, preliminary forecasting of their flow rate is a key factor that determines whether a new gas well will be drilled in the developed area.
To determine such a parameter in the gas industry, there is a certain formula (which will be given below).
1.1 How to calculate the flow rate of an artesian well?
To perform calculations, you need to know two source parameters - static and dynamic water levels.
To do this, you will need a rope, with a bulky weight at the end (so that when you touch the water surface, a splash is clearly audible).
You can measure the indicators after one day after the end. Waiting a day after completion of drilling and flushing is necessary for the amount of fluid in the well to stabilize. It is not recommended to take measurements earlier - the result may be inaccurate, since on the first day there is a constant increase in the maximum water level.
Take measurements after the required time has elapsed. You need to do this in depth - determine how long the part of the pipe in which there is no water is. If the well is made in accordance with all technological requirements, then the static water level in it will always be higher than the top point of the filter section.
The dynamic level is a variable indicator that will change depending on the operating conditions of the well. When water is taken from the source, its amount in the casing is constantly decreasing. In the case when the intensity of water intake does not exceed the productivity of the source, then after some time the water stabilizes at a certain level.
Based on this, the dynamic level of the liquid in the well is an indicator of the height of the water column, which will be maintained with a constant intake of liquid at a given intensity. Using different power the dynamic water level in the well will be different.
Both of these indicators are measured in "meters from the surface", that is, the lower the actual height of the water column in the siege column, the lower the dynamic level will be. In practice, calculating the dynamic water level helps to find out to what maximum depth a submersible pump can be lowered..
The calculation of the dynamic water level is carried out in two stages - you need to perform an average and intensive water intake. Make a measurement after the pump has been running continuously for one hour.
Having determined both factors, you can already obtain indicative information on the flow rate of the source - the smaller the difference between the static and dynamic levels, the greater the well flow rate. For a good artesian well, these indicators will be identical, and the average productivity source has a difference of 1-2 meters.
The calculation of the well flow rate can be done in several ways. It is easiest to calculate the flow rate using the following formula: V * Hv / Hdyn - Hstat.
Wherein:
- V is the intensity of water withdrawal when measuring the dynamic level of the well;
- H dyn - dynamic level;
- H stat - static level;
- H in - the height of the water column in the casing (the difference between the total height of the casing and the static level of the liquid)
How to determine the flow rate of a well in practice: take as an example a well with a height of 50 meters, while the perforated filtration zone is located at a depth of 45 meters. The measurement showed a static water level with a depth of 30 meters. Based on this, we determine the height of the water column: 50-30 \u003d 20 m.
To determine the dynamic indicator, suppose that two cubic meters of water were pumped out of the source in one hour of operation by the pump. After that, the measurement showed that the height of the water column in the well became less by 4 meters (there was an increase in the dynamic level by 4 m)
That is, N dyn \u003d 30 + 4 \u003d 34 m.
In order to minimize possible calculation errors, after the first measurement, it is necessary to calculate the specific flow rate, with which it will be possible to calculate the real indicator. To do this, after the first liquid intake, it is necessary to give the source time to fill up so that the level of the water column rises to a static level.
After that, we take water with a greater intensity than the first time, and again measure the dynamic indicator.
To demonstrate the calculation of the specific flow rate, we use the following conditional indicators: V2 (pumping intensity) - 3 m³, if we assume that with a pumping intensity of 3 cubic meters per hour, Ndyn is 38 meters, then 38-30 = 8 (h2 = 8).
The specific flow rate is calculated by the formula: Du = V 2 - V 1 / H 2 - H 1, where:
- V1 - intensity of the first water intake (smaller);
- V2 - intensity of the second water intake (large);
- H1 - decrease in the water column when pumping out at a lower intensity;
- H2 - a decrease in the water column during pumping of greater intensity
We calculate the specific flow rate: D y \u003d 0.25 cubic meters per hour.
The specific flow rate shows us that an increase in the dynamic water level by 1 meter entails an increase in the well flow rate by 0.25 m 3 /hour.
After the specific and usual indicator is calculated, it is possible to determine the actual flow rate of the source using the formula:
Dr \u003d (H filter - H stat) * Du, where:
- H filter - the depth of the upper edge of the filter section of the casing string;
- H stat - static indicator;
- Du - specific debit;
Based on the previous calculations, we have: Dr \u003d (45-30) * 0.25 \u003d 3.75 m 3 / hour - this is high level debit for (classification of high-yield sources starts from 85 m³/day, for our well it is 3.7*24=94 m³)
As you can see, the error of the preliminary calculation, in comparison with the final result, was about 60%.
