An abnormal well temperature warning method

Abstract

The present invention discloses an abnormal well temperature warning method, belonging to the technical field of oilfield development. It includes the following steps: (1) According to the Remay theory wellbore heat dissipation model, taking the water equivalent as the key parameter determining the liquid outlet temperature and regarding the secondary parameters with less influence on the well temperature as constants, establish a liquid outlet temperature prediction model: #imgabs0# where T is the liquid outlet temperature at the wellhead; Q is the liquid production of a single well; f w is the water cut; a, b, c are constants; (2) Fit the measured oil well data to determine the values of a, b, and c; (3) Form a reasonable well temperature range for the liquid outlet temperature at the wellhead under different ambient temperatures, establish a well temperature chart, export the real-time well temperature data of each well through the remote transmission system, and check for abnormal well temperatures. This method has strong applicability, can timely detect abnormal liquid production of oil wells, improve the processing efficiency, and greatly save costs.

Description

Technical Field

[0001] The present invention belongs to the technical field of oilfield development, and particularly relates to a method for warning of abnormal well temperature. Background Art

[0002] As most oilfields in China have reached the middle and late stages of exploitation, a large amount of professional production data has been accumulated in various auxiliary production links such as oil seismic exploration, oil well logging production, downhole operation production, oil production, oil and gas gathering and transportation, etc. These data not only contain the specific conditions of development and production in each stage, but also record the production abnormal events that occurred in a certain exploitation stage and the remedial measures taken to deal with the events. By analyzing the data of a certain production abnormal event in a certain time interval, the data change law of this abnormal event can be obtained. By effectively using these laws, the real-time oilfield development dynamic data can be used to predict whether similar abnormal events will occur in the future exploitation process, give early warning at the initial stage of the abnormal event, and take corrective measures in advance to ensure the normal progress of oil production.

[0003] With the development of oil and gas fields, the proportion of mechanical production wells is increasing, and the production ratio of mechanical production wells shows an upward trend. During the management of mechanical production wells, the liquid production temperature is an important parameter for the normal production of oil wells. In the later stage of oilfield development, the number of wells converted from natural flow to pumping production gradually increases, and the production ratio shows a gradually increasing trend. There are problems in the management of mechanical production wells such as large oil well measurement errors, complex working conditions of deep well pumps, and great difficulty in diagnosing indicator diagrams.

[0004] Chinese Patent Application CN200820080672.8 discloses a well temperature warning controller, which is applied to the detection of the temperature at the oil production wellhead of an oilfield to warn of gas channeling accidents in oil wells. It mainly consists of an alarm temperature probe, a forced stop temperature probe, an alarm temperature controller, a forced stop temperature controller, an alarm indicator light, and an AC contactor. The characteristics are that the forced stop temperature controller and the alarm temperature controller are connected in parallel on the DC power line. The alarm indicator light is connected in series with the alarm temperature controller; the AC contactor is connected in series with the forced stop temperature controller. The forced stop temperature controller is connected to the forced stop temperature probe by a wire. The alarm temperature controller is connected to the alarm temperature probe by a wire. It can detect abnormal changes in the temperature at the wellhead of an oil well, promptly detect gas channeling and interference phenomena in the oil well, notify the duty personnel; and can also automatically take power-off measures in the first time to delay gas channeling in the oil well and prevent accidents from occurring.

[0005] The above patent is used for gas channeling and interference situations in oil wells caused by well temperature fluctuations. It is necessary to install temperature controllers, alarm indicator lights, and temperature probes on each oil well, and the maintenance cost is relatively high. It is only applicable to the individual monitoring of key wells.

[0006] In view of this, the present invention proposes an abnormal well bottom-hole temperature warning method. Based on the Ramey wellbore heat dissipation model, through the processing of a large number of measured data, a simplified model of the wellhead liquid production temperature is derived, forming a bottom-hole temperature chart considering the environmental temperature. This chart can predict the reasonable liquid production temperature range of oil wells under different liquid volumes. Summary of the Invention

[0007] The purpose of the present invention is to provide an abnormal well bottom-hole temperature warning method. Based on the Ramey wellbore heat dissipation model, considering the influence of environmental temperature on the liquid production temperature, coefficient regression is performed on the maximum and minimum temperatures of the oil well over a period of time to obtain a reasonable bottom-hole temperature range considering the environmental temperature. Through the bottom-hole temperature chart, it is possible to directly and effectively check whether the actual liquid production of the oil well is normal. This method has strong applicability, can timely detect abnormal liquid production in oil wells, improve the processing efficiency, and greatly save costs.

