Abstract:In order to predict the corrosion resistance of aluminum alloy drill pipes （ADP） in scientific ultra-deep drilling， COMSOL software was used to establish a multi physical field corrosion analysis model for simulation and analysis of the corrosion law of ADP used in SK-2 well under the action of “stress temperature electrochemistry”. The results show that when the corrosion system reaches equilibrium， the electrolyte potential on one side of the aluminum alloy electrode is higher than the steel joint electrode， and the current density of the aluminum rod near the steel joint electrode is higher. With the increase of stress and temperature， the corrosion rate of ADP is accelerated. Compared with temperature， the influence of stress on corrosion is smaller. It is a positive linear relationship between the corrosion rate and the working time. The closer to the galvanic corrosion site， the higher the interface current density of ADP， exhibiting an exponential relationship. The intensive influence area in the outer wall is about 0~200mm away from galvanic corrosion and that in the inner wall 0~110mm away from. The research results can provide reference for the anti-corrosion of aluminum alloy drill pipes.

Abstract:PDC bits have the advantages of high rate of penetrate （ROP）， long service life and flexible design when drilling in soft to medium-hard formation. The demand of PDC bits in drilling field is increasing yearly. As a new type of rock breaking technology， ultrasonic drilling has attracted wide attention due to its strong penetration and low drilling cost. However， the understanding of the formation mechanism of rock cuttings at micro level and the change of cutting force in the cutting process is not enough， which makes the wide application of this technology limited. In order to deeply understand the cutting mechanism of ultrasonic drilling， based on the linear Drucker-Prager model and ABAQUS software， a two-dimensional finite element model for ultrasonic vibration assisted rock cutting is established， and the formation mechanism of rock cuttings at micro level of ultrasonic vibration cutting is analyzed and compared with the conventional single tooth cutting process. In addition， the variation law of rock breaking specific work and cutting force at different frequencies is analyzed. The results show that， in the process of ultrasonic vibration assisted cutting， the cutting force decreases to zero more obviously than conventional cutting； when the excitation frequency is close to the natural frequency of rock， ultrasonic vibration cutting has smaller cutting force than conventional cutting， which is conducive to improve the stress state of the tool and reduce the wear degree of the tool； ultrasonic vibration cutting is easier to produce large blocks than conventional cutting when the frequency increases from 20kHz to 40kHz； the rock breaking specific work and average cutting force decrease first and then increase， indicating that there is an optimal frequency at which the specific work of rock breaking is minimum while drilling efficiency is highest.

Abstract:In order to improve wear resistance and anti-balling of the drill bit during shale oil and gas drilling， Fe₄₈Cr₁₅Mo₁₄C₁₅B₆Y₂ amorphous alloy coatings were prepared on 35CrMo steel substrates by cold spraying （CS） and high velocity air fuel （HVAF） spraying with the hydrophobic surface of coatings made by UV laser. The microstructure and mechanical properties of the coatings were analyzed by scanning electron microscopy （SEM）， X-ray energy spectrometer （EDS） and X-ray diffractometer （XRD）， a contact angle meter was used to characterize the wettability of the coating， and the wetting mechanism was analyzed. The results showed that the Fe-based amorphous alloy coating prepared by CS technology had a denser microstructure and better thermal stability with the amorphous mass fraction up to 90%. The melt in the laser process rapidly cooled on the surface of the coating to form nano-sized condensation and agglomerates to form a micro-nano composite structure. With 7 laser scans， the CS coating had the highest water contact angle on the surface， which represented good hydrophobicity.

Abstract:The accuracy of sedimentary facies and facies interface identification is not high due to the complex grain size composition and low core recovery in sandy sediment. In this paper， a lithology identification model based on the support vector machine （SVM） is established based on core and logging data， and the influence of the training set size on the identification accuracy of the model is analyzed and compared with the BP neural network model. The results show that the SVM model has high accuracy of lithology identification and low demand for training samples， which can effectively make up for the insufficient core recovery and reduce the drilling cost. It is feasible to use the logging lithology identification model based on SVM to identify the sedimentary sequence automatically in unconsolidated sediment investigation， which is a beneficial attempt to implement green exploration.