2 Application of the Dupuis formula
The classification of wells in the oil and gas industry requires the calculation of their flow rate using the Dupuis formula.
The Dupuis formula for a gas well has the following form:
To calculate the oil production rate, there are three versions of this formula, each of which is used for different types wells - since each classification has a number of features.
For an oil well with an unsteady supply regime.
Well flow rate is main well parameter, showing how much water can be obtained from it in a certain period of time. This value is measured in m 3 / day, m 3 / hour, m 3 / min. Therefore, the higher the well flow rate, the higher its productivity.
First of all, you need to determine the well flow rate in order to know how much liquid you can count on. For example, is there enough water for uninterrupted use in the bathroom, in the garden for watering, etc. Besides, given parameter great help in choosing a pump for water supply. So, the larger it is, the more efficient the pump can be used. If you buy a pump without paying attention to the flow rate of the well, then it may happen that it will suck water out of the well faster than it will be filled.
Static and dynamic water levels
In order to calculate the flow rate of a well, it is necessary to know the static and dynamic water levels. The first value indicates the water level in a calm state, i.e. at a time when the pumping of water has not yet been made. The second value determines the established water level while the pump is running, i.e. when the rate of its pumping is equal to the rate of filling the well (water stops decreasing). In other words, this debit directly depends on the performance of the pump, which is indicated in its passport.
Both of these indicators are measured from the surface of the water to the surface of the earth. The unit of measurement is usually the meter. So, for example, the water level was fixed at 2 m, and after turning on the pump, it settled at 3 m, therefore, the static water level is 2 m, and the dynamic one is 3 m.
I would also like to note here that if the difference between these two values is not significant (for example, 0.5-1 m), then we can say that the flow rate of the well is large and most likely higher than the pump performance.
Well flow rate calculation
How is the flow rate of a well determined? This requires a high-performance pump and a measuring tank for pumped water, preferably as large as possible. The calculation itself is best considered on a specific example.
Initial data 1:
- Well depth - 10 m.
- The beginning of the level of the filtration zone (the zone of water intake from the aquifer) - 8 m.
- Static water level - 6 m.
- The height of the water column in the pipe - 10-6 = 4m.
- Dynamic water level - 8.5 m. This value reflects the remaining amount of water in the well after pumping out 3 m 3 of water from it, with the time spent on this being 1 hour. In other words, 8.5 m is the dynamic water level at a debit of 3 m 3 / h, which decreased by 2.5 m.
Calculation 1:
Well flow rate is calculated by the formula:
D sk \u003d (U / (H dyn -H st)) H in \u003d (3 / (8.5-6)) * 4 \u003d 4.8 m 3 / h,
Conclusion: well debit is equal to 4.8 m3/h.
The presented calculation is very often used by drillers. But it carries a very large error. Since this calculation assumes that the dynamic water level will increase in direct proportion to the pumping speed of the water. For example, with an increase in pumping water to 4 m 3 / h, according to him, the water level in the pipe drops by 5 m, which is not true. Therefore, there is a more accurate method with the inclusion in the calculation of the parameters of the second water intake to determine the specific flow rate.
What should be done about it? It is necessary after the first water intake and data recording (previous option), to allow the water to settle and return to its static level. After that, pump out water at a different speed, for example, 4 m 3 /hour.
Initial data 2:
- The well parameters are the same.
- Dynamic water level - 9.5 m. With a water intake intensity of 4 m 3 / h.
Calculation 2:
The specific well flow rate is calculated by the formula:
D y \u003d (U 2 -U 1) / (h 2 -h 1) \u003d (4-3) / (3.5-2.5) \u003d 1 m 3 / h,
As a result, it turns out that an increase in the dynamic water level by 1 m contributes to an increase in the flow rate by 1 m 3 / h. But this is only on condition that the pump will be located not lower than the beginning of the filtration zone.
The real flow rate is calculated here by the formula:
D sc \u003d (N f -H st) D y \u003d (8-6) 1 \u003d 2 m 3 / h,
- H f = 8 m- the beginning of the level of the filtration zone.
Conclusion: well debit is equal to 2 m 3 /h.