[0008] To achieve the above-mentioned invention purpose, the technical solution of the present invention is as follows:

[0009] An abnormal well bottom-hole temperature warning method includes the following steps:

[0010] (1) According to the Remay theoretical wellbore heat dissipation model, taking the water equivalent as the key parameter determining the liquid production temperature and regarding the secondary parameters with less influence on the bottom-hole temperature as constants, a liquid production temperature prediction model is established as follows:

[0011]

[0012] Wherein,

[0013] T is the wellhead liquid production temperature, °C;

[0014] Q is the liquid production volume of a single well, m 2 ;

[0015] f w is the water cut, %;

[0016] a, b, c are constants;

[0017] (2) Fit the measured oil well data to determine the values of a, b, and c;

[0018] (3) For the wellhead liquid production temperature under different environmental temperatures, form a reasonable bottom-hole temperature range, establish a bottom-hole temperature chart, export the real-time bottom-hole temperature data of each well through a remote transmission system, and check for abnormal bottom-hole temperatures.

[0019] Furthermore, before step (1), the following steps are also included:

[0020] Using the Remay theoretical wellbore heat dissipation model, select key oil well parameters and study the influence of parameter changes on the produced liquid temperature respectively.

[0021] Furthermore, in step (1), the secondary parameters include the geothermal gradient, heat transfer coefficient, and well depth.

[0022] Furthermore, in step (2), the fitting method is the least squares method.

[0023] Furthermore, step (2) is specifically as follows:

[0024] A. Using the measured liquid production temperature of the oil well as the abscissa and the liquid production rate as the ordinate, collect the measured data of the oil well and fit the curve by the least squares method;

[0025] B. Find the empirical formula of the fitted curve;

[0026] C. Convert the empirical formula into a linear equation and calculate the values of a, b, and c.

[0027] Even further, step (2) is specifically as follows:

[0028] A. Using the measured liquid production temperature of the oil well as the abscissa and the liquid production rate as the ordinate, collect the measured data of the oil well and fit the curve by the least squares method;

[0029] B. Find the empirical formula of the fitted curve, which is

[0030] C. Take a representative point (x0, y0) in the coordinate system and substitute it into the above formula, then we have: For this representative point (x0, y0), a point with a relatively small value that can pass through the curve can be selected from the measured data. Subtract formula (2) from formula (1) to get:

[0031]

[0032] Through the above transformation, let

[0033]

[0034] Simplify to: D = A + Bx (5)

[0035] According to the general formula for finding the constants in the linear equation by the least squares method, the intercept of the line is A, and the slope of the line is B. According to the principle of selecting the representative point in the early stage, select x0 and y0, calculate the values of A and B, and substitute the values of A and B into formula (5) to obtain the regression equation;

[0036] Since there is a certain regularity between the liquid production rate of the oil well and the liquid production temperature at the wellhead, x = Q 油 +2Q 水 , assuming the water cut of the oil well is f w , then

[0037] Among them, Q液 is the liquid production volume per single well, m 2 ; Q_oil is the oil production volume per single well, m2; f w is the water cut, %,

[0038] Substitute the regression equation into the empirical formula to obtain the values of a, b, and c.

[0039] Further, in step (2), the produced liquid temperature prediction model is:

[0040]

[0041] Further, in step (3), establishing the well temperature chart specifically includes the following steps:

[0042] Perform coefficient regression on the maximum and minimum temperatures of the oil well over a period of time to obtain two different well temperature curves. These two curves form a strip, and this strip is the reasonable well temperature range considering the ambient temperature, thus obtaining the well temperature chart.

[0043] Further, in step (3), if the measured well temperature falls outside the normal well temperature range of the well temperature chart, it is initially determined as abnormal.

[0044] The beneficial effects of the present invention are:

[0045] The present invention provides a simple and direct method to timely and effectively detect various abnormalities occurring during the production process of oil wells, improve the disposal efficiency of abnormal wells, enhance the management level of oil wells, reduce the workload of traditional abnormal well investigation by auxiliary means such as dynamometer cards, current, and load, and greatly save costs. A reasonable well temperature range is formed for the wellhead produced liquid temperature under different ambient temperatures, which has practical guiding significance for improving the management of abnormal wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a schematic diagram of the wellbore heat transfer model;

[0047] Figure 2 is a diagram showing the influence of different parameters on the produced liquid temperature;

[0048] Figure 3 is a least squares fitting curve diagram;

[0049] Figure 4 is a curve diagram of the wellhead temperature varying with water cut under different liquid volumes. Among them, the lines in the figure from top to bottom represent the daily liquid volumes of 280t, 250t, 220t, 190t, 160t, 130t, 100t, 70t, 40t, and 10t in sequence;

[0050] Figure 5 is a schematic diagram of the well temperature chart of the present invention;

[0051] Figure 6 It is a schematic diagram for the application of the well temperature chart of Well TK910. Specific implementation manners

[0052] The following non-restrictive embodiments can enable those of ordinary skill in the art to more comprehensively understand the present invention, but do not limit the present invention in any way. The following content is merely an exemplary illustration of the scope claimed in the present application. Those skilled in the art can make various changes and modifications to the invention of the present application based on the disclosed content, and it should also fall within the scope claimed in the present application. The present invention will be further described below by way of specific embodiments.

[0053] In the following embodiments, the term "Ramey wellbore heat dissipation model" refers to the wellbore heat transfer theoretical model proposed by Ramey in 1962, which is recorded in the paper "Ramey, H J Jr. Wellbore Heat Transmission, JPT, 1962, 14(4): 427-435".

[0054] Embodiment

[0055] 1. Ramey theoretical wellbore heat dissipation model

[0056] During the oil production process, when the crude oil is lifted from the bottom of the well to the wellhead, the temperature will change greatly. During the lifting process, heat exchange occurs between the fluid and the formation, and the temperature will continuously decrease. The remaining temperature is the wellhead temperature. According to the principles of fluid mechanics and heat transfer, the Ramey theoretical wellbore heat dissipation model is established.

[0057] 1.1 Selection of key parameters

[0058] (1) Water equivalent of produced fluid (w / ℃)

[0059] Taking Well TK7217 as an example, given the production status of the well and the heat-carrying capacities of oil, gas, and water, the heat carried by each of the three fluids is calculated respectively, and the water equivalent of the produced fluid is calculated to be 1145 w / ℃ through a program.

[0060] Water equivalent = mass flow rate (kg / s) × specific heat of medium (J / kg·℃)

[0061] Table 1. Calculation table of water equivalent of Well TK7217

[0062] Well TK7217 <![CDATA[Gas m 3 / h]]> <![CDATA[Water m 3 / d]]> <![CDATA[Oil m 3 / d]]> <![CDATA[Output m 3 / d]]> 1988 15 13.9 Mass flow rate kg / s 0.021 0.198 0.143 Specific heat J / kg·℃ 200 4200 2000 Water equivalent w / ℃ 4.17 831.25 286.37

[0063] (2) Total heat transfer coefficient Kl (w / m·℃) between the produced fluid and the formation

[0064] Such as Figure 1As shown in the figure, for the schematic diagram of the wellbore heat transfer model, the heat transfer from the wellbore fluid to the surrounding formation rock must overcome the thermal resistances generated by the tubing wall, the annulus between the tubing and the casing, the casing wall, and the cement sheath. The heat transfer amount between the produced fluid and the wellbore wall is equal to the heat transfer amount between the wellbore wall and the formation, and the total heat transfer coefficient between the produced fluid and the formation can be obtained.

[0065] Total heat transfer coefficient calculation formula:

[0066]

[0067] U to is the total heat transfer coefficient between the produced fluid and the formation, W / (m·°C);

[0068] r ti , r to are the inner and outer radii of the tubing, m;

[0069] r ci , r co are the inner and outer radii of the casing, m;

[0070] r h is the outer radius of the cement sheath, m;

[0071] h f , h c are the convective heat transfer coefficients of the fluids inside the tubing and the casing, W / (m·°C);

[0072] k cas , k cem , k tub are the thermal conductivities of the casing, the cement sheath, and the tubing, W / (m·°C);

[0073] The total heat transfer coefficient between the produced fluid and the formation obtained by formula calculation is 3.95 W / (m·°C).

[0074] (3) Temperature of the produced fluid (°C)

[0075] T1(Z) = aZ + b + aA + (T0 + aA - b)e -Z / A

[0076]

[0077] T o is the initial formation temperature, °C

[0078] T1(Z) is the fluid temperature, °C;

[0079] Z is the well depth, m;

[0080] k is the geothermal gradient (m / °C);

[0081] r1 is the radius of the tubing, m;

[0082] U is the overall heat transfer coefficient, W / (m·°C);

[0083] f t is a dimensionless time function;

[0084] a, b, and c are undetermined coefficients;

[0085] According to the Ramey wellbore heat dissipation model, with a water equivalent of 1145 W / °C and a thermal conductivity of 3.95 W / (m·°C), the produced fluid temperature of Well TK7217 is 20 °C through program calculation when migrating from the bottom of the 4200 m well to the wellhead.

