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Abstract:Drill bits with PDC（Polycrystalline Diamond Compact）are used widely in geological exploration ， oil and gas drilling and other corresponding fields and good technical， and economic results have been obtained. However， the research on the rock fragmentation process and relationship with drilling parameters in not enough and it affects the further increase of the technical and economic indexes of the PDC bits. Russian drillers have made a lot of work in this field，including the bits，and obtained definite success and it worth us pay attention to. For example， they propose that rock fragmentation should be proceeded under volumetric fragmentation state as well as possible because the rock fragmentation mode is changed； If energy consumption of penetration per revolution of bit is included as an evaluation index， the evaluation system will be more scientific and more overall； Penetration per revolution of bit is not the higher the better， it has an optimum value. The value is depended from drilling parameters closely； it is put forward an idea of critical drilling parameters， meaning that while the product of bit weight and rotary speed is more， than the product， the temperature of the bit will rise drastically， the bit will wear seriously and any large quantity of drilling fluid cannot help resolve the problems. In this case it is necessary to take measures， adjust drilling parameters and avoid drilling process being in the critical state， so that drilling is in the normal state and the drilling can be continued.

Abstract:It is easy for drill string to be cracked when it is subjected to complex forces. Evaluating the corrosion fatigue life of drill string according to the actual situation on site can provide a basis for the safe use of drill string. By calculating the axial force， cyclic stress and fatigue limit of the drill string in the wellbore， the fatigue evaluation methods of drill string based on fatigue coefficient， drill string tension and rotation counting are determined， and the influence of acidic fluids is considered. The results show that the increase of the bending stress and buckling will lead to the fatigue failure of the drill string when drilled with severe dogleg. The remaining service life of the drill string will be greatly reduced when the corresponding ROP is reduced and the rotating speed is increased significantly. When severe acid corrosion occurs， the remaining service life of the drill string will be rapidly reduced. The drill strings in the well section with high tension and large dogleg should be regularly shifted to ensure the safe and normal use of drilling string on site.

Abstract:The combined operation technology of horizontal well pumping bridge plug perforation has been widely used in the development of unconventional oil and gas reservoirs such as shale gas， shale oil and tight oil. In this process， the toolstring with drillable bridge plug and multistage perforating gun is sent to the designated position by hydraulic pumping. Due to the complexity of wellbore trajectory and wellbore environment， the pumping blocked and stuck occasionally occurs. According to the structural characteristics of the pumping bridge plug tool string for horizontal wells， this paper simplifies the tool string， the rigid geometric relationship between the tool string and the wellbore in the curved well section under a certain dogleg degree is analyzed， the method for determining the contact point between the pumping bridge plug tool string and the pipe wall is proposed， the stress bending characteristics in curved well sections are analysed， and the criteria for passability is established. According to the actual cases， the influencing factors including the well trajectory， the largest dogleg degree and the inner diameter of the pipe wall are analyzed， and the optimized scheme of pumping process parameters is given to reduce the occurrence of downhole accidents.

Abstract:With the technological development of multi-branch horizontal wells and complex structural wells， hole cleaning technology is facing new difficulties and challenges. The problems urgent to be resolved are how to solve the problem of cuttings-bed under complex geological conditions and complex well type conditions， to help judge and solve the complex situation downhole. The cuttings transport model is adopted based on the mechanism of cuttings transport. The indoor visualization of cuttings transport experiments was conducted to analyzed the cuttings transport patterns. The results show that the critical velocity of drill cutting is the highest at the well slope angle of 36°， and the drill cutting is most difficult to be carried. The trend of model predicted was validated by comparison with experimental results， and a good accordance was obtained. Its field application also indicates a good agreement between prediction and actual situations， which validated the reliability of this model. The model and experiments are of reference significance for borehole cleaning of large displacement horizontal wells.

Abstract:In order to improve the rock breaking efficiency and service life of the large diameter drill hammer in hard formation， ABAQUS software was used to establish the simulation model of rock breaking with spherical teeth. The curves of crushing specific work， invasion depth， crushing range and stress influence range of φ18mm spherical teeth in the process of impact cutting rock breaking under different drilling parameters were compared and analyzed， and the drilling parameters and tooth layout were optimized. The analysis results show that when the weight on bit is 1.2kN and the impact energy is 30J， the crushing efficiency of the rock is higher， the displacement of the spherical teeth into the rock can reach 0.67mm， and the stress limit of the rock is divided， and the influence range of the stress is 43.4mm. Through the simulation of double-tooth impact cutting， the better ring distance and spacing were determined： the ring distance was 47.4mm， and the spacing was 43.4~51.4mm. Considering the wear of the spherical teeth， using the ring distance and spacing， the teeth of the 711mm large-diameter drill hammer were optimized.

Abstract:Medium and deep geothermal energy is a kind of renewable energy which is abundant， widespread， stabable and reliable. It is characterized of green and low-carbon， clean and environmental protection， safe and high quality， sustainable and stable energy supply， which plays an important role in the implementation path of carbon peak and carbon neutrality. Combined with an engineering case in Changsha Basin， this paper tests the hardness， uniaxial compressive strength and lithology of rock samples using the rock pression sclerometer， electric-stress direct shear instrument and polarizing microscope.The influence of rock cementing material， mineral particles and bedding development degree on the drillability of the strata is analyzed and studied. The drillability grade of the strata is established， and some suggestions on the drill bit optimization are put forward， which has certain reference significance for drilling engineering in this area and such similar areas.

Abstract:Aiming at the technical problem of poor cementing quality of offshore gas wells with narrow pressure window， the goal of safe and efficient cementing is achieved through the application of light drilling fluid to optimize the slurry column structure and the application of annular backpressure. Three key technical requirements are considered in this paper： the annular backpressure value during the pump stopping process should not exceed 5MPa， the turbulent contact time of the flushing fluid should be greater than 10 minutes， and the wellbore should be self-stable after cementing ending. Then the optimized slurry column structure and the calculated wellbore equivalent cycle density （ECD） with managed pressure cementing （MPC） technology were conducted by which a design method of cementing slurry column structure of MPC for offshore gas wells with narrow pressure window was formed. Taking a high-temperature and high-pressure well in Ledong 10-1 Gas Field as an example， the cementing slurry column structure was optimized， and the wellbore ECD and turbulent contact time was simulated during the entire MPC process. The results indicate that： the requirements of turbulent contact time greater than 10 minutes and leakproof pressure stability can be achieved under the following three conditions： the volume of light drilling fluid is 14~50m³ and the density is 1.822~2.142g/cm³， the volume of the pad fluid is greater than 13m³ and the density is 2.36~2.45g/cm³ and the density of cement slurry is 2.4~2.51g/cm³. The goal of improving the efficiency of cementing displacement and safety construction is feasible with this method.

Abstract:South Sichuan work area is a key shale gas exploration and development area of Sinopec. The high formation pressure coefficient and harsh drilling geological conditions in this work area lead to complex drilling and frequent failures， among which sticking fault is the most prominent which seriously restricts the safe and efficient development of shale gas in South Sichuan. There are some problems in the existing technology， such as poor comprehensive utilization of monitoring information， not timely risk warning and strong subjectivity. In this paper， through the analysis of the expert knowledge judgment of sticking fault in the drilling process， the key characterization parameters corresponding to the risk of sticking are determined， the change trend of the key characterization parameters at the location of sticking is studied and the corresponding change rules are obtained. On this basis， a real-time early warning method for sticking fault based on abnormal diagnosis of engineering parameter change trend is established. Well WY-XX is selected as an example for analysis， as a result， the warning results by this software is consistent with the actual downhole risk which verified the correctness and reliability of the model with the success rate of 83%.

Abstract:In order to achieve the scientific research goal of drilling through the ice sheet and directly obtaining subglacial bedrock samples， this paper designs an aluminum alloy double-wall drill pipe for polar drilling， which can meet the drilling requirements of air reverse circulation， hydraulic reverse circulation， and matching with wire-line core drilling in different formations such as overlying snow layer， ice layer， ice-rock interlayer and subglacial bedrock on the polar region. According to the stress of aluminum alloy double-wall drill pipe under the condition of ultimate tensile and ultimate tensile torsion， the finite element analysis of double-wall drill pipe was carried out， and the tensile test and torsion test of the connection specimen between the outer pipe of the double-wall drill pipe and the steel joint were carried out. The finite element analysis results show that the maximum stresses generated in the aluminum alloy double-wall drill pipe under the combination of ultimate tensile and extreme tensile torsion conditions are 183.8MPa and 161.9MPa， respectively， which are less than the yield strength of 489.99MPa of aluminum alloy material. The test results of the specimen strength test of the connection between the outer pipe of the double-wall drill pipe and the steel joint also show that the ultimate bearing tensile force of the tensile specimen during failure is 399.5kN， which is much greater than the tensile force required to lift the 1000m double-wall drill pipe （208.11kN）； the limit bearable torque during torsional specimen failure is 8264.7N·m， which is also greater than the maximum torque of the drill pipe in the normal drilling process （1990.56N·m）. The above results show that the design scheme of aluminum alloy double-wall drill pipe for polar drilling can meet the requirements of polar drilling.

Abstract:Borehole expandable tubular drilling technology is one of the effective techniques to ensure the stability of borehole wall in complex formation. In this paper， a self-tensioning expandable tubular wall protection method is proposed for the strong water-sensitive strata prone to shrinkage， collapse and falling block. According to the wall protection principle of the method， a new type of reaming drill tool， expandable tubular and expandable tubular delivery device are developed to adapt to this method. Local reaming can be carried out on complex hole sections without changing the drilling structure. The delivery expansion tube naturally springs open with its own tension and is fixed in the corresponding reaming section to realize wall protection during drilling. The machine was optimized through indoor and field tests， and finally achieved good application results. The tests proved that： The method is simple， reliable and easy to locate. Compared with cement slurry wall protection， it has the advantages of fast processing speed， short stop time and less repeated processing. It is suitable for the solid wall and wall protection of complex formation in porous section in core drilling field， which is conducive to reducing the cost of in-hole accident treatment and improving drilling efficiency， and has good application value.

Abstract:In order to solve the problems of low mud recovery rate and low automation level of equipment in the treatment of geotechnical engineering waste slurry， a new high-efficiency intelligent mud separation system is developed based on the characteristics of geotechnical engineering slurry. The system adopts a two-stage separation process which combines vibration and swirling flow. It can automatically control the equipment’s on-off and speed based on the mud level. It can also upload the operating data to the cloud for engineers for analysis. After the completion of system development， the performance of the equipment was verified through indoor experiments and the influence of mud parameters on solid-liquid separation efficiency was explored. The results showed that， when the slurry flow rate and screen size unchanged， the particle removal rate is related to the size of solid particles and the viscosity of slurry， and the influence of the solid content is not obvious. The separation effect can meet the environmental purification treatment requirements of on-site mud. Over the duration of the workload， the system can achieve unmanned automation control and effectively separating large harmful solid particles. The invention of this equipment can significantly improve the reuse rate of mud， reduce labor intensity and save construction costs.

Abstract:In order to study the characteristics of rock mass， karst development， ground stress and groundwater in the tunnel of the Dadu River to the Min River Replenishment Project， 8 horizontal boreholes with a total of 2300 m were arranged in the diversion route of the Luding Water intake Middle route scheme. In order to meet the demand of horizontal hole comprehensive testing， a set of storage comprehensive logging instrument suitable for horizontal drilling is developed. This paper analyzes the basic working principle of the horizontal hole multi-parameter comprehensive measuring instrument. The circuit composition selection of each functional unit is described in detail. DSP microprocessor and large-scale integrated circuit are mainly used， and the sensor technology is combined to realize the comprehensive measurement of many parameters， including： pressure， temperature， natural gamma ray， acoustic wave velocity， and TV image in the hole. Integrated testing instrument integrates analog sensor， analog conditioning circuit， data acquisition， data processing， information storage， data communication， information exchange， measurement and control hardware and software， computer display and other functions， is an indispensable technology for horizontal hole comprehensive testing. It has been successfully applied in the horizontal directional hole of the Dadu River to the Min River Replenishment Project， and the problems of incline， azimuth， pressure， temperature， natural gamma ray and TV test in the hole have been solved in one trip， thus ensuring the safety of the hole and reducing the labor intensity as far as possible.

Abstract:The existing anchor cable prestress detection equipments can only be used when the length of the exposed section of the anchor is above 70cm and the anchor cable is not in operation and maintenance period. Most of these devices weigh more than 150 kg， which is too heavy for detectiing the anchor in high and steep slopes. In order to overcome the above problems， a new anchor cable prestress detection equipment HRAD-300 was developed. It can be applied to the prestress detection of in-service anchor with exposed length of 7cm. The measurement error is less than 0.01mm when the displacement range of the detector is 200mm， while the measurement error is ±1%FS when the force range is 300kN. The weight of a single box of the equipment is less than 15kg， and the total weight is less than 40kg. Based on the principle of reverse pull method and the shape of detection curve， the effective anchored prestress algorithm was proposed， and the software is programmed. The indoor test shows that there are no obvious mutation points in the detection curve. The calculated values were basically consistent with the original locked values. The equipment was used to detect the anchor of the unstable slope of Fenghuang rock. The field anchor detection curves has obvious mutation points and steep drops. The anchor cable runs well and keeps on working. The prestress loss of the No.2 anchor cable is more obvious， and the way of compensate and stretch can be taken. Uneven stress exists in the same anchor cable. In conclusion， the HRAD-300 is intelligent and light， which can provide data for the health evaluation of anchorage engineering.

Abstract:Well JMKZ-1 in Jiama is the first 3000m scientific drilling project for solid mineral survey in Tibet Plateau.The project was lasted 488 d from June 2019 to October 2020. The total depth is 3003.33m with the final hole diameter of 98mm and a core recovery rate of 99.38%， which made a record in the field of small-bore solid mineral exploration on the Qinghai-Tibet Plateau at an altitude of 5200m. In this paper， detailed technical statistics of the drilling time， drilling efficiency， round footage and other indexes are made， the main factors which affect the ultra-deep geological drilling efficiency on the plateau are analyzed including the environment， the formation， drilling techniques， equipment， management actions and so on. Meanwhile， the measures to improve the efficiency of deep drilling are summarized such as drilling design， equipment configuration， drilling method selection， hole accident prevention， new technology and new method application， construction organization， etc. The project experience has obtained good results through popularization and application， which can provide some technical reference for improving the efficiency of ultra-deep hole drilling in the future.

Abstract:With the continuous construction of geostress monitoring stations， the drilling technology of geostress monitoring holes has been continuously improved in practice. This paper briefly introduces the drilling technical requirements， selection of drilling equipment and drilling technology of geostress monitoring holes， systematic statistics and analysis were conducted on the drilling time and drilling efficiency of the completed geostress monitoring holes. Through analysis and research， several factors affecting the drilling efficiency of geostress monitoring holes are summarized， including location selection for monitoring holes， management of drilling process， drilling technology， and test cooperation， etc. According to these influencing factors， suggestions were put forward to improve drilling efficiency by strengthening management of drilling process， utilizing key technologies such as technical casing and graded reaming technology， strengthening technical management of important links such as drilling and inclination measurement， and doing well in test cooperation， it provides reference bases for the implementation of similar drilling projects in the future to improve drilling efficiency.

Abstract:Aiming at the difficulties exist in thermal reservoir drilling in bedrock of Xiong’an New Area such as drilling in weathered crust， plugging severe formation lost and coring at bedrock， an effective solution for drilling in bedrock thermal reservoir is proposed including small diameter exploration wells， effectively mud plugging using packers and borrowed the principle of diamond full hole coring tool technology through the analysis of the geothermal geological conditions and lithological characteristics of Niutuozhen Geothermal Field， Rongcheng Geothermal Field and Gaoyang Geothermal Field.

Abstract:The Permian igneous rocks formation in Shunbei Block of Tarim Basin has the characteristics of large thickness， high hardness， developed fractures and strong heterogeneity， which leads to low ROP and long plugging time. the average drilling cycle increases by 1.5 times compared with the adjacent areas. In recent years， through continuous strengthening the drilling fluid plugging technology and the optimization of high-efficiency drilling technology， the leakage and plugging time have been gradually shortened， and the drilling index has been increased year by year. In this paper， the main controlling factors affecting the long plugging time and low penetration rate are analyzed， and the plugging technology is improved by adding bamboo fiber and deformed particles into the plugging slurry. The applicable conditions of the impact tool are clarified， and the PDC bit with aggressiveness and impact resistance is optimized. Technical countermeasures such as improving the structure of the mixed bit and supporting the high torque and long life screw have achieved remarkable results in increasing drilling speed and reducing cost， which provides guidance for accelerating the efficient exploration and development of Shunbei Oil and Gas Field.

Abstract:The shear strength of the rock-soil body， especially the shear strength of the rock body structural plane of the weak layer， plays a vital role in the stable analysis of landslides. The sample was lightly disturbed and the test status was more consistent with the real state of the rock-soil body in the in-situ shear test， moreover， the parameters obtained were more real， which is one of the important methods of in-situ test for landslides investigation. It is suitable for determining the shear strength of the rock and soil structure surface， geotechnical contact surface， sliding surface， mixed soil layer and other coarse granular soil layers. This study takes Chongqing Huayu · Guanlanhuafu project as an example， the original sample was collected for laboratory direct shear test while the in-situ shear tests were made， by which two shear strength parameters under different experiments were obtained. The stability of the landslides under different operating conditions were analyzed and calculated using the above two parameters， and compared with the actual deformation characteristics of the landslide body， thereby the rationality of the rock-soil body shear strength parameter was verified， which can provide reference for similar projects.

Abstract:The interlocking pile has been widely used in deep foundation pit engineering， and accidents of support piles invasion often occur due to factors such as geological conditions， construction organization， and operational ability. This article uses a fiber model finite element calculation program to calculate the bending bearing capacity of support piles before and after the invasion treatment. At the same time， combined with the back analysis results of the deep horizontal displacement monitoring of the pile， it is demonstrated that the use of adhesive steel reinforcement method to treat the invasion support piles is feasible. Using the spatial effect of the foundation pit， the step-by-step pile jumping construction is used to cut and reinforce the invasion support piles， and the foundation pit is in a safe and stable state. Analysis of the monitoring results after reinforcement treatment and bending condition of pile body shows that the bending moment value borne by the section is less than the bending bearing capacity of the section.The reinforcement construction of this project has achieved good results， effectively solving the invasion limit problem of the support piles in foundation pits， which can provide reference for similar projects.

Abstract:In shield tunneling， the method of replacing the shield tail brushes with grouting needs to forma closed and stable water stop ring， including a polyurethane ring and a slurry ring. This paper combines the example of shield tunneling construction in a water-rich sand strata at the coast， collects the in-situ groundwater to conduct indoor test about the polyurethane including the initial setting time， foaming rate， solid strength， etc. The results show that hydrophilic polyurethane reacts rapidly with groundwater， forming a compact and uniform consolidated body with low foaming rate and low strength， while the hydrophobic polyurethane is in the opposite state. Both can be considered to use on site actual injection at the same time， first injecting hydrophilic polyurethane， then injecting hydrophobic polyurethane with the dosage of 5∶1.The on-site application proves that the formed inclusions are stable and of good quality.