After comparison, it can be seen that the values of the well flow rate, depending on the calculation method, differ from each other by more than 2 times. But the second calculation is also not accurate. The well flow rate, calculated through the specific flow rate, is only close to the real value.
Ways to increase well production
In conclusion, I would like to mention how the well flow rate can be increased. There are essentially two ways. The first way is to clean the production pipe and the filter in the well. The second is to check the performance of the pump. Suddenly, it was for his reason that the amount of produced water decreased.
Vladimir Khomutko
Reading time: 4 minutes
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Methods for calculating oil production
When determining productivity, its flow rate is determined, which is a very important indicator when calculating the planned productivity.
It is difficult to overestimate the importance of this indicator, since it is used to determine whether the raw material received from a particular site will pay off the cost of its development or not.
There are several formulas and methods for calculating this indicator. Many enterprises use the formula of the French engineer Dupuy (Dupuy), who devoted many years to studying the principles of movement ground water. Using the calculation according to this method, it is quite simple to determine whether it is expedient to develop one or another section of the field from an economic point of view.
The flow rate in this case is the volume of fluid that the well supplies for a certain period of time.
It is worth saying that quite often miners neglect the calculation of this indicator when installing mining equipment, but this can lead to very sad consequences. The calculated value, which determines the amount of oil produced, has several determination methods, which we will discuss later.
Often this indicator is called “pump performance” in another way, but this definition does not quite accurately characterize the value obtained, since the properties of the pump have their own errors. In this regard, the volume of liquids and gases determined by calculation in some cases differs greatly from the declared one.
In general, the value of this indicator is calculated in order to select pumping equipment. Having determined in advance the performance of a certain section by means of a calculation, it is possible to exclude pumps that are not suitable in terms of their parameters already at the development planning stage.
The calculation of this value is necessary for any mining enterprise, since oil-bearing areas with low productivity may simply turn out to be unprofitable, and their development will be unprofitable. In addition, incorrectly selected pumping equipment due to untimely calculations can lead to the fact that the company will receive significant losses instead of the planned profit.
Another an important factor, indicating that such a calculation is mandatory for each specific well is the fact that even the flow rates of already operating wells located nearby can differ significantly from the flow rate of a new one.
Most often, such a significant difference is explained by the specific values \u200b\u200bof the quantities substituted into the formulas. For example, the permeability of a reservoir can vary significantly depending on the depth of the reservoir, and the lower the permeability of the reservoir, the lower the productivity of the area and, of course, the lower its profitability.
The calculation of the flow rate not only helps in the selection pumping equipment, but allows us to determine optimal location well drilling.
Installing a new mining rig is a risky business, because even the most qualified specialists in the field of geology do not fully know all the secrets of the earth.
There are currently many varieties professional equipment for oil production, but in order to make right choice, you must first determine all the necessary drilling parameters. The correct calculation of such parameters will allow you to choose the optimal working set, which will be most effective for a site with a specific performance.
Methods for calculating this indicator
As we said earlier, there are several methods for calculating this indicator.
Most often, two methods are used - the standard one, and using the Dupuis formula mentioned above.
It should be said right away that the second method, although more complicated, gives a more accurate result, since the French engineer devoted his whole life to studying this area, as a result of which many more parameters are used in his formula than in the standard method. However, we will consider both methods.
Standard Calculation
This technique is based on the following formula:
D = H x V / (Hd - Hst), where
D is the value of the well flow rate;
H is the height of the water column;
V - pump performance;
Нд – dynamic level;
Hst - static level.
In this case, the distance from the initial level is taken as an indicator of the static level groundwater to the initial soil layers, and the absolute value is used as the dynamic level, which is determined by measuring the water level after it is pumped out, using measuring tools.
There is a concept of the optimal rate of production of the oil-bearing section of the field. It is determined both to determine the general level of drawdown of a particular well, and for the entire productive formation as a whole.
The formula for calculating the average drawdown level implies the value of the bottom hole pressure Рzab = 0. The flow rate of a particular well, which was calculated for the optimal drawdown indicator, is the optimal value of this indicator.
Mechanical and physical pressure on the formation can lead to the collapse of some parts of the inner walls of the wellbore. As a result, the potential flow rate often has to be reduced mechanically, so as not to disturb the continuity of production and maintain the strength and integrity of the walls of the trunk.
As you can see, the standard formula is the simplest, as a result of which it gives the result with a fairly significant error. To get a more accurate and objective result, it is advisable to use the more complex, but much more accurate Dupuy formula, which takes into account a greater number of important parameters of a particular area.
Dupuis calculation
It is worth saying that Dupuy was not only a qualified engineer, but also an excellent theoretician.
He even deduced not one, but two formulas, the first of which is used to determine the potential hydraulic conductivity and productivity for pumping equipment and an oil-bearing reservoir, the second allows for calculation for a non-ideal pump and field, based on their actual productivity.
So, let's analyze the first Dupuis formula:
N0 = kh / ub * 2∏ / ln(Rk/rc), where
N0 is an indicator of potential productivity;
Kh/u is the coefficient of hydraulic conductivity of the oil-bearing formation;
b is the coefficient taking into account the volume expansion;
∏ is Pi = 3.14;
Rk is the value of the loop feed radius;
Rc is the value of the bit radius, measured over the entire distance to the exposed reservoir.
Dupuy's second formula:
N = kh/ub * 2∏ / (ln(Rk/rc)+S, where
N is an indicator of actual productivity;
S is the so-called skin factor, which determines the flow resistance.
The remaining parameters are deciphered in the same way as in the first formula.
The second Dupuis formula for determining the actual productivity of a particular oil-bearing area is currently used by almost all producing companies.
It is worth saying that in some cases, in order to increase the productivity of the field, the technology of hydraulic fracturing of the productive formation is used, the essence of which is the mechanical formation of cracks in it.
Periodically, it is possible to carry out the so-called mechanical adjustment of the oil flow rate in the well. It is carried out by increasing the bottom hole pressure, which leads to a decrease in the level of production and shows the actual potential of each oil-bearing area of the field.
In addition, to increase the flow rate, thermal acid treatment is also used.
With the help of various solutions containing acidic liquids, the rock is cleaned from deposits of resins, salts and other chemicals formed during drilling and operation, which interfere with the high-quality and efficient development of a productive formation.
First, the acid fluid is poured into the wellbore until it fills the area in front of the formation being developed. Then the valve is closed, and under pressure this solution passes further inland. The remains of this solution are washed out either with oil or water after the resumption of hydrocarbon production.
It is worth saying that the natural decline in the productivity of oil fields is at the level of 10 to 20 percent per year, if we count from the initial values of this indicator obtained at the time of the start of production. The technologies described above make it possible to increase the intensity of oil production at the field.
The debit must be calculated after certain periods of time. This helps in shaping the development strategy of any modern oil producing company that supplies raw materials to enterprises producing various petroleum products.
One of the characteristics of a drilled well is the rate of production from a drilled subterranean formation, or the ratio of volume to a certain time period. It turns out that the flow rate of a well is its performance, measured in m 3 / hour (second, day). The value of the well flow rate must be known when choosing the productivity of a well pump.
Factors determining filling rate:
Debit: calculation methods
The power of the pump for an artesian well must correspond to its productivity. Before drilling, it is necessary to calculate the volume required for water supply and compare the obtained data with the indicators of the exploration of the geological service in relation to the depth of the reservoir and its volume. The well flow rate is determined by a preliminary calculation of statistical and dynamic indicators relative to the water level.
Wells with a productivity of less than 20 m 3 /day are considered low-rate.
Reasons for a small well flow rate:
The calculation of the well flow rate is carried out at the stage of determining the depth of the aquifer, drawing up the design of the well, choosing the type and brand of pumping equipment. At the end of drilling, experimental filtration work is carried out with the indicators recorded in the passport. If an unsatisfactory result is obtained during commissioning, this means that errors were made in determining the design or selection of equipment.
Small well flow rate, what to do? There are several options:
Basic parameters for calculating the flow rate
The debit calculation formula is based on an exact mathematical calculation:
D \u003d H x V / (Hd - Hst), meter:
Well rate calculation example:
Substituting the data, we get the estimated flow rate - 5.716 m 3 / h.
For verification, a trial pumping with a larger pump is used, which will improve the dynamic level readings.
The second calculation must be performed according to the above formula. When both flow rates are known, the specific indicator is known, which gives an accurate idea of how much productivity increases with an increase in the dynamic level by 1 meter. For this, the formula is applied:
Dsp = D2 – D1/H2 – H1, where:
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