A method for obtaining original formation temperature

Abstract

A method for obtaining the original formation temperature. It mainly solves the problem that the existing method for measuring the original formation temperature cannot be applied to the entire well section, resulting in inaccurate measurement results. It includes: collecting well logging temperature data and temperature data of the formation produced fluid; drawing the fluid temperature T 产出流体 and t’ , select a straight line segment on the relationship diagram, and obtain the flow temperature straight line segment formula, which is recorded as T 原始地层温度 Calibrate the temperature curve of the well logging; draw a relationship diagram between the above temperature curve and the well logging temperature curve at the same depth, and establish a relationship model between the original formation temperature and the well logging temperature; according to the relationship model between the original formation temperature and the well logging temperature, obtain the original formation temperature T of the specified depth and the specified layer 原始地层温度 The method for obtaining the original formation temperature only needs to use the well temperature curve of the well logging and the temperature curve of the formation production fluid of the individual layer to obtain the original formation temperature of each target layer.

Description

Technical Field

[0001] The invention relates to the technical field of formation testing and well logging, in particular to a method for obtaining original formation temperature. Background Art

[0002] The original formation temperature not only plays an important role in the generation, migration and accumulation of oil and gas, but also has an important influence on the physical properties of oil, gas, water and rocks. Therefore, studying the spatial distribution and temporal changes of the earth's temperature field can solve many important problems in geothermal, petroleum geological theory and oil and gas exploration and development. The formation temperature is usually obtained from well temperature logging or formation testing data, but the temperature obtained by these two methods cannot represent the original formation temperature because the geothermal field such as drilling and mud circulation has been artificially changed. In order to reduce the interference of mud circulation on the well temperature during the drilling process, the temperature measurement in the drilling well is generally carried out 48 hours after the drilling is stopped. The well temperature recovery after the drilling is stopped is very slow. If the measurement allowable error is 0.2℃, a recovery period of 5 days is required; if the high-precision measurement allowable error is 0.02℃, it takes two months to recover. During the formation testing process, only the temperature change of the fluid produced by the formation can be measured, which cannot be applied to the entire well section, and the original formation temperature cannot be directly obtained, resulting in inaccurate measurement results of the original formation temperature. Summary of the invention

[0003] In order to overcome the deficiency that the existing method for measuring the original formation temperature cannot be applied to the whole well section, resulting in inaccurate measurement results, the present invention provides a method for obtaining the original formation temperature, which can solve the problems of temperature comparison between different sections and obtaining the original formation temperature of the layers with incomplete temperature data. The original formation temperature of each target layer can be obtained by using the well temperature curve of the logging and the temperature curve of the formation production fluid of the individual layer.

[0004] The technical solution of the present invention is: a method for obtaining the original formation temperature, comprising:

[0005] Step 1: Collect the well temperature data of the well logging and the temperature data of the formation produced fluid, and record the well temperature of the well logging as T 测井 =T, depths ; The temperature of the fluid produced from the formation is recorded as T 产出流体 =T,Depth=constant, t ,

[0006] Among them, depths, Depth – depth value;

[0007] t --time;

[0008] Step 2: Convert the temperature data of the produced fluid from the formation: 产出流体=T,Depth=constant, t , converted to T 产出流体 =T,Depth=constant, t’ , t'=1 / t ;

[0009] Where, T is temperature; t For time;

[0010] Step 3: Plot the fluid temperature T 产出流体 and t’ The relationship diagram, the vertical axis is the fluid temperature, the horizontal axis is t';

[0011] Step 4: At the fluid temperature T 产出流体 and t’ Select a straight line segment on the relationship diagram and record it as the flow temperature straight line segment;

[0012] Step 5: Obtain the formula for the straight line segment of flow temperature, recorded as T = a × t’ +b, a, b are constants, when t’ = 0, T = b, and the T value at this time is the original formation temperature, recorded as T 原始地层温度 ;

[0013] Step 6: Calibrate the temperature curve of the well logging. Use the result obtained in step 5 to make a relationship diagram with the well logging temperature curve at the same depth, and establish a relationship model between the original formation temperature and the well logging temperature, recorded as T 原始地层温度 = f(T 测井 depths ), establish the well temperature profile of the original formation temperature;

[0014] Step 7: According to the well temperature profile of the original formation temperature established in step 6, the original formation temperature T at the specified depth and the specified layer is obtained. 原始地层温度 , Depth=constant value.

