Method for determining, treating and preventing balling of a pdc drill bit in oil drilling

Abstract

The application discloses a method for determining, processing and preventing mud ball of a PDC drill bit in oil drilling, and comprises the following steps: S1, setting a risk trend of a parameter sign of the drill bit mud ball as A 渐进 , when A 渐进 reaches a corresponding area value, it is determined that the risk of a slight drill bit mud ball, a serious drill bit mud ball or a mud ball sticking occurs downhole; S2, setting a support degree of the drill bit mud ball as K, when K<20%, it is determined that there is no drill bit mud ball, when 20%≤K<55%, it is determined that there is a slight drill bit mud ball, when 55%≤K<85%, it is determined that there is a serious drill bit mud ball, and when K>85%, it is determined that there is a mud ball sticking; S3, after comprehensively considering the two indexes of A 渐进 and K, the degree B j of the drill bit mud ball is determined, wherein B1 is no drill bit mud ball, B2 is a slight drill bit mud ball, B3 is a serious drill bit mud ball, and B4 is a mud ball sticking; when the conclusions of the two determination indexes are inconsistent, the more serious one is processed. The method can accurately determine the mud ball risk downhole, reduce the tripping frequency and shorten the construction period.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of petroleum drilling PDC drill bit, especially to a kind of petroleum drilling PDC drill bit mud cake determination method, the present application also relates to a kind of petroleum drilling PDC drill bit mud cake processing method and a kind of petroleum drilling PDC drill bit mud cake prevention method, belong to petroleum drilling technical field. BACKGROUND

[0002] In the oilfield drilling industry, PDC drill bit has the characteristics of high penetration rate, single trip footage, low failure rate, excellent comprehensive performance, and is more and more widely used. At present, in order to develop low cost, the well structure is simplified, resulting in the open hole section is longer and longer, PDC drill bit is easy to produce drill bit mud cake in multilayer formation drilling, which seriously affects the use efficiency of PDC drill bit. For a 3000-4000m medium deep well, one trip up and down drill needs a day or even longer, and even mud cake several times, frequent tripping not only affects the drilling period, but also brings certain influence to wellbore stability, well control safety and so on. After drill bit mud cake, tripping operation is easy to induce downhole suction or pressure excitement, causing overflow, well kick and other well control risks. In severe cases, due to inaccurate prediction of tripping blockage, improper operation and treatment measures are taken, which leads to mud cake sticking and other downhole complex conditions. The main reasons for PDC drill bit mud cake are formation characteristics, drilling parameters, drilling fluid performance and drill bit structure, and the drilling site judges the drill bit mud cake mainly relying on the experience of site operators.

[0003] After years of practice, the common measures to prevent PDC drill bit mud cake on the drilling site at present are:

[0004] 1. Control reasonable drilling fluid performance

[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 inhibitor in drilling fluid, generally use KPAM inhibitor, through shale inhibitor compounding, ensure that the total amount of inhibitor is not less than 0.6%, inhibit shale hydration dispersion, and reduce the possibility of drill bit mud cake.

[0007] 3. Add mud cake prevention agent, cleaning agent, lubricant and other agents in drilling fluid to form a water-repellent film on the metal surface, 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 drilling fluid does not foam.

[0008] 4. Add alkaline substance before entering the gypsum-containing formation to prevent calcium invasion; when drilling to the strong permeability sandstone layer, add QS-2 temporary plugging agent, use shielding temporary plugging technology to reduce permeability loss and reduce the possibility of drill bit mud cake.

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

[0010] II. Optimize the bit structure

[0011] 1. On the premise of ensuring the unbalanced force requirement, reasonably arrange the included angle between each blade to avoid the balling caused by the too small included angle of the junk slot. The inclination angle of the junk slot is 20°-30°, and it is recommended to use the PDC bit with no more than five blades for the upper formation construction.

[0012] 2. Optimize the hydraulic design of the bit, use the asymmetrically arranged nozzles, and the size of the center nozzle is larger than that of the other nozzles to realize the full coverage of the nozzle jet on the bottom of the well.

[0013] 3. The anti-balling PDC bit selects the large size cutting teeth, the size of the composite piece is not less than 16 mm, the back rake angle of the composite piece is 15°-20°, the low density tooth arrangement, and the number of teeth is less than 28; at the same time, ensure the high exposure amount and large tooth spacing of the large size cutting teeth.

[0014] 4. The back of the blade uses the large chamfer design, increases the root arc chamfer of the attack surface of the blade, and uses the variable radius chamfer way in the main blade to as far as possible increase the chamfer of the root of the blade.

[0015] The main phenomena of the bit balling precursors at present are as follows:

[0016] 1. The drilling time changes. Under the condition that the drilling parameters such as the drilling pressure, the displacement, and the rotation speed are unchanged, the drilling time gradually increases compared with the normal drilling time of the adjacent well or the upper formation, and the maximum is 3-5 times more than the normal drilling time. When the drilling pressure, the rotation speed, and the displacement are increased, the drilling time still has no obvious change, and when the formation changes obviously, the drilling time also has no change.

[0017] 2. The torque changes. The initial balling torque increases slightly, and with the aggravation of the bit balling, the torque gradually increases or the torque fluctuation range becomes larger. At this time, the difference between the bit tripping torque and the bit drilling torque is small.

[0018] 3. The hanging weight changes. During the drilling or the circulation, the hanging weight has no obvious change, and with the aggravation of the balling phenomenon, the jump drilling phenomenon appears, and the drilling pressure pointer changes in a large range. The hanging weight during the tripping is larger than the normal well condition, and the serious sticking occurs. Under the condition of opening the pump, the pump pressure suddenly increases, and then the hanging weight suddenly decreases.

[0019] The current method for treating the bit balling in the drilling construction site is as follows:

[0020] After judging the bit balling, the following treatment methods are taken in turn to remove the balling. During the treatment of balling, the starting of the while-drilling jar is strictly prohibited.

[0021] 1. Large displacement flushing method

[0022] In the equipment operating range, the displacement is opened to the maximum, and hydraulic flushing is carried out. In one drill pipe single range, the drilling tool is quickly moved, and the up and down is suddenly braked. Then the equipment is started at the upper limit speed to rotate the drilling tool, and the balling object is shaken out.

[0023] 2. Bottom hole grinding method

[0024] The drilling tool is lifted, and the bit is 5m away from the bottom hole. The top drive / rotary table is not opened, the displacement is gradually increased to the upper limit of the machine pump equipment. Then the bit is lowered to the bottom hole at low speed, the same drilling pressure as the hook load is applied, the large displacement is circulated for 5 minutes, the bit is lifted away from the bottom hole, and the drilling tool is rotated at high speed for 5 minutes. The top drive / rotary table is stopped again, and the above operation is repeated.

[0025] 3. Thin slurry flushing method

[0026] The drilling tool is lifted, and the large displacement is circulated with drilling fluid. The bit is lowered to about 0.5m away from the bottom hole at 30rpm, 4-5m 3 low viscosity drilling fluid is injected, the bit is lowered to 0.1m away from the bottom hole to replace the thin slurry, and the rotation is maintained at 30rpm to flush the adhering objects by using the reaction force.

[0027] 4. After the above methods are invalid, the drilling is lifted to the wellhead, and the bit balling object is manually removed.

[0028] The above prevention of bit balling and treatment measures play a good role to a certain extent, but in actual field construction, due to many reasons such as drilling fluid performance not meeting the downhole requirements, drilling parameters and operation methods being improper, bit structure design being unreasonable, etc., bit balling phenomenon still occurs from time to time. With the current simplification of well structure in oilfields, the long shale open hole section is getting longer and longer, the sand-shale interbedding is getting more and more, and the probability of PDC bit balling is also increasing. After the field judges the balling, although the large displacement flushing method, the bottom hole grinding method, the thin slurry flushing method and other conventional methods are used, they have a certain effect, but cannot completely remove the balling, the effect of removing the balling is poor, the rate of penetration is not significantly improved, and finally the drilling is lifted to the wellhead, the bit balling object is manually removed, the drilling period is prolonged to a certain extent, and the construction risk is also increased.

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

[0030] 1. At present, in order to reduce investment cost, the well structure is simplified in various oilfields, the long shale open hole section is getting longer and longer, the sand-shale interbedding is getting more and more, and the probability of PDC bit balling is also increasing.

[0031] 2, The formation of bit balling is not instantaneous, but a complex nonlinear dynamic process, with many influencing factors and large random disturbances. Conventional precursors, judgment and treatment measures, etc. Qualitative evaluation is difficult to effectively solve the abnormal complexity. Coupled with the lack of theoretical knowledge and the accumulation of construction experience of the current operating personnel, the basic skills are weak, and in the face of abnormal phenomena in construction, they cannot identify and correctly handle them in a timely and effective manner, leading to more and more heavy balling, which ultimately makes the preventive measures ineffective, and also leads to poor effect of conventional balling removal treatment measures. For example, it cannot effectively identify whether the problem is the cutting ability of the drill bit or the balling problem, leading to misdrilling; unable to accurately determine the balling level, leading to further deterioration, etc.

[0032] 3, The measures such as smearing butter on the surface of the drill bit body and winding metal mesh have short time effectiveness and poor effect, and the metal mesh will affect the normal cutting of the drill bit into the formation and affect the sand return.

[0033] 4, The performance of the drilling fluid cannot meet the needs of the easy balling formation.

[0034] 5, In the long open hole section, multiple pressure layer systems coexist, and increasing the construction discharge capacity to improve the flushing and sand carrying effect will lead to leakage in the upper formation with weak bearing capacity, and due to the limitation of the equipped pump conditions, it is impossible to simply rely on increasing the discharge capacity to achieve the purpose of flushing and preventing balling.

[0035] 6, During the construction of the medium-deep well, the drill bit is lifted, the discharge capacity is increased, the top drive / rotary table speed is increased, and the operation is greatly active, under the premise of considering the drill tool elongation and the pump conditions, there are risks such as the drill tool cannot be fully active, the large discharge capacity causes annular blockage, and the high torque stops the top drive / rotary table, and the drill bit has a small rotating radius, and the centrifugal force generated cannot shake off the balling material. SUMMARY

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

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

[0038] The primary purpose of the present application is to overcome the fuzzy risk determination of bit balling in the prior art, and to provide a petroleum drilling PDC bit balling determination method, which can accurately determine the risk degree of balling under the well, facilitate the development of treatment programs for different balling risk degrees, reduce the frequency of tripping, and shorten the construction cycle.

[0039] To solve the above technical problems, the present invention provides a method for determining mud packing in oil drilling PDC bits, comprising the following steps in sequence:

[0040] S1. Set the drill bit mud packing parameter symptom risk trend to A. 渐进 , when A 渐进 When the corresponding zone value is reached, it indicates the risk of minor drill bit mud packing, severe drill bit mud packing, or mud packing stuck in the well.

[0041] S2. Set the support level for drill bit mud packing to K. When K < 20%, it is judged as no drill bit mud packing; when 20% ≤ K < 55%, it is judged as slight drill bit mud packing; when 55% ≤ K < 85%, it is judged as severe drill bit mud packing; when K > 85%, it is judged as mud packing stuck drill bit.

[0042] S3, the risk trend of the comprehensive drill bit mud bag parameters is A. 渐进 After considering two indicators, namely the support K value and the drill bit mud packing, the degree of drill bit mud packing (B) is determined. j ∈A 渐进 ∩K, where B1 is no drill bit mud bag, B2 is slight drill bit mud bag, B3 is severe drill bit mud bag, and B4 is mud bag stuck drill bit; when the conclusions of the two judgment indicators are inconsistent, the more severe mud bag risk shall be treated.

[0043] Furthermore, A 渐进i The values ​​represent the range of variation for each parameter under different degrees of mudpacking, including the gradual trend value A during drilling. 渐进1 The gradual trend value of torque change A 渐进2 The gradual trend value of pump pressure change A 渐进3 Gradual trend value A of weight change 渐进4 Gradual trend value A of liquid level change 渐进5 and the gradual trend value A of rock cuttings change 渐进6 .

[0044] Furthermore, the gradual trend value A of the drilling time variation. 渐进1 Under normal drilling conditions, it is defined as 100%. When 100% < A 渐进1 If the mud content is ≤180%, it is considered a minor mud-covering condition; if the mud content is <A, it is considered a minor mud-covering condition. 渐进1 ≤300% is considered a severe mud-covering condition; 300% <A 渐进1 A value ≤500% is considered a mud-covered, stuck drill condition.

[0045] A gradual trend value of torque change 渐进2 Under normal drilling conditions, it is defined as 100%. When 100% < A 渐进2 When the mud content is ≤230%, it is considered to be in a slight mud-packing condition; when the mud content is <A, it is considered to be in a slightly mud-packed condition. 渐进2 ≤360% is considered a severe mud-covering condition; 360% <A渐进2 ≤660% is determined to be in the condition of mud ball and stuck;

[0046] Pump pressure change gradual trend value A 渐进3 100% is defined as normal drilling condition, when 100% < A 渐进3 ≤150% is determined to be in the condition of slight mud ball, 150% < A 渐进3 ≤220% is determined to be in the condition of serious mud ball, 220% < A 渐进3 ≤420% is determined to be in the condition of mud ball and stuck;

[0047] Hook load change gradual trend value A 渐进4 100% is defined as normal drilling condition, when 100% < A 渐进4 ≤130% is determined to be in the condition of slight mud ball, 130% < A 渐进4 ≤180% is determined to be in the condition of serious mud ball, 180% < A 渐进4 ≤260% is determined to be in the condition of mud ball and stuck;

[0048] Fluid level change gradual trend value A 渐进5 100% is defined as normal drilling condition, when 75% ≤ A 渐进5 <100% is determined to be in the condition of serious mud ball, 50% ≤ A 渐进5 <75% is determined to be in the condition of mud ball and stuck;

[0049] Cuttings change gradual trend value A 渐进6 100% is defined as normal drilling condition, when 85% ≤ A 渐进6 <100% is determined to be in the condition of slight mud ball, 70% ≤ A 渐进6 <85% is determined to be in the condition of serious mud ball, 50% ≤ A 渐进6 <70% is determined to be in the condition of mud ball and stuck.

[0050] Further, K i Including drilling time change K1, torque change K2, pump pressure change K3, hook load change K4, fluid level change K5 and cuttings change K6, K i The value is divided into two modes of 0 or 1, when the change of each parameter is within the allowable change range, K i The value is 0; when exceeding the allowable change range, K i The value is 1; α i Is the credible weight of each parameter change.

[0051] Furthermore, the confidence weight α1 for the change in drilling time K1 is 25%, the confidence weight α2 for the change in torque K2 is 15%, the confidence weight α3 for the change in pump pressure K3 is 15%, the confidence weight α4 for the change in suspended weight K4 is 15%, the confidence weight α5 for the change in fluid level K5 is 10%, the confidence weight α6 for the change in cuttings K6 is 15%, and the confidence weight for the changes in other parameters is 5%.

[0052] The allowable range of variation for drilling time variation K1 is 6%, for torque variation K2 it is 12%, for pump pressure variation K3 it is 10%, for suspended weight variation K4 it is 5%, for fluid level variation K5 it is 3%, for cuttings variation K6 it is 3%, and for other parameters it is 5%.

[0053] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. The present invention combines the formation mechanism of PDC drill bit mud bag and establishes a quantitative evaluation method for judging drill bit mud bag based on conventional drill bit mud bag identification. It clarifies the changes of various characteristic parameters during the mud bag formation process, forms a drill bit mud bag symptom risk trend prediction chart, and closely monitors the changes in characteristic parameters such as drilling time, returned cuttings, torque, pump pressure, suspended weight, and wellhead annular fluid level. It quantitatively evaluates the influence of multiple parameters on drill bit mud bag and can make rapid predictions of drill bit mud bag.

[0054] 2. A quantitative evaluation of the signs of drill bit mud packing was conducted, establishing the interrelationships between two or more abnormal conditions or between key parameters when drill bit mud packing occurs. These relationships are represented by support and confidence. Support refers to the cumulative proportion of all complex anomalies occurring simultaneously, while confidence refers to the confidence proportion of a single anomaly. Through the quantitative evaluation of drill bit mud packing support and confidence, drill bit mud packing risk warning categories were established, providing a theoretical and data basis for accurately identifying drill bit mud packing.

[0055] 3. This invention addresses the abnormal changes in various characteristic parameters during the early stages of drill bit mud packing, creating a drill bit mud packing symptom risk trend prediction chart, and clarifying the drill bit mud packing parameter symptom risk trend A. 渐进 A quantitative evaluation of the signs of drill bit mud packing was conducted, defining the support level K for drill bit mud packing occurrence, and considering the risk trend of drill bit mud packing symptoms and A. 渐进 The degree of drill bit mud packing (B) is determined by two indicators: the support value (K) and the mud packing index (B). j This allows for dual identification of the risks and signs of drill bit mud packing, thus enabling more accurate early warning of drill bit mud packing risks.

[0056] 4. This invention is applicable to the identification of mud bags in various well types. It can effectively analyze the risk of mud bags during drilling and provide a strong basis for decision-making on mud bag treatment methods and mud bag stuck drill bit effect evaluation after mud bags occur. Targeted treatment measures can be taken to reduce drilling operation risks, reduce non-productive time and lower operating costs.

[0057] 5. Through comprehensive analysis of drill bit mud bag parameters, signs of risk trends A 渐进 The degree of drill bit mud packing is determined by the support K value, based on B. j Depending on the magnitude of the value, corresponding targeted measures should be taken to effectively reduce operational risks.

[0058] Another objective of this invention is to overcome the drawbacks and poor effectiveness of conventional drill bit mud removal methods in the prior art, and to provide a method for removing mud from PDC drill bits in oil drilling, which can improve the mud removal effect, reduce the frequency of tripping in and out of the hole, and shorten the construction cycle.

[0059] To address the above technical problems, this invention provides a method for treating mud buildup in PDC drill bits during oil drilling. When minor mud buildup occurs downhole, the following steps are performed:

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

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

[0062] A3. Perform bottom grinding. If effective, continue drilling; if ineffective, proceed to the next step.

[0063] A4. Pull out the drill bit and clean it.

[0064] To address the above technical problems, this invention provides a method for treating PDC drill bit mud packing in oil drilling. When severe drill bit mud packing occurs downhole, the following steps are performed:

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

[0066] B2. Perform bottom grinding. If effective, continue drilling; if ineffective, proceed to the next step.

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

[0068] B4. Inject the unsticking agent near the drill bit, shut in the well and pressurize it to soak and unstick the drill bit. Pressurize it to 3-5 MPa to improve the penetration of the unsticking agent. After soaking for more than 2 hours, open the well and move the drill string. If it is effective, continue drilling. If it is ineffective, proceed to the next step.

[0069] B5. Pull out the drill bit and clean it.

[0070] To solve the above technical problems, the present invention provides a method for treating mud packing on PDC drill bits in oil drilling. When mud packing and stuck drill bits occur downhole, the following steps are performed:

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

[0072] C2. Inject the unsticking agent near the drill bit, shut in the well and pressurize it to soak and unstick the drill bit. Pressurize it to 3-5 MPa to improve the penetration of the unsticking agent. After soaking for more than 2 hours, open the well and move the drill string. If it is effective, continue drilling. If it is ineffective, proceed to the next step.

[0073] C3. Reverse the drill string above the drill bit and then lower the milling string to mill the bottom of the well.

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

[0075] The formula for the unblocking 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] Furthermore, first pump 10m into the wellbore. 3 Pre-emptive isolation fluid, then inject the unblocking agent, followed by 7m 3 After the release fluid reaches the stuck point, stop the pressure soaking process and keep the water in the hole open at regular intervals during the soaking period. The density of both the pre- and post-release fluids should be consistent with the density of the drilling mud when the drill string is stuck. After the set soaking time is reached, replace the drill string with ordinary drilling mud, and then try to pull the drill string up with great force and apply positive and negative torque to move the drill string.

[0077] Compared with existing technologies, this invention achieves the following beneficial effects: 1. The drill bit mud bag treatment method of this invention is an optimization and improvement on the slurry flushing method. Walnut shells, quartz sand, and other materials for removing mud bags are added to the slurry flushing fluid to improve the flushing effect. Conventional drilling fluid has little effect on soaking mud balls, reducing them by only 14% after 3 hours. However, the improved slurry flushing fluid has a significant effect on soaking mud balls, achieving 36% reduction in 1 hour, and reducing the friction coefficient by 73.12%.

[0078] 2. Drawing on the working principle of pre-cementing separator fluid flushing drilling fluid gelling substances on the wellbore and casing walls, a high-efficiency flushing fluid formula for severe drill bit mud buildup was developed. This formula effectively dilutes the bottom hole drilling fluid and achieves 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 its flushing efficiency is 40% higher than that of conventional flushing fluids. It also has good sealing and wall protection performance, effectively maintaining wellbore stability and preventing wellbore conditions from deteriorating.

[0079] 3. This invention, based on conventional methods for dealing with mud packing, involves injecting an unsticking agent near the drill bit when mud packing occurs, followed by shutting in the well and applying pressure to soak and dislodge the stuck pipe. Practical application of the unsticking agent formula shows that it is simple to prepare on-site, and experimental data indicates that the mud packing reduction rate reaches over 85% after using the unsticking agent, demonstrating a significant anti-mud packing effect. Furthermore, the unsticking time is short, with a success rate of up to 95% on the first attempt, and it does not affect the rheology and filtration loss of the drilling fluid system in the well, while also meeting environmental protection requirements. The pressure soaking method further improves the removal effect; it can successfully handle mud packing while ensuring downhole safety and preventing drill string from tripping, and minimizes the occurrence of mud packing stuck pipe.

[0080] Another objective of this invention is to overcome the problem of inadequate conventional drill bit mud packing prevention measures in the prior art, and to provide a method for preventing mud packing in PDC drill bits for oil drilling, which can reduce the probability of mud packing and improve the effectiveness of mud packing removal, reduce the frequency of tripping in and out of the hole, and shorten the construction cycle.

[0081] To solve the above technical problems, the present invention provides a method for preventing mud packing in PDC drill bits for oil drilling. Before drilling, the surface of the drill bit is modified to prevent mud packing. The method includes: coating the surface of the PDC drill bit with a Teflon anti-mud packing hydrophobic coating with strong negative charge, polishing the cutting teeth, and nitriding the drill bit body.

[0082] To solve the above technical problems, the present invention provides a method for preventing mud buildup in PDC drill bits for oil drilling. Before drilling, grease is applied to the surface of the chip removal groove and the cutting edge of the drill bit to form a protective film. The chip removal groove of the drill bit is then wrapped with 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 mudstone formations, high-speed and high-volume drilling should be used to reduce the concentration of cuttings in the drilling fluid; the drilling flow rate should be no less than 55L / s for Φ311.1mm wellbore, no less than 45L / s for Φ241.3mm wellbore, and no less than 34L / s for Φ215.9mm wellbore.

[0084] In soft mudstone formations, low drilling pressure and uniform feed are used. When drilling time reaches 24 hours, footage reaches 300m, or abnormal torque, pump pressure, friction parameters, or abnormal sand return are found, a short trip trip operation is performed.

[0085] Furthermore, the short trip trip operation is carried out according to the "two short and one long" principle, where "short" means that the trip trip section should exceed the newly drilled section, and "long" means that the short trip trip section should enter the upper-level casing shoe.

[0086] Furthermore, select stable formations for segmented pumping or circulation, and strictly prohibit starting the pump in formations prone to mud buildup; when encountering resistance during drilling, the pump must be started first to establish circulation; when drilling to the bottom of the well, the pump also needs to be started first to circulate, using a large displacement to thoroughly clean the drill bit and the bottom of the well, and when the displacement reaches the drilling requirements, then drill 0.5-1.0m with low drilling pressure, and then proceed with normal drilling.

[0087] Furthermore, during normal drilling, after drilling a single section or column, wait for the drill pressure to drop before raising the drill string. After reaming 1-2 times, connect a single section or column. Pay close attention to the sand return situation to ensure that the annular cuttings concentration is controllable. When reaming, pay attention to the weight indicator, vertical pressure gauge and top drive torque gauge to prevent jamming, pump stalling, or top drive stalling.

[0088] If the drill rod gets stuck, lift it up by no more than 20kN of normal hook load and pull it out by reversing the top drive. Lift it out in small increments without stopping the top drive. Each time the square drill rod is lifted, the lifting force should not exceed 50kN.

[0089] If pump stalling or top drive stalling occurs, after stopping the pump, apply strong downward pressure. If the drill string can descend, then try a small displacement top pump.

[0090] Compared to existing technologies, this invention achieves the following beneficial effects: This invention provides drill bit mud packing prevention measures. Building upon existing preventative measures, a mud packing prevention coating is applied to the surface of the PDC drill bit. This coating repels negatively charged formation cuttings, effectively preventing cuttings from adhering to the drill bit surface and reducing the adhesion between the drill bit surface and muddy cuttings. This reduces the probability of drill bit mud packing from the source, effectively increasing the prevention effect. Simultaneously, it further optimizes conventional mud packing treatment measures, improving the removal effect and achieving successful mud packing removal without tripping the drill string, thus shortening the construction cycle. This further reduces the risk of mud packing, making the preventative measures more effective and shortening the handling cycle for complex downhole faults, saving drilling costs. Attached Figure Description

[0091] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used 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 those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The drawings are provided for reference and illustration only and are not intended to limit the present invention.

[0092] in:

[0093] Figure 1 This is a flowchart of the minor drill bit mud packing treatment process in this invention;

[0094] Figure 2 This is a flowchart illustrating the process of treating severe drill bit mud buildup in this invention.

[0095] Figure 3 This is a flowchart of the drill bit mud-stuck treatment process in this invention;

[0096] Figure 4 This is a graph showing the signs and risk trends of various parameters in the actual drilling of well HY5HF in Embodiment 1 of the present invention.

[0097] Figure 5 This is a graph showing the signs and risk trends of various parameters in the actual drilling of well SHB5-14H in Embodiment 2 of the present invention.

[0098] Figure 6 This is a graph showing the signs and risk trends of various parameters in the actual drilling of well QY1-201HF in Embodiment 3 of the present invention. Detailed Implementation

[0099] In the following description of the present invention, the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship 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 orientation.

[0100] To make the technical means, creative features, objectives, and effects of this invention easier to understand, the invention is further described below with reference to specific illustrations. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them.

[0101] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0102] The method for determining mud packing in PDC drill bits for oil drilling of the present invention includes the following steps in sequence:

[0103] S1. Set the drill bit mud packing parameter symptom risk trend to A. 渐进 , when A 渐进 When the corresponding zone value is reached, it indicates the risk of minor drill bit mud packing, severe drill bit mud packing, or mud packing stuck in the well.

[0104] A 渐进i The values ​​represent the range of variation for each parameter under different degrees of mudpacking, including the gradual trend value A during drilling. 渐进1 The gradual trend value of torque change A 渐进2 The gradual trend value of pump pressure change A 渐进3 Gradual trend value A of weight change 渐进4 Gradual trend value A of liquid level change 渐进5 and the gradual trend value A of rock cuttings change 渐进6 ;

[0105] The gradual trend value A during drilling time 渐进1 Under normal drilling conditions, it is defined as 100%. When 100% < A 渐进1 If the mud content is ≤180%, it is considered a minor mud-covering condition; if the mud content is <A, it is considered a minor mud-covering condition. 渐进1 ≤300% is considered a severe mud-covering condition; 300% <A 渐进1 A value ≤500% is considered a mud-covered, stuck drill condition.

[0106] A gradual trend value of torque change 渐进2 Under normal drilling conditions, it is defined as 100%. When 100% < A 渐进2 When the mud content is ≤230%, it is considered to be in a slight mud-packing condition; when the mud content is <A, it is considered to be in a slightly mud-packed condition. 渐进2 ≤360% is considered a severe mud-covering condition; 360% <A 渐进2 A value ≤660% is considered to be in a mud-covered, 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 A mud-covered condition is defined as ≤150% when the mud content is slightly below A. 渐进3 ≤220% is considered a severe mud-covering condition; 220% <A 渐进3 A value ≤420% is considered a mud-covered, stuck drill condition.

[0108] Gradual trend value A of weight change 渐进4 Under normal drilling conditions, it is defined as 100%. When 100% < A 渐进4 A mud-covered condition is defined as ≤130% when the mud content is slightly below A. 渐进4 ≤180% is considered a severe mud-covering condition; 180% <A渐进4 A value ≤260% is considered a mud-covered, stuck drill condition.

[0109] Gradual trend value A of liquid level change 渐进5 Under normal drilling conditions, it is defined as 100%, when 75% ≤ A 渐进5 When the percentage is less than 100%, it is considered a severe mud-packing condition; when it is 50% ≤ A, it is considered a severe mud-packing condition. 渐进5 <75% is considered to be in a mud-covered stuck drill condition;

[0110] A gradual trend value of rock cuttings change 渐进6 Under normal drilling conditions, it is defined as 100%, when 85% ≤ A. 渐进6 When the percentage is less than 100%, it is considered a minor mud-covering condition; when the percentage is 70% ≤ A, it is considered a minor mud-covering condition. 渐进6 <85% is considered to be in severe mud-covering condition, 50% ≤A 渐进6 <70% is considered to be in a mud-covered stuck drill condition.

[0111] S2. Set the support level for drill bit mud packing to K. When K < 20%, it is judged as no drill bit mud packing; when 20% ≤ K < 55%, it is judged as slight drill bit mud packing; when 55% ≤ K < 85%, it is judged as severe drill bit mud packing; when K > 85%, it is judged as mud packing stuck drill bit.

[0112] K i This includes variations in drilling time (K1), torque (K2), pump pressure (K3), suspended weight (K4), fluid level (K5), and cuttings (K6). i The value can be either 0 or 1. When the changes in each parameter are within the allowable range, K... i The value is 0; K is set to 0 when the allowable range of change is exceeded. i The value is 1;

[0113] α i Assigning confidence weights to the changes in each parameter, the confidence weight α1 for the change in drilling time K1 is 25%, the confidence weight α2 for the change in torque K2 is 15%, the confidence weight α3 for the change in pump pressure K3 is 15%, the confidence weight α4 for the change in suspended weight K4 is 15%, the confidence weight α5 for the change in fluid level K5 is 10%, the confidence weight α6 for the change in cuttings K6 is 15%, and the confidence weight for the changes in other parameters is 5%.

[0114] The allowable range of variation for 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 >6%, the value of drilling time variation K1 is 1, multiplied by its confidence weight of 25%, and included in the K value.

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

[0116] S3, the risk trend of the comprehensive drill bit mud bag parameters is A. 渐进 After considering two indicators, namely the support K value and the drill bit mud packing, the degree of drill bit mud packing (B) is determined. j ∈A 渐进 ∩K, where ∈ indicates belonging, ∩ indicates union, B1 is no drill bit mud bag, B2 is slight drill bit mud bag, B3 is severe drill bit mud bag, and B4 is mud bag stuck drill bit; when the conclusions of the two judgment indicators are inconsistent, the more severe mud bag risk shall be treated. For example, A 渐进 If the drill bit mud is determined to be a minor drill bit mud bag, but the drill bit mud bag has a support level K that determines it to be a severe drill bit mud bag, it shall be treated as a severe drill bit mud bag.

[0117] like Figure 1 As shown, when a minor bit mud bag occurs downhole, the following steps should be taken:

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

[0119] A2. Use a diluted slurry flushing solution for rinsing. The solution formula is: water + 2-3% caustic soda + 0.1-0.2% anti-mud coating agent RH4 + 2-4% walnut shells + 3-5% quartz sand. Following industry practice, all percentages in this document refer to weight percentages 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. The same applies below. The walnut shell particle size is 2-5mm. If rinsing is effective, continue drilling; if rinsing is ineffective, proceed to the next step.

[0120] A3. Perform bottom grinding. If effective, continue drilling; if ineffective, proceed to the next step.

[0121] A4. Pull out the drill bit and clean it.

[0122] The manufacturers and material properties of each component in the slurry rinsing solution are shown in Table 1:

[0123] Table 1

[0124]

[0125] A mud ball soaking experiment was conducted on the slurry flushing fluid, and the results were compared with those of a mud ball soaking experiment on a conventional drilling fluid system. The data are shown in Table 2.

[0126] Table 2

[0127]

[0128] As shown in Table 2, the conventional drilling fluid had little effect on mud ball soaking, reducing the mud cake by only 14% after 3 hours. However, the improved slurry flushing fluid showed a significant effect, reducing the mud cake by 36% after 1 hour, and also reducing the friction coefficient by 73.12%. This indicates that the improved slurry flushing fluid has a strong dispersing ability for mudstone, effectively dispersing the mud cake on the drill bit. Combined with the scouring effect of rigid particles, it greatly improves the mud cake removal rate on the drill bit.

[0129] like Figure 2 As shown, when a severe drill bit mud bag occurs downhole, the following steps should be taken to handle it:

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

[0131] B2. Perform bottom grinding. If effective, continue drilling; if ineffective, proceed to the next step.

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

[0133] B4. Inject the unsticking agent near the drill bit, shut in the well and pressurize it to soak and unstick the drill bit. Pressurize it to 3-5 MPa to improve the penetration of the unsticking agent. After soaking for more than 2 hours, open the well and move the drill string. If it is effective, continue drilling. If it is ineffective, proceed to the next step.

[0134] B5. Pull out the drill bit and clean it.

[0135] In B4, first pump 10m into the wellbore. 3 Pre-emptive isolation fluid, then inject the unblocking agent, followed by 7m 3 After the release fluid reaches the stuck point, stop the pressure soaking process and keep the water in the hole open at regular intervals during the soaking period. The density of both the pre- and post-release fluids should be consistent with the density of the drilling mud when the drill string is stuck. After the set soaking time is reached, replace the drill string with ordinary drilling mud, and then try to pull the drill string up with great force and apply positive and negative torque to move the drill string.

[0136] In B4, the unblocking agent for mudstone formations is formulated as follows: diesel oil + water + 3-4% emulsifier SR301 + 12% fast T + barite, with an oil-to-water ratio of 85:15; the unblocking agent for sandstone and limestone formations is formulated as follows: water + 20% hydrofluoric acid + 15% hydrochloric acid + 3% chromate corrosion inhibitor + 1% iron ion stabilizer IRON-2066A.

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

[0138] Table 3

[0139]

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

[0141] Table 4

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

[0143] Table 4 shows that the viscosities of the two flushing fluids are basically the same, but the high-efficiency flushing fluid has lower surface tension and a larger contact angle. Lower surface tension allows for better wetting of the drill bit surface, and a larger contact angle indicates greater hydrophobicity, preventing drill cuttings and mud cake from adhering to the drill bit surface.

[0144] Table 5 shows the manufacturers and material properties of each component in the card release agent in B4:

[0145] Table 5

[0146]

[0147] The evaluation method for the unblocking agent is as follows: ① An iron rod is used to simulate a drill bit. It is placed in an aging tank containing on-site mud, mudstone unblocking agent, and sandstone / limestone unblocking agent. A roller heating furnace is used, with conditions set at 100℃ and hot rolling for 1 hour. The mud coating on the iron rod is then observed, and the mass of the mud-coated clay on the surface of the iron rod is weighed to evaluate the effectiveness of the unblocking agent. ② Steel sheets are placed in the three mud systems respectively and kept at 100℃ for 48 hours. The corrosion inhibition performance of the drilling fluid is evaluated using the weight loss method.

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

[0149] Table 6

[0150] Iron bar surface mud ball mass / g Corrosion rate / g-m2-h-1 Blank slurry 142.65 0.148 Blank slurry + mudstone release agent 10.20 0.022 Blank slurry + sandstone, limestone release agent 20.88 0.018

[0151] As shown in Table 6, the blank slurry resulted in severe mud buildup, with the mud buildup on the iron rod surface reaching 142.65g. After adding the anti-blocking agent, the mud buildup amounted to 10.20g and 20.88g, respectively, representing reductions of 92.85% and 85.36%, demonstrating a significant anti-mud buildup effect. Furthermore, the addition of the anti-blocking agent significantly reduced the corrosion rate of the steel sheet. This is because the corrosion inhibitor in the anti-blocking agent contains sulfonic acid groups, which adsorb onto the steel sheet surface at multiple points, forming an inhibitory film and delaying corrosion.

[0152] like Figure 3 As shown, when mud bagging and stuck pipe occur downhole, the following steps should be taken:

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

[0154] C2. Inject the unsticking agent near the drill bit, shut in the well and pressurize it to soak and unstick the drill bit. Pressurize it to 3-5 MPa to improve the penetration of the unsticking agent. After soaking for more than 2 hours, open the well and move the drill string. If it is effective, continue drilling. If it is ineffective, proceed to the next step.

[0155] C3. Reverse the drill string above the drill bit and then lower the milling string to mill the bottom of the well.

[0156] Methods for preventing mud packing in PDC drill bits for oil drilling include modifying the drill bit surface before drilling to prevent mud packing, including: coating the PDC drill bit surface with a Teflon anti-mud packing hydrophobic coating with strong negative charge, polishing the cutting teeth, and nitriding the drill bit body.

[0157] Methods to prevent mud buildup in PDC drill bits for oil drilling include applying grease to the surface of the chip removal grooves and cutter wings of the drill bit before running it down into the well to form a protective film, and wrapping the chip removal grooves 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 mudstone formations, high-speed and high-volume drilling should be used to reduce the concentration of cuttings in the drilling fluid; the drilling flow rate should be no less than 55L / s for Φ311.1mm wellbore, no less than 45L / s for Φ241.3mm wellbore, and no less than 34L / s for Φ215.9mm wellbore.

[0159] In soft mudstone formations, low drilling pressure and uniform feed are adopted. When the drilling time reaches 24 hours, the footage reaches 300m, or abnormal torque, pump pressure, friction parameters, or abnormal sand return are found, a short trip trip operation is carried out according to the "two short and one long" principle. "Short" means that the trip section should exceed the newly drilled section, and "long" means that the short trip section enters the upper-level casing shoe.

[0160] Select stable formations for segmented pumping or circulation, and strictly prohibit starting the pump in formations prone to mud buildup; 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 first to circulate, using a large displacement to thoroughly clean the drill bit and the bottom of the well, and when the displacement reaches the drilling requirements, drill 0.5-1.0m with low drilling pressure, and then proceed with normal drilling.

[0161] During normal drilling, after drilling a single section or column, wait for the drill pressure to drop before raising the drill string. After reaming 1-2 times, reconnect a single section or column. Pay close attention to the sand return situation to ensure that the annular cuttings concentration is controllable. When reaming, pay attention to the weight indicator, vertical pressure gauge and top drive torque gauge to prevent jamming, pump stalling, or top drive stalling.

[0162] If the drill rod gets stuck, lift it up by no more than 20kN of normal hook load and pull it out by reversing the top drive. Lift it out in small increments without stopping the top drive. Each time the square drill rod is lifted, the lifting force should not exceed 50kN.

[0163] If pump stalling or top drive stalling occurs, after stopping the pump, apply strong downward pressure. If the drill string can descend, then try a small displacement top pump.

[0164] Example 1: Well HY5HF

[0165] The HY5HF well, with a diameter of 311.1 mm, was drilled to a depth of 2609.14 m using a combination of PDC drill bit and screw drill string. The drilling fluid displacement was 50 L / s, and the drilling fluid density was 1.28 g / cm³. 3 The lithology is brown mudstone of the Dainan Formation. Drilling time initially slowed down, and after short trips, the lowest drilling time per meter was 45 minutes, compared to 17.5 minutes in the adjacent well at the same formation, with a pump pressure of 20 MPa. After lifting the drill bit from the bottom of the well, increasing the displacement, and applying 20 tons of pressure, the drill string was lifted after 5 minutes. The angle was changed, and pressure was applied again for 5 minutes. After multiple flushing operations, the drilling time per meter recovered to 20 minutes, with a pump pressure of 25 MPa. At this point, the main characteristics were a drilling time 115% higher than the adjacent well and a pump pressure 125% higher, with no other significant abnormalities in other parameters.

[0166] For reference Figure 4The chart showing the risk trend prediction of drill bit mud packing and the percentage of support for drill bit mud packing, K = K1 + K3 = 25% + 15% = 40%, indicate a minor drill bit mud packing. Following quantitative evaluation criteria, and given the previous attempt at high-volume flushing, a thin slurry flushing fluid was directly injected for flushing. After a trial drilling of 2m, the drilling time per meter returned to 10 minutes, still significantly lower than normal. To completely remove the mud packing, bottom hole grinding was employed, with subsequent drilling speeds of 20-25 m / h. This effectively resolved the minor mud packing and prevented further deterioration of downhole conditions.

[0167] Example 2: SHB5-14H well

[0168] The SHB5-14H well, with a diameter of 241.3mm, was drilled to a depth of 4594.02m using a combination of PDC drill bit and screw drill string. The drilling fluid displacement was 38L / s, and the drilling fluid density was 1.24g / cm³. 3 The lithology is Triassic dark gray mudstone. Drilling time initially slowed down, reaching a maximum of 35 minutes per meter. The maximum drilling torque was 29 kN·m, the pump pressure was 35 MPa, and the suspended weight was 245 tons. When drilling the same formation in an adjacent well, the drilling time was 10.5 minutes, the drilling torque was 8.5 kN·m, the pump pressure was 12.7 MPa, and the suspended weight was 95 tons. The main characteristics observed at this time were that the drilling time was 233.33% higher than that of the adjacent well, the drilling torque was 241.18% higher than that of the normal well section, the pump pressure was 175.59% higher than that of the normal well section, and the suspended weight was 157.89% higher than that of the normal well section. Other parameters showed no significant abnormalities.

[0169] For reference Figure 5 The chart showing the risk trend prediction of drill bit mud packing symptoms and the mud packing support rate K = K1 + K2 + K3 + K4 = 25% + 15% + 15% + 15% = 70% indicate a severe drill bit mud packing. Following quantitative evaluation criteria, a thin slurry flushing fluid was first injected for flushing. After a trial drilling of 0.5m, the effect was found to be unsatisfactory. Then, bottom hole grinding was used, but after a trial drilling of 1m, the effect was still unsatisfactory. A high-efficiency flushing fluid was then prepared for flushing, effectively relieving the severe mud packing. Subsequent drilling time was 10 minutes per meter. By effectively identifying the degree of mud packing and taking targeted measures, deep well tripping was avoided, and the drilling speed was improved.

[0170] Example 3: QY1-201HF Well

[0171] The QY1-201HF well, with a diameter of 215.9mm, was drilled to a depth of 2336m using a combination of PDC drill bit and screw drill string. The drilling fluid displacement was 32L / s, and the drilling fluid density was 1.15g / cm³. 3The lithology is reddish-brown mudstone from the Sanduo Formation. Drilling slowed down initially, with intermittent pump stalling and top drive shutdowns. Simultaneously, lifting the drill string became difficult, and mud return decreased. When this phenomenon occurred, the maximum drilling time per meter was 22 minutes, the maximum drilling torque was 35 kN·m, the pump pressure was 30 MPa, the suspended weight during lifting and lowering was 195 tons, the mud return rate at the wellhead was 40%, and the cuttings return rate was 80 kg / m. When drilling in the same formation of an adjacent well, the drilling time was 5 minutes, the drilling torque was 7.5 kN·m, the pump pressure was 8.5 MPa, the suspended weight during lifting and lowering was 60 tons, the mud return rate at the wellhead was 60%, and the cuttings return rate was 130 kg / m. The main characteristics observed at this time are: drilling time 340% higher than adjacent wells, drilling torque 366.67% higher than normal well sections, pump pressure 252.94% higher than normal well sections, suspended weight during lifting and lowering 225% higher than normal suspended weight, wellhead mud return only 66.7% of the normal value, and cuttings return only 61.54% of the normal value.

[0172] For reference Figure 6 The chart showing the risk trend prediction of drill bit mud bagging and the mud bagging support rate K = K1 + K2 + K3 + K4 + K5 + K6 = 25% + 15% + 15% + 15% + 10% + 15% = 95% indicate a mud bag stuck drill bit. Following quantitative evaluation criteria, a high-efficiency flushing fluid was first injected for flushing. This improved the pump and top drive blockage phenomena, but the lifting tonnage remained too high, failing to completely release the stuck drill bit. Based on the formation lithology, a pressure-locking soaking method using an unblocking agent was adopted, injecting 7.5m of unblocking agent. 3 The well was shut in and pressurized to 3 MPa. After soaking for 2 hours, the drill string was moved and successfully unstuck. After removing the unsticking agent, the drilling was resumed normally with a short trip, and subsequent drilling proceeded as usual. By taking targeted measures, the incident handling time was shortened, and downhole safety was ensured.

[0173] The above description is merely a preferred embodiment of the present invention, showing and describing the basic principles, main features, and advantages of the present invention. It is not intended to limit the scope of patent protection of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. In addition to the above embodiments, the present invention may have other implementations without departing from the spirit and scope of the invention. Various changes and modifications to the present invention are possible, and all technical solutions formed by equivalent substitutions or equivalent transformations fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents. Technical features not described in the present invention can be implemented by or using existing technology, and will not be elaborated here.

Claims

1. A method for determining balling of a petroleum drilling PDC bit, the method comprising: Comprise the following steps in turn: S1, set the bit balling parameter sign risk trend as A 渐进 When A 渐进 reaches the corresponding area value, it is judged that there is a risk of slight bit balling, serious bit balling or balling sticking in the well. S2, set the bit ball occurrence support degree K, when K < 20%, it is determined that there is no bit ball, 20% ≤ K < 55%, it is determined that there is slight bit ball, 55% ≤ K < 85%, it is determined that there is serious bit ball, K > 85%, it is determined that the bit ball is stuck; S3, the comprehensive bit balling parameter sign risk trend is A 渐进 and the bit balling occurrence support K value, judging the bit balling degree B j ∈A 渐进 I K, wherein B1 is no bit balling, B2 is slight bit balling, B3 is severe bit balling, and B4 is bit balling sticking; when the conclusions of the two judgment indexes are inconsistent, the more serious bit balling risk is handled; A 渐进i are the change interval values of each parameter under different mud ball levels, including the drilling time change progressive trend value A 渐进1 , the torque change progressive trend value A 渐进2 , the pump pressure change progressive trend value A 渐进3 , the hanging load change progressive trend value A 渐进4 , the liquid level change progressive trend value A 渐进5 and the cuttings change progressive trend value A 渐进6 ; K i K1, K2, K3, K4, K5, and K6, K i is divided into two modes of 0 or 1, when each parameter change is within the allowable change range, K i is 0; when exceeding the allowable change range, K i is 1; α i is the credible weight of each parameter change.

2. The method of claim 1, wherein: The gradual trend value A during drilling time 渐进1 Under normal drilling conditions, it is defined as 100%. When 100% < A 渐进1 If the mud content is ≤180%, it is considered a minor mud-covering condition; if the mud content is <A, it is considered a minor mud-covering condition. 渐进1 ≤300% is considered a severe mud-covering condition; 300% <A 渐进1 A value ≤500% is considered a mud-covered, stuck drill condition. torque change gradual trend value A 渐进2 defined as 100% under normal drilling conditions, determined to be in a slight balling-up condition when 100% < A 渐进2 ≤ 230%, determined to be in a severe balling-up condition when 230% < A 渐进2 ≤ 360%, determined to be in a balling-up and sticking condition when 360% < A 渐进2 ≤ 660%. Pump pressure change gradual trend value A 渐进3 100% when 100% < A 渐进3 ≤ 150% is determined to be in a light balling condition, 150% < A 渐进3 ≤ 220% is determined to be in a severe balling condition, 220% < A 渐进3 ≤ 420% is determined to be in a balling stuck condition; A progressive trend value of the suspended weight change 渐进4 defined as 100% under normal drilling conditions, when 100% < A 渐进4 is determined to be in a slight balling-up condition, 130% < A 渐进4 is determined to be in a severe balling-up condition, 180% < A 渐进4 is determined to be in a balling-up and sticking condition; Liquid level change gradual trend value A 渐进5 100% is defined under normal drilling conditions, when 75%≤A 渐进5 When <100%, it is determined to be in serious mud ball drilling conditions, 50%≤A 渐进5 <75% is determined to be in mud ball sticking drilling conditions; A value of the progressive trend of the cuttings variation 渐进6 defined as 100% in normal drilling conditions, when 85% ≤ A 渐进6 < 100% is determined to be in a light balling condition, 70% ≤ A 渐进6 < 85% is determined to be in a severe balling condition, 50% ≤ A 渐进6 < 70% is determined to be in a balling and sticking condition.

3. The method of claim 1, wherein: The reliable weight of the drilling time change K1 is 25%, the reliable weight of the torque change K2 is 15%, the reliable weight of the pump pressure change K3 is 15%, the reliable weight of the hanging weight change K4 is 15%, the reliable weight of the liquid level change K5 is 10%, the reliable weight of the rock debris change K6 is 15%, and the reliable weight of other parameter changes is 5%; The allowable change range of the drilling time change K1 is 6%, the allowable change range of the torque change K2 is 12%, the allowable change range of the pump pressure change K3 is 10%, the allowable change range of the hanging weight change K4 is 5%, the allowable change range of the liquid level change K5 is 3%, the allowable change range of the rock debris change K6 is 3%, and the allowable change range of other parameter changes is 5%.

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