Shale oil horizontal well casing selection recommendation method

Abstract

The present application belongs to the technical field of oil and gas well drilling and completion process design, and relates to a shale oil horizontal well casing selection recommendation method. The present application provides a shale oil horizontal well casing selection method through seven steps of establishing different horizontal well casing downhole difficulty degree sequence, obtaining the type of a to-be-drilled shale oil horizontal well, horizontal section length, casing running friction resistance prediction value and running frequency, determining the casing downhole difficulty degree of the to-be-drilled shale oil horizontal well, classifying the pre-set casing, respectively testing the casing thread dynamic sealing quality of different types of casing, sequencing the sealing quality of the provided horizontal well casing and selecting the casing. The present application meets the targeted selection within the casing use range, meets the purpose of safely running the casing on site, greatly reduces the risk of sealing failure of the horizontal well casing after being run downhole, reduces the repair cost of the post-casing string sealing failure, achieves the best use of the casing, and controls the overall cost of the casing.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil and gas well drilling and completion process design, and particularly relates to a shale oil horizontal well casing selection recommendation method. BACKGROUND

[0002] Shale oil horizontal well casing selection is one of important links in drilling and completion engineering design, and at present, casing selection is mainly made by Party A according to drilling manual, API standard and oil and gas field development (exploration) scheme; casing selection is made according to oil well, gas well and deep well; due to a large number of drilling and completion wells in oil field every year, one kind of casing is used for oil and gas wells in multiple blocks, without considering casing running difficulty and risk of each well.

[0003] The shale oil exploitation technology in oil field mainly uses "large well group + long horizontal section + multi-section volume fracturing" as main technology, and the purpose is to maximize wellhead production. However, casing sealing failure occurs frequently in the development process of shale oil horizontal well. The main reasons are as follows:

[0004] Firstly, the offset distance of shale oil horizontal well is large, and the horizontal section is long.

[0005] Secondly, in the actual casing running construction process of horizontal well, due to complex well trajectory, large offset distance of inflection point and large casing running friction, casing is repeatedly lowered at wellhead in order to continue casing running, and the casing is overloaded and bent in local well section, so that (micro crack) damage occurs at the root of casing thread, and casing thread sealing failure is prone to occur.

[0006] Thirdly, the casing used does not meet the actual well condition of oil well.

[0007] Some measures are used in the prior art to solve the problem of casing sealing failure.

[0008] At present, the selection of horizontal well casing is mainly based on "Drilling Party A Manual" and "Drilling Technology", and three technical parameters, i.e. tensile strength, internal pressure resistance and external extrusion resistance, are used to measure casing selection; when the tensile strength, internal pressure resistance and external extrusion resistance of casing meet the casing running depth, the casing selection is determined.

[0009] The tonnage requirement of casing running and resistance lowering is less than 20-30 tons, which has a large gap with the current field situation, and cannot meet the field requirement, resulting in casing running sealing failure hidden trouble in the field.

[0010] Horizontal well casing friction calculation and downhole analysis. Author: Zhang Yang. Southwest Petroleum University, Master's electronic journal publishing information: 2015, No. 09. Its research comes out a set of horizontal well casing friction and load calculation method suitable for field application, which can accurately calculate the friction and load in the process of casing running, and analyze the wellbore compatibility and pipe string strength. First of all, according to the well trajectory data, the three-dimensional rigid rod model is selected to analyze the effects of drilling fluid viscosity resistance, pressure difference resistance, dynamic load that may occur in the process of casing running, and the matching of casing size and wellbore clearance, well trajectory parameters on friction and load; Then calculate the maximum passing curvature of the casing, and use the rigid geometric compatibility model to calculate the maximum passing length of single casing; Secondly, the effective external pressure, effective internal pressure and true axial force of the casing string are calculated, and the Von-Mises stress is synthesized based on the calculation results, and the fourth strength theory is used to check the strength of the pipe string. Finally, the horizontal well casing running feasibility analysis software is compiled by using VB, which realizes the calculation of casing friction and load, wellbore compatibility analysis and pipe string strength checking, and analyzes the feasibility of casing running.

[0011] Horizontal well casing string running process simulation based on finite element analysis. Author: Chen Yingchao; Chengde; Petroleum College Petroleum Engineering Department. It models the relevant mechanical problems in the process of casing running, and quantitatively analyzes the friction resistance and the strength of the casing after running to the bottom of the well. Through finite element modeling, the stress state of any node of the casing at any time can be obtained, and the allowable strength is compared to determine whether the casing can be safely run in.