[0015] In step 5, the least square method is used to obtain the flow temperature straight line segment formula.

[0016] Before proceeding to step 6, steps 1 to 5 are repeated multiple times to obtain the original formation temperatures of multiple target layers.

[0017] The present invention has the following beneficial effects: Due to the adoption of the above scheme, the present invention uses the flow temperature curve of the formation produced fluid to transform, and combines the selection of the flow temperature change straight line segment to deduce and obtain the original formation temperature; obtain the change trend of the well temperature of the entire well section with the depth through the well temperature curve of the logging, and combine the original formation temperature at the known depth point to obtain the corresponding original formation temperature of the entire well section, thereby realizing the correction of the well temperature profile of the logging. The transformation of the well temperature curve of the logging and the flow temperature curve of the produced fluid from the qualitative evaluation of the well temperature to the quantitative comprehensive evaluation of the original formation temperature has great practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a flow chart of the present invention;

[0019] Figure 2 It is a schematic diagram of a temperature logging curve of a certain well;

[0020] Figure 3 It is a schematic diagram of the temperature curve of the fluid pumped out of a certain well at a certain depth;

[0021] Figure 4 It is a conversion diagram of the temperature curve of the fluid pumped out of a certain well at a certain depth;

[0022] Figure 5 Select a straight line segment on the temperature curve conversion diagram of the pumped fluid at a certain depth in a certain well;

[0023] Figure 6 It is an interpretation diagram of the temperature treatment of the fluid pumped out of a certain well at a certain depth;

[0024] Figure 7 This is a comprehensive interpretation result diagram of the well temperature data of a certain well. DETAILED DESCRIPTION

[0025] The following is an example of the method for obtaining the original formation temperature of the QY layer of a shale oil reservoir in a well. The well was routinely logged with a well temperature curve, and a formation test was performed on the QX layer above the QY layer. Here, only the formation output fluid temperature change curve in the formation test is used. Figure 1 As shown, the present invention comprises the following steps:

[0026] Step 1: Collect the well temperature data of the well logging and the temperature data of the formation produced fluid, remove the abnormal points and invalid values, and record the well temperature of the well logging as T 测井 =T( depths ),See Figure 2 ; The temperature of the fluid produced from the QX formation is recorded as T 产出流体 =T(Depth=constant, t ),See Figure 3 ;

[0027] Among them, depths and Depth are depth values. Here, the depth of the QX formation is 1650m.

[0028] t --time.

[0029] Step 2: Convert the temperature data of the produced fluid from the formation: 产出流体 =T(Depth=constant, t ) Transformation T 产出流体 =T(Depth=constant, t’)、t'=1 / t ;

[0030] Where T is the temperature, t For time.

[0031] Step 3: Plot the fluid temperature T 产出流体 and t’ The vertical axis is the fluid temperature, using a linear scale; the horizontal axis is t', using a logarithmic scale, and the origin of the coordinate is set on the left side and at the minimum value of the horizontal axis scale. The converted temperature T 产出流体 and t’ For the relationship diagram, see Figure 4 .

[0032] Step 4: At the fluid temperature T 产出流体 and t’ The straight line segment is usually selected from the relationship diagram. The straight line segment selection usually starts from the beginning of the relationship diagram, removes the part that is obviously not a straight line, and then selects a straight line segment of any length. Multiple straight line segments can be divided on the diagram, and the most reasonable segment is selected and recorded as the flow temperature straight line segment. The two endpoints of the selected straight line segment are shown in Figure 5 The two triangle marks on the

[0033] Step 5: Use the least square method to find the flow temperature straight line segment formula, which is recorded as T = a × t’ +b, a, b are constants, when t’ = 0, T = b, and the T value at this time is the original formation temperature, recorded as T 原始地层温度 ,See Figure 6 .