Abstract:Shale is a typical low-permeability sedimentary rock， and wellbore stability in shale has always been a difficult and hot spot in shale gas （oil） exploration and development at home and abroad. In this paper， experimental testing， microscopic observation， theoretical analysis and numerical simulation are used to study the influence of salt solutions on the physical-chemical seepage performance of shale under shale pressure transfer experiments. Furthermore， a numerical simulation model is provided to program and reconstruct the mechanical model of particles in nanopores， and to simulate the influence of particle size， concentration， shape and fluid viscosity on shale pore plugging efficiency. The results show that： （1） Particle size and concentration can affect plugging efficiency in terms of physical plugging. When the particle size does not exceed the outlet size， with increase of the particle size from 1/5 to 1/3 and 1/2 of the outlet size， the particle blocking effect increases by 13% and 23% as particle concentration is 5wt%. （2） Change of fluid physical properties affects shale nanopore plugging. The plugging efficiency of 5 mPa·s nanoparticle solution is 16.26% higher than that of 1mPa·s nanoparticle solution. （3） In terms of chemical inhibition， the best salt solution and its concentration to prevent the transmission of shale pore pressure are 20% HCOONa. The research results can provide a good theoretical and technical basis for the selection of water-based drilling fluid systems suitable for Longmaxi shale drilling.

Abstract:The existing power supply methods of measurement while drilling systems have their own applicable conditions， so it is necessary to explore new underground power supply methods as a supplement to the existing methods or use them in conjunction with th existing power supply methods. The triboelectric nanogenerator is derived from the phenomenon of contact electrification and electrostatic induction （ie， common static electricity in life）， and has the dual functions of a generator and a sensor. Based on this， this study brings the triboelectric nanogenerators into the field of geological exploration， and proposes a new measurement while drilling method that with the function of self-powered （also called self-powered） and self-sensing base on the principle of triboelectric nanogenerator， and uses a self-powered downhole vibration sensor as an example to introduce this method in detail. Subsequent tests verified the high signal-to-noise ratio and good power generation characteristics of the sensor， and further high-temperature tests in the range of 280℃ showed that this method has obvious advantages in developing ultra-high temperature downhole sensors and ultra-high temperature downhole real-time generators. In addition， since the current research of our team in this new field is still in infancy， there are still a lot of work to be carried out in detail， so this study also gives the next key research directions and solutions in order to provide some reference for interested researchers.

Abstract:This paper introduces the construction management of Well MSD-1， Well MAZD-1 and Well MED-2 in regard to the separate budget drilling projects carried out in Yin’e Basin from 2017 to 2019. During the implementation of the projects， with exploitation of the advantages of the Institute of Exploration Technology in drilling technology and regional business management， the practical problems have been solved， the maximum deliverables and the interdisciplinary collaborative development have been achieved， and a project management mode to achieve the dual objectives of “Geology and Drilling” has been sought out. It provides a reference for the implementation of geological survey drilling projects in the future.

Abstract:Experimental hot dry rock development wells are drilled under high-temperature and hard rock formation conditions where there are still many technical difficulties in how to achieve efficient drilling. Air DTH hammer drilling technology is one of the effective methods to solve the problems with drilling in hard rock formations. The DTH hammer bit is the key tool for air drilling. Through the application of air DTH hammer drilling technology in the hot dry rock well GH-01 in Gonghe of Qinghai， the paper analyzes and discusses the problems of broken teeth， severe wear and short service life of the air DTH hammer bits. The air DTH hammer drill bit was optimized from several aspects， such as drill bit structure design， drill bit processing material selection， and drill bit cold pressing and tooth fitting technology. The finite element analysis method was used in the optimization process of tooth fitting to simulate and calculate the interference of the cold-pressing tooth fitting process， and according to the results of analysis and calculation， the optimal interference of tooth fitting was determined. The optimized structure， materials， and processing of the DTH hammer bit can provide some reference for the development of air DTH hammer bits suitable for drilling high-temperature hard rock， improve the comprehensive drilling efficiency of air DTH hammer drilling， and provides technical support and reserve for the development of hot dry rock.

