Abstract:In 2011， Shandong Provincial Bureau of Geology and Mineral Resources implemented the first domestic hot dry rock survey and evaluation project in Lijin County， Shandong Province， where rotary drilling was adopted， but the drilling efficiency was low and energy consumption was high. To improve drilling efficiency， shortening drilling cycle， reduce production cost in hard rock drilling at high temperature， in both the southeast coast deep scientific drilling hot dry rock geothermal well HDR-1 of China Geological Survey （depth of 4000.86m， hole bottom temperature 109℃） implemented in Zhangzhou， Fujian Province in 2015， and the hot dry rock scientific exploration well GR1 （well depth of 3705m， hole bottom temperature 236 ℃） implemented in Qinghai province in 2017， the compound drilling technology of “rotary table and mud motor” was tried， and the “rotary+turbodrill” compound coring drilling technology was tested over the coring section for the first time at high temperature with good results obtained. Some comments and suggestions are put forward on the future research direction， which provides valuable experience on high-temperature drilling for the in-depth study of the PDM drill and turbodrill， and also provides new technical support for hot dry rock scientific drilling and deep geothermal resource exploration in China.

Abstract:The eccentric mechanism of the mechanical automatic vertical drilling tool can not always be held stable on the low side of the wellbore in the actual drilling conditions due to its own inertia and the influence of the external environment， resulting in the reduction of deviation correction accuracy. In order to study the change law of the angular position of the eccentric mechanism in the drilling process， a non-contact angular position measurement method based on the absolute magnetic encoder is proposed in this paper with the measurement data acquisition interface constructed， and the laboratory verification and reliability analysis carried out. The measurement error is less than 3 degrees， indicating that the non-contact angular position measurement method can monitor the angular displacement and the error is within the allowable error range. It can provide reliable data for the subsequent research and development experiment， and optimization of the mechanical vertical drilling system.

Abstract:The deviation of borehole trajectory leads to the extraction blind zone easily， which seriously threatens the safety and efficient mining of coal mines. Through the analysis of geological， technical and process factors， the root cause of borehole deflection is obtained. This paper analyzes and summarizes the principle and applicability of the existing straight drilling technology. Borehole straightness is a factor that affects the drilling quality. However， the current straight drilling technology has more or less some technical problems and cannot be widely used in coal mines. Therefore， continuous progress should be made on straight drilling so as to develop a kind of straight drilling technology with strong adaptability and easy field application. The in-depth research on deflection factors and the development of straight drilling equipment and tools should be strengthened.

Abstract:The Xuefengshan pilot hole is a shale gas geological survey hole deployed in the Mayang syncline in the Yuanma Basin in Western Hunan. This paper introduces the engineering and geological conditions of the borehole with focus on the drilling and completion technology. The complex formations and drilling technical difficulties encountered during the drilling process are also summarized and analyzed with specific solutions put forward for different drilling difficulties. The solutions mainly include improving drilling and coring tools， adopts wire-line coreing tool that does not lift the drill to replace the inner drill bit with a spring core protector cord. Micro-foam drilling fluid and a drilling fluid formula of bentonite+lignite resin+broad-spectrum wall protectant type III+high temperature and salt resistance fluid loss agent+limestone powder are used. Developing the relevant management measures. As a result， drilling efficiency has been improved， drilling quality has met the geological requirements， and the drilling tasks have been effectively completed. It is desired the drilling experiences can provide technical reference for drilling of similar shale gas survey boreholes.

Abstract:Air-lift reverse circulation drilling is an efficient drilling technique which can be used in deep well drilling in hard rock formation since it is not affected by rock fractures and karst caves with thorough removal of the cuttings. A special continuous coring bit has been developed to carry out continuous coring operations in deep-sea hard rock to improve drilling efficiency and core recovery in deep-sea hard rock； thus， providing a novel coring approach for deep-sea drilling. With studies on the selection of the cone profile， the structure of the core lifter， the optimum design of the passage for the cores and cuttings， etc.， the design of the continuous coring bit was put forward， and the test drill bit was made. The bit has been applied in a geothermal well， with core recovery in limestone and sandstone over 80%， higher than that measured in ocean drilling. The verifying test on land has laid a technical foundation for the further application of this technique in deep-sea core drilling.

Abstract:As a key technical method for the exploration of marine natural gas hydrates， pressure-temperature sampling is a core technical method for obtaining in-situ samples of hydrates. This article reviews the relevant data of pressure-temperature core samplers at home and abroad， and analyzes domestic marine natural gas hydrate pressure-temperature core samplers in terms of the working principle， structural characteristics， and experimental applications. The domestic pressure-temperature core sampler has been able to sample in soft to medium-hard to hard formations by adopting different working principles. The performance indicators of domestic pressure-temperature core samplers in field applications， such as pressure retention success rate， core recovery， can also meet the sampling needs； thus effectively facilitating the process of independent natural gas hydrate exploration and evaluation by China.

Abstract:When drilling into a stratum that is prone to collapse in shallow sea coring drilling， it is necessary to install casing to seal the stratum to ensure mud circulation and to continue drilling at smaller diameter. The conventional casing installation method is used to install casing from the drilling ship with both the drill floor platform deck and the casing platform deck； while for the drilling ships without the casing platform deck， it needs to be temporarily installed if casing must be installed. But installation of the casing platform is limited by the volume and mass of the drill rig and drill string. In order to solve the problem of installing casing in offshore drilling and coring with drilling ships without casing platform decks， a casing running process for installing multi-tier casing in offshore drilling is designed， where telescopic casing and related equipment is used to establish a mud return channel from the subsea wellhead to the small drilling ship to isolate unstable formations， and realize mud recycling and drilling heave compensation. In the drilling process， the telescopic casing can also provide guiding and positioning to prevent the drilling tool from influence of changes in tidal current flow speeds， saving time and cost for shallow sea drilling.

Abstract:The LF7-2 Oilfield is a small-scale oilfield located in the LF block of the Pearl River Mouth Basin in the South China Sea. According to previous exploration wells， the upper stratum is dominated by thick mudstone which is easily hydrated and dispersed， leading to poor performance of the drilling fluid， frequent drilling string sticking and resistance during tripping， and bit balling due to improper bit selection. The lower stratum is dominated by alternate sand and mudstone which is dense， and of poor drillability. As a result， the drilling torque/drag increased with difficulty in slide drilling and control of the well trajectory during directional drilling， which brough many difficulties to the drilling speed and efficiency. According to the geological conditions and rock mechanics profiles from exploratory wells， drilling software was used to optimise the platform location and simulate development well drilling in terms of the wellbore structure， wellbore trajectory， drill string mechanics， drilling fluid， cementing and other aspects， so as to formulate proper drilling design. For the vertical well section， the “rock bit+mudmotor+MWD” drill assembly was used for vertical drilling； for build-up sections， the “PDC bit+mudmotor+MWD/LWD” was used for compound drilling； and for horizontal sections， the “PDC bit+PowerDriver+MWD/LWD” was used for rotary steering drilling to achieve precision drilling. In such a way， 6 development wells were successfully completed. Field use indicated the average ROP was 29.43m/h with the total drilling period per well of 191.59 days， 28.41 days ahead of the design， which improved drilling efficiency， and reduced development costs. Near-bit inclination and gamma real-time measurement and transmission of PowerDriver reduced geological misdiagnosis， and can provide real-time detection of the roof of the reservoir with the reservoir intersection rate reaching 100%， resulting in good economic benefits and investment return to achieve profitable development of small oilfields.

Abstract:In view of abnormal high pressure， the narrow three-pressure window and faults in the high-pressure zone in Well L in Bohai Oilfield， fine pressure-control drilling technology was developed through use of fine pressure control surface equipment and proper control of drilling parameters to reduce the risk of both leakage and blowout in the same layer during well drilling， and achieved early prevention， early discovery and early settlement of overflow. In combination with safe operation measures such as pressure-controlled drilling， connecting drill pipe stands， and tripping of drilling strings， Well L was successfully side-tracked， laying a technical foundation for the exploration and development of the abnormal high-pressure area in Bohai Oilfield.

Abstract:The Shunbei-52A well is an exploratory well deployed in the southern part of the 5# fault zone in the Shunbei Oil and Gas Field， and is difficult to complete with high drilling risks due to complex Silurian formation encountered. A salt water layer is present in the Silurian stratum； thus， the density window is narrow， and leakage and collapse may happen concurrently； the formation has developed fissures with high risk of leakage； there are large intervals of mudstone with strong water sensitivity， and the wellbore is easy to lose stability. Therefore， the KCl-NaCl composite under-saturated brine drilling fluid system was used for the Shunbei-52A well to enhance the ability to resist salt water intrusion； inhibitors such as polyamines were added to work together to inhibit hydration swelling of the mudstone， and enhance the inhibition of the system； in addition， the plugging agent and the plugging-while drilling material were used to prevent lost circulation， and enhance the plugging performance of the system. Field use showed that the composite under-saturated brine drilling fluid system not only reduces the risk of lost circulation， but also maintains the wellbore stability of the Silurian formation well. It enables safe and quick drilling of the Shunbei-52A well in the Shunbei Oil and Gas Field， providing valuable experience and technical support for the drilling operations in the Silurian strata in the southern part of the 5# fault.

Abstract:X well and Y well were two exploration wells deployed in Shunbei Oilfield of Tarim Basin. X well was a field test well with enhanced drilling parameters. Compared with Y well， X well was drilled with better measures for enhanced drilling parameters in actual drilling. The mechanical drilling rate of X well in the third section from 5600 to 7500m was increased by 119% over that of Y well. Comparative analysis showed that X well was drilled with surface equipment with higher pressure； thus achieving higher volume and pump pressure in actual drilling. The bit impact forces for X well and Y well were 0.73 to 1.02kN and 0.61 to 0.85kN， bit hydraulic power 6.79 to 11.38kW and 5.37 to 8.79kW， and specific mechanical energy 0.23 to 2.15MPa and 0.52 to 3.5MPa respectively. In the experiment with enhanced drilling parameters， higher downhole mechanical energy and hydraulic energy were obtained in X well with better rock breaking environment. The mechanical ROP at the third drilling section was significantly higher than that in Y well， which met the expected ROP improvement with enhanced drilling parameters.

Abstract:In view of the drilling technical difficulties of poor wellbore stability and high friction torque in the long horizontal section of Well Yang101h3-6， high-density oil-based drilling fluid was proposed as the solution. With incorporation of a new “Ⅰ” type main emulsifier， the formulation of high density oil-based drilling fluid was determined at 2.2g/cm³ with the composition of 2% primary emulsifier+3% co-emulsifier+3% wetting agent+4% filtration reducer+1% organic soil+3% CaO， oil-water ratio 80∶20（diesel oil∶25% CaCl₂ aqueous solution）. Evaluation on its performance showed that the system has strong inhibition， good anti-pollution ability， and stable performance； the field application showed that the high-density oil-based drilling fluid has good rheology， high demulsification voltage， low filtration at high temperature and high pressure， meeting the drilling needs for the long horizontal section of Well Yang101H3-6. During the drilling of the horizontal section of Well Yang101H3-6， the performance of the drilling fluid was stable， the borehole wall was stable， and the downhole was safe， leading to smooth completion of the well.

Abstract:Well JZ04 is a geothermal exploration well in Jizhong depression. As the region’s deepest geothermal exploration well， its drilling design is mainly based on its geological design， adjacent well stratigraphic data and related geophysical data. The detailed design of the well hole structure is conducted through analysis of the regional geological data， with design and selection of the drilling equipment， the drilling stem， the drilling fluid system， the cementing method， well control device and so on. The relevant measures and operation requirements are put forward for reservoir protection. Considering high risk in later drilling operations due to great well depth， complex strata， and compromised accuracy of formation data， the drilling difficulties and the corresponding solutions are given in the design. The design can provide some guide for later drilling operations； hence support for drilling smoothly to the target layer to complete the drilling task.

Abstract:The exploration of the central uplift belt in northern Songliao Basin shows that the reservoir conditions are greatly influenced by fractures. Therefore， Well Changtan-1 was deployed in the northeast of Well Longtan-X3 which is closer to the fracture belt of Xuxi， and where the fault activity is obvious. The total designed depth is 5086.90m with vertical depth of 3906.70m and maximum inclination of 81.95°.The basal structure of Songliao Basin is very complex and the type and composition of the fault is variegated because of multiphase tectonic activities， which increases the difficulty on drilling design and field operations. In view of the difficulties and risks that may be encountered in the drilling process of the well， the safety feasibility analysis is conducted with optimization of the well structure， well trajectory， drilling parameter and drill bit. Field drilling results showed that the average rate of penetration is 4.20 m/h with the drilling period of 120.67d which is shortened by 20.35% compared with nearby wells， increasing drilling efficiency to a great extent. It provides valuable experience for exploration of the basal structure in the region.

Abstract:The square chisel is an important trench cutting tool for the underground diaphragm wall. This paper briefly introduces the structural design， construction method and application of a new square chisel. The integral frame of the new square chisel is welded with proper structure， and its size can be adjusted according to the needs of users. It has the advantages of good guidance， large water passage， high impact power per unit area and ease for fishing. After the successful development of the chisel， it has been used on percussive reverse circulation drilling rig with air-lift reverse circulation for subway construction in Xiamen and Shenzhen with significant construction efficiency， achieving good economic and social benefits. The successful development of the new type square chisel provides a better trenching tool for the construction of underground diaphragm walls.

Abstract:The 12 bored piles for the 2^# pier of the Dashu Dadu River Bridge in Hanyuan county have a diameter of 2500mm and a depth of 63~75m， posing some construction difficulty due to large diameter and great depth and drilling in massive sandy gravel formation below the river water level. There are multiple layers of sand and pebble soil overlying the bedrock at the 2^# pier， and the sand layer is very thick. Sandy soil prevails between 11.5~49.4m except for a layer of 5.5m thick gravel cobble with soil inclusion， which is very disadvantageous to drilling of pile boreholes. Percussion drilling was used to sink the holes with the mud purification device to remove cuttings； meanwhile， some technical measures were adopted to ensure successful completion of the works， such as control of the bit diameter， use of the inner casing， control of the tremie pipe buried depth during concreting. The relevant technical measures can provide reference for other similar projects.

Abstract:In domestic metal mines， the drilling and blasting method is used for deep mining， and it has a long construction period with high risks. The TBM method has been widely used in water conservancy， municipal engineering and highway construction because of its fast construction speed， safety and good quality. With the continuous application of “four new technologies”， the continuous improvement of equipment， and the continuous improvement of domestic TBM performance and quality， construction costs are significantly reduced. However， the TBM method has not been applied to develop deep mining roadways. The main reasons are： the deep geological conditions of the mine are complex； the roadway cross-sections change， and the adaptability of TBM is poor. This paper analyzes the possible risks of water inrush， rock burst， high ground temperature and so on when the TBM method is used in deep roadway development in metal mines， and expounds the solutions for these risks. It is concluded that these risks can be eliminated with the solutions， and TBM can be applied in deep roadway boring in metal mines.

Abstract:In Tianjin， construction waste mud is disposed in a simple way with serious environment pollution； thus， posing a construction difficulty which needs to be solved urgently. Taking a pile foundation construction site as the test site， the physical pressure filtration treatment test of waste slurry on site was carried out by using a small filter press， where the Type 1 press cloth of 28~30L/（m²·s） was selected with 60min as the optimal treatment time for a single press to achieve solid-liquid separation of waste mud on site. In actual operation of the construction equipment， the single pressure filtration time can be reduced to 45min by adding a small amount of lime. The on-site pressure filtration method solves the problem of on-site mud discharge effectively， and achieves the purpose of resource saving and environmental protection.

Abstract:Curtain grouting is a common technical method for dam foundation anti-seepage treatment. Because of karst development in karst areas where karst fissures and channels crisscross， and it is difficult to find out their regularity， the grouting volume is often high. In order to effectively control the cost of curtain grouting and ensure the construction quality of curtain grouting， it is necessary to adopt proper and reliable construction technical measures and means to control and improve the situation of high grouting volume. In relation to the high volume consumed in curtain grouting for the karst dam foundation of a hydropower station， comprehensive exploration and application of specific technical measures and control means was conducted to achieve the purpose of dam foundation seepage prevention with the curtain grouting time reduced to the minimum and the cost of high material consumption effectively controlled， as well as some experience gained for curtain grouting for similar projects.