[0034] Figure 5 is Figure 4 On this basis, the data within the two endpoints are retained and the data outside the two endpoints are removed. The formula for the straight line segment obtained here is T=-5172.3×t'+63.024. When t'=0, T=63.024℃. The T value at this time is the original formation temperature of the QX formation.

[0035] Step 6: Steps 1 to 5 may be repeated multiple times to obtain the original formation temperatures of several target layers. In this embodiment, only one original formation temperature of a QX formation is provided.

[0036] The temperature curve of the calibration logging is plotted with the result obtained in step 5 and the logging temperature curve at the same depth. That is, when there is only one original formation temperature of the QX formation, the logging temperature curve at the same depth is translated to the original formation temperature of the QX formation; when there are several original formation temperatures of the target layers, the coordinates of the original formation temperatures of the several target layers are connected. A relationship model between the original formation temperature and the logging temperature is established, denoted as T 原始地层温度 ( depths ) = f (T 测井 ( depths )), Figure 7 The dotted line in the figure is the scaled well temperature curve, from which the well temperature profile of the original formation temperature is established, which represents the change of the original formation temperature.

[0037] Step 7: According to the well temperature profile of the original formation temperature established in step 6, the original formation temperature T at the specified depth and the specified layer is obtained. 原始地层温度 (Depth = constant value). The depth of the target layer QY here is 1969.37m, that is, T original formation temperature (Depth = 1969.37). Through the scaled well temperature curve, it is determined that the original formation temperature of the QY layer is 72.38℃ (read according to the point marked by the triangle icon).

[0038] from Figure 3 It can be seen from the temperature curve of the fluid pumped out at medium depth that the temperature is in the rising stage. The test was ended prematurely before the temperature returned to the equilibrium stage, so the original formation temperature could not be measured. Because this well adopted this method, the original formation temperature can be calculated using the measured data without further extending the measurement time, thus shortening the test time.

[0039] Figure 7 It reflects the correction of the well temperature curve of the well logging. It can be seen that the well temperature of the well logging only truly reflects the temperature of each layer, but does not reflect the real formation temperature. After correction by this method, the well temperature profile reflecting the real formation temperature is obtained.

Claims

1. A method for obtaining the original formation temperature, characterized in that include: Step 1: Collect the well temperature data of the well logging and the temperature data of the formation produced fluid, and record the well temperature of the well logging as T 测井 =T, depths; the temperature of the fluid produced from the formation is recorded as T 产出流体 =T, Depth = constant, t, Among them, depths, Depth – depth value; t——time; Step 2: Convert the temperature data of the produced fluid from the formation: 产出流体 =T, Depth = constant, t, converted to T 产出流体 =T, Depth = constant, t', t' = 1 / t; Where, T is temperature; t is time; Step 3: Plot the fluid temperature T 产出流体 The relationship diagram with t', the ordinate is the fluid temperature and the abscissa is t'; Step 4: At the fluid temperature T 产出流体 Select a straight line segment on the relationship graph with t' and record it as the flow temperature straight line segment; Step 5: Obtain the formula for the straight line segment of flow temperature, recorded as T = a × t' + b, where a and b are constants. When t' = 0, T = b, and the T value at this time is the original formation temperature, recorded as T 原始地层温度 ; Step 6, calibrate the temperature curve of the well logging, and use the result obtained in step 5 to make a relationship diagram with the well logging temperature curve at the same depth; when there is only one original formation temperature of the formation, translate the well logging temperature curve at the same depth to the original formation temperature of the formation; when there are several original formation temperatures of the target layer sections, connect the coordinates of the original formation temperatures of the several target layer sections; Establish the relationship model between the original formation temperature and the logging temperature, denoted as T 原始地层温度 =f(T 测井 , depths), establish the well temperature profile of the original formation temperature; Step 7: According to the well temperature profile of the original formation temperature established in step 6, the original formation temperature T at the specified depth and the specified layer is obtained. 原始地层温度 , Depth = constant value.

2. The method for obtaining the original formation temperature according to claim 1, characterized in that: In step 5, the least square method is used to obtain the flow temperature straight line segment formula.

3. The method for obtaining the original formation temperature according to claim 2, characterized in that: Before proceeding to step 6, steps 1 to 5 are repeated multiple times to obtain the original formation temperatures of multiple target layers.

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