Well temperature recovery water injection profile evaluation method based on distributed optical fiber temperature logging

Abstract

The invention discloses a well temperature recovery water injection profile evaluation method based on distributed optical fiber temperature logging, and relates to the technical field of oil and gas field development water injection. DTS logging data are read for filtering and noise reduction processing; extracting shaft temperature data of a continuous time sequence; calculating the function relationship between the wellbore temperature Tw and the shut-in time delta t during the temperature recovery period, and calculating dTw / dln (tR); drawing a cross plot of Tw and dTw / dln (tR) to obtain a temperature return relaxation parameter of each interpretation layer; solving a basic value of the lithologic temperature return relaxation parameter of the target; and calculating the relative water absorption capacity of each interpretation layer. According to the method, the relation between the shaft temperature and the injection rate is deduced through a heat balance equation in a reservoir in the temperature recovery stage after the water injection well is shut in, an explanation model is established, and temperature return relaxation parameters of all injection layers of the injection well in the well shut-in temperature recovery stage are determined through distributed optical fiber temperature sensing DTS logging information data processing; and the explanation model is substituted for injection profile evaluation, so that the accuracy and efficiency of DTS injection profile evaluation are improved.

Description

Technical Field

[0001] The invention relates to the technical field of water injection for oil and gas field development, and in particular to a method for evaluating a well temperature recovery water injection profile based on distributed optical fiber temperature logging. Background Art

[0002] In the process of oil and gas field development, water injection technology is the core technical means to maintain formation pressure and enhance oil recovery (EOR). According to statistics, about 75% of the world's oil fields are developed by water injection. The accurate evaluation of injection profiles is directly related to the optimization of water injection efficiency and the prediction of remaining oil distribution. Traditional injection profile monitoring mainly relies on conventional production logging (such as radioisotope tracing, flowmeter, pulse neutron oxygen activation, etc.). These monitoring technologies vary in their adaptability to different water injection structures in the well, and have disadvantages such as difficulty in test construction, poor timeliness, and some radioactive elements causing certain pollution and danger to the environment.

[0003] Distributed fiber temperature sensing (DTS) is a new monitoring method with the advantages of real-time, continuous, high spatial resolution and low cost, and has been widely used in the field of oil and gas field development. DTS technology can provide continuous temperature profile information along the wellbore, providing a new idea for injection profile evaluation.

[0004] The current DTS injection profile evaluation method is mainly based on the steady-state / quasi-steady-state temperature field model, and its core assumption is that the temperature field reaches thermal equilibrium during the injection stage. Typical methods include heat loss model method, temperature profile fitting method and transient temperature inversion method. The heat loss model method inverts the flow rate by establishing the wellbore-formation heat transfer equation (such as the improved algorithm of the Ramey model), but does not consider the dynamic rebalancing process of the temperature field after the well is shut in. In the actual water injection process, due to the influence of factors such as formation heterogeneity and injection parameter changes, the wellbore temperature is often difficult to reach a true steady state, resulting in large errors in the evaluation results of the model. The temperature profile fitting method uses machine learning (such as random forests, LSTM, etc.) to establish a temperature-flow mapping relationship, but this method requires a large amount of labeled data and has insufficient generalization ability. The transient temperature inversion method uses the finite difference method to solve the non-steady-state heat transfer equation. This method considers the dynamic process of temperature changing with time and can more accurately describe the temperature change law in the actual water injection process, but the calculation complexity is high (single well simulation takes more than 6 hours) and it is difficult to apply in engineering.

[0005] The above-mentioned evaluation methods are too dependent on the selection of key injection temperature curves and original formation temperatures. In addition, in the case of long-term injection, the relationship between the temperature change of the injection layer and the injection volume is no longer sensitive, and it is difficult to reflect the injection volume of each layer. In addition, most of the existing DTS injection profile evaluation methods ignore the impact of the temperature recovery process after the injection is completed on the evaluation results. The so-called temperature recovery process refers to the process in which the wellbore temperature gradually returns to the original formation temperature after the well is shut down. The temperature recovery process contains rich injection information. Using the temperature recovery stage data for injection profile evaluation can effectively improve the evaluation accuracy. Summary of the invention

[0006] In order to solve the above technical problems, the present invention discloses a method for evaluating well temperature recovery water injection profile based on distributed optical fiber temperature logging. The relationship between wellbore temperature and injection rate is derived from the heat balance equation inside the reservoir during the temperature recovery stage after the water injection well is shut in to establish an interpretation model. The temperature recovery relaxation parameters of each injection layer of the injection well during the temperature recovery stage after the well is shut in are determined by data processing of distributed optical fiber temperature sensor DTS logging data, and then substituted into the interpretation model for injection profile evaluation, thereby improving the accuracy and efficiency of DTS injection profile evaluation.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] The well temperature recovery water injection profile evaluation method based on distributed optical fiber temperature logging specifically includes the following:

[0009] Step 1, establishing a temperature recovery model;

[0010] Step 2, reading the DTS logging data during the water injection period and the shut-in period of the evaluation well, and performing filtering and noise reduction processing;

[0011] Step 3, extracting the wellbore temperature data of the interpretation layer of the evaluation well during the shut-in time of the warming period from the perforation data of the evaluation well;

[0012] Step 4, using the wellbore temperature data of the continuous time series during the water injection period and the shut-in period obtained in step 3, calculate the functional relationship between the wellbore temperature Tw during the temperature recovery period and the shut-in time Δt;

[0013] Step 5: Use the functional relationship obtained in step 4 to further calculate dT w / dln(t R );

[0014] Step 6: Draw the T w With dT w / dln(t R ) intersection diagram, and linear fitting is performed on part of the data to obtain the slope of the straight line, and the temperature recovery relaxation parameter β of the small layer is obtained through the slope;

[0015] Step 7, repeating steps 4 to 6 for each interpretation layer to obtain the temperature recovery relaxation parameter of each interpretation layer;

[0016] Step 8, selecting a stable lithology section in the non-injection area to obtain a base value β0 of the target lithology temperature recovery relaxation parameter;

[0017] Step 9, calculating the relative injection volume of each interpretation layer;

[0018] Step 10: Based on the total water injection volume Q at the wellhead all , calculate the absolute water injection volume Q of each interpretation layer i .

[0019] Furthermore, in step 1, during temperature recovery or shut-in, the temperature rise is controlled by heat diffusion inside the reservoir and heat obtained from the surrounding environment. The analytical solution of the wellbore temperature is as follows:

[0020]

[0021] Among them, β is called the temperature recovery relaxation parameter; T w is the temperature measured in the well; T inj is the temperature of the injected fluid before shutting in the well; T0 is the formation temperature; h is the thickness of the water absorbing layer; q is the amount of water injected; ρ f is the density of injected water; c f is the specific heat of injected water; e is the effective thermal conductivity of the formation; t inj is the injection time; Δt is the shut-in time; β0 is the base value of the target lithology temperature recovery relaxation parameter.

[0022] Furthermore, in order to correct the influence of lithology on the temperature recovery relaxation parameter of the injection layer, it is also necessary to obtain the base value β0 of the temperature recovery relaxation parameter of the injection layer lithology. This base value can be obtained by finding a relatively long stable lithology section in the uppermost injection layer and calculating the base value of the temperature recovery relaxation parameter of the lithology.

[0023] Assume that there are n interpretation layers, each of which is divided into m small layers, and the temperature recovery relaxation parameter of each small layer is β ij , where i represents the i-th interpretation layer (i=1,2,…,n), j represents the j-th sublayer (j=1,2,…,m), then the relative injection amount K of each interpretation layer is i The calculation formula is as follows:

[0024]

[0025] Furthermore, in step 5, dT w / dln(t R ) is calculated as follows:

[0026]

[0027] in,

[0028] Further, in step 6, the temperature recovery relaxation parameter β is obtained by the following formula:

[0029]

[0030] Furthermore, the absolute water injection volume Q i It is obtained by the following formula:

[0031] Q i =Q all ×K i (6).

[0032] The beneficial effect of the present invention is that the method uses distributed optical fiber temperature sensing (DTS) to dynamically monitor water injection wells, has the characteristics of simple well access, low overall cost, and the ability to work in harsh environments of high temperature, high pressure, corrosion, or geomagnetic and geoelectric interference.

[0033] The temperature recovery model established by the present invention is simple and practical, independent of the original formation temperature, has a small amount of calculation, and can meet the needs of on-site real-time evaluation and adjustment of development plans.

[0034] Aiming at the defects and shortcomings of the existing DTS water injection profile evaluation technology, the present invention provides a new method for oilfield water injection profile evaluation, which is simple to operate, easy to implement and has good prospects for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a DTS temperature waterfall diagram of an evaluation well in an embodiment of the present invention;

[0036] Figure 2 It is a schematic diagram of the temperature profile noise reduction result diagram in an embodiment of the present invention;

[0037] Figure 3 : is a relationship diagram between the wellbore temperature Tw at the measuring depth point of the water absorption layer of the evaluation well and the shut-in time Δt in an embodiment of the present invention;

[0038] Figure 4 is the depth point T measured in the embodiment of the present invention w With dT w / dln(t R ) intersection diagram;

[0039] Figure 5 This is a diagram showing the interpretation results of the injection profile of an evaluation well in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] The present invention establishes an interpretation model by deriving the relationship between wellbore temperature and injection rate through the heat balance equation inside the reservoir during the temperature recovery stage after the water injection well is shut in. The temperature recovery relaxation parameters of each injection layer of the injection well during the temperature recovery stage after the well is shut in are determined by data processing of distributed optical fiber temperature sensor DTS logging data, and then substituted into the interpretation model for injection profile evaluation.

