A Feasibility Assessment Method for Sidetracking in Old Wells

Abstract

The present application relates to the technical field of oil exploration, in particular to a kind of old well side drilling feasibility evaluation method, including sequentially carrying out side drilling wellbore evaluation, side drilling process feasibility evaluation and economic evaluation, and when side drilling wellbore evaluation meets the condition, then side drilling process feasibility evaluation is carried out, when side drilling process feasibility evaluation meets the condition, then economic evaluation is carried out;Finally judge whether side drilling wellbore evaluation, side drilling process feasibility evaluation and economic evaluation meet the condition simultaneously, if yes, then judge that old well side drilling construction can be carried out, if not, then judge that old well side drilling construction cannot be carried out.Through the evaluation method, the problem that existing technology cannot carry out feasibility evaluation on old well side drilling can be effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil exploration, in particular to a method for evaluating the feasibility of sidetracking old wells. BACKGROUND

[0002] With the development of oil fields into the middle and later stages, problems such as low recovery rate and high water production rate are faced, such as a large number of sidetracking wells are implemented every year in Daqing and Changqing, and the number of construction is increasing year by year, and part of the old wells are facing shutdown. Reasonably revitalizing old well resources is an effective technical means to effectively tap remaining oil reservoirs and reduce investment costs, and old well sidetracking is an effective means of reasonably utilizing old wells. Before sidetracking, sidetracking feasibility evaluation is needed to accurately identify the risks of sidetracking, provide success rate, and reduce construction risks. At present, the purposes of domestic oil and gas well sidetracking mainly include: (1) the quality of the old well bore cannot meet the production demand; (2) watered-out oil and gas wells; (3) replacing the bottom of the original production layer.

[0003] The prior art does not have a method for evaluating the feasibility of opening a window and sidetracking an old well from the aspects of comprehensive geology, engineering and economy. SUMMARY

[0004] To solve the above technical problems, the present application provides a method for evaluating the feasibility of sidetracking an old well, which can effectively solve the problem that the prior art cannot evaluate the feasibility of sidetracking an old well.

[0005] The present application is realized by adopting the following technical solutions:

[0006] A method for evaluating the feasibility of sidetracking an old well, characterized by comprising the following steps:

[0007] S1. sequentially performing sidetracking well bore evaluation, sidetracking process feasibility evaluation and economic evaluation, and when the sidetracking well bore evaluation meets the conditions, then performing the sidetracking process feasibility evaluation, and when the sidetracking process feasibility evaluation meets the conditions, then performing the economic evaluation; wherein the indexes of the sidetracking well bore evaluation include sidetracking well bore casing damage and cementing quality, the casing damage includes the pressure bearing capacity of the casing, the passability of the casing and the stability of the annular cement sheath; the indexes of the sidetracking process feasibility evaluation include the matching of the sidetracking tool, the stability of the sidetracking well section formation and the drillability of the sidetracking well section formation; the index of the economic evaluation includes the vertical depth from the sidetracking point to point A, and the point A is the starting point of the horizontal section;

[0008] S2. judging whether the sidetracking well bore evaluation, the sidetracking process feasibility evaluation and the economic evaluation meet the conditions at the same time, if yes, then judging that the old well sidetracking construction can be performed, and if no, then judging that the old well sidetracking construction cannot be performed.

[0009] The indexes of the sidetracking well bore evaluation are represented as:

[0010] ,

[0011] wherein, is an index for evaluating the lateral wellbore; is the casing damage condition of the lateral wellbore; is the cementing quality.

[0012] The evaluation method of the casing damage condition of the lateral wellbore is:

[0013] If the casing damage exists and the drilling tool cannot pass through, or the casing damage exists and the casing damage has not been treated or the pressure-bearing capacity after treatment does not meet the requirements of the lateral well construction, it is determined as "not passing". If the casing damage exists and has been treated, but there is no clear record of pressure test, it is determined as "cautious". If the casing damage does not exist or the casing damage has been treated and the wellbore pressure-bearing capacity meets the requirements of the lateral well, and the drilling tool can pass through, it is determined as "passing".

[0014] The evaluation method of the cementing quality is:

[0015] S 111 . Determine whether the section outside the lateral drilling point pipe is a free section. If yes, it is determined as "not passing". If no, go to step S 112 .

[0016] S 112 . Determine whether there is cement sealing outside the lateral drilling point pipe. If yes, go to step S 113 . If no, it is determined as "not passing".

[0017] S 113 . Determine the cementing quality. If the cementing quality is poor-unqualified, it is determined as "cautious". If the cementing quality is excellent or moderate, it is determined as "passing".

[0018] The index for evaluating the lateral drilling process feasibility is represented as:

[0019] ,

[0020] wherein, is an index for evaluating the lateral drilling process feasibility; is the matching of the lateral drilling tool; is the formation stability of the lateral well section; is the drillability of the lateral well section.

[0021] The evaluation method of the matching of the lateral drilling tool is:

[0022] S 121. Determine whether the size, temperature resistance, pressure resistance and strength of the matched screw and MWD tool meet the requirements respectively;

[0023] The determination of whether the size of the matched screw and MWD tool meets the requirements specifically refers to determining whether the size of the screw and MWD tool meets the size requirement of the lateral wellbore, and if yes, determining as "pass"; if no, determining as "not pass";

[0024] The determination of whether the temperature resistance of the matched screw and MWD tool meets the requirements specifically refers to determining the temperature resistance according to the bottom hole temperature, i.e. if the bottom hole temperature is ≤ 150℃, determining as "pass"; if the bottom hole temperature is between 150-160℃, determining as "cautious"; if the bottom hole temperature is ≥ 160℃, determining as "not pass";

[0025] The determination of whether the pressure resistance of the matched screw and MWD tool meets the requirements specifically refers to determining the pressure resistance according to the bottom hole static pressure, i.e. if the bottom hole static pressure is ≤ 150MPa, determining as "pass"; if the bottom hole static pressure is between 150-155MPa, determining as "cautious"; if the bottom hole static pressure is ≥ 155MPa, determining as "not pass";

[0026] The determination of whether the strength of the matched screw and MWD tool meets the requirements specifically refers to determining whether the strength, buckling and water power of the drilling tool all meet the requirements, and if yes, determining as "pass", and if one of the strength, buckling and water power does not meet the requirements, determining as "not pass";

[0027] S 122 . Determine whether the lateral drilling tool is matched, specifically including: if the strength is determined as "not pass", directly determining the matching of the lateral drilling tool as "not pass"; if the size and strength are both "pass", at least one of the temperature resistance and pressure resistance is "cautious", and there is no "not pass" item, determining the matching of the lateral drilling tool as "cautious"; if the size and strength are both met, at least one of the temperature resistance and pressure resistance is not met, but the tool can be used, determining the matching of the lateral drilling tool as "cautious"; if the size, temperature resistance, pressure resistance and strength all meet the lateral drilling, determining the matching of the lateral drilling tool as "pass".

[0028] The evaluation method of the formation stability of the lateral drilling section includes the evaluation of hole diameter expansion rate and lithology;

[0029] The evaluation of the hole diameter expansion rate specifically refers to: if the average hole diameter expansion rate of the lateral drilling section is ≤ 50%, determining as "pass"; if the average hole diameter expansion rate of the lateral drilling section is between 50-100%, determining as "cautious"; if the average hole diameter expansion rate of the lateral drilling section is ≥ 100%, determining as "not pass";

[0030] The evaluation of the lithology specifically refers to: if the formation lithology is water-sensitive mudstone or salt rock, it is determined as "not passed"; and if the formation lithology is sandstone or limestone, it is determined as "passed".

[0031] The evaluation method of the drillability of the sidetracked well section formation The evaluation method of the drillability of the sidetracked well section formation

[0032] S 131 . The drilling time and the lithology are evaluated;

[0033] The evaluation of the drilling time specifically refers to: if the drilling time is less than or equal to 50 min / m, it is determined as "passed"; if the drilling time is between 50 min / m and 100 min / m, it is determined as "cautious"; and if the drilling time is greater than 100 min / m, it is determined as "not passed".

[0034] The evaluation of the lithology specifically refers to: if the lithology is basalt, it is determined as "not passed"; and if the lithology is sandstone or limestone, it is determined as "passed".

[0035] S 132 . The drillability of the sidetracked well section formation is evaluated;

[0036] If the drilling time is greater than 100 min / m or the lithology is basalt, it is determined as "not passed"; if the drilling time is between 50 min / m and 100 min / m, it is determined as "cautious"; and if the drilling time is less than or equal to 50 min / m or the lithology is sandstone or limestone, it is determined as "passed".

[0037] The index of the economic evaluation is represented as:

[0038] ,

[0039] Wherein, is the economic evaluation index; is the vertical depth from the sidetracking point to point A.

[0040] The evaluation method of the vertical depth z from the sidetracking point to point A is: if the vertical depth z from the sidetracking point to point A is greater than 1000 m, it is determined as "not passed"; if the vertical depth z from the sidetracking point to point A is between 500 m and 1000 m, it is determined as "cautious"; and if the vertical depth z from the sidetracking point to point A is less than 500 m, it is determined as "passed".

[0041] Compared with the prior art, the beneficial effects of the present application are shown in:

[0042] 1. The present application establishes an old well sidetracking feasibility evaluation method, which can more accurately evaluate the old well sidetracking, and provides a scientific basis for the design and construction of the old well sidetracking, so as to effectively prevent the occurrence of downhole complex accidents in the drilling construction process.

[0043] 2. Before the side drilling is implemented, the present invention can make a scientific feasibility judgment on the side drilling with the existing logging data, well repair data and geological data, and then provide guidance for the side drilling construction to ensure the efficiency of the side drilling construction.

[0044] 3. When the present invention determines that "cautious" construction is required after the side drilling well is evaluated, the operator can be reminded to prepare corresponding emergency measures and deal with corresponding accidents, thereby providing guidance for the smooth construction of the side drilling well.

[0045] 4. The feasibility analysis of side drilling wells after comprehensive evaluation of engineering, geology and economic benefits can effectively guide the construction unit to make scientific judgments and ensure that the side drilling wells can achieve profitability after construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, wherein:

[0047] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0048] Example 1

[0049] As a basic embodiment of the present invention, the present invention includes a method for assessing the feasibility of sidetracking in an old well, comprising the following steps:

[0050] S1. Conduct sidetrack wellbore assessment, sidetrack process feasibility assessment, and economic evaluation in sequence. When the sidetrack wellbore assessment meets the requirements, conduct a sidetrack process feasibility assessment. When the sidetrack process feasibility assessment meets the requirements, conduct an economic evaluation. The indicators for the sidetrack wellbore assessment include the sidetrack wellbore casing damage and cementing quality. The sidetrack wellbore casing damage includes the pressure bearing capacity of the casing, the passability of the casing, and the stability of the annular cement ring. The indicators for the sidetrack process feasibility assessment include the compatibility of the sidetrack tools, the stability of the formation in the sidetrack well section, and the drillability of the formation in the sidetrack well section. The indicators for the economic evaluation include the vertical depth from the sidetrack point to point A, where point A is the starting point of the horizontal section.

[0051] S2. Determine whether the sidetracking wellbore assessment, sidetracking process feasibility assessment, and economic feasibility assessment all meet the requirements. If so, determine that sidetracking of the old well can be performed. If not, determine that sidetracking of the old well cannot be performed.

[0052] Example 2

[0053] As a preferred embodiment of the present invention, the present invention includes a method for assessing the feasibility of sidetracking in an old well, comprising the following steps:

[0054] S1. sequentially performing lateral wellbore evaluation, lateral drilling process feasibility evaluation and economic evaluation, and when the lateral wellbore evaluation meets the condition, then performing the lateral drilling process feasibility evaluation, and when the lateral drilling process feasibility evaluation meets the condition, then performing the economic evaluation.

[0055] The index of the lateral wellbore evaluation includes lateral wellbore casing damage and cementing quality, and the lateral wellbore casing damage includes casing pressure-bearing capacity, casing passability and annular cement sheath stability.

[0056] More specifically, the index of the lateral wellbore evaluation is represented as:

[0057] ,

[0058] The index of the lateral wellbore evaluation is represented as: The lateral wellbore casing damage; The cementing quality.

[0059] The evaluation method of the lateral wellbore casing damage is as follows:

[0060] If there is casing damage and the drilling tool cannot pass, or there is casing damage and the casing damage has not been treated or the pressure-bearing capacity after treatment does not meet the requirements of lateral drilling well construction, it is determined as "not passing"; if there is casing damage and the casing damage has been treated, but there is no clear record of pressure test qualification, it is determined as "cautious"; if there is no casing damage or the casing damage has been treated and the wellbore pressure-bearing capacity meets the requirements of lateral drilling, and the drilling tool can pass, it is determined as "passing".

[0061] The evaluation method of the cementing quality is as follows:

[0062] S 111 . determining whether the lateral drilling point is a free section outside the pipe, if yes, determining as "not passing", if no, entering step S 112 ;

[0063] S 112 . determining whether the lateral drilling point is cemented outside the pipe, if yes, entering step S 113 , if no, determining as "not passing";

[0064] S 113 . judging the cementing quality, if the cementing quality is poor-unqualified, determining as "cautious", if the cementing quality is excellent or moderate, determining as "passing".

[0065] The index of the lateral drilling process feasibility evaluation includes matching of lateral drilling tools, formation stability of the lateral drilling well section and drillability of the lateral drilling well section.

[0066] ​The index of the economic evaluation includes a lateral drilling point to a vertical depth of point A, the point A being a starting point of a horizontal section.

[0067] S2. Determine whether the lateral wellbore evaluation, the lateral drilling process feasibility evaluation and the economic evaluation meet the conditions simultaneously, if yes, determine that the old well lateral drilling construction can be carried out, if not, determine that the old well lateral drilling construction cannot be carried out.

[0068] Embodiment 3

[0069] As another preferred embodiment of the present application, the present application comprises a method for evaluating the feasibility of old well lateral drilling, comprising the following steps:

[0070] S1. Perform the lateral wellbore evaluation, the lateral drilling process feasibility evaluation and the economic evaluation in sequence, and when the lateral wellbore evaluation meets the conditions, then perform the lateral drilling process feasibility evaluation, and when the lateral drilling process feasibility evaluation meets the conditions, then perform the economic evaluation.

[0071] The index of the lateral wellbore evaluation includes casing damage of the lateral wellbore and cementing quality, and the casing damage of the lateral wellbore includes pressure bearing capacity of the casing, passability of the casing and stability of the annular cement sheath. The index of the lateral drilling process feasibility evaluation includes matching of the lateral drilling tool, formation stability of the lateral drilling section and drillability of the formation of the lateral drilling section.

[0072] The index of the lateral drilling process feasibility evaluation is represented as:

[0073] ,

[0074] wherein, is the index of the lateral drilling process feasibility evaluation; is the matching of the lateral drilling tool; is the formation stability of the lateral drilling section; is the drillability of the formation of the lateral drilling section.

[0075] The matching of the lateral drilling tool is evaluated by:

[0076] S 121 . Determine whether the size, temperature resistance, pressure resistance and strength of the matched screw rod and MWD tool meet the requirements respectively;

[0077] wherein, determining whether the size of the matched screw rod and MWD tool meets the requirements specifically refers to determining whether the size of the screw rod and the MWD tool meets the size requirement of the lateral drilling hole, if yes, determining as “pass”; if not, determining as “not pass”;

[0078] Determining whether the temperature resistance of the matching screw and MWD tool meets the requirements specifically refers to: judging whether the temperature resistance is met based on the bottom hole temperature, that is, if the bottom hole temperature is ≤150℃, it is judged as "pass"; if the bottom hole temperature is between 150-160℃, it is judged as "cautious"; if the bottom hole temperature is ≥160℃, it is judged as failed;

[0079] To judge whether the pressure resistance of the matching screw and MWD tool meets the requirements, specifically: judging whether the pressure resistance is met is based on the bottom hole static pressure. That is, if the bottom hole static pressure is ≤150MPa, it is judged as "pass"; if the bottom hole static pressure is between 150-155MPa, it is judged as "cautious"; if the bottom hole static pressure is ≥155MPa, it is judged as "fail";

[0080] Determining whether the strength of the matching screw and MWD tool meets the requirements specifically refers to determining whether the drill tool strength, buckling and water power all meet the requirements. If so, it is judged as "passed". If any of the drill tool strength, buckling and water power does not meet the requirements, it is judged as "failed".

[0081] S 122 . Determine whether the side drilling tool is compatible, specifically including: if the strength is judged as "fail", the compatibility of the side drilling tool is directly judged as "fail"; if the size and strength are both "passed", at least one of the temperature resistance and pressure resistance is "cautious", and there are no failed items, the compatibility of the side drilling tool is judged as "cautious"; if the size and strength are both met, at least one of the temperature resistance and pressure resistance is not met, but the tool can be used, the compatibility of the side drilling tool is judged as "cautious"; if the size, temperature resistance, pressure resistance and strength all meet the requirements for side drilling, the compatibility of the side drilling tool is judged as "passed".

[0082] The formation stability of the side drilling section The evaluation methods include the evaluation of wellbore expansion rate and lithology;

[0083] Among them, the evaluation of the wellbore expansion rate specifically refers to: if the average wellbore expansion rate of the side drilling section is ≤50%, it is judged as "pass"; if the average wellbore expansion rate of the side drilling section is between 50-100%, it is judged as "cautious"; if the average wellbore expansion rate of the side drilling section is ≥100%, it is judged as "fail".

[0084] The specific evaluation of lithology means: if the stratum lithology is water-sensitive mudstone or salt rock, it is judged as "fail"; if the stratum lithology is sandstone or limestone, it is judged as "pass".

[0085] The drillability of the formation in the sidetracked well section The assessment method includes the following steps:

[0086] S 131 . Evaluate drilling time and lithology;

[0087] The evaluation of drilling time specifically refers to: if the drilling time is ≤50min / m, it is judged as "pass"; if the drilling time is between 50-100min / m, it is judged as "cautious"; if the drilling time is ≥100min / m, it is judged as "fail".

[0088] The specific evaluation of rock type means: if the rock type is basalt, it is judged as "fail"; if the rock type is sandstone or limestone, it is judged as "pass".

[0089] S 132 . Evaluate the drillability of the formation in the sidetracked well section:

[0090] If the drilling time is ≥100min / m or the rock type is basalt, it is judged as "fail"; if the drilling time is between 50-100min / m, it is judged as "cautious"; if the drilling time is ≤50min / m or the rock type is sandstone or limestone, it is judged as "pass".

[0091] The economic evaluation indicators include the vertical depth from the sidetracking point to point A;

[0092] S2. Determine whether the sidetracking wellbore assessment, sidetracking process feasibility assessment, and economic feasibility assessment all meet the requirements. If so, determine that sidetracking of the old well can be performed. If not, determine that sidetracking of the old well cannot be performed.

[0093] Example 4

[0094] As the best embodiment of the present invention, refer to the attached Figure 1 The present invention includes a method for evaluating the feasibility of sidetracking in an old well, comprising the following steps:

[0095] S1. Conduct sidetrack wellbore assessment, sidetrack process feasibility assessment, and economic assessment in sequence. Once the sidetrack wellbore assessment meets the requirements, conduct sidetrack process feasibility assessment. Once the sidetrack process feasibility assessment meets the requirements, conduct economic assessment. Specifically, it includes:

[0096] S 11 . Conduct sidetrack wellbore evaluation.

[0097] The indicators for the sidetracked wellbore assessment include the casing damage and cementing quality of the sidetracked wellbore. The casing damage includes the pressure bearing capacity of the casing, the passability of the casing, and the stability of the annular cement ring. The indicators for the sidetracked wellbore assessment are expressed as:

[0098] ,

[0099] in, Metrics evaluated for sidetracked wellbores; The casing damage of the side-drilling wellbore; For cementing quality.

[0100] The side drilling wellbore casing damage situation The evaluation method is:

[0101] Determine whether there is casing damage in the planned sidetracking section. If there is casing damage and the drill string cannot pass through, it is judged as "fail"; if there is casing damage and the casing damage has not been treated or the pressure bearing capacity after treatment does not meet the sidetracking construction requirements, it is judged as "fail"; if there is casing damage and it has been treated, but there is no clear record of qualified pressure test, it is judged as "cautious" and a pressure test is required during sidetracking. If the pressure test requirements are met, sidetracking can be carried out; if there is no casing damage or the pressure bearing capacity of the wellbore meets the sidetracking requirements after the casing damage is treated, and the drill string can pass through, it is judged as "pass".

[0102] The cementing quality The evaluation method is:

[0103] S 111 . Determine whether the side drilling point outside the pipe is a free section. If so, determine "fail". If not, go to step S 112 ;

[0104] S 112 . Determine whether there is cement sealing outside the side drilling point pipe. If so, go to step S 113 If not, it is judged as "failed" and the side drilling well construction is terminated;

[0105] S 113 The cementing quality is judged. If the cementing quality is poor or unqualified, it is judged as "cautious". If the cementing quality is excellent or medium, it is judged as "passed".

[0106] S 12 . Conduct feasibility assessment of side drilling process.

[0107] The indicators for evaluating the feasibility of the sidetracking process include the compatibility of the sidetracking tools, the stability of the formation in the sidetracking section, and the drillability of the formation in the sidetracking section. The indicators for evaluating the feasibility of the sidetracking process are expressed as follows:

[0108] ,

[0109] in, An indicator for evaluating the feasibility of sidetracking technology; Compatibility with side drilling tools; The formation stability of the side-drilled well section; The drillability of the formation in the side drilling section.

[0110] Compatibility of the sidetracking tool The evaluation method is:

[0111] S 121 . Determine whether the size, temperature resistance, pressure resistance and strength of the matching screw and MWD tool meet the requirements;

[0112] Among them, judging whether the sizes of the matching screw and MWD tool meet the requirements specifically refers to: judging whether the sizes of the screw and MWD tool meet the sidetracking wellbore size requirements, if so, it is judged as "passed"; if not, it is judged as "failed";

[0113] Determining whether the temperature resistance of the matching screw and MWD tool meets the requirements specifically refers to: judging whether the temperature resistance is met based on the bottom hole temperature, that is, if the bottom hole temperature is ≤150℃, it is judged as "pass"; if the bottom hole temperature is between 150-160℃, it is judged as "cautious"; if the bottom hole temperature is ≥160℃, it is judged as failed;

[0114] To judge whether the pressure resistance of the matching screw and MWD tool meets the requirements, specifically: judging whether the pressure resistance is met is based on the bottom hole static pressure. That is, if the bottom hole static pressure is ≤150MPa, it is judged as "pass"; if the bottom hole static pressure is between 150-155MPa, it is judged as "cautious"; if the bottom hole static pressure is ≥155MPa, it is judged as "fail";

[0115] Determine whether the strength of the matching screw and MWD tool meets the requirements. Specifically, determine whether the drill tool strength, buckling and water power all meet the requirements. If so, it is judged as "passed". If any one of the drill tool strength, buckling and water power does not meet the requirements, it is judged as "failed";

[0116] S 122 . Determine whether the side drilling tool is compatible, specifically including: if the strength is judged as "fail", the compatibility of the side drilling tool is directly judged as "fail"; if the size and strength are both "passed", at least one of the temperature resistance and pressure resistance is "cautious", and there are no failed items, the compatibility of the side drilling tool is judged as "cautious"; if the size and strength are both met, at least one of the temperature resistance and pressure resistance is not met, but the tool can be used, the compatibility of the side drilling tool is judged as "cautious"; if the size, temperature resistance, pressure resistance and strength all meet the requirements for side drilling, the compatibility of the side drilling tool is judged as "passed".

[0117] The formation stability of the side drilling section Evaluation methods include wellbore expansion rate and lithology assessment.

[0118] The evaluation of the wellbore expansion rate specifically refers to: if the average wellbore expansion rate of the sidetracking section is ≤50%, it is judged as "pass"; if the average wellbore expansion rate of the sidetracking section is between 50-100%, it is judged as "cautious"; if the average wellbore expansion rate of the sidetracking section is ≥100%, it is judged as "fail";

[0119] The specific evaluation of lithology means: if the stratum lithology is water-sensitive mudstone or salt rock, it is judged as "fail"; if the stratum lithology is sandstone or limestone, it is judged as "pass".

[0120] Evaluation method of drillability of sidetracked well section formation The evaluation method comprises the following steps:

[0121] S 131 . Evaluate drilling time and lithology.

[0122] Wherein, the evaluation of drilling time specifically refers to: if the drilling time is ≤50 min / m, it is determined as "pass"; if the drilling time is between 50-100 min / m, it is determined as "cautious"; if the drilling time is ≥100 min / m, it is determined as "not pass";

[0123] The evaluation of lithology specifically refers to: if the lithology is basalt, it is determined as "not pass"; if the lithology is sandstone or limestone, it is determined as "pass";

[0124] S 132 . Evaluate the drillability of the sidetracked well section formation.

[0125] If the drilling time is ≥100 min / m or the lithology is basalt, it is determined as "not pass"; if the drilling time is between 50-100 min / m, it is determined as "cautious"; if the drilling time is ≤50 min / m or the lithology is sandstone or limestone, it is determined as "pass".

[0126] S 13 . Perform economic evaluation. The index of the economic evaluation includes the sidetracking point position and the sidetracked section length, specifically, the vertical depth from the sidetracking point to point A, and the point A is the starting point of the horizontal section.

[0127] The index of the economic evaluation is represented as:

[0128] ,

[0129] Wherein, is the economic evaluation index; is the vertical depth from the sidetracking point to point A.

[0130] The evaluation method of the vertical depth from the sidetracking point to point A z is: if the vertical depth from the sidetracking point to point A is greater than 1000 m, it is determined as "not pass"; if the vertical depth from the sidetracking point to point A is between 500 m-1000 m, it is determined as "cautious"; if the vertical depth from the sidetracking point to point A is less than 500 m, it is determined as "pass".

[0131] Each assessment indicator and sidetracking feasibility assessment result is divided into three levels: fail, cautious, and pass. "Fail" indicates that the assessment result of the individual indicator does not meet the sidetracking requirements of the corresponding assessment item, and the final sidetracking feasibility assessment result still needs to comprehensively consider the assessment results of the other individual items; "Caution" indicates that the individual assessment result has a certain impact on the sidetracking related items and even the feasibility of the entire sidetracking, and the decision to proceed with sidetracking needs to be comprehensively considered after considering the assessment results of other assessment items; "Pass" indicates that the assessment result of the individual indicator meets the relevant requirements of sidetracking and meets the basic conditions for sidetracking.

[0132] S2. Determine whether the sidetracking wellbore assessment, sidetracking process feasibility assessment, and economic feasibility assessment all meet the requirements. That is, if all assessment results are "passed," then sidetracking of the old well can proceed. If not, then sidetracking of the old well cannot proceed.

[0133] In summary, after reading the present invention document, ordinary technicians in this field can make various other corresponding transformation schemes based on the technical solutions and technical concepts of the present invention without creative mental work, which all fall within the scope of protection of the present invention.

Claims

1. A method for assessing the feasibility of sidetracking in an old well, characterized by: The following steps are involved: S1. Sequentially perform a sidetracking wellbore assessment, a sidetracking process feasibility assessment, and an economic assessment. Once the sidetracking wellbore assessment satisfies the requirements, a sidetracking process feasibility assessment is performed. Once the sidetracking process feasibility assessment satisfies the requirements, an economic assessment is performed. The sidetracking wellbore assessment includes indicators for casing damage and cementing quality. The casing damage includes the pressure bearing capacity, passability, and stability of the annulus cement ring. The sidetracking process feasibility assessment includes indicators for sidetracking tool compatibility, formation stability, and drillability of the sidetracking well section. The economic assessment includes indicators for the vertical depth from the sidetracking point to point A, where point A is the starting point of the horizontal section. Among them, the assessment method for sidetracking wellbore casing damage is as follows: Determine whether there is casing damage in the planned sidetracking section. If there is casing damage and the drill string cannot pass through, or if there is casing damage and it has not been treated, or the casing pressure bearing capacity after treatment does not meet the sidetracking construction requirements, then the test is judged as "failed". If there is casing damage and it has been treated, but there is no clear record of passing the pressure test, then the test is judged as "cautious". If there is no casing damage or the casing pressure bearing capacity meets the sidetracking requirements after treatment, and the drill string can pass through, then the test is judged as "passed". The evaluation method for formation stability in the sidetracked well section includes the assessment of wellbore expansion rate and lithology. Specifically, the assessment of wellbore expansion rate means: if the average wellbore expansion rate of the sidetracked well section is less than 50%, it is judged as "pass"; if the average wellbore expansion rate of the sidetracked well section is between 50% and 100%, it is judged as "cautious"; if the average wellbore expansion rate of the sidetracked well section is greater than 100%, it is judged as "fail". Specifically, the assessment of lithology means: if the formation lithology is water-sensitive mudstone or salt rock, it is judged as "fail"; if the formation lithology is sandstone or limestone, it is judged as "pass". S2. Determine whether the sidetracking wellbore assessment, sidetracking process feasibility assessment, and economic feasibility assessment all meet the requirements. If so, determine that sidetracking of the old well can be performed. If not, determine that sidetracking of the old well cannot be performed.

2. The method for assessing the feasibility of sidetracking in an old well according to claim 1, wherein: The indicators of the sidetrack wellbore evaluation are expressed as: ， in, Metrics evaluated for sidetracked wellbores; The casing damage of the side-drilling wellbore; For cementing quality.

3. The method for assessing the feasibility of sidetracking in an old well according to claim 2, wherein: The cementing quality The evaluation method is: S 111 . Determine whether the outside of the casing at the side drilling point is a free section. If so, determine "failure". If not, proceed to step S 112 ; S 112 . Determine whether the outside of the casing at the side drilling point is cement sealed. If so, proceed to step S 113 If not, it is judged as "failed"; S 113 The cementing quality is judged. If the cementing quality is poor or unqualified, it is judged as "cautious". If the cementing quality is excellent or medium, it is judged as "passed".

4. The method for assessing the feasibility of sidetracking in an old well according to claim 1, wherein: The indicators for the feasibility evaluation of the sidetracking process are expressed as: ， in, An indicator for evaluating the feasibility of sidetracking technology; Compatibility with side drilling tools; The formation stability of the side-drilled well section; The drillability of the formation in the side drilling section.

5. The method for assessing the feasibility of sidetracking in an old well according to claim 4, wherein: The drillability of the formation in the sidetracked well section The assessment method includes the following steps: S 131 . Evaluate drilling time and lithology; The specific evaluation of drilling time is as follows: if the drilling time is less than 50 min / m, it is judged as "pass"; if the drilling time is between 50 min / m and 100 min / m, it is judged as "cautious"; if the drilling time is greater than 100 min / m, it is judged as "fail"; Lithology assessment specifically means: if the lithology is water-sensitive mudstone or salt rock, it is judged as "fail"; if the lithology is sandstone or limestone, it is judged as "pass"; S 132 . Evaluate the drillability of the formation in the sidetracked well section: If the drilling time is greater than 100 min / m or the rock type is water-sensitive mudstone or salt rock, it is judged as "fail"; if the drilling time is between 50 min / m and 100 min / m, it is judged as "cautious"; if the drilling time is less than 50 min / m or the rock type is sandstone or limestone, it is judged as "pass".

6. The method for assessing the feasibility of sidetracking in an old well according to claim 1, wherein: The indicators of economic evaluation are expressed as: ， in, It is an economic evaluation indicator; It is the vertical depth from the side drilling point to point A.

7. The method for assessing the feasibility of sidetracking in an old well according to claim 6, wherein: The evaluation method for the vertical depth z from the sidetracking point to point A is as follows: if the vertical depth z from the sidetracking point to point A is greater than 1000m, it is judged as "fail"; if the vertical depth z from the sidetracking point to point A is between 500m and 1000m, it is judged as "cautious"; if the vertical depth z from the sidetracking point to point A is less than 500m, it is judged as "pass".

8. A method for assessing the feasibility of sidetracking in an old well according to any one of claims 1 to 7, characterized in that: The "fail" mentioned above means that the evaluation result of a single indicator cannot meet the sidetracking requirements of the corresponding evaluation item, and the final sidetracking feasibility evaluation result needs to comprehensively consider the evaluation results of the remaining single indicators.

9. A method for assessing the feasibility of sidetracking in an old well according to any one of claims 1 to 7, characterized in that: The word "cautious" indicates that the evaluation result of this single indicator has an impact on the sidetracking related items and even the feasibility of the entire sidetracking, and whether to conduct sidetracking needs to be comprehensively considered after considering the evaluation results of other evaluation items.

10. A method for assessing the feasibility of sidetracking in an old well according to any one of claims 1 to 7, characterized in that: The "pass" indicates that the evaluation result of this single indicator can meet the relevant requirements of sidetracking and has the basic conditions for sidetracking.

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