Shale oil horizontal well casing selection recommendation method

Abstract

The invention 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. According to the method, the well descending difficulty degree sequence of different horizontal well sleeves is established, the type, the horizontal section length, the sleeve descending friction resistance predicted value and the descending frequency of the shale oil horizontal well to be drilled are obtained, the well descending difficulty degree of the sleeves of the shale oil horizontal well to be drilled is determined, the preset used sleeves are classified, and the well descending difficulty degree of the shale oil horizontal well to be drilled is determined. The method for selecting the rock oil horizontal well casing comprises the seven steps of conducting casing thread dynamic sealing quality testing on casing pipes of different types, conducting sealing quality sorting on the provided horizontal well casing pipes and selecting the casing pipes, and the method for selecting the rock oil horizontal well casing pipes is provided. According to the invention, targeted selection is carried out within the application range of the casing, and the purpose of safely tripping in the casing on site is achieved. The risk of sealing failure after the horizontal well casing pipe is put into the well is greatly reduced. The repair cost for sealing failure of the casing string in the later period is reduced, the best use of materials is achieved, and the overall cost of the casing is controlled.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas well drilling and completion process design, and in particular relates to a method for recommending the selection of shale oil horizontal well casing. Background Art

[0002] The selection of casing for shale oil horizontal wells is one of the important links in the design of drilling and completion projects. At present, the selection of casing is mainly made by Party A based on the drilling manual, API standards, and oil and gas field development (exploration) plans; casing is selected according to oil wells, gas wells, and deep wells; due to the large number of wells drilled and completed in oil fields each year, oil and gas wells in multiple blocks often use the same casing, without considering the difficulty and risk of casing lowering in each well.

[0003] The main technology of shale oil extraction in oil fields is "large well group + long horizontal section + multi-stage volume fracturing", which aims to maximize the wellhead production. However, in the process of shale oil horizontal well development, the problem of casing seal failure occurs frequently. The main reasons are as follows: One reason is that shale oil horizontal wells have large offset distances and long horizontal sections.

[0004] Secondly, during the actual construction process of lowering casing into horizontal wells, due to the complex wellbore trajectory, multiple turning points and large offset distance, the friction resistance of casing lowering is large. In order to continue lowering the casing, the wellhead usually adopts the measure of repeatedly lowering the casing. The casing in some parts of the well is overloaded and bent, causing damage (micro cracks) at the root of the casing thread; thus, the casing thread seal failure is prone to occur.

[0005] Third, the casing used does not conform to the actual well conditions of the oil well.

[0006] In the prior art, there are some measures to solve the problem of casing seal failure.

[0007] At present, the selection of horizontal well casing is mainly based on the "Drilling Party A Manual" and "Drilling Technology". There are three main technical parameters to measure the selection of casing, namely, tensile strength, internal pressure resistance, and external squeeze resistance. When the tensile strength, internal pressure resistance, and external squeeze resistance of the casing meet the casing insertion depth; The tonnage requirement for lowering the casing when encountering resistance is less than 20-30 tons. The data is quite different from the current on-site conditions and cannot meet the on-site requirements; this creates the risk of casing sealing failure on site.

[0008] "Calculation of Friction and Analysis of Runnability of Horizontal Well Casing" Author: Zhang Yang. Southwest Petroleum University, Master Electronic Journal Publication Information: Year and Issue 2015 Issue 09. A set of calculation methods for friction and load of horizontal well casing suitable for field application has been developed, which can accurately calculate the friction and load during the casing running process, and conduct wellbore compatibility and string strength analysis. First, according to the wellbore trajectory data, a three-dimensional rigid rod model is selected to analyze the drilling fluid viscosity resistance, pressure difference resistance, dynamic load that may be generated during the casing running process, the matching of casing size and wellbore clearance, and the influence of wellbore trajectory parameters on friction and load; then the maximum passing curvature of the casing is calculated, and the maximum passing length of a single casing is calculated using a rigid geometric compatibility model; secondly, the effective external extrusion 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 string strength. Finally, VB was used to compile a feasibility analysis software for casing running in horizontal wells. The software was used to calculate casing friction and load, analyze wellbore compatibility and check string strength, and analyze the feasibility of casing running.

[0009] "Simulation of casing string running into horizontal wells based on finite element analysis" Author: Chen Yingchao; Chengde; Petroleum Engineering Department of Petroleum College. It models the mechanical problems related to the casing running process, quantitatively analyzes the friction resistance and the strength of the casing after it is lowered into the well. Through finite element modeling, the stress state of any node of the casing at any time can be obtained, and compared with its allowable strength, it can be determined whether the casing can be safely run.

[0010] "Finite Element Simulation of Shale Horizontal Well Casing" Author: Wang Yang Petrochemical Applications. 2020, 39(10). Finite element software is used to simulate the stress changes of casing under the combined effects of temperature, non-uniform load and two factors. As the formation temperature drops, the additional temperature stress continues to increase, but the stress distribution remains basically unchanged; under the action of non-uniform load on the casing, the stress in the middle part of the casing is greater, and the stress is smaller as it approaches the end face; under the combined effects of temperature and non-uniform load on the casing, the casing undergoes elliptical deformation.

[0011] "Finite Element Analysis of the Contact State between Casing and Wellbore Wall during Casing in Horizontal Wells" Author: Shin So-hee Petroleum Pipes and Instruments. 2022, 8(06). The finite element numerical simulation method was used to analyze the contact between the casing and the wellbore wall during casing lowering in a two-dimensional plane state. The area with high contact pressure is mainly in the deflection section, including the starting, middle and end points of the deflection section.

[0012] "Study on Friction Analysis and Control Technology of Casing String in Shale Gas Horizontal Wells" author: Chen Pengju. He proposed an inversion method for multi-segment friction coefficient of large-reach wells. This method divides the entire wellbore into different sections according to the wellbore shape, and introduces a corresponding friction coefficient in each section to describe the friction distribution of the wellbore. Based on the soft rope model, a friction calculation model based on the dynamic movement of the casing was established, which can simulate the force and movement of the casing string during the casing downstroke process in the lifting and downstroke operation.

[0013] "Analysis and Safety Evaluation of Casing Passability in Ultra-deep Horizontal Wells" author: Yang Weixing. Considering casing bending and rigid downhole tools, a model of the ultimate wellbore curvature of casing lowering was established, which can calculate the ultimate wellbore curvature of casings of different steel grades and outer diameters. Then a finite element model for casing bending stress simulation was established, which can obtain the stress distribution of casing in the curved well section under different wellbore curvatures, different internal and external pressures, and different axial forces.

[0014] "Mechanical Analysis of Frictional Resistance of Casing in Horizontal Wells" author: Li Qingming. The main content is to divide the pipe string into units, calculate the parameters required for the mechanical friction of the unit measuring points according to the divided units, and finally start from the drill bit, gradually solve the pipe string units and recursively transfer them to the wellhead to achieve mechanical analysis of the entire well section.

[0015] The above measures cannot make recommendations for the selection of casing for horizontal oil wells based on the actual area and specific location of the oil wells, and are less targeted. Summary of the invention

[0016] The present invention provides a method for recommending the selection of shale oil horizontal well casings, the purpose of which is to be able to select shale oil horizontal well casings in a targeted manner to meet on-site construction requirements, reduce drilling and completion costs, and provide data support for subsequent remote technical support.

[0017] To achieve the above object, the technical solution adopted by the present invention is: A recommended method for selecting casing for shale oil horizontal wells includes the following steps: Step 1: Establish a ranking of the difficulty of running casing into different horizontal wells; Step 2: Obtain the type of the shale oil horizontal well to be drilled, the length of the horizontal section, the predicted value of the casing running friction and the number of times of running; Step 3: According to the data obtained in step 2, the difficulty level of casing lowering in the horizontal well established in step 1 is compared to determine the difficulty level of casing lowering in the shale oil horizontal well to be drilled; Step 4: Classify the preset casings; Step 5, performing casing thread dynamic sealing quality tests on different types of casings in step 4 respectively; Step 6: rank the sealing quality of the provided horizontal well casings according to the test results of step 5; Step 7: Select matching casing according to the difficulty of lowering the casing of the shale oil horizontal well to be drilled in step 3.

[0018] The order of difficulty of setting the casing in the horizontal well in step 1 is as follows: When the offset distance of the completed 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 number of casing runs at the same location is less than 65 times, the casing is easy to run: When the horizontal well offset is less than 300-600m, the horizontal section length is less than 1500-2000m, the casing running friction is predicted to be 40-45 tons, and the number of casing runs at the same location is less than 65-85 times, the casing running difficulty is medium: When the offset distance of the completed 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 number of casing runs at the same position is less than 85-100 times, it is difficult to run the casing.

[0019] In step 4, the preset sleeves are classified into the following categories: The purchased casings are divided into three types according to their prices: high price, medium price, and low price; Economical casing: Economical casing refers to casing with low price and casing thread sealing performance that meets on-site requirements; Anti-fatigue casing: Anti-fatigue casing refers to the casing with moderate price and casing thread sealing performance that meets the site requirements and can adapt to the site conditions; Large coupling impact-resistant casing: Large coupling impact-resistant casing refers to the casing with high price and casing thread sealing performance that meets the site requirements and can fully adapt to the site conditions.

[0020] The method for performing thread dynamic sealing quality test on the horizontal well casing provided in step 5 is as follows: The first step is to screw the two sleeves together, support and fix both ends of the sleeves so that they are placed horizontally. The second step is to apply a preset pressure to the casing axially to bend the casing string specimen and apply a preset pressure inside the casing; Step 3: Release the internal pressure and bending force; Step 4: Test the thread tightness of the test casing. If the thread tightness of the test casing is intact, return to step 1 and repeat the bending several times; otherwise, the test is terminated.

[0021] The bending test is repeated 100-200 times.

[0022] The casing is subjected to an axial pressure of 100 tons, the casing string specimen is bent by 12 degrees / 30m, and a pressure of 40MOPa is applied inside the casing.

[0023] The method for testing the thread tightness of the tested casing in the fourth step is to pressurize the inside of the test casing, maintain it for one minute, and then test the pressure condition; if the pressure remains stable, the thread tightness is good, otherwise the casing thread tightness fails.

[0024] The method for selecting the casing in step 7 is as follows: If it is easy to go down the well, choose economical casing; if it is moderately difficult to go down the well, choose anti-fatigue casing; if it is difficult to go down the well, choose large-hoop impact-resistant casing.

[0025] Beneficial effects: (1) The present invention makes targeted selection within the scope of casing use, selects casing that meets the requirements according to a preset plan, and specifically meets the purpose of safely running casing on site.

[0026] (2) The present invention greatly reduces the risk of sealing failure after the horizontal well casing is lowered into the well.

[0027] (3) The present invention reduces the cost of repairing casing string seal failure.

[0028] (4) The present invention achieves the purpose of making the best use of the casing, thereby controlling the overall cost of the casing.

[0029] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0033] Embodiment 1: according to Figure 1 A recommended method for selecting casing for a shale oil horizontal well is shown, comprising the following steps: Step 1: Establish a ranking of the difficulty of running casing into different horizontal wells; Step 2: Obtain the type of the shale oil horizontal well to be drilled, the length of the horizontal section, the predicted value of the casing running friction and the number of times of running; Step 3: According to the data obtained in step 2, the difficulty level of casing lowering in the horizontal well established in step 1 is compared to determine the difficulty level of casing lowering in the shale oil horizontal well to be drilled; Step 4: Classify the preset casings; Step 5, performing casing thread dynamic sealing quality tests on different types of casings in step 4 respectively; Step 6: rank the sealing quality of the provided horizontal well casings according to the test results of step 5; Step 7: Select casing According to the difficulty of lowering the casing of the shale oil horizontal well to be drilled in step 3, a matching casing is selected.

[0034] The technical solution of the present invention requires understanding the requirements for casing performance data in the drilling manual and API standards, understanding the requirements for casing in the oil and gas field development (exploration) plan and the casing purchase situation of the oil and gas field material and equipment department, classifying the preset casing and conducting product quality test verification, fully considering the actual conditions of the oil well, and being more targeted. The present invention greatly reduces the risk of sealing failure of the horizontal well casing after it is lowered into the well.

[0035] The invention reduces the repair cost of casing column sealing failure.

[0036] The present invention achieves the purpose of making the best use of the casing, thereby controlling the overall cost of the casing.

[0037] Embodiment 2: according to Figure 1 The recommended method for selecting casing for shale oil horizontal wells shown in the embodiment is different from that in the first embodiment in that the order of difficulty of running casing into the horizontal wells in the first step is as follows: When the offset distance of the completed 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 number of casing runs at the same location is less than 65 times, the casing is easy to run: When the horizontal well offset is less than 300-600m, the horizontal section length is less than 1500-2000m, the casing running friction is predicted to be 40-45 tons, and the number of casing runs at the same location is less than 65-85 times, the casing running difficulty is medium: When the offset distance of the completed 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 number of casing runs at the same position is less than 85-100 times, it is difficult to run the casing.

[0038] In actual use, a ranking of the difficulty of inserting horizontal well casing is established, which makes the subsequent use of shale oil horizontal well casing more convenient and intuitive.

[0039] Embodiment three: according to Figure 1 The recommended method for selecting casing for shale oil horizontal wells shown in the embodiment is different from the embodiment 1 in that: the casings to be used in step 4 are classified into the following categories; The purchased casings are divided into three types according to their prices: high price, medium price, and low price; Economical casing, economical casing refers to the casing with low price and casing thread sealing performance that meets the on-site requirements; Anti-fatigue casing, anti-fatigue casing refers to the casing with moderate price and casing thread sealing performance that meets the on-site requirements and can adapt to on-site working conditions; Large coupling impact-resistant casing refers to the casing with high price and casing thread sealing performance that meets the on-site requirements and can fully adapt to on-site working conditions.

[0040] In actual use, the preset casings are classified, making the subsequent recommendations for the selection of shale oil horizontal well casings more direct and easier to operate.

[0041] Embodiment 4: according to Figure 1 The recommended method for selecting a shale oil horizontal well casing shown in the embodiment is different from the embodiment 1 in that the method for performing a thread dynamic sealing quality test on the provided horizontal well casing in step 5 is as follows: The first step is to screw the two sleeves together, support and fix both ends of the sleeves so that they are placed horizontally. The second step is to apply a preset pressure to the casing axially to bend the casing string specimen and apply a preset pressure inside the casing; Step 3: Release the internal pressure and bending force; Step 4: Test the thread tightness of the test casing. If the thread tightness of the test casing is intact, return to step 1 and repeat the bending several times; otherwise, the test is terminated.

[0042] In actual use, the dynamic sealing quality test of the thread by the present invention lays a foundation for the targeted applicability of the sleeve.

[0043] Embodiment five: according to Figure 1 The recommended method for selecting casing for shale oil horizontal wells shown in the figure is different from that of Example 4 in that the bending test is repeated 100-200 times.

[0044] The number of bending tests set in this embodiment fully considers the possible number of times the sleeve may bend due to various situations in the actual use of the sleeve in the prior art, ensuring that the data after the test can provide more scientific suggestions for the subsequent selection of the sleeve.

[0045] Embodiment six: according to Figure 1 The recommended method for selecting casing for shale oil horizontal wells shown in the figure is different from that of Example 4 in that: a pressure of 100 tons is applied axially to the casing, the casing string specimen is bent by 12 degrees / 30m, and a pressure of 40MOPa is applied inside the casing.

[0046] The parameter values ​​set in this embodiment fully consider the upper limit of the force that the casing needs to withstand in various situations during actual use in the prior art, ensuring that the tested casing data meets the requirements of the corresponding use conditions, is more targeted, and ensures that there is no risk of sealing failure after the horizontal well casing is lowered into the well.

[0047] Embodiment seven: according to Figure 1 The recommended method for selecting casing for shale oil horizontal wells shown in the figure is different from that of Example 4 in that: the method for testing the thread tightness of the test casing in the fourth step is to pressurize the inside of the test casing, maintain it for one minute, and then test the pressure condition; if the pressure remains stable, the thread tightness is good, otherwise the casing thread seal fails.

[0048] In actual use, the adoption of the above technical solution makes the casing tolerance test more in line with the actual conditions of the shale oil horizontal well location, and basically avoids the risk of sealing failure after the horizontal well casing is lowered into the well.

[0049] Embodiment eight: according to Figure 1 The recommended method for selecting casing for shale oil horizontal wells shown in the figure is different from that in the first embodiment in that the method for selecting casing in step seven is as follows: If it is easy to go down the well, choose economical casing; if it is moderately difficult to go down the well, choose anti-fatigue casing; if it is difficult to go down the well, choose large-hoop impact-resistant casing.

[0050] The technical solution of the present invention makes the selection of the sleeve more intuitive and simple.

[0051] In the absence of conflicts, technicians in this field can combine the relevant technical features in the above examples according to actual conditions to achieve corresponding technical effects. The specific combinations are not described here one by one.

[0052] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0053] In addition, the descriptions of "first", "second", etc. in the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0054] The above are only preferred embodiments of the present invention. The present invention will not be limited to the embodiments shown herein, but should conform to the widest scope consistent with the principles and novel features disclosed herein. Any simple modification, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A recommended method for selecting casing for shale oil horizontal wells, characterized by: The steps include: Step 1: Establish a ranking of the difficulty of running casing into different horizontal wells; Step 2: Obtain the type of the shale oil horizontal well to be drilled, the length of the horizontal section, the predicted value of the casing running friction and the number of times of running; Step 3: According to the data obtained in step 2, the difficulty level of casing lowering in the horizontal well established in step 1 is compared to determine the difficulty level of casing lowering in the shale oil horizontal well to be drilled; Step 4: Classify the preset casings; Step 5, performing casing thread dynamic sealing quality tests on different types of casings in step 4 respectively; Step 6: rank the sealing quality of the provided horizontal well casings according to the test results of step 5; Step 7: Select casing; According to the difficulty of lowering the casing of the shale oil horizontal well to be drilled in step 3, a matching casing is selected.

2. A method for selecting and recommending casing for shale oil horizontal wells according to claim 1, characterized in that: The order of difficulty of setting the casing in the horizontal well in step 1 is as follows: When the horizontal well offset is less than 300m, the horizontal section length is less than 1500m, the predicted casing running friction is less than 40 tons, and the number of casing runs at the same location is less than 65, the casing is easy to run; When the horizontal well offset is less than 300-600m, the horizontal section length is less than 1500-2000m, the casing running friction is predicted to be 40-45 tons, and the number of casing runs at the same location is less than 65-85 times, the casing running difficulty is medium; When the offset distance of the completed 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 number of casing runs at the same position is less than 85-100 times, it is difficult to run the casing.

3. A method for selecting and recommending casing for shale oil horizontal wells according to claim 1, characterized in that: In step 4, the preset sleeves are classified into the following categories: The purchased casings are divided into three types according to their prices: high price, medium price, and low price; Economical casing: Economical casing refers to casing with low price and casing thread sealing performance that meets on-site requirements; Anti-fatigue casing: Anti-fatigue casing refers to the casing with moderate price and casing thread sealing performance that meets the site requirements and can adapt to the site conditions; Large coupling impact-resistant casing: Large coupling impact-resistant casing refers to the casing with high price and casing thread sealing performance that meets the site requirements and can fully adapt to the site conditions.

4. A method for selecting and recommending casing for shale oil horizontal wells according to claim 1, characterized in that: The method for performing thread dynamic sealing quality test on the horizontal well casing provided in step 5 is as follows: The first step is to screw the two sleeves together, support and fix both ends of the sleeves so that they are placed horizontally. The second step is to apply a preset pressure to the casing axially to bend the casing string specimen and apply a preset pressure inside the casing; Step 3: Release the internal pressure and bending force; Step 4: Test the thread tightness of the test casing. If the thread tightness of the test casing is intact, return to step 1 and repeat the bending several times; otherwise, the test is terminated.

5. A method for selecting and recommending casing for shale oil horizontal wells according to claim 4, characterized in that: The bending test is repeated 100-200 times.

6. A method for selecting and recommending casing for shale oil horizontal wells according to claim 4, characterized in that: The casing is subjected to an axial pressure of 100 tons, the casing string specimen is bent by 12 degrees / 30m, and a pressure of 40MOPa is applied inside the casing.

7. A method for selecting and recommending casing for shale oil horizontal wells according to claim 4, characterized in that: The method for testing the thread tightness of the tested casing in the fourth step is to pressurize the inside of the test casing, maintain it for one minute, and then test the pressure condition; if the pressure remains stable, the thread tightness is good, otherwise the casing thread tightness fails.

8. A method for selecting and recommending casing for shale oil horizontal wells as claimed in claim 4, characterized in that: The method for selecting the casing in step 7 is as follows: If it is easy to go down the well, choose economical casing; if it is moderately difficult to go down the well, choose anti-fatigue casing; if it is difficult to go down the well, choose large-hoop impact-resistant casing.

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