[0042] The present invention discloses a method for evaluating a well temperature recovery water injection profile based on distributed optical fiber temperature logging, and the specific steps are as follows:

[0043] (1) Establish a temperature recovery model.

[0044] During temperature recovery or shut-in, the temperature rise is controlled by heat diffusion inside the reservoir and heat gained from the surrounding environment. The analytical solution for the wellbore temperature is as follows:

[0045]

[0046]

[0047] Among them, β is called the temperature recovery relaxation parameter; T w is the temperature measured in the well; T inj is the temperature of the injected fluid before shutting in the well; T0 is the formation temperature; h is the thickness of the water absorbing layer; q is the amount of water injected; ρ f is the density of injected water; c f is the specific heat of injected water; e is the effective thermal conductivity of the formation; t inj is the injection time; Δt is the shut-in time; β0 is the base value of the target lithology temperature recovery relaxation parameter.

[0048] In order to correct the influence of lithology on the temperature recovery relaxation parameters of the injection layer, it is also necessary to obtain the base value β0 of the temperature recovery relaxation parameters of the injection layer lithology. This base value can be obtained by finding a relatively long stable lithology section in the uppermost injection layer and calculating the base value of the temperature recovery relaxation parameter of the lithology.

[0049] Assume that there are n interpretation layers, each of which is divided into m small layers, and the temperature recovery relaxation parameter of each small layer is β ij, where i represents the i-th interpretation layer (i=1,2,…,n), j represents the j-th sublayer (j=1,2,…,m), then the relative injection amount K of each interpretation layer is i The calculation formula is as follows:

[0050]

[0051] (2) Read the DTS logging data during the water injection and shut-in periods of the evaluation well and perform filtering and noise reduction processing.

[0052] (3) Based on the perforation data of the evaluation well, the continuous time series of wellbore temperature data of the interpretation layer of the well during the shut-in time during the warming period is extracted.

[0053] (4) Using the continuous time series of wellbore temperature data during water injection and shut-in periods obtained in step (3), calculate the functional relationship between the wellbore temperature Tw during the temperature recovery period and the shut-in time Δt.

[0054] (5) Using the functional relationship obtained in step (4), further calculate dT w / dln(t R ).

[0055] In step (5), dT w / dln(t R ) is calculated as follows:

[0056]

[0057] in,

[0058] (6) Draw T w With dT w / dln(t R ) intersection diagram, and linear fitting is performed on part of the data to obtain the slope of the straight line, and the temperature recovery relaxation parameter β of the small layer is obtained through the slope.

[0059] In step (6), the temperature recovery relaxation parameter β is obtained by the following formula:

[0060]

[0061] (7) Repeat steps (4) to (6) for each interpretation layer to obtain the reheating relaxation parameters of each interpretation layer.

[0062] (8) Select a stable lithology section in the non-injection area to obtain the base value β0 of the target lithology temperature recovery relaxation parameter.

[0063] (9) Calculate the relative injection volume of each interpretation layer.

[0064] (10) According to the total water injection volume Qall , calculate the absolute water injection volume Q of each interpretation layer i .

[0065] Absolute water injection volume Q i It is obtained by the following formula:

[0066] Q i =Q all ×K i (6).

[0067] Example

[0068] The well temperature recovery water injection profile evaluation method based on distributed optical fiber temperature logging is as follows:

[0069] 1. Determine the characteristic parameters in the temperature recovery evaluation model according to the well conditions.

[0070] 2. The distributed optical fiber and DTS acquisition system are used to measure the wellbore temperature data of the evaluated well during the water injection and shut-in periods. The temperature waterfall diagram is shown in the figure below: Figure 1 shown.

[0071] The process went through four stages: shut-in, first injection system, second injection system, and shut-in. The first injection system was based on 30m 3 / d was measured after 5h of injection. The second injection system was 60m 3 / d was injected for 4.5h, and then the shut-in temperature recovery data was measured.

[0072] 2. The original DTS data contains a large amount of noise data, which covers up a lot of downhole information, making it difficult to intuitively see the temperature profile distribution trend, and there is obvious accidental data interference.

[0073] Therefore, it is necessary to perform noise reduction on the original DTS data to eliminate the noise data caused by the photoelectric pulse. Compared with the original DTS data, the distribution trend of the temperature profile data after noise reduction is clearer and can be used for subsequent injection profile evaluation. Figure 2 This is the noise reduction effect diagram of the evaluation well DTS data.

[0074] 3. Extract temperature recovery data from the filtered DTS data to obtain the wellbore temperature T during temperature recovery w In order to obtain a smooth derivative, we use a cubic polynomial to fit the relationship between the wellbore temperature Tw and the shut-in time Δt, as shown in Figure 3 As shown, dT is then calculated based on the obtained polynomial w / dln(t R ).

[0075] 4. Plot the wellbore temperature T w With dTw / dln(t R ) intersection diagram, and linear fitting is performed on some data to obtain the slope of the straight line, and the temperature recovery relaxation parameter β of the small layer is obtained through the slope, such as Figure 4 This operation is repeated for all interpretation layers to obtain the temperature recovery relaxation parameter β at the corresponding depth of all interpretation layers.

[0076] 5. Correct the influence of lithology. The injection layer of this well is sandstone. Find a relatively long sandstone section above the first injection layer and calculate the average temperature recovery relaxation parameter β0 of this section.

[0077] 6. Calculate the relative injection volume of each injection layer by using formula (3), and combine it with the wellhead injection data to get the absolute injection volume of each layer. Figure 5 shown.

[0078] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for evaluating well temperature recovery and water injection profile based on distributed optical fiber temperature logging, characterized in that: Specifically include the following: Step 1, establishing a temperature recovery model; Step 2, reading the DTS logging data during the water injection period and the shut-in period of the evaluation well, and performing filtering and noise reduction processing; Step 3, extracting the wellbore temperature data of the interpretation layer of the evaluation well during the shut-in time of the warming period from the perforation data of the evaluation well; Step 4, using the wellbore temperature data of the continuous time series during the water injection period and the shut-in period obtained in step 3, calculate the functional relationship between the wellbore temperature Tw during the temperature recovery period and the shut-in time Δt; Step 5: Use the functional relationship obtained in step 4 to further calculate dT w / dln(t R ); Step 6: Draw the T w With dT w / dln(t R ) intersection diagram, and linear fitting is performed on part of the data to obtain the slope of the straight line, and the temperature recovery relaxation parameter β of the small layer is obtained through the slope; Step 7, repeating steps 4 to 6 for each interpretation layer to obtain the temperature recovery relaxation parameter of each interpretation layer; Step 8, selecting a stable lithology section in the non-injection area to obtain a base value β0 of the target lithology temperature recovery relaxation parameter; Step 9, calculating the relative injection volume of each interpretation layer; Step 10: Based on the total water injection volume Q at the wellhead all , calculate the absolute water injection volume Q of each interpretation layer i .

2. The method for evaluating well temperature recovery and water injection profile based on distributed optical fiber temperature logging according to claim 1, characterized in that: In step 1, during temperature recovery or shut-in, the temperature rise is controlled by heat diffusion inside the reservoir and heat gained from the surrounding environment. The analytical solution for the wellbore temperature is as follows: Among them, β is called the temperature recovery relaxation parameter; T w is the temperature measured in the well; T inj is the temperature of the injected fluid before shutting in the well; T0 is the formation temperature; h is the thickness of the water absorbing layer; q is the amount of water injected; ρ f is the density of injected water; c f is the specific heat of injected water; e is the effective thermal conductivity of the formation; t inj is the injection time; Δt is the shut-in time; β0 is the base value of the target lithology temperature recovery relaxation parameter.

3. The method for evaluating well temperature recovery and water injection profile based on distributed optical fiber temperature logging according to claim 2, characterized in that: In order to correct the influence of lithology on the temperature recovery relaxation parameter of the injection layer, it is also necessary to obtain the base value β0 of the temperature recovery relaxation parameter of the injection layer lithology. This base value can be obtained by finding a relatively long stable lithology section through the top injection layer and calculating the base value of the temperature recovery relaxation parameter of the lithology. Assume that there are n interpretation layers, each of which is divided into m small layers, and the temperature recovery relaxation parameter of each small layer is β ij , where i represents the i-th interpretation layer (i=1,2,…,n), j represents the j-th sublayer (j=1,2,…,m), then the relative injection amount K of each interpretation layer is i The calculation formula is as follows:

4. The method for evaluating well temperature recovery and water injection profile based on distributed optical fiber temperature logging according to claim 3, characterized in that: In step 5, dT w / dln(t R ) is calculated as follows: in, 5. The method for evaluating well temperature recovery and water injection profile based on distributed optical fiber temperature logging according to claim 4, characterized in that: In step 6, the temperature recovery relaxation parameter β is obtained by the following formula:

6. The method for evaluating well temperature recovery and water injection profile based on distributed optical fiber temperature logging according to claim 5, characterized in that: Absolute water injection volume Q i It is obtained by the following formula: Q i =Q all ×K i (6)。

Images