Abstract:Western Guizhou is an important area for exploration of both coalbed methane and shale gas， and presents huge challenge for drilling engineering because of circulation loss induced by karst caves and fractures. Analysis of the surface geological condition and drilling practice in the area with reference to the drilling experience from nearby areas finds that circulation loss， often accompanied by wellbore collapse， is mainly caused by the caves and fractures developed in Western Guizhou. In view of circulation loss and wellbore collapse， it is proposed that the specific well structure should be designed for the coalbed methane well and the shale gas well to prevent circulation loss and wellbore collapse. The drilling technical system， including air drilling， water drilling， casing while drilling， reverse circulation， has been developed to deal with the challenges and to increase the ROP. The drilling experience from Well QSD-1 is also described. This paper can provide the technological solution and reference for drilling in Western Guizhou.

Abstract:In order to solve the difficulty in drilling holes in fractured complex rock strata due to wall collapse in underground directional drilling at coal mines， a casing while directional drilling technique for complex rock strata was invented to protect the hole section over complex fractured rock. First， the concentric directional drilling stem drills to pass through the complex strata with the outer casing； then， the concentric directional drilling stem is tripped out of the hole and the outer casing is left in place to protect the hole section over the complex strata， and finally， the directional drilling stem of smaller size is run through the outer casing to continue drilling. In this paper， the design of the casing while directional drilling tool and the research on the casing while directional drilling process are described. The technique was tested for drilling a high-position directional hole at a mine in Huaibei， where it successfully protected the 103.5m complex strata hole section composed of two layers of coal lines and one layer of mudstone with the completion depth of 530m. The test showed that this technology can effectively protect the complex strata hole section， and increase the directional drilling depth in complex strata and protect the extraction channel.

Abstract:Due to the diversity of geological conditions， distributed in complex formation such as loose and broken formation， high stress formation， faults broken zone in the Qinghai-Tibet Plateau. In geological drilling， we often suffer problems such as hole collapse， slurry leakage， diameter reduction， stuck drill， buried drill， etc. At the same time， the mud cake formed by the mud is thin， the cementing ability is poor， and the rock carrying ability is weak. Therefore， flushing fluid is the key to achieve drilling smoothly in complex formation. Combining the geological characteristics of the complex formation of the Qinghai-Tibet Plateau， developed a new flushing fluid for low solid phase polymers. The flushing fluid based on sodium bentonite and additives such as micro foaming agent， etc. It has the characteristics of good fluidity， strong cementation， and moderate water loss， suitable for use in geological drilling of complex formation in the Qinghai-Tibet Plateau.

Abstract:In this paper， based on the geological model of the first offshore natural gas hydrate production test of China， the production of nature gas hydrate reservoir after reservoir stimulation in the near wellbore area using depressurization was numerically studied through Tough+Hydrate. The influence mechanism of porous skeleton channel on gas/water transport， pressure drop propagation， hydrate decomposition was investigated， and the contribution of reservoir stimulation in the near wellbore area in different layers and in whole production process to productivity improvement was evaluated. The following simulated results were obtained. First， the gas/water velocity in the porous skeleton channel is high， which is helpful to diversion and sand control. Second， reservoir stimulation in the near wellbore area can promote the pressure drop propagation， and increase the decomposition rate of hydrate. However， the favorable effect of porous skeleton channel gradually decreases with the development of production. Third， the stimulation effect of reservoir stimulation in the near wellbore area in different layers is different， the result of three-phase layer is the most obvious. In this simulation， due to the small reservoir stimulation range and low permeability of the fracture， the increase in gas production is not obvious， the maximum increase was only 11.7 percent in two years when the height of porous skeleton channel is 50cm.

Abstract:With maintaining gas hydrate stability in the pressure coring tool as research purposes， and in view of the problems with the existing large diameter pressure coring system， such as small core diameter at large drilling diameter， complex drilling tool structure， heavy weight， which makes it not applicable to the actual working condition of the underwater drilling rig， the pressure coring tool was redesigned structurally and indoor pressure tests were carried out. The results showed that the small diameter thin wall pressure-coring tool is reasonable in size and compact in structure， which can meet the requirements of the underwater drilling rig. Laboratory tests showed that when the pressure was maintained below 10MPa， the pressure decreased by 15% within 6 hours； when the pressure was maintained between 10MPa and 30MPa， the pressure dropped by 10% within 6 hours， and the pressure-coring tool can meet the design and service requirements when used within the above pressure ranges.

Abstract:Reservoir with low porosity and permeability accounts for 93% of all reserves of the E Sea； thus， