Petroleum drilling PDC drill bit balling drum judging, processing and preventing method

Abstract

The invention discloses a petroleum drilling PDC (Polycrystalline Diamond Compact) drill bit balling drum judging, processing and preventing method, which comprises the following steps of: S1, setting a drill bit balling drum parameter symptom risk trend as Aprogressive, and when the Aprogressive reaches a corresponding area value, judging that a slight drill bit balling drum, a serious drill bit balling drum or a balling drum drilling jamming risk occurs underground; s2, setting the drill bit balling occurrence support degree as K, determining no drill bit balling when K is less than 20%, determining slight drill bit balling when K is more than or equal to 20% and less than 55%, determining serious drill bit balling when K is more than or equal to 55% and less than 85%, and determining balling jamming when K is more than 85%; s3, after the two indexes of the A < progressive > and the K value are synthesized, the bit balling degree Bj is judged, B1 is no bit balling, B2 is slight bit balling, B3 is serious bit balling, and B4 is balling jamming; and when the conclusions of the two judgment indexes are inconsistent, processing is carried out according to a relatively serious condition. According to the method, the underground balling risk can be accurately judged, the tripping frequency is reduced, and the construction period is shortened.

Description

Technical Field

[0001] The invention relates to a PDC drill bit for oil drilling, in particular to a method for determining mud balling of a PDC drill bit for oil drilling. The invention also relates to a method for treating mud balling of a PDC drill bit for oil drilling and a method for preventing mud balling of a PDC drill bit for oil drilling, belonging to the technical field of oil drilling. Background Art

[0002] In the oilfield drilling industry, PDC drill bits have the characteristics of high mechanical drilling speed, high single-trip footage, low failure rate, etc., with excellent comprehensive performance and more and more extensive applications. At present, in order to carry out low-cost development, various oil fields continue to simplify the wellbore structure, resulting in longer and longer open hole sections. PDC drill bits are very likely to produce drill bit mud packing when drilling in multi-layer formations, which seriously affects the efficiency of PDC drill bits. For a 3000-4000m medium-deep well, a trip to drill takes a day or even longer, and a well may even have mud packing several times. Frequent tripping not only affects the drilling cycle, but also has a certain impact on the stability of the well wall and well control safety. Tripping and drilling after the drill bit is mud-packed can easily induce downhole suction or pressure excitement, causing well control risks such as overflow and well kick. In severe cases, due to inaccurate prediction of the drill bit blocking, improper operation and handling measures may lead to mud packing and drill jamming or other downhole complex situations. The main causes of PDC drill bit mud packing include formation characteristics, drilling parameters, drilling fluid properties and drill bit structure. The judgment of drill bit mud packing at the drilling construction site mainly depends on the experience of the on-site operators.

[0003] After years of practice, the common measures to prevent PDC drill bit mud packing at drilling construction sites are:

[0004] 1. Control reasonable drilling fluid properties

[0005] 1. Use low viscosity, low shear, low solid content polyamine polymer drilling fluid system, and use solid-free drilling fluid system when conditions permit.

[0006] 2. Increase the content of polymer and shale inhibitors in the drilling fluid. Generally, inhibitors such as KPAM are used. By compounding shale inhibitors, ensure that the total amount of inhibitors is not less than 0.6% to inhibit the hydration and dispersion of shale and reduce the possibility of mud packing on the drill bit.

[0007] 3. Add anti-balling agent, cleaning agent, lubricant, etc. to the drilling fluid to form a hydrophobic film on the metal surface to reduce or remove the adhesion of hydrated clay on the drill bit surface. The addition standard of lubricant is 1%-3%, and the addition standard of cleaning agent is that the drilling fluid does not foam.

[0008] 4. Add alkaline substances before entering the gypsum-containing formation to prevent calcium invasion; when drilling into the highly permeable sandstone layer, add temporary plugging agents such as QS-2, and use shielding temporary plugging technology to reduce permeability loss and reduce the possibility of mud packing on the drill bit.

[0009] 5. Control water loss and improve filter cake quality. Increase the content of fluid loss reducer in the drilling fluid, control medium pressure water loss to no more than 4mL, and control HTHP water loss to less than 10mL, to avoid excessive water loss resulting in shrinkage and virtual thick filter cake.

[0010] 2. Optimize drill bit structure

[0011] 1. Under the premise of ensuring the unbalanced force requirements, the angles between the blades should be arranged reasonably to avoid mud packing caused by too small angles of the chip grooves. The inclination angle of the chip groove is 20°-30°. It is recommended to use a PDC drill bit with no more than five blades for construction in the upper formation.

[0012] 2. Optimize the hydraulic design of the drill bit, adopt an asymmetrical nozzle arrangement, and make the size of the central nozzle larger than that of other nozzles to achieve full coverage of the well bottom by the nozzle jet.

[0013] 3. For the anti-mud packing PDC drill bit, choose larger cutting teeth, the size of the composite piece should not be less than 16mm, the back angle of the composite piece should be 15°-20°, the teeth should be arranged at a low density, and the number of teeth should be less than 28; at the same time, ensure that the large-size cutting teeth have a high exposure and a large tooth spacing.

[0014] 4. The back of the blade adopts a large chamfer design to increase the arc chamfer at the root of the blade attack surface. The main blade adopts a variable radius chamfer to increase the chamfer at the root of the blade as much as possible.

[0015] At present, the main phenomena for judging the precursors of drill bit mud packing at the drilling construction site are as follows:

[0016] 1. Drilling time changes. When drilling parameters such as drilling pressure, displacement, and rotation speed remain unchanged, the drilling time gradually increases compared with the normal drilling time of the local formation or upper formation of adjacent wells, and at most increases by more than 3-5 times than the normal drilling time. There is still no obvious change in drilling time when the drilling pressure, rotation speed, and displacement are increased, and there is no change in drilling time when the formation changes significantly.

[0017] 2. Torque change. The initial mud packing torque increases slightly. As the drill bit becomes more mud packed, the torque gradually increases or the torque fluctuation range increases. At this time, the difference between the drill bit lifting off the bottom hole circulation torque and the drill bit drilling torque is small.

[0018] 3. Changes in suspended weight. During drilling or circulation, there is no obvious change in suspended weight. As the mud packing phenomenon intensifies, the drill will be stuck and the drill pressure pointer will change in a wide range. The suspended weight during tripping is greater than normal well conditions, and serious sticking occurs. When the pump is turned on, the suspended weight will suddenly drop after the pump pressure suddenly increases.

[0019] At present, the methods for dealing with drill bit mud packing at the drilling construction site are as follows:

[0020] After determining that the drill bit is mud-packed, take the following treatment methods in sequence to remove the mud packing. It is strictly forbidden to start the drilling jar for jarring during the process of dealing with the mud packing.

[0021] 1. Large-volume flushing method

[0022] Within the operating range of the equipment, the displacement is opened to the maximum for hydraulic flushing. The drill tool is moved quickly within the range of a single drill rod, and the brakes are applied sharply when lifting and lowering. Then the upper limit speed of the equipment is started to rotate the drill tool, and the mud packing is thrown out in an effort to be thrown out.

[0023] 2. Bottom hole grinding method

[0024] Lift the drill bit up, and when the drill bit is 5m away from the bottom of the well, do not start the top drive / rotary table, and gradually increase the displacement to the upper limit of the pump equipment. Then lower the drill bit to the bottom of the well at a low speed, apply the same drilling pressure as the unloaded tonnage of the big hook, and after a large displacement cycle for 5 minutes, lift the drill bit away from the bottom of the well, and rotate the drill bit at a high speed for 5 minutes. Stop the top drive / rotary table again and repeat the above operation.

[0025] 3. Slurry flushing method

[0026] Lift the drill bit, circulate the drilling fluid at a large volume, lower the drill bit to about 0.5m from the bottom of the well at a speed of 30rpm, and inject 4-5m 3 Use low-viscosity drilling fluid, lower the drill bit to 0.1m from the bottom of the well to displace the slurry, maintain rotation at 30rpm, and use the reaction force to wash away the adhesion.

[0027] 4. If the above methods fail, pull the drill bit to the wellhead and manually remove the mud on the drill bit.

[0028] The above measures to prevent drill bit mud packing and treatment have played a good role to a certain extent. However, in actual on-site construction, due to many reasons such as the performance of the drilling fluid cannot meet the downhole requirements, the drilling parameters and operation methods are improper, and the drill bit structure design is unreasonable, the drill bit mud packing phenomenon still occurs from time to time. Moreover, with the current simplified wellbore structure of the oil field, the long mudstone open hole section is getting longer and longer, and the sandstone and mudstone interlayers are increasing. The probability of PDC drill bit mud packing is also increasing. After the mud packing was determined on site, although conventional methods such as large-volume flushing, bottom hole grinding, and slurry flushing were used, although there were certain effects, the mud packing could not be completely removed, the mud packing removal effect was poor, and the mechanical drilling speed was not significantly improved. In the end, the drill was pulled to the wellhead and the mud packing of the drill bit was removed manually, which extended the drilling cycle to a certain extent and also increased the construction risk.

[0029] The reasons for the above defects are further analyzed as follows:

[0030] 1. At present, in order to reduce investment costs and simplify wellbore structures, various oil fields have longer and longer long mudstone open hole sections, more and more sandstone and mudstone interlayers, and the probability of PDC drill bit mud packing is also increasing.

[0031] 2. The formation of drill bit mud bag is not instantaneous, but a complex nonlinear dynamic process with many influencing factors and large random interference. It is difficult to effectively solve the abnormal complexity by using conventional precursor judgment and treatment measures. In addition, the current operators lack theoretical knowledge and construction experience accumulation, and their basic skills are weak. When faced with abnormal phenomena in construction, they cannot effectively identify and correctly handle them in time, resulting in heavier mud bags, and ultimately making the preventive measures ineffective. At the same time, it also leads to poor results of conventional mud bag removal treatment measures. For example, it is impossible to effectively identify whether it is a problem with the drill bit's cutting ability or a mud bag problem, resulting in incorrect drilling; the mud bag level cannot be accurately judged, and inappropriate measures are taken, leading to further deterioration.

[0032] 3. Measures such as applying butter on the surface of the drill bit and wrapping a metal mesh are short-lived and have poor effects. The metal mesh will affect the drill bit's normal penetration into the formation and affect the return of sand.

[0033] 4. The performance of the drilling fluid cannot meet the needs of formations prone to mud packing.

[0034] 5. In the long open hole section, there are multiple pressure layers. Increasing the construction displacement to improve the flushing and sand carrying effect will cause leakage in the upper formation with weak pressure bearing capacity. In addition, due to the limitations of the equipment pump conditions, it is impossible to achieve the purpose of flushing and preventing mud packing simply by increasing the displacement.

[0035] 6. During the construction of medium-deep wells, operations such as lifting the drill bit, increasing the displacement and top drive / rotary speed, and large-scale movement are performed. Under the premise of considering the elongation of the drill bit and the conditions of the machine pump, there are risks such as the drill bit cannot be fully moved, the large displacement causes annular blockage, and the high torque stops the top drive / rotary. In addition, the drill bit rotation radius is small, and the centrifugal force generated cannot get rid of the mud packing. Summary of the invention

[0036] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0037] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0038] The primary purpose of the present invention is to overcome the ambiguity in the determination of drill bit mud balling risk in the prior art and to provide a method for determining mud balling of a PDC drill bit in oil drilling, which can accurately determine the degree of mud balling risk in the well, facilitate the formulation of treatment plans for different mud balling risk degrees, reduce the frequency of drilling and drilling, and shorten the construction period.

[0039] In order to solve the above technical problems, a method for determining mud balling of a PDC drill bit for oil drilling of the present invention comprises the following steps in sequence:

[0040] S1. Set the drill bit mud balling parameter symptom risk trend to A 渐进 , when A 渐进 When the corresponding area value is reached, it is judged that there is a risk of slight drill bit mud packing, severe drill bit mud packing or mud packing jamming in the well;

[0041] S2. Set the support degree of drill bit mud bag occurrence as K. When K < 20%, it is determined that there is no drill bit mud bag. When 20% ≤ K < 55%, it is determined that there is slight drill bit mud bag. When 55% ≤ K < 85%, it is determined that there is severe drill bit mud bag. When K > 85%, it is determined that the drill is stuck due to mud bag.

[0042] S3, comprehensive drill bit mud balling parameter symptom risk trend is A 渐进 The degree of drill bit mud bagging B is determined by using the two indicators of support degree K value and drill bit mud bagging occurrence. j ∈A 渐进 ∩K, where B1 means no drill bit mud bagging, B2 means slight drill bit mud bagging, B3 means severe drill bit mud bagging, and B4 means drill stuck due to mud bagging. When the conclusions of the two judgment indicators are inconsistent, the more serious mud bagging risk shall be treated.

[0043] Furthermore, A 渐进i is the range of changes of each parameter under different mud packing degrees, including the gradual trend value A during drilling 渐进1 , Torque change progressive trend value A 渐进2 , Pump pressure change progressive trend value A 渐进3 , Suspended weight change gradual trend value A 渐进4 , Liquid level change gradual trend value A 渐进5 and the progressive trend value of cuttings change A 渐进6 .

[0044] Furthermore, the gradual trend value A of drilling time changes 渐进1 Under normal drilling conditions, it is defined as 100%. When 100% < A 渐进1 When ≤180%, it is judged to be in a slight mud packing condition, 180%<A 渐进1 ≤300% is considered to be in a serious mud balling condition, 300%<A 渐进1 ≤500% is judged as being in mud bag and drill stuck condition;

[0045] Torque change gradual trend value A 渐进2 Under normal drilling conditions, it is defined as 100%. When 100% < A 渐进2 When ≤230%, it is judged to be in a slight mud ball condition, 230%<A 渐进2 ≤360% is considered to be in a serious mud balling condition, 360%<A渐进2 ≤660% is judged as mud bag stuck drill condition;

[0046] Pump pressure change gradual trend value A 渐进3 Under normal drilling conditions, it is defined as 100%. When 100% < A 渐进3 ≤150% is considered as a slight mud packing condition, 150%<A 渐进3 ≤220% is considered to be in a serious mud balling condition, 220%<A 渐进3 ≤420% is judged as mud packing and drill stuck condition;

[0047] Suspended weight change gradual trend value A 渐进4 Under normal drilling conditions, it is defined as 100%. When 100% < A 渐进4 ≤130% is considered as a slight mud packing condition, 130%<A 渐进4 ≤180% is considered to be in a serious mud balling condition, 180%<A 渐进4 ≤260% is judged as mud bag stuck drill condition;

[0048] Liquid level change gradual trend value A 渐进5 Under normal drilling conditions, it is defined as 100%, when 75% ≤ A 渐进5 When the value is less than 100%, it is judged to be in a serious mud balling condition; 50%≤A 渐进5 <75% is judged as mud packing and drill stuck condition;

[0049] Asymptotic trend value of cuttings change 渐进6 Under normal drilling conditions, it is defined as 100%, when 85% ≤ A 渐进6 When the value is less than 100%, it is judged to be in a slight mud ball condition; 70%≤A 渐进6 <85% is judged as being in a serious mud balling condition, 50%≤A 渐进6 <70% is judged as being in mud pack and drill stuck condition.

[0050] Furthermore, K i Including drilling time change K1, torque change K2, pump pressure change K3, suspended weight change K4, liquid level change K5 and cuttings change K6, K i The value can be divided into two modes: 0 or 1. When the parameters change within the allowable range, K i The value is 0; when it exceeds the allowable range, K i The value is 1; i is the credible weight for each parameter change.

[0051] Furthermore, the credible weight α1 of the drilling time change K1 is 25%, the credible weight α2 of the torque change K2 is 15%, the credible weight α3 of the pump pressure change K3 is 15%, the credible weight α4 of the suspended weight change K4 is 15%, the credible weight α5 of the liquid level change K5 is 10%, the credible weight α6 of the cuttings change K6 is 15%, and the credible weights of other parameter changes are 5%;

[0052] The allowable range of variation of drilling time change K1 is 6%, the allowable range of variation of torque change K2 is 12%, the allowable range of variation of pump pressure change K3 is 10%, the allowable range of variation of suspended weight change K4 is 5%, the allowable range of variation of liquid level change K5 is 3%, the allowable range of variation of cuttings change K6 is 3%, and the allowable range of variation of other parameter changes is 5%.

[0053] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. In combination with the formation mechanism of PDC drill bit mud balling, the present invention has established a quantitative evaluation method for judging drill bit mud balling on the basis of conventional drill bit mud balling identification, clarified the changes of various characteristic parameters in the process of mud balling, formed a drill bit mud balling symptom risk trend prediction chart, paid close attention to the changes in characteristic parameters such as drilling time changes, returned rock cuttings changes, torque changes, pump pressure changes, suspended weight changes, and wellhead annulus liquid level changes, conducted a quantitative evaluation of the effects of multiple parameters on drill bit mud balling, and was able to make a rapid prediction of drill bit mud balling.

[0054] 2. The signs of drill bit mud balling were quantitatively evaluated, and the relationship between two or more abnormal situations or the relationship between key parameters when drill bit mud balling occurred was established. This relationship is expressed by support and credibility. Support refers to the cumulative proportion of all abnormal complexities occurring at the same time, and credibility refers to the credibility ratio of a single abnormal phenomenon. Through the quantitative evaluation of drill bit mud balling support and credibility, the drill bit mud balling risk warning category was established, providing a theoretical and data basis for the accurate judgment of drill bit mud balling.

[0055] 3. The present invention aims at the abnormal changes of various characteristic parameters in the early stage of drill bit mud balling, forms a drill bit mud balling symptom risk trend prediction chart, and clarifies the drill bit mud balling parameter symptom risk trend A 渐进 The signs of drill bit balling were quantitatively evaluated, the support degree K of drill bit balling was defined, and the risk trend of drill bit balling parameters and A were comprehensively analyzed. 渐进 The two indicators of drill bit mud bag support K value determine the degree of drill bit mud bag B j , double identification of drill bit mud balling risk and its signs, so as to provide more accurate early warning of drill bit mud balling risk.

[0056] 4. The present invention is applicable to the judgment of mud balling in various well types, and can effectively analyze the risk of mud balling during drilling. After the occurrence of mud balling, it provides a strong decision-making basis for the analysis of mud balling treatment methods and the evaluation of mud balling sticking effect, and takes targeted treatment measures, thereby reducing the risk of drilling operations, reducing non-productive time and reducing operating costs.

[0057] 5. Comprehensively analyze the risk trend of drill bit mud balling parameters 渐进 and the drill bit mud bag support K value, judge the drill bit mud bag degree, according to B j According to the value, take corresponding targeted treatment measures to effectively reduce the operation risk.

[0058] Another object of the present invention is to overcome the problems of many disadvantages and poor effects of conventional drill bit mud balling treatment methods in the prior art, and to provide a method for treating mud balling of a PDC drill bit for oil drilling, which can improve the effect of removing mud balling, reduce the frequency of drilling and drilling, and shorten the construction period.

[0059] In order to solve the above technical problems, a method for treating mud balling of a PDC drill bit for oil drilling is provided in the present invention. When slight mud balling of the drill bit occurs underground, the treatment is performed according to the following steps:

[0060] A1. Perform large-volume flushing. If flushing is effective, continue drilling. If flushing is ineffective, proceed to the next step.

[0061] A2. Use slurry flushing liquid for flushing. The formula of slurry flushing liquid is: water + 2-3% caustic soda + 0.1-0.2% anti-mud bag agent RH4 + 2-4% walnut shell + 3-5% quartz sand. The particle size of walnut shell is 2-5mm. If flushing is effective, continue drilling. If flushing is ineffective, proceed to the next step.

[0062] A3. Perform bottom hole grinding. If effective, continue drilling. If not, proceed to the next step.

[0063] A4. Start drilling and clean the drill bit.

[0064] In order to solve the above technical problems, a method for treating mud balling of a PDC drill bit in oil drilling is provided in the present invention. When serious mud balling of the drill bit occurs underground, the treatment is performed according to the following steps:

[0065] B1. Use slurry flushing liquid for flushing. The formula of slurry flushing liquid is: water + 2-3% caustic soda + 0.1-0.2% anti-mud bag agent RH4 + 2-4% walnut shell + 3-5% quartz sand. The particle size of walnut shell is 2-5mm. If flushing is effective, continue drilling. If flushing is ineffective, proceed to the next step.

[0066] B2. Perform bottom hole grinding. If effective, continue drilling. If not, proceed to the next step.

[0067] B3. Use high-efficiency flushing fluid for flushing. The formula of high-efficiency flushing fluid is: water + 8% isolation agent JS-7 + 1% surfactant OP-10 + 1% fluid loss reducer JS-12 + 0.2% viscosity enhancer CMC + 0.5% glass microsphere JS-3; if flushing is effective, continue drilling; if flushing is ineffective, proceed to the next step;

[0068] B4. Inject a jam-releasing agent near the drill bit, shut down the well and soak it to release the jam. Pressurize it to 3-5MPa to increase the penetration of the jam-releasing agent. After soaking for more than 2 hours, start the well and move the drilling tools. If it is effective, continue drilling. If not, proceed to the next step.

[0069] B5. Start drilling and clean the drill bit.

[0070] In order to solve the above technical problems, a method for treating mud balling of a PDC drill bit for oil drilling is provided in the present invention. When mud balling and drilling are stuck in the well, the treatment is carried out according to the following steps:

[0071] C1. Use high-efficiency flushing fluid for flushing. The formula of high-efficiency flushing fluid is: water + 8% isolation agent JS-7 + 1% surfactant OP-10 + 1% fluid loss reducer JS-12 + 0.2% viscosity enhancer CMC + 0.5% glass microsphere JS-3; if flushing is effective, continue drilling; if flushing is ineffective, proceed to the next step;

[0072] C2. Inject a jam-releasing agent near the drill bit, shut down the well and soak it to release the jam. Pressurize it to 3-5MPa to improve the penetration of the jam-releasing agent. After soaking for more than 2 hours, start the well and move the drilling tools. If it is effective, continue drilling. If not, proceed to the next step.

[0073] C3. Withdraw the tubing above the drill bit by reverse cutting, and then lower the milling tubing to mill the bottom of the well.

[0074] Furthermore, the formula of the mudstone formation deblocking agent is: diesel + water + 3-4% emulsifier SR301 + 12% fast T + barite, where the oil-water ratio is 85:15;

[0075] The formula of the de-blocking agent for sandstone and limestone formations is: water + 20% hydrofluoric acid + 15% hydrochloric acid + 3% chromate corrosion inhibitor + 1% iron ion stabilizer IRON-2066A.

[0076] Further, first pump 10m into the wellbore 3 Pre-insulation fluid, then inject the de-blocking agent, and then inject 7m 3 When the post-placement isolation fluid and the release agent reach the stuck point, the pressure-holding soaking is stopped, and the water hole is kept open at regular intervals during the soaking period; the density of the pre-placement isolation fluid and the post-placement isolation fluid are consistent with the density of the well slurry when the drill is stuck. After the set soaking time is reached, it is replaced with ordinary well slurry, and then an attempt is made to lift up vigorously and apply positive and negative torque to the movable drill bit.

[0077] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. The drill bit mud ball treatment method of the present invention is optimized and improved on the basis of the slurry flushing method, and materials such as walnut shells and quartz sand for removing mud balls are added to the slurry flushing liquid to improve the flushing effect. Conventional drilling fluid has no obvious effect on mud ball soaking, and only reduces 14% in 3 hours, while the improved slurry flushing liquid has a significant effect on mud ball soaking, which can reach 36% in 1 hour, and the friction coefficient is reduced by 73.12%.

[0078] 2. Drawing on the working principle of pre-cementing isolation fluid to flush the drilling fluid gelling substances on the well wall and casing wall, a high-efficiency flushing fluid formula for use in severe drill bit mud packing has been developed. It has a good dilution effect on the bottom hole drilling fluid and realizes turbulent flushing of the drilling fluid. The viscosity of the high-efficiency flushing fluid is 30-40s. Practical application shows that it has good compatibility with the drilling fluid system in the well, and the flushing efficiency is 40% higher than that of conventional flushing fluids. It also has good sealing and wall protection performance, can effectively maintain the stability of the wellbore, and will not cause the wellbore conditions to deteriorate.

[0079] 3. Based on the conventional method of dealing with mud packing, the present invention injects a jamming agent near the drill bit when mud packing and drilling is stuck, and the well is shut down for holding pressure and soaking to jam. The jamming agent formula has been shown in actual application to be simple to configure on site. Experimental data show that the mud packing reduction rate after using the jamming agent is more than 85%, and the anti-mud packing effect is significant. In addition, the jamming release time is short, the one-time jamming success rate is as high as 95%, and it does not affect the rheology and filtration loss of the drilling fluid system in the well, and meets environmental protection requirements. The cleaning effect is further improved by holding pressure and soaking to jam, and the mud packing phenomenon can be successfully handled without drilling while ensuring underground safety, and the occurrence of mud packing and drilling is reduced.

[0080] Another object of the present invention is to overcome the problem of imperfect conventional drill bit mud balling prevention measures in the prior art, and to provide a method for preventing mud balling of a PDC drill bit in oil drilling, which can reduce the probability of mud balling and improve the effect of removing mud balling, reduce the frequency of drilling and drilling, and shorten the construction period.

[0081] In order to solve the above technical problems, the present invention provides a method for preventing mud balling of a PDC drill bit for oil drilling, which performs a modified anti-mud balling treatment on the drill bit surface before drilling to prevent mud balling, including: coating a Teflon anti-mud balling hydrophobic coating with strong negative charge on the surface of the PDC drill bit, polishing the cutting teeth and nitriding the drill bit body.

[0082] In order to solve the above technical problems, the present invention provides a method for preventing mud balling of a PDC drill bit for oil drilling. Before drilling, the chip groove and the blade surface of the drill bit are coated with butter to form a protective film, and the chip groove of the drill bit is wrapped with a wire mesh to reduce the contact time between the drill bit body and the inferior solid phase of the drilling fluid.

[0083] When drilling in soft mudstone formations, high speed and large displacement are used to reduce the concentration of cuttings in the drilling fluid; the displacement for Φ311.1mm wellbore construction is not less than 55L / s, the displacement for Φ241.3mm wellbore construction is not less than 45L / s, and the displacement for Φ215.9mm wellbore construction is not less than 34L / s;

[0084] In soft mudstone formations, low drilling pressure is used for drilling, and the drill is fed evenly. When the drilling time reaches 24 hours, the footage reaches 300 meters, or when abnormal torque, pump pressure, friction parameters are found, or abnormal sand return occurs, a short-distance drilling operation is carried out.

[0085] Furthermore, the short-distance drilling operation is carried out according to "two short and one long", wherein "short" means that the well-lifting section should exceed the newly drilled well section, and "long" means that the short well-lifting section starts from the well-lifting section and enters the upper-level casing shoe.

[0086] Furthermore, select stable formations for segmented top pumping or circulation, and it is strictly forbidden to start pumping in layers prone to mud packing; when encountering resistance while drilling, you must first start pumping to establish circulation; when drilling to the bottom of the well, you also need to start pumping and circulation first, use a large displacement to thoroughly clean the drill bit and the bottom of the well, and when the displacement reaches the drilling requirements, use low drilling pressure to drill 0.5-1.0m, and then enter normal drilling.

[0087] Furthermore, during normal drilling, after drilling a single rod or column, wait for the drilling pressure to drop before lifting the drill bit, ream the hole 1-2 times before connecting the single rod or column, pay close attention to the sand return situation, and ensure that the concentration of cuttings in the annulus is controllable; when ream the hole, pay attention to observe the weight gauge, vertical pressure gauge and top drive torque gauge to prevent jamming, pump blockage, and top drive stop;

[0088] If stuck, the top drive shall be pulled out with the normal hook load of 20kN and the top drive shall be pulled out without stopping the top drive. The kelly rod shall be pulled out with the load of no more than 50kN each time.

[0089] In case of pump blocking and top drive stopping, apply strong downward pressure after stopping the pump. If the drill bit can go down, try a small-displacement top pump.

[0090] Compared with the prior art, the present invention has achieved the following beneficial effects: the present invention provides drill bit mud balling prevention measures. On the basis of the original prevention measures, a coating for preventing mud balling is applied on the surface of the PDC drill bit, which repel the formation rock cuttings with negative charge, effectively prevents the rock cuttings from being adsorbed on the drill bit surface, reduces the adhesion between the drill bit surface and the muddy rock cuttings, reduces the probability of drill bit mud balling from the source, and effectively increases the prevention effect; at the same time, it further optimizes the conventional mud balling treatment measures, improves the removal effect, achieves the purpose of successfully treating mud balling without drilling, and shortens the construction period. Further reducing the risk of mud balling, the effect of the prevention measures is better, and the complex fault handling cycle in the well can be more effectively shortened, saving drilling costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0091] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor. The accompanying drawings are only provided for reference and explanation, and are not used to limit the present invention.

[0092] in:

[0093] Figure 1 This is a flow chart of the treatment of slight drill bit balling in the present invention;

[0094] Figure 2 This is a flow chart of the treatment of severe drill bit balling in the present invention;

[0095] Figure 3 This is a flow chart of the drill bit mud bag and drill sticking treatment process in the present invention;

[0096] Figure 4 This is a diagram showing the signs and risk trend prediction of various parameters of the actual drilling of the HY5HF well in Example 1 of the present invention;

[0097] Figure 5 This is a diagram showing the signs and risk trend prediction of various parameters of the actual drilling of the SHB5-14H well in Example 2 of the present invention;

[0098] Figure 6 This is a diagram showing the signs and risk trend prediction of various parameters in the actual drilling of the QY1-201HF well in Example 3 of the present invention; DETAILED DESCRIPTION

[0099] In the following description of the present invention, the directions or positional relationships indicated by terms such as "up", "down", "front", "back", "left", "right", "inside" and "outside" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description, and do not mean that the device must have a specific direction.

[0100] In order to make the technical means, creative features, objectives and effects of the present invention easier to understand, the present invention is further described below in conjunction with specific diagrams. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them.

[0101] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0102] The method for determining mud balling of a PDC drill bit for oil drilling of the present invention comprises the following steps in sequence:

[0103] S1. Set the drill bit mud balling parameter symptom risk trend to A 渐进 , when A 渐进 When the corresponding area value is reached, it is judged that there is a risk of slight drill bit mud packing, severe drill bit mud packing or mud packing jamming in the well;

[0104] A 渐进i is the range of changes of each parameter under different mud packing degrees, including the gradual trend value A during drilling 渐进1 , Torque change progressive trend value A 渐进2 , Pump pressure change progressive trend value A 渐进3 , Suspended weight change gradual trend value A 渐进4 , Liquid level change gradual trend value A 渐进5 and the progressive trend value of cuttings change A 渐进6 ;.

[0105] Drilling time change gradual trend value A 渐进1 Under normal drilling conditions, it is defined as 100%. When 100% < A 渐进1 When ≤180%, it is judged to be in a slight mud packing condition, 180%<A 渐进1 ≤300% is considered to be in a serious mud balling condition, 300%<A 渐进1 ≤500% is judged as being in mud bag and drill stuck condition;

[0106] Torque change gradual trend value A 渐进2 Under normal drilling conditions, it is defined as 100%. When 100% < A 渐进2 When ≤230%, it is judged to be in a slight mud ball condition, 230%<A 渐进2 ≤360% is considered to be in a serious mud balling condition, 360%<A 渐进2 ≤660% is judged as mud bag stuck drill condition;

[0107] Pump pressure change gradual trend value A 渐进3 Under normal drilling conditions, it is defined as 100%. When 100% < A 渐进3 ≤150% is considered as a slight mud packing condition, 150%<A 渐进3 ≤220% is considered to be in a serious mud balling condition, 220%<A 渐进3 ≤420% is judged as mud packing and drill stuck condition;

[0108] Suspended weight change gradual trend value A 渐进4 Under normal drilling conditions, it is defined as 100%. When 100% < A 渐进4 ≤130% is considered as a slight mud packing condition, 130%<A 渐进4 ≤180% is considered to be in a serious mud balling condition, 180%<A渐进4 ≤260% is judged as mud bag stuck drill condition;

[0109] Liquid level change gradual trend value A 渐进5 Under normal drilling conditions, it is defined as 100%, when 75% ≤ A 渐进5 When the value is less than 100%, it is judged to be in a serious mud balling condition; 50%≤A 渐进5 <75% is judged as mud packing and drill stuck condition;

[0110] Asymptotic trend value of cuttings change 渐进6 Under normal drilling conditions, it is defined as 100%, when 85% ≤ A 渐进6 When the value is less than 100%, it is judged to be in a slight mud ball condition; 70%≤A 渐进6 <85% is judged as being in a serious mud balling condition, 50%≤A 渐进6 <70% is judged as being in mud pack and drill stuck condition.

[0111] S2. Set the support degree of drill bit mud bag occurrence as K. When K < 20%, it is determined that there is no drill bit mud bag. When 20% ≤ K < 55%, it is determined that there is slight drill bit mud bag. When 55% ≤ K < 85%, it is determined that there is severe drill bit mud bag. When K > 85%, it is determined that the drill is stuck due to mud bag.

[0112] K i Including drilling time change K1, torque change K2, pump pressure change K3, suspended weight change K4, liquid level change K5 and cuttings change K6, K i The value can be divided into two modes: 0 or 1. When the parameters change within the allowable range, K i The value is 0; when it exceeds the allowable range, K i The value is 1;

[0113] α i is the credible weight of each parameter change, the credible weight α1 of drilling time change K1 is 25%, the credible weight α2 of torque change K2 is 15%, the credible weight α3 of pump pressure change K3 is 15%, the credible weight α4 of suspended weight change K4 is 15%, the credible weight α5 of liquid level change K5 is 10%, the credible weight α6 of cuttings change K6 is 15%, and the credible weight of other parameter changes is 5%;

[0114] The allowable variation range of drilling time variation K1 is 6%, that is, when the fluctuation range of drilling time variation K1 is ≤6%, its fluctuation is ignored and the value of drilling time variation K1 is 0; when the fluctuation range of drilling time variation K1 is greater than 6%, the value of drilling time variation K1 is 1, multiplied by its credible weight of 25%, and included in the K value.

[0115] By analogy, the allowable range of torque change K2 is 12%, the allowable range of pump pressure change K3 is 10%, the allowable range of suspended weight change K4 is 5%, the allowable range of liquid level change K5 is 3%, the allowable range of rock cuttings change K6 is 3%, and the allowable range of other parameter changes is 5%.

[0116] S3, comprehensive drill bit mud balling parameter symptom risk trend is A 渐进 The degree of drill bit mud bagging B is determined by using the two indicators of support degree K value and drill bit mud bagging occurrence. j ∈A 渐进 ∩K, where the symbol ∈ indicates belonging, the symbol ∩ indicates a union, B1 indicates no drill bit mud bagging, B2 indicates slight drill bit mud bagging, B3 indicates severe drill bit mud bagging, and B4 indicates drill bit stuck due to mud bagging; when the conclusions of the two judgment indicators are inconsistent, the more serious mud bagging risk shall be used. 渐进 It is judged to be a slight drill bit mud bag, but when the drill bit mud bag occurrence support degree K is judged to be a serious drill bit mud bag, it shall be handled as a serious drill bit mud bag.

[0117] like Figure 1 As shown in the figure, when a slight drill bit balling occurs underground, follow the steps below to handle it:

[0118] A1. Perform large-volume flushing. If flushing is effective, continue drilling. If flushing is ineffective, proceed to the next step.

[0119] A2. Use slurry flushing liquid for flushing. The formula of slurry flushing liquid is: water + 2-3% caustic soda + 0.1-0.2% anti-mud bag agent RH4 + 2-4% walnut shell + 3-5% quartz sand. According to the common practice in the industry, the percentages in this article refer to the weight percentage with water as the denominator. For example, 2-3% caustic soda means that when water is 100 parts by weight, caustic soda is 2-3 parts by weight, and the same below. The particle size of walnut shell is 2-5mm; if flushing is effective, continue drilling, if flushing is ineffective, proceed to the next step;

[0120] A3. Perform bottom hole grinding. If effective, continue drilling. If not, proceed to the next step.

[0121] A4. Start drilling and clean the drill bit.

[0122] The manufacturers and material properties of the components in the slurry flushing fluid are shown in Table 1:

[0123] Table 1

[0124]

[0125] The mud ball immersion test was carried out on the slurry flushing fluid and compared with the mud ball immersion test of the conventional drilling fluid system. The data obtained are shown in Table 2.

[0126] Table 2

[0127]

[0128] From the experimental data in Table 2, it can be seen that the conventional drilling fluid has no obvious effect on mud ball soaking, and only reduces 14% in 3 hours, while the mud ball soaking effect of the improved slurry flushing fluid is significant, reaching 36% in 1 hour, and the friction coefficient is reduced by 73.12%. This shows that the improved slurry flushing fluid has a strong dispersing ability for mudstone, can fully disperse the mud cake on the drill bit, and coupled with the flushing effect of rigid particles, it greatly improves the removal rate of mud packing on the drill bit.

[0129] like Figure 2 As shown in the figure, when serious drill bit mud balling occurs underground, follow the steps below to handle it:

[0130] B1. Use slurry flushing liquid for flushing. The formula of slurry flushing liquid is: water + 2-3% caustic soda + 0.1-0.2% anti-mud bag agent RH4 + 2-4% walnut shell + 3-5% quartz sand. The particle size of walnut shell is 2-5mm. If flushing is effective, continue drilling. If flushing is ineffective, proceed to the next step.

[0131] B2. Perform bottom hole grinding. If effective, continue drilling. If not, proceed to the next step.

[0132] B3. Use high-efficiency flushing fluid for flushing. The formula of high-efficiency flushing fluid is: water + 8% isolation agent JS-7 + 1% surfactant OP-10 + 1% fluid loss reducer JS-12 + 0.2% viscosity enhancer CMC + 0.5% glass microsphere JS-3; if flushing is effective, continue drilling; if flushing is ineffective, proceed to the next step;

[0133] B4. Inject a jam-releasing agent near the drill bit, shut down the well and soak it to release the jam. Pressurize it to 3-5MPa to increase the penetration of the jam-releasing agent. After soaking for more than 2 hours, start the well and move the drilling tools. If it is effective, continue drilling. If not, proceed to the next step.

[0134] B5. Start drilling and clean the drill bit.

[0135] In B4, first pump 10m into the wellbore. 3 Pre-insulation fluid, then inject the de-blocking agent, and then inject 7m 3 When the post-placement isolation fluid and the release agent reach the stuck point, the pressure-holding soaking is stopped, and the water hole is kept open at regular intervals during the soaking period; the density of the pre-placement isolation fluid and the post-placement isolation fluid are consistent with the density of the well slurry when the drill is stuck. After the set soaking time is reached, it is replaced with ordinary well slurry, and then an attempt is made to lift up vigorously and apply positive and negative torque to the movable drill bit.

[0136] In B4, the formula of the de-stuck agent for mudstone formations is: diesel + water + 3-4% emulsifier SR301 + 12% Quick T + barite, where the oil-water ratio is 85:15; the formula of the de-stuck agent for sandstone and limestone formations is: water + 20% hydrofluoric acid + 15% hydrochloric acid + 3% chromate corrosion inhibitor + 1% iron ion stabilizer IRON-2066A.

[0137] In B3, the manufacturers and material properties of each component in the high-efficiency flushing fluid are shown in Table 3:

[0138] Table 3

[0139]

[0140] The wetting and adsorption properties of the high-efficiency flushing fluid were tested and compared with those of the conventional flushing fluid. The experimental data are shown in Table 4.

[0141] Table 4

[0142] Viscosity / s <![CDATA[Surface tension mN / m]]> Contact angle / ° Conventional flushing fluid 35 28.6 101.8 High efficiency flushing fluid 36 24.2 106.2

[0143] The experimental data in Table 4 show that the viscosities of the two flushing fluids are basically the same, and the surface tension of the high-efficiency flushing fluid is smaller and the contact angle is larger. The lower the surface tension, the better the wetting of the drill bit surface. The larger the contact angle, the more hydrophobic it is, which prevents drill cuttings and mud cakes from adhering to the drill bit surface.

[0144] In B4, the manufacturers and material properties of the components in the deblocking agent are shown in Table 5:

[0145] Table 5

[0146]

[0147] The experimental method for evaluating the de-stuck agent is as follows: ① Use an iron rod to simulate the drill bit, put it into an aging tank with field mud, mudstone de-stuck agent, and sandstone limestone de-stuck agent, use a roller heating furnace, set the conditions to 100℃, hot rolling for 1h, then observe the mud packing of the iron rod, weigh the quality of the mud-packed clay on the surface of the iron rod to evaluate the effect of the de-stuck agent. ② Place the steel sheet in three mud systems respectively, and place it in an environment of 100℃ for 48h. The corrosion inhibition performance of the drilling fluid is evaluated by the weight loss method.

[0148] The experimental data of the anti-mud packing and anti-corrosion performance evaluation of the de-blocking agent are shown in Table 6:

[0149] Table 6

[0150] Mass of mud on the iron rod surface / g Corrosion rate / g·m-2·h-1 Blank pulp 142.65 0.148 Blank slurry + mudstone deblocking agent 10.20 0.022 Blank slurry + sandstone, limestone deblocking agent 20.88 0.018

[0151] From the experimental data in Table 6, it can be seen that the blank slurry has very serious mud packing, and the weight of the mud packing on the iron rod surface is 142.65g. After adding the de-blocking agent, the amount of clay in the mud packing is 10.20g and 20.88g, and the mud packing reduction rate is 92.85% and 85.36%, and the anti-mud packing effect is significant. Secondly, after adding the de-blocking agent, the corrosion rate of the steel sheet is significantly reduced, because the corrosion inhibitor in the de-blocking agent contains sulfonic acid groups, which form a corrosion inhibition film by multi-point adsorption on the steel sheet surface to delay corrosion.

[0152] like Figure 3 As shown in the figure, when mud packing and drilling are stuck in the well, the following steps should be taken to deal with it:

[0153] C1. Use high-efficiency flushing fluid for flushing. The formula of high-efficiency flushing fluid is: water + 8% isolation agent JS-7 + 1% surfactant OP-10 + 1% fluid loss reducer JS-12 + 0.2% viscosity enhancer CMC + 0.5% glass microsphere JS-3; if flushing is effective, continue drilling; if flushing is ineffective, proceed to the next step;

[0154] C2. Inject a jam-releasing agent near the drill bit, shut down the well and soak it to release the jam. Pressurize it to 3-5MPa to improve the penetration of the jam-releasing agent. After soaking for more than 2 hours, start the well and move the drilling tools. If it is effective, continue drilling. If not, proceed to the next step.

[0155] C3. Withdraw the tubing above the drill bit by reverse cutting, and then lower the milling tubing to mill the bottom of the well.

[0156] The method for preventing mud balling of PDC drill bits in oil drilling is to modify the surface of the drill bit to prevent mud balling before drilling, including: coating the surface of the PDC drill bit with a strong negative charge Teflon anti-mud balling hydrophobic coating, polishing the cutting teeth and nitriding the drill bit body.

[0157] The method of preventing mud balling of PDC drill bits in oil drilling includes applying butter to the chip groove and blade surface of the drill bit before drilling to form a protective film, and wrapping the chip groove of the drill bit with wire mesh to reduce the contact time between the drill bit body and the inferior solid phase of the drilling fluid;

[0158] When drilling in soft mudstone formations, high speed and large displacement are used to reduce the concentration of cuttings in the drilling fluid; the displacement for Φ311.1mm wellbore construction is not less than 55L / s, the displacement for Φ241.3mm wellbore construction is not less than 45L / s, and the displacement for Φ215.9mm wellbore construction is not less than 34L / s;

[0159] In soft mudstone formations, low drilling pressure is adopted for drilling, and the drill is fed evenly. When the drilling time reaches 24 hours and the footage reaches 300 meters, or abnormal torque, pump pressure, friction parameters, or abnormal sand return are found, a short-distance drilling operation is carried out according to the "two short and one long" method, where "short" means that the well start section should exceed the newly drilled well section, and "long" means starting from the short well start section and entering the upper casing shoe.

[0160] Select stable formations for staged top pumping or circulation. It is strictly forbidden to start pumping in layers prone to mud packing. When encountering resistance during drilling, the pump must be started first to establish circulation. When drilling to the bottom of the well, the pump must also be started for circulation. Use a large displacement to thoroughly clean the drill bit and the bottom of the well. When the displacement reaches the drilling requirement, use low drilling pressure to drill 0.5-1.0m, and then enter normal drilling.

[0161] During normal drilling, after drilling a single rod or column, wait for the drilling pressure to drop before lifting the drill bit, ream the hole 1-2 times before connecting the single rod or column, pay close attention to the sand return situation, and ensure that the concentration of cuttings in the annulus is controllable; when ream the hole, pay attention to observe the weight gauge, vertical pressure gauge and top drive torque gauge to prevent jamming, pump blockage, and top drive stop;

[0162] If stuck, the top drive shall be pulled out with the normal hook load of 20kN and the top drive shall be pulled out without stopping the top drive. The kelly rod shall be pulled out with the load of no more than 50kN each time.

[0163] In case of pump blocking and top drive stopping, apply strong downward pressure after stopping the pump. If the drill bit can go down, try a small-displacement top pump.

[0164] Example 1: HY5HF Well

[0165] The HY5HF well Φ311.1mm borehole was drilled to a depth of 2609.14m using a PDC drill bit + screw drill tool combination, with a construction displacement of 50L / s and a drilling fluid density of 1.28g / cm 3 The lithology is brown mudstone of Dainan Formation. The drilling time starts to slow down. After short tripping, the lowest drilling time per meter is 45 minutes. The lowest drilling time in the same layer of the adjacent well is 17.5 minutes, and the pump pressure is 20MPa. The drill bit is lifted off the bottom of the well, and the displacement is increased and the pressure is pressed down by 20T. After 5 minutes, the drill tool is lifted, the angle is changed and the pressure is pressed down for another 5 minutes. After multiple cleanings, the drilling time per meter is restored to 20 minutes, and the pump pressure is 25MPa. The main characteristics at this time are that the drilling time is 115% higher than that of the adjacent wells, and the pump pressure is 125% higher than that of the adjacent wells. There are no obvious abnormalities in other parameters.

[0166] Refer to Figure 4The drill bit mud packing symptom risk trend prediction chart and the drill bit mud packing support percentage K = K1 + K3 = 25% + 15% = 40% are shown. It is comprehensively judged as slight drill bit mud packing. According to the quantitative evaluation criteria, in view of the fact that a large displacement flushing has been tried in the early stage, the slurry flushing fluid was directly injected for flushing. After the trial drilling of 2m, the drilling time per meter was restored to 10 minutes, which is still a large gap compared with the normal drilling time. In order to completely remove the mud packing, the bottom hole grinding method was adopted, and the subsequent drilling time was 20-25m / h. The slight mud packing was effectively removed and the further deterioration of the underground working conditions was avoided.

[0167] Example 2: SHB5-14H Well

[0168] The Φ241.3 mm wellbore of SHB5-14H was drilled to a depth of 4594.02 m using a PDC drill bit + screw drill bit combination. The operation displacement was 38 L / s and the drilling fluid density was 1.24 g / cm 3 The lithology is dark grey mudstone of Triassic system. The drilling time starts to slow down. The maximum drilling time per meter is 35 minutes, the maximum drilling torque is 29KN·m, the pump pressure is 35MPa, and the lifting and lowering hanging weight is 245 tons. The drilling time of the same layer of the adjacent well is 10.5 minutes, the drilling torque is 8.5KN·m, the pump pressure is 12.7MPa, and the lifting and lowering hanging weight is 95 tons. The main characteristics at this time are that the drilling time is 233.33% higher than that of the adjacent well, the drilling torque is 241.18% higher than that of the normal well section, the pump pressure is 175.59% higher than that of the normal well section, and the lifting and lowering hanging weight is 157.89% higher than that of the normal well section. There are no obvious abnormalities in other parameters.

[0169] Refer to Figure 5 The drill bit mud packing symptom risk trend prediction chart and drill bit mud packing support K = K1 + K2 + K3 + K4 = 25% + 15% + 15% + 15% = 70% are shown, and the drill bit mud packing is comprehensively judged to be serious. According to the quantitative evaluation criteria, the slurry flushing fluid was first injected for flushing. After the trial drilling of 0.5m, it was found that the effect was not good. Then the bottom hole grinding method was adopted. After the trial drilling of 1m, it was found that the effect was still not good. The high-efficiency flushing fluid was configured for flushing, which effectively eliminated the serious mud packing. The subsequent drilling time was 10 minutes per meter. By effectively identifying the degree of mud packing and taking targeted measures, deep well drilling was avoided and the drilling speed was improved.

[0170] Example 3: QY1-201HF Well

[0171] The Φ215.9 mm borehole of QY1-201HF well was drilled to a depth of 2336 m using a PDC drill bit + screw drill tool combination, with a construction displacement of 32 L / s and a drilling fluid density of 1.15 g / cm 3, the lithology is brown-red mudstone of the Sanduo Formation, the drilling time began to slow down, and the phenomenon of pump blocking and top drive blocking occurred intermittently. At the same time, it was difficult to lift the drill bit and the return slurry decreased. When this phenomenon occurred, the drilling time per meter was up to 22 minutes, the maximum drilling torque was 35KN·m, the pump pressure was 30MPa, the lifting and lowering hanging weight was 195 tons, the wellhead return slurry was 40%, and the cuttings return volume was 80kg / m; when drilling in the same layer of the adjacent well, the drilling time was 5 minutes, the drilling torque was 7.5KN·m, the pump pressure was 8.5MPa, the lifting and lowering hanging weight was 60 tons, the wellhead return slurry was 60%, and the cuttings return volume was 130kg / m. The main characteristics at this time are that the drilling time is 340% higher than that of adjacent wells, the drilling torque is 366.67% higher than that of the normal well section, the pump pressure is 252.94% higher than that of the normal well section, the lifting and lowering suspended weight is 225% higher than the normal suspended weight, the slurry return at the wellhead is only 66.7% of the normal value, and the cuttings return amount is only 61.54% of the normal value.

[0172] Refer to Figure 6 The drill bit mud packing symptom risk trend prediction chart and drill bit mud packing support K = K1 + K2 + K3 + K4 + K5 + K6 = 25% + 15% + 15% + 15% + 10% + 15% = 95%, which is comprehensively judged as mud packing and drilling. According to the quantitative evaluation criteria, high-efficiency flushing fluid was first injected for flushing, and the pump and top drive blocking phenomena improved, but the lifting tonnage was still large and the jam could not be completely released. According to the lithology of the formation, the pressure-holding soaking method of foaming and de-jamming agent was adopted, and 7.5m of de-jamming agent was injected. 3 The well was shut down and the pressure was 3MPa. After soaking for 2 hours, the drill bit was moved and the jam was successfully released. After replacing the jam-releasing agent, the short trip was normal and the subsequent drilling was normal. By taking targeted measures, the accident handling time was shortened and underground safety was guaranteed.

[0173] The above is only a preferred embodiment of the present invention, which shows and describes the basic principles, main features and advantages of the present invention, but does not limit the scope of patent protection of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. In addition to the above embodiments, the present invention may have other implementation modes without departing from the spirit and scope of the present invention. The present invention may also have various changes and improvements, and all technical solutions formed by equivalent substitution or equivalent transformation fall within the scope of protection required by the present invention. The scope of protection required by the present invention is defined by the attached claims and their equivalents. The technical features not described in the present invention can be realized by or using existing technologies, which will not be repeated here.

Claims

1. A method for determining mud balling of a PDC drill bit for oil drilling, characterized in that: The steps are as follows: S1. Set the drill bit mud balling parameter symptom risk trend to A 渐进 , when A 渐进 When the corresponding area value is reached, it is judged that there is a risk of slight drill bit mud packing, severe drill bit mud packing or mud packing jamming in the well; S2. Set the support degree of drill bit mud bag occurrence as K. When K < 20%, it is determined that there is no drill bit mud bag. When 20% ≤ K < 55%, it is determined that there is slight drill bit mud bag. When 55% ≤ K < 85%, it is determined that there is severe drill bit mud bag. When K > 85%, it is determined that the drill is stuck due to mud bag. S3, comprehensive drill bit mud balling parameter symptom risk trend is A 渐进 The degree of drill bit mud bagging B is determined by using the two indicators of support degree K value and drill bit mud bagging occurrence. j ∈A 渐进 ∩K, where B1 means no drill bit mud bagging, B2 means slight drill bit mud bagging, B3 means severe drill bit mud bagging, and B4 means drill stuck due to mud bagging. When the conclusions of the two judgment indicators are inconsistent, the more serious mud bagging risk shall be treated.

2. The method for determining mud balling of a PDC drill bit for oil drilling according to claim 1, characterized in that: A 渐进i is the range of changes of each parameter under different mud packing degrees, including the gradual trend value A during drilling 渐进1 , Torque change progressive trend value A 渐进2 , Pump pressure change progressive trend value A 渐进3 , Suspended weight change gradual trend value A 渐进4 , Liquid level change gradual trend value A 渐进5 and the progressive trend value of cuttings change A 渐进6 .

3. The method for determining mud balling of a PDC drill bit for oil drilling according to claim 2, characterized in that: Drilling time change gradual trend value A 渐进1 Under normal drilling conditions, it is defined as 100%. When 100% < A 渐进1 ≤180% is considered as a slight mud packing condition, 180%<A 渐进1 ≤300% is considered to be in a serious mud balling condition, 300%<A 渐进1 ≤500% is judged as being in mud bag and drill stuck condition; Torque change gradual trend value A 渐进2 Under normal drilling conditions, it is defined as 100%. When 100% < A 渐进2 When ≤230%, it is judged to be in a slight mud ball condition, 230%<A 渐进2 ≤360% is considered to be in a serious mud balling condition, 360%<A 渐进2 ≤660% is judged as mud bag stuck drill condition; Pump pressure change gradual trend value A 渐进3 Under normal drilling conditions, it is defined as 100%. When 100% < A 渐进3 ≤150% is considered as a slight mud packing condition, 150%<A 渐进3 ≤220% is considered to be in a serious mud balling condition, 220%<A 渐进3 ≤420% is judged as mud packing and drill stuck condition; Suspended weight change gradual trend value A 渐进4 Under normal drilling conditions, it is defined as 100%. When 100% < A 渐进4 ≤130% is considered as a slight mud packing condition, 130%<A 渐进4 ≤180% is considered to be in a serious mud balling condition, 180%<A 渐进4 ≤260% is judged as mud bag stuck drill condition; Liquid level change gradual trend value A 渐进5 Under normal drilling conditions, it is defined as 100%, when 75% ≤ A 渐进5 When the value is less than 100%, it is judged to be in a serious mud balling condition; 50%≤A 渐进5 <75% is judged as mud packing and drill stuck condition; Asymptotic trend value of cuttings change 渐进6 Under normal drilling conditions, it is defined as 100%, when 85% ≤ A 渐进6 When the value is less than 100%, it is judged to be in a slight mud ball condition; 70%≤A 渐进6 <85% is judged as being in a serious mud balling condition, 50%≤A 渐进6 <70% is judged as being in mud pack and drill stuck condition.

4. The method for determining mud balling of a PDC drill bit for oil drilling according to claim 1, characterized in that: K i Including drilling time change K1, torque change K2, pump pressure change K3, suspended weight change K4, liquid level change K5 and cuttings change K6, K i The value can be divided into two modes: 0 or 1. When the parameters change within the allowable range, K i The value is 0; when it exceeds the allowable range, K i The value is 1; α i is the credible weight for each parameter change.

5. The method for determining mud balling of a PDC drill bit for oil drilling according to claim 4, characterized in that: The credible weight α1 of drilling time change K1 is 25%, the credible weight α2 of torque change K2 is 15%, the credible weight α3 of pump pressure change K3 is 15%, the credible weight α4 of suspended weight change K4 is 15%, the credible weight α5 of liquid level change K5 is 10%, the credible weight α6 of cuttings change K6 is 15%, and the credible weights of other parameter changes are 5%; The allowable range of variation of drilling time change K1 is 6%, the allowable range of variation of torque change K2 is 12%, the allowable range of variation of pump pressure change K3 is 10%, the allowable range of variation of suspended weight change K4 is 5%, the allowable range of variation of liquid level change K5 is 3%, the allowable range of variation of cuttings change K6 is 3%, and the allowable range of variation of other parameter changes is 5%.

6. A method for treating mud balls in a PDC drill bit for oil drilling, characterized in that: When a slight drill bit balling occurs underground, follow the steps below to handle it: A1. Perform large-volume flushing. If flushing is effective, continue drilling. If flushing is ineffective, proceed to the next step. A2. Use slurry flushing liquid for flushing. The formula of slurry flushing liquid is: water + 2-3% caustic soda + 0.1-0.2% anti-mud bag agent RH4 + 2-4% walnut shell + 3-5% quartz sand. The particle size of walnut shell is 2-5mm. If flushing is effective, continue drilling. If flushing is ineffective, proceed to the next step. A3. Perform bottom hole grinding. If effective, continue drilling. If not, proceed to the next step. A4. Start drilling and clean the drill bit.

7. A method for treating mud balls in a PDC drill bit for oil drilling, characterized in that: When serious drill bit mud balling occurs underground, follow the steps below to handle it: B1. Use slurry flushing liquid for flushing. The formula of slurry flushing liquid is: water + 2-3% caustic soda + 0.1-0.2% anti-mud bag agent RH4 + 2-4% walnut shell + 3-5% quartz sand. The particle size of walnut shell is 2-5mm. If flushing is effective, continue drilling. If flushing is ineffective, proceed to the next step. B2. Perform bottom hole grinding. If effective, continue drilling. If not, proceed to the next step. B3. Use high-efficiency flushing fluid for flushing. The formula of high-efficiency flushing fluid is: water + 8% isolation agent JS-7 + 1% surfactant OP-10 + 1% fluid loss reducer JS-12 + 0.2% viscosity enhancer CMC + 0.5% glass microsphere JS-3; if flushing is effective, continue drilling; if flushing is ineffective, proceed to the next step; B4. Inject a jam-releasing agent near the drill bit, shut down the well and soak it to release the jam. Pressurize it to 3-5MPa to increase the penetration of the jam-releasing agent. After soaking for more than 2 hours, start the well and move the drilling tools. If it is effective, continue drilling. If not, proceed to the next step. B5. Start drilling and clean the drill bit.

8. A method for treating mud balls in a PDC drill bit for oil drilling, characterized in that: When mud packing and drilling are stuck in the well, follow the steps below to handle it: C1. Use high-efficiency flushing fluid for flushing. The formula of high-efficiency flushing fluid is: water + 8% isolation agent JS-7 + 1% surfactant OP-10 + 1% fluid loss reducer JS-12 + 0.2% viscosity enhancer CMC + 0.5% glass microsphere JS-3; if flushing is effective, continue drilling; if flushing is ineffective, proceed to the next step; C2. Inject a jam-releasing agent near the drill bit, shut down the well and soak it to release the jam. Pressurize it to 3-5MPa to improve the penetration of the jam-releasing agent. After soaking for more than 2 hours, start the well and move the drilling tools. If it is effective, continue drilling. If not, proceed to the next step. C3. Withdraw the tubing above the drill bit by reverse cutting, and then lower the milling tubing to mill the bottom of the well.

9. The method for treating mud balls in a PDC drill bit for oil drilling according to claim 7 or 8, characterized in that: The formula of mudstone formation deblocking agent is: diesel + water + 3-4% emulsifier SR301 + 12% fast T + barite, where the oil-water ratio is 85:15; The formula of the de-blocking agent for sandstone and limestone formations is: water + 20% hydrofluoric acid + 15% hydrochloric acid + 3% chromate corrosion inhibitor + 1% iron ion stabilizer IRON-2066A.

10. The method for treating mud balls in a PDC drill bit for oil drilling according to claim 9, characterized in that: First pump 10m into the wellbore 3 Pre-insulation fluid, then inject the de-blocking agent, and then inject 7m 3 When the post-placement isolation fluid and the release agent reach the stuck point, the pressure-holding soaking is stopped, and the water hole is kept open at regular intervals during the soaking period; the density of the pre-placement isolation fluid and the post-placement isolation fluid are consistent with the density of the well slurry when the drill is stuck. After the set soaking time is reached, it is replaced with ordinary well slurry, and then an attempt is made to lift up vigorously and apply positive and negative torque to the movable drill bit.

11. A method for preventing balling of a PDC drill bit in oil drilling, characterized in that: Before drilling, the drill bit surface is modified to prevent mud balling, including: coating the surface of the PDC drill bit with a strong negatively charged Teflon anti-mud balling hydrophobic coating, polishing the cutting teeth and nitriding the drill bit body.

12. A method for preventing balling of a PDC drill bit in oil drilling, characterized in that: Before drilling, apply butter to the chip groove and blade surface of the drill bit to form a protective film, and wrap the chip groove of the drill bit with wire mesh to reduce the contact time between the drill bit body and the inferior solid phase of the drilling fluid; When drilling in soft mudstone formations, high speed and large displacement are used to reduce the concentration of cuttings in the drilling fluid; the displacement for Φ311.1mm wellbore construction is not less than 55L / s, the displacement for Φ241.3mm wellbore construction is not less than 45L / s, and the displacement for Φ215.9mm wellbore construction is not less than 34L / s; In soft mudstone formations, low drilling pressure is used for drilling, and the drill is fed evenly. When the drilling time reaches 24 hours, the footage reaches 300 meters, or when abnormal torque, pump pressure, friction parameters are found, or abnormal sand return occurs, a short-distance drilling operation is carried out.

13. The method for preventing balling of a PDC drill bit in oil drilling according to claim 12, characterized in that: The short-distance drilling operation is carried out according to "two short and one long", wherein "short" means that the well-lifting section should exceed the newly drilled well section, and "long" means that the short well-lifting section starts from the well-lifting section and enters the upper-level casing shoe.

14. The method for preventing balling of a PDC drill bit in oil drilling according to claim 12, characterized in that: Select stable formations for staged top pumping or circulation. It is strictly forbidden to start pumping in layers prone to mud packing. When encountering resistance during drilling, the pump must be started first to establish circulation. When drilling to the bottom of the well, the pump must also be started for circulation. Use a large displacement to thoroughly clean the drill bit and the bottom of the well. When the displacement reaches the drilling requirement, use low drilling pressure to drill 0.5-1.0m, and then enter normal drilling.

15. The method for preventing balling of a PDC drill bit in oil drilling according to claim 12, characterized in that: During normal drilling, after drilling a single rod or column, wait for the drilling pressure to drop before lifting the drill bit, ream the hole 1-2 times before connecting the single rod or column, pay close attention to the sand return situation, and ensure that the concentration of cuttings in the annulus is controllable; when ream the hole, pay attention to observe the weight gauge, vertical pressure gauge and top drive torque gauge to prevent jamming, pump blockage, and top drive stop; If stuck, the top drive shall be pulled out with the normal hook load of 20kN and the top drive shall be pulled out without stopping the top drive. The kelly rod shall be pulled out with the load of no more than 50kN each time. In case of pump blocking and top drive stopping, apply strong downward pressure after stopping the pump. If the drill bit can go down, try a small-displacement top pump.

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