Method for judging water absorption possibility of plugging layer of injection well and determining water absorption well of plugging layer

Abstract

The invention discloses a method for judging the water absorption possibility of an injection well plugging layer and determining a plugging layer water absorption well, and the method comprises the steps: taking the percentage of the actual injection amount of an injection layer adjacent to the plugging layer in the whole well actual injection amount and the percentage of the injection allocation amount of the injection layer in the whole well injection allocation amount as water absorption risk coefficients under the condition that logging is not carried out; by utilizing the characteristic that the risk coefficient can ensure that the discovery rate of the non-water-absorbing well of the plugging layer is 100%, firstly, most injection wells without water-absorbing risks in the plugging layer can be quickly screened out, and the water-absorbing well of the plugging layer can be continuously determined by virtue of isotope profile verification when a few wells with water-absorbing risks are left, so that the detection efficiency of the non-water-absorbing well of the plugging layer is greatly improved. Therefore, the workload of isotope profile verification is reduced, and the task of determining the plugging layer water absorption well is quickly and accurately completed with low cost. And the method is simple to apply, and the water absorption risk coefficient k value of the plugging layer is regularly measured, adjusted and calculated according to measurement and adjustment data, so that the plugging layer water absorption well can be accurately and timely found.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of oilfield water injection development, and in particular to a method for determining whether a plugging layer absorbs water by using data obtained by measurement and adjustment. BACKGROUND

[0002] With the end of displacement of the first type of oil layer in old oilfields, the displacement target gradually shifts to the second and third types of oil layers, and a large number of injection and production wells need to be plugged up and down. For water injection development wells, due to reasons such as interlayer channeling, unsealed packers, and excessive leakage of sealed connections, the plugging layer may absorb water, thereby affecting the water injection efficiency and the development degree of the oilfield, making it difficult to improve the sweep efficiency, increasing the development cost, and increasing the difficulty of measures.

[0003] Currently, whether the plugging layer absorbs water is determined by using isotope logging and oxygen activation logging, and judging by profile test conditions. Obviously, this profile test method has problems such as high test cost and high construction difficulty. SUMMARY

[0004] Therefore, the present disclosure provides a method for determining whether a plugging layer of an injection well absorbs water and a method for determining a plugging layer water absorption well, to solve the problems of high test cost and high construction difficulty in the current isotope logging and oxygen activation logging methods for determining whether the plugging layer absorbs water.

[0005] To achieve the above-mentioned purposes, in a first aspect, the method for determining whether a plugging layer of an injection well absorbs water comprises:

[0006] calculating the difference between the percentage of the actual injection amount of the injection layer adjacent to the plugging layer of the injection well in the actual injection amount of the whole well and the percentage of the injection allocation amount of the injection layer in the injection allocation amount of the whole well;

[0007] taking the difference as a water absorption risk coefficient k, wherein the k≤10, and determining that the plugging layer does not absorb water; and the k>10, and determining that the plugging layer may have a water absorption risk.

[0008] In the present disclosure and possible embodiments, the actual injection amount of the injection layer and the actual injection amount of the whole well are obtained by field injection allocation, and the injection allocation amount of the injection layer and the injection allocation amount of the whole well are obtained by referring to the injection well measurement and adjustment data.

[0009] In the present disclosure and possible embodiments, the method for field injection allocation uses wireline or cable measurement and adjustment means.

[0010] In a second aspect, the method for determining a plugging layer water absorption well comprises:

[0011] using the method for determining whether a plugging layer of an injection well absorbs water in the first aspect to divide the injection wells in a block into plugging layer non-water absorption wells and plugging layer water absorption risk wells.

[0012] In the present disclosure and possible embodiments, the method for determining the plugging layer water absorbing well further comprises:

[0013] For the well with the plugging layer water absorption risk, the plugging layer water absorbing well is determined through the isotope profile test.

[0014] The present application has the following beneficial effects:

[0015] The method for determining the plugging layer water absorbing possibility of the injection well in the present disclosure can obtain the actual injection amount of the injection layer adjacent to the plugging layer and the actual injection amount of the whole well through the conventional logging data without logging, calculate the percentage of the actual injection amount of the injection layer in the actual injection amount of the whole well, and subtract the percentage of the injection allocation amount of the injection layer in the injection allocation amount of the whole well, so as to obtain the water absorption risk coefficient. The water absorption possibility of the plugging layer is determined by whether the risk coefficient exceeds the water absorption judgment limit value. The method has the feature of ensuring that the discovery rate of the plugging layer non-water absorbing well is 100%. First, most of the injection wells with no water absorption risk of the plugging layer can be quickly screened out. The few wells with water absorption risk can be further verified by the isotope profile to accurately find the plugging layer water absorbing well, so as to reduce the workload of the isotope profile verification, and complete the determination task of the plugging layer water absorbing well at low cost, quickly and accurately. Moreover, the method is simple to apply. The logging and adjustment team or squad technician can regularly calculate the plugging layer water absorption risk coefficient k value according to the logging and adjustment data, so as to timely find the plugging layer water absorbing well and greatly reduce the workload of the isotope profile verification. BRIEF DESCRIPTION OF DRAWINGS

[0016] The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of the embodiments of the present disclosure with reference to the accompanying drawings. In the drawings:

[0017] Figure 1 The structure and positional relationship of the injection well plugging layer and the injection layer according to the embodiments of the present disclosure are shown in the figure.

[0018] In the figure, 1 is a packer, 2 is an injection distributor, 100 is a plugging layer, 200 is an injection layer a, and 300 is another injection layer. DETAILED DESCRIPTION

[0019] The present disclosure is described below based on specific embodiments, but it is worth noting that the present disclosure is not limited to these specific embodiments. In the following detailed description of the present disclosure, some specific details are described in detail. However, those skilled in the art can also fully understand the present disclosure without detailed description.

[0020] Furthermore, unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as including rather than exclusive or exhaustive; that is, meaning "including but not limited to."

[0021] The method for judging water absorption in the sealing layer of the injection well disclosed herein uses conventional injection well wire or cable measurement and adjustment methods to measure the actual injection volume of the injection layer adjacent to the sealing layer and the actual injection volume of the entire well. The difference between the percentage of the actual injection volume of the adjacent injection layer to the actual injection volume of the entire well and the percentage of the injection volume of that layer to the total injection volume of the entire well can be calculated to intuitively judge the water absorption of the sealing layer.

[0022] Regarding the method for determining water absorption in the sealing layer of the injection well as described above, the embodiments of this disclosure employ the following specific technical measures, the steps of which are as follows:

[0023] 1. Review the measurement and adjustment data of the injection well to be judged. Figure 1 As shown, the injection volume Q of the adjacent injection layer a 200 of the blocking layer 100 in the test data is recorded. 配a and total well injection volume Q 全井配 In addition, the actual injection volume Q of the adjacent injection layer a 200 is measured on-site. 注a and the actual injection volume Q of the whole well 全井注 ;

[0024] 2. Calculate the actual injection volume Q of the adjacent injection layer a 200. 注a Q, representing a percentage of total well injection 全井注 percentage η 实 ;

[0025] 3. Calculate the injection volume Q of the adjacent injection layer a 200. 配a Q, representing a portion of the total well injection volume 全井配 percentage η 配 ;

[0026] 4. Calculate the water absorption risk coefficient k = (η 实－ η 配 )*100;

[0027] 5. Determine the likelihood of water absorption in the sealing layer 100 by checking whether the water absorption risk coefficient k exceeds the water absorption judgment threshold. In this embodiment, the water absorption judgment threshold is set to 10. If k > 10, the sealing layer 100 is judged to have absorbed water. If k ≤ 10, the sealing layer 100 is judged to have a risk of water absorption.

[0028] The process of setting the water absorption threshold value to 10 in this embodiment is as follows: To accurately determine the likelihood of water absorption in the sealing layer based on the injection volume of adjacent layers, a large amount of well measurement and actual injection data from sealing layers in different regions and blocks were collected on-site. The water absorption risk coefficient k was then calculated, resulting in a large amount of water absorption risk coefficient k and corresponding water absorption data. Statistical analysis of this data revealed the following pattern: for injection wells with k values ​​below 10, the proportion of non-water-absorbing wells in the sealing layer is 100%; for wells with k values ​​above 10, the proportion of water-absorbing wells in the sealing layer exceeds 55%. Therefore, regression analysis of a large amount of on-site data shows that using a k value of 10 as the dividing line between water-absorbing and non-water-absorbing wells ensures a 100% accuracy rate for non-water-absorbing wells in the sealing layer, while also ensuring a 100% detection rate for water-absorbing wells.

[0029] In addition, the method disclosed herein has been applied to a certain well re-entry sealing block, using the water absorption risk coefficient to determine whether the sealing layer of 37 wells absorbs water. The calculated results were compared with the results of isotope profiling tests conducted in the field. The comparison results are shown in Table 1.

[0030] Table 1 Verification of Single Well Conditions at the Site

[0031]

[0032]

[0033] The calculation process for the water absorption risk coefficient of the sealing layer in well number 18 in Table 1 above is as follows:

[0034] The water absorption risk coefficient of the sealing layer is k = (38 / 81 - 30 / 80) * 100 = 9.4.

[0035] Since k = 9.4, which is less than 10, it can be determined that the sealing layer does not absorb water. The subsequent isotope profile test results also showed that the sealing layer does not absorb water, verifying the accuracy of the conclusion.

[0036] The calculation process for the water absorption risk factor of the sealing layer in well No. 1 is as follows:

[0037] The water absorption risk coefficient of the sealing layer is k = (60 / 76 - 20 / 75) * 100 = 52.3.

[0038] Since k = 52.3, which is greater than 10, it can be determined that the sealing layer absorbs water. The conclusion was later verified to be accurate by isotope profile testing.

[0039] Based on the analysis of data from 37 wells, 20 injection wells with a water absorption risk coefficient k value less than 10, indicating that the sealing layer does not absorb water, were all verified to be non-absorbent through isotope profiling, achieving an accuracy rate of 100%. Of the 17 injection wells with a water absorption risk coefficient k value greater than 10, indicating that the sealing layer absorbs water, 13 were verified to absorb water through isotope profiling, achieving an accuracy rate of 76.4%. The overall accuracy rate of the 37 injection wells was 89.2%.

[0040] Since injection wells with a k value less than 10 can be 100% determined to have no water absorption risk, under normal circumstances, among a large number of injection wells, the proportion of wells with no water absorption risk in the sealing layer is large. Therefore, the water absorption probability judgment method of the sealing layer of the present invention can be used to quickly screen out the injection wells with no water absorption risk in the sealing layer from the large proportion of injection wells. The remaining wells with a small proportion of water absorption risk can be further verified by isotope profiling to accurately find the water absorption wells in the sealing layer among the wells with a small proportion of water absorption risk.

[0041] Furthermore, since the method of this invention can determine 100% that there are no wells with water absorption risk, these wells do not require isotope profile verification. Since the number of injection wells that require isotope profile verification is small, the workload of isotope profile verification can be greatly reduced, thus achieving the task of quickly and accurately identifying wells with water absorption in the sealing layer.

[0042] In summary, the method of this invention can be used to periodically measure and calculate the water absorption risk coefficient k, thereby accurately, quickly, and promptly identifying water-absorbing wells in the sealing layer.

[0043] The embodiments described above are merely illustrative of implementation methods of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent disclosure. It should be noted that those skilled in the art can make various modifications, equivalent substitutions, and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent disclosure should be determined by the appended claims.

Claims

1. A method for judging water influx possibility of a plugging zone in an injection well, characterized by, Comprising: calculating the difference between the percentage of actual injection volume of the injection layer adjacent to the injection well sealing layer in the total well actual injection volume and the percentage of injection allocation volume of the injection layer in the total well injection allocation volume; the difference as a water absorption risk factor k using the water absorption risk factor k to judge the water absorption possibility of the plugging layer.

2. The injection well sealing layer water absorption possibility judgment method according to claim 1, characterized in that: The k ≤10, judging that the plugging layer is not water-absorbing; the k >10, judging that the plugging layer may have a water-absorbing risk.

3. The injection well sealing layer water absorption possibility judgment method according to claim 1 or 2, characterized in that: The actual injection volume of the injection layer and the total well actual injection volume are obtained by field injection allocation, and the injection allocation volume of the injection layer and the total well injection allocation volume are obtained by referring to the injection well adjustment data.

4. The injection well sealing layer water absorption possibility judgment method according to claim 3, characterized in that: The method of field injection allocation uses injection well steel wire or cable adjustment means.

5. A method for determining a plugging layer water injection well, characterized by, Comprising: Using the injection well sealing layer water absorption possibility judgment method according to any one of claims 1-4, the injection wells in the block are divided into sealing layer non-water absorption wells and sealing layer wells that may have water absorption risk.

6. The method of claim 5, wherein, Further comprising: For the sealing layer wells that may have water absorption risk, the sealing layer water absorption wells are determined out through isotope profile test verification.

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