[0086] 1.2 Model accuracy verification

[0087] Eleven oil wells with stable metering and flowing temperature data in Tuoputai were selected for comparison between model calculation and measured flowing temperature. The coincidence rate is good, and the error is controlled within 2 °C.

[0088] Table 2. Statistical table of measured well temperature and model calculation

[0089]

[0090] 1.3 Model sensitivity analysis

[0091] By taking the 4 independent variables in the numerical calculation formula of the Ramey heat dissipation model as single factors and selecting reasonable parameter ranges in the Tahe oilfield area, the effects of changes in water equivalent, geothermal gradient, heat transfer coefficient, and well depth parameters on the produced fluid temperature were studied respectively. The results are as Figure 2 shown. It can be seen from the influence curves of water equivalent, well depth, tubing radius, and geothermal gradient on the produced fluid temperature that the water equivalent has the greatest influence on the produced fluid temperature.

[0092] 2. Establish a simplified well temperature chart model

[0093] Through the sensitivity analysis of the theoretical wellbore heat dissipation model, the key parameter determining the outlet fluid temperature is the water equivalent, and the secondary parameters with less influence on the well temperature are regarded as constants. Finally, a simplified heat dissipation model with the outlet fluid temperature T, the produced fluid volume Q, and the water cut fw as two independent variables is obtained. Regarding the values of Z, U, and K in the Ramey wellbore heat dissipation model as constants and taking the average values in the Tahe oilfield area, the simplified well temperature chart model is obtained:

[0094]

[0095] Among them,

[0096] T is the outlet fluid temperature at the wellhead, °C;

[0097] Q is the produced fluid volume of a single well, m 2 ;

[0098] f wis the water content, %;

[0099] a, b, and c are undetermined coefficients.

[0100] 2.1 Determination of undetermined coefficients

[0101] By analyzing and sorting out the data of 205 oil wells actually measured in Tahe Oilfield, with the measured liquid production temperature of the oil wells as the abscissa and the liquid production volume as the ordinate, the fitting curve is as Figure 3 shown.

[0102] It can be seen that although the points are not completely distributed on a regular curve, these points do form a "band-shaped" and smooth curve. An approximate curve can be found by the least squares method to better fit the regularity reflected by these points, making the sum of the squares of the distances from the curve to each point reach the minimum, and an empirical formula for this curve can be found through the processing of the measured data.

[0103] Observing the change curve of the produced liquid temperature and the liquid production volume in the simplified well temperature chart model belongs to

[0104] the type of regression equation, and the graph is a hyperbola. For this kind of hyperbola, it can be transformed into a straight line by the following method to determine the undetermined coefficients a, b, and c.

[0105] Taking a representative point (x0, y0) in the coordinate system and substituting it into the above formula, then there is: This representative point (x0, y0) can be selected from the measured data as a value that is relatively small and can pass through the curve at the same time. Subtracting formula (2) from formula (1) gives:

[0106]

[0107] Through the above transformation, let

[0108]

[0109] It is simplified to: D = A + Bx (5)

[0110] According to the general formula for finding the constants in the straight line equation by the least squares method, the intercept of the straight line is A, and the slope of the straight line is B. According to the principle of selecting the representative point in the early stage, select x0 = 34.2, y0 = 178.3383;

[0111] Table 3. Calculation table for finding the straight line equation by the least squares method

[0112]

[0113] Calculated to get A = 12.271, B = 0.0204. Substitute the values of A and B into formula (5), then the regression equation is:

[0114] D = 12.271 + 0.0204x(6)

[0115] Since there is a certain regularity between the liquid production of the oil well and the outlet liquid temperature at the wellhead, x = Q 油 + 2Q 水 Let the water cut of the oil well be f w Then

[0116] Substitute formula (6) into the empirical formula, and we get a = 9.465, b = 0.015, c = 19.66

[0117]

[0118] T is the outlet liquid temperature at the wellhead, °C;

[0119] Q is the liquid production of a single well, m 2 ;

[0120] f w is the water cut, %.

[0121] This formula is the empirical formula for predicting the outlet liquid temperature of the oil well

[0122] 2.2 Model sensitivity analysis

[0123] Through the sensitivity analysis of the simplified model, as the water cut increases, the wellhead temperature gradually rises, and the larger the liquid volume, the higher the well temperature

[0124] 2.3 Establishment of well temperature chart

[0125] In practical applications, the change of the external environmental temperature at different times has a certain impact on the outlet liquid temperature at the wellhead. Considering the influence of the environmental temperature, the coefficient regression of the maximum and minimum temperatures of the oil well for a period of time is carried out, and two different well temperature curves are obtained. These two curves form a strip, and this strip is the reasonable well temperature range considering the environmental temperature, thus establishing a well temperature chart applicable to the Tahe Oilfield, as Figure 5 .

[0126] Application example

[0127] Taking the electric pump well TK910H as an example, the current liquid volume of this well is 140t, the water cut is 92%, and the daily oil production is 10t. By drawing the chart, as Figure 6As shown, the normal well temperature range at a liquid volume of 140 t was obtained. Combining with the remotely measured well temperature, it was found that it fell outside the normal well temperature range, and it was initially determined as abnormal. At the same time, routine inspections were carried out, and it was found that the well produced liquid normally on site, and the current card showed that the electric pump was working normally, which was in contradiction with the low well temperature. Further arrangements were made to inspect the process, and it was found that the constant-pressure gas release valve in this well had internal leakage, resulting in the liquid flowing out of the tubing into the casing, forming a circulation. Timely arrangements were made to replace the constant-pressure gas release valve and sweep the line, and finally the production capacity was restored to 10 t / d after the line was cleared.

[0128] It can be seen that just through conventional means: data such as current, dynamogram, and load cannot directly reflect whether the oil well produces liquid normally. Through the well temperature chart, it is possible to most directly and effectively check whether the actual inlet liquid volume of the oil well is normal.

[0129] Using this method to check the abnormal well temperature from January to June 2020, the results are as follows in the table:

[0130] Table 4. Well Temperature Abnormality Inspection Table from January to June 2020

[0131]

[0132]

[0133] Using this well temperature warning method, a total of 86 well inspections were carried out from January to June. 59 well inspections with abnormalities caused by the decrease in liquid production were solved, 425 t of abnormal well production was reduced, and the production loss of 720,800 yuan was reduced. Through the well temperature chart method, 42 well washing and line sweeping operations were reduced, and 8 pump inspections caused by abnormalities were reduced, saving about 3.52 million yuan in costs.

[0134] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An abnormal well temperature warning method, characterized in that The steps include the following: (1) According to the Remay theory wellbore heat dissipation model, taking the water equivalent as the key parameter determining the liquid production temperature and regarding the secondary parameters with little influence on the well temperature as constants, a liquid production temperature prediction model is established as follows: Wherein, T is the liquid production temperature at the wellhead, °C; Q is the liquid production volume of a single well, m 2 ; is the moisture content, %; a, b, c are constants; (2) Fit the measured oil well data to determine the values of a, b, and c; (3) Conduct coefficient regression on the highest and lowest temperatures of the oil well over a period of time to obtain two different well temperature curves. These two curves form a strip, and this strip is the reasonable well temperature range considering the ambient temperature, thus obtaining the well temperature chart. Export the real-time well temperature data of each well through the remote transmission system to check for abnormal well temperatures; Among them, step (2) is specifically: A. Taking the liquid production volume as the abscissa and the measured liquid production temperature of the oil well as the ordinate, collect the measured oil well data and fit the curve by the least squares method; B. Find the empirical formula of the fitting curve, which is ; C. Take a representative point in the coordinate system ( , ), substitute it into the above formula, then we have: This representative point ( , ), select a value from the measured data, and at the same time a point that can pass through the curve. Subtract formula (2) from formula (1) to get: Through the above transformation, let Simplified to: According to the general formula for finding the constants in the straight-line equation by the least squares method, the intercept of the straight line is A, and the slope of the straight line is B. According to the principle of selecting representative points in the early stage, select , , calculate the values of A and B, substitute the values of A and B into formula (5) to obtain the regression equation; Substitute the regression equation into the empirical formula to obtain the values of b and c.

2. The abnormal well temperature warning method according to claim 1, characterized in that Before step (1), the following steps are also included: Using the Remay theory wellbore heat dissipation model, select the key oil well parameters and study the influence of parameter changes on the produced liquid temperature respectively.

3. The abnormal well temperature warning method according to claim 1, characterized in that In step (1), the secondary parameters include the geothermal gradient, heat transfer coefficient, and well depth.

4. The abnormal well temperature warning method according to claim 1, characterized in that In step (2), the fitting method is the least squares method.

5. The abnormal well temperature warning method according to claim 1, characterized in that In step (2), the liquid production temperature prediction model is: 。 6. The abnormal well temperature warning method according to claim 1, characterized in that, In step (3), if the measured well temperature falls outside the normal well temperature range of the well temperature chart, it is initially determined as abnormal.

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