[0012] Finite element simulation of shale horizontal well casing. Author: Wang Yang. Petroleum Chemical Industry Application. 2020, 39(10). It uses finite element software to simulate the stress changes of the casing under three conditions of temperature, non-uniform load and the combined action of the two factors. With the decrease of formation temperature, the additional temperature stress increases continuously, but the stress distribution remains basically unchanged; under the action of non-uniform load on the casing, the stress on the middle part of the casing is larger, and the closer to the end face, the smaller the stress; under the combined action of temperature and non-uniform load on the casing, the casing has undergone elliptical deformation.

[0013] Finite element analysis of the contact state between casing and well wall during the running of horizontal well casing. Author: Shen Zhaoxi. Petroleum Tubular Goods and Instruments. 2022, 8(06). It uses finite element numerical simulation method to analyze the contact between casing and well wall during the running of casing in two-dimensional plane state. The area with larger contact pressure is mainly in the build-up section, including the build-up section starting point, middle and end point accessories.

[0014] Shale gas horizontal well casing string running friction analysis and control technology research author: Chen Peng holds. It puts forward the inversion method of multi-section friction coefficient of large displacement well. The method divides the whole wellbore into different well sections according to the shape of the wellbore, and introduces a corresponding friction coefficient in each well section to describe the friction distribution of the well section. Based on the soft rope model, a friction calculation model based on the dynamic movement of the casing is established, which can simulate and calculate the stress and movement of the casing string during the casing running process in the up and down operation.

[0015] Ultra-deep horizontal well casing capacity analysis and safety evaluation author: Yang Weixing. Considering the casing bending and rigid downhole tools, the limit wellbore curvature model of casing running is established, which can calculate the limit running wellbore curvature of casing with different steel grades and outer diameters. Then the finite element model of casing bending stress simulation is established, which can obtain the stress distribution of the casing in the bending well section under different wellbore curvatures, different internal and external pressures and different axial forces.

[0016] Horizontal well casing running friction mechanics analysis author: Li Qingming. The main content is to divide the pipe string into units, calculate the parameters required for unit friction mechanics of unit measuring point according to the division, and finally solve the pipe string unit step by step from the drill bit to the wellhead to realize the mechanical analysis of the whole well section.

[0017] The above measures cannot recommend the selection of oil horizontal well casing according to the actual situation of the area and specific location of the oil well, and the pertinence is poor. SUMMARY

[0018] The present application provides a shale oil horizontal well casing selection recommendation method, which aims to select shale oil horizontal well casing in a targeted manner, meet the requirements of field construction, reduce drilling and completion costs, and provide data support for subsequent remote technical support.

[0019] To achieve the above purpose, the technical scheme adopted by the present application is:

[0020] A shale oil horizontal well casing selection recommendation method, comprising the following steps:

[0021] Step 1: Establish the difficulty level of different horizontal well casing running;

[0022] Step 2: Obtain the type, horizontal section length, casing running friction prediction value and running frequency of the shale oil horizontal well to be drilled;

[0023] Step 3: According to the data obtained in step 2, compare the horizontal well casing running difficulty level established in step 1 to determine the casing running difficulty of the shale oil horizontal well to be drilled;

[0024] Step 4: Classify the preset casing;

[0025] Step five, the casing thread dynamic sealing quality test is carried out on the casing of different types in step four respectively;

[0026] Step six, the sealing quality of the provided horizontal well casing is sorted according to the test results of step five;

[0027] Step seven, the casing is selected according to the difficulty of the shale oil horizontal well casing to be drilled in step three.

[0028] The step one establishes the horizontal well casing running difficulty sorting as follows:

[0029] When the offset distance of the drilled horizontal well is less than 300m, the horizontal section length is less than 1500m, the predicted casing running friction is less than 40 tons, and the dropping frequency at the same position is less than 65 times, the casing running is easy:

[0030] When the offset distance of the drilled horizontal well is less than 300-600m, the horizontal section length is less than 1500-2000m, the predicted casing running friction is 40-45 tons, and the dropping frequency at the same position is less than 65-85 times, the casing running difficulty is medium:

[0031] When the offset distance of the drilled horizontal well is less than 600-900m, the horizontal section length is less than 2000-3000m, the predicted casing running friction is 45-50 tons, and the dropping frequency at the same position is less than 85-100 times, the casing running is difficult.

[0032] The step four classifies the casing to be used into the following types:

[0033] The purchased casing is divided into three types according to the price: high price, medium price, and low price.

[0034] Economic casing: the economic casing refers to the casing with low price and casing thread sealing performance meeting the field requirements;

[0035] Fatigue-resistant casing: the fatigue-resistant casing refers to the casing with medium price and casing thread sealing performance meeting the field requirements and adapting to the field conditions;

[0036] Large coupling impact-resistant casing: the large coupling impact-resistant casing refers to the casing with high price and casing thread sealing performance meeting the field requirements and completely adapting to the field conditions.

[0037] The step five carries out the thread dynamic sealing quality test on the provided horizontal well casing as follows:

[0038] First step, after the two casings are screwed, the two ends are supported and fixed, and the casings are placed horizontally;

[0039] Second step, axial casing is applied to the preset pressure, the casing string test piece bending, the casing is applied to the preset pressure;

[0040] Third step, the inner pressure and the bending force release;

[0041] Fourth step, the threaded sealing test of the test casing is carried out, the threaded sealing of the test casing is good, return to step one, repeatedly implement bending for several times, otherwise the test is finished.

[0042] The repeated bending test times are 100-200 times.

[0043] In the second step, the axial casing is applied to the 100 tons pressure, the casing string test piece is bent 12 degrees / 30m, and the casing is applied to the 40MPa pressure.

[0044] The threaded sealing test method of the test casing in the fourth step is to pressurize the inside of the test casing, maintain for one minute, and then test the pressure condition, if the pressure remains stable, the threaded sealing is good, otherwise the threaded sealing of the casing is invalid.

[0045] The casing selection method in the seventh step is as follows:

[0046] The economic casing is selected when the casing is easily lowered, the fatigue-resistant casing is selected when the casing is moderately difficult to lower, and the large-coupling impact-resistant casing is selected when the casing is difficult to lower.

[0047] Beneficial effects:

[0048] (1) The application meets the targeted selection within the casing use range, selects the casing meeting the requirements according to the preset scheme, and meets the purpose of safely lowering the casing on site.

[0049] (2) The application greatly reduces the risk of sealing failure of the casing after being lowered in the horizontal well.

[0050] (3) The application reduces the repair cost of the casing string sealing failure.

[0051] (4) The application achieves the purpose of making the best use of the casing, thereby controlling the overall cost of the casing.

[0052] The above description is only a summary of the technical scheme of the application, in order to more clearly understand the technical means of the application, and the content of the specification can be implemented, the following preferred embodiments of the application are described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0053] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described below only illustrate some of the embodiments of the present application, and for those skilled in the art, other drawings can be obtained based on these drawings without creative labor.

[0054] Figure 1 Flow chart of the present application. DETAILED DESCRIPTION

[0055] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0056] Embodiment one:

[0057] According to Figure 1 A shale oil horizontal well casing selection recommendation method as shown in the figure, comprising the following steps:

[0058] Step one, establish the difficulty level of different horizontal well casings;

[0059] Step two, obtain the type, horizontal section length, casing running friction prediction value and number of times of the shale oil horizontal well to be drilled;

[0060] Step three, according to the data obtained in step two, compare with the difficulty level of horizontal well casing running established in step one, to determine the difficulty level of casing running of the shale oil horizontal well to be drilled;

[0061] Step four, classify the preset casing;

[0062] Step five, respectively test the casing thread dynamic sealing quality of the casings of different types in step four;

[0063] Step six, through the test results of step five, sort the sealing quality of the provided horizontal well casings;

[0064] Step seven, select the casing

[0065] According to the difficulty level of the casing running of the shale oil horizontal well to be drilled in step three, select the matching casing.

[0066] The technical scheme of the present application needs to understand the casing related performance data requirements in the drilling manual and API standard, understand the casing requirements of the oil and gas field development (exploration) scheme and the casing selection and purchase situation of the oil and gas field material equipment department, classify and perform product quality test verification on the preset used casing, fully consider the actual situation of the oil well, and be more targeted. The present application greatly reduces the risk of sealing failure of the horizontal well casing after being lowered into the well.

[0067] The present application reduces the repair cost of casing string sealing failure.

[0068] The present application achieves the purpose of making full use of casing, thereby controlling the overall cost of casing.

[0069] Example two:

[0070] According to the shale oil horizontal well casing selection recommendation method shown in FIG. 1, the difference from example one is that the step one of establishing the horizontal well casing running difficulty level sequence is specifically as follows: Figure 1 When the offset distance of the drilled horizontal well is less than 300m, the horizontal section length is less than 1500m, the predicted casing running friction is less than 40 tons, and the dropping frequency at the same position is less than 65 times, the casing running is easy:

[0071] When the offset distance of the drilled horizontal well is less than 300-600m, the horizontal section length is less than 1500-2000m, the predicted casing running friction is 40-45 tons, and the dropping frequency at the same position is less than 65-85 times, the casing running difficulty is medium:

[0072] When the offset distance of the drilled horizontal well is less than 600-900m, the horizontal section length is less than 2000-3000m, the predicted casing running friction is 45-50 tons, and the dropping frequency at the same position is less than 85-100 times, the casing running is difficult.

[0073] In actual use, the horizontal well casing running difficulty level sequence is established, which is more convenient and intuitive for subsequent shale oil horizontal well casing needs.

[0074] Example three:

[0075] According to the shale oil horizontal well casing selection recommendation method shown in FIG. 1, the difference from example one is that the step one of establishing the horizontal well casing running difficulty level sequence is specifically as follows:

[0076] Figure 1 The purchased casing is divided into three types according to the price; high price, medium price and low price.

[0077] The purchased casing is divided into three types according to the price; high price, medium price and low price.

[0078] The economic type casing refers to the casing with low price and the casing thread sealing performance meeting the field requirements.​

[0079] Fatigue-resistant casing, fatigue-resistant casing refers to the price in the middle, and the casing thread sealing performance meets the site requirements and can adapt to the site working conditions;

[0080] Large coupling impact-resistant casing, large coupling impact-resistant casing refers to high price, and the casing thread sealing performance meets the site requirements and can fully adapt to the site working conditions.

[0081] In actual use, the pre-set casing is classified, so that the subsequent shale oil horizontal well casing selection recommendation is more direct and easier to operate.

[0082] Example four:

[0083] According to Figure 1 A shale oil horizontal well casing selection recommendation method is shown in FIG. 1, which is different from example one in that the step five is a method for testing the thread dynamic sealing quality of the provided horizontal well casing as follows:

[0084] First, after screwing two casings, support and fix their two ends to make them horizontally placed;

[0085] Second, apply a pre-set pressure to the casing in the axial direction to bend the casing string test piece, and apply a pre-set pressure to the casing;

[0086] Third, release the internal pressure and bending force;

[0087] Fourth, test the thread sealing performance of the test casing, and if the test casing thread sealing is good, return to step one and repeatedly bend for several times; otherwise, the test is ended.

[0088] In actual use, the thread dynamic sealing quality test by the present application lays a foundation for the specific application of the casing.

[0089] Example five:

[0090] According to Figure 1 A shale oil horizontal well casing selection recommendation method is shown in FIG. 1, which is different from example four in that the repeated bending test is 100-200 times.

[0091] The number of bending tests set in this embodiment fully considers the possible number of casing bending caused by various conditions in the actual use of the casing in the prior art, and ensures that the data after the test can provide more scientific suggestions for the subsequent selection of the casing.

[0092] Example six:

[0093] According to Figure 1The recommended method for selecting a shale oil horizontal well casing is different from that of the fourth embodiment in that, in the second step, the casing is axially pressed by 100 tons to bend the casing string test piece by 12 degrees per 30 m, and the pressure in the casing is 40 MPa.

[0094] The parameter values set in the embodiment fully consider the upper limit of the force required to be borne by the casing in various situations in the prior art, ensure that the casing data tested meet the requirements of the corresponding use conditions, are more targeted, and guarantee that the horizontal well casing will not fail to seal after being lowered into the well.

[0095] Embodiment seven:

[0096] According to the recommended method for selecting a shale oil horizontal well casing shown in the first embodiment, the method for selecting the casing in the seventh step is as follows: Figure 1 The recommended method for selecting a shale oil horizontal well casing is different from that of the fourth embodiment in that, in the fourth step, the method for testing the thread sealing performance of the test casing is to pressurize the inside of the test casing, maintain for one minute, and then test the pressure condition; if the pressure remains stable, the thread sealing performance is good, otherwise the thread sealing performance of the casing fails.

[0097] In actual use, the adoption of the above technical solution makes the casing resistance test more in line with the actual conditions of the shale oil horizontal well site, and basically avoids the risk that the horizontal well casing will not fail to seal after being lowered into the well.

[0098] Embodiment eight:

[0099] According to the recommended method for selecting a shale oil horizontal well casing shown in the first embodiment, the method for selecting the casing in the seventh step is as follows: Figure 1 The recommended method for selecting a shale oil horizontal well casing is different from that of the fourth embodiment in that, in the fourth step, the method for testing the thread sealing performance of the test casing is to pressurize the inside of the test casing, maintain for one minute, and then test the pressure condition; if the pressure remains stable, the thread sealing performance is good, otherwise the thread sealing performance of the casing fails.

[0100] The easier the casing is lowered into the well, the more the economic casing is selected; the more difficult the casing is lowered into the well, the more the fatigue-resistant casing is selected; and the more difficult the casing is lowered into the well, the more the large-coupling impact-resistant casing is selected.

[0101] The technical solution of the present application makes the selection of the casing more intuitive and simple.

[0102] In the case of no conflict, a person skilled in the art can combine the relevant technical features in the above examples according to the actual situation to achieve the corresponding technical effect, and specific combinations are not described here.

[0103] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative positional relationship, movement condition, etc. between the components in a certain posture (as shown in the drawings), and if the certain posture changes, the directional indications also change accordingly.

[0104] In addition, the terms "first", "second", and the like, as used in the description, are used for distinguishing like from like and do not imply or imply any importance or any relative meaning. Thus, a "first" feature discussed above could be termed a "second" feature without departing from the scope of the present application.

[0105] The above description is merely that of the preferred embodiments of the application, and the application is not limited to the details of the foregoing description. Rather, the present application is intended to cover modifications and variations of this application that come within the scope of the appended claims, along with their equivalents.

Claims

1. A method for recommending a casing selection for a horizontal well in a shale oil reservoir, the method comprising: It comprises the following steps: ​ Step one, establishing the difficulty level of casing running in different horizontal wells; Step two, obtaining the type of the shale oil horizontal well to be drilled, the length of the horizontal section, the predicted value of casing running friction and the number of running; Step three, according to the data obtained in step two, and comparing with the difficulty level of casing running in horizontal wells established in step one, the difficulty level of casing running in the shale oil horizontal well to be drilled is determined; Step four, classifying the casing to be used; Step five, testing the dynamic sealing quality of the casing thread of different types in step four; Step six, ranking the sealing quality of the casing provided according to the test results in step five; Step seven, selecting the casing; According to the difficulty level of casing running in the shale oil horizontal well to be drilled in step three, the matching casing is selected; The difficulty level of casing running in horizontal wells established in step one is as follows: When the lateral distance of the drilled horizontal well is less than 300m, the length of the horizontal section is less than 1500m, the predicted casing running friction is less than 40 tons, and the number of running at the same position is less than 65 times, the casing running is easy; When the lateral distance of the drilled horizontal well is less than 300-600m, the length of the horizontal section is less than 1500-2000m, the predicted casing running friction is 40-45 tons, and the number of running at the same position is less than 65-85 times, the casing running is moderately difficult; When the lateral distance of the drilled horizontal well is less than 600-900m, the length of the horizontal section is less than 2000-3000m, the predicted casing running friction is 45-50 tons, and the number of running at the same position is less than 85-100 times, the casing running is difficult.

2. The method for recommending casing selection for horizontal wells in shale oil reservoirs according to claim 1, wherein, The casing to be used in step four is classified as follows: The purchased casing is divided into three types according to the price: high price, medium price and low price; Economical casing: economical casing refers to the casing with low price and the thread sealing performance of which meets the field requirements; Fatigue-resistant casing: fatigue-resistant casing refers to the casing with medium price and the thread sealing performance of which meets the field requirements and can adapt to the field conditions; Large coupling impact-resistant casing: large coupling impact-resistant casing refers to the casing with high price and the thread sealing performance of which meets the field requirements and can completely adapt to the field conditions.

3. The method of claim 1, wherein, The method for testing the thread dynamic sealing quality of the casing provided in step five is as follows: First step, after screwing two casings, support and fix the two ends to make them horizontally placed; Second step, apply a preset pressure to the casing in the axial direction to make the casing string test piece bend, and apply a preset pressure to the casing; Third step, release the internal pressure and bending force; Fourth step, test the thread sealing performance of the test casing. If the thread sealing performance of the test casing is good, return to step one and repeatedly implement the bending for several times; otherwise, the test is ended.

4. The method of claim 3, wherein, The number of times of repeatedly implementing the bending test is 100-200 times.

5. The method of claim 3, wherein, In the second step, a 100-ton pressure is applied to the casing in the axial direction to make the casing string test piece bend 12 degrees per 30m, and a pressure of 40MPa is applied to the casing.

6. The method of claim 3, wherein, The method for testing the thread sealing property of the tested casing in the fourth step is to pressurize the inside of the tested casing, maintain for one minute, and then test the pressure condition; if the pressure remains stable, the thread sealing property is good, otherwise the thread sealing property of the casing is failed.

7. The method of claim 3, wherein, The method for selecting the casing in the seventh step is as follows: If the casing is easy to be lowered into the well, the economic casing is selected; if the casing is difficult to be lowered into the well, the fatigue-resistant casing is selected; if the casing is very difficult to be lowered into the well, the large-coupling impact-resistant casing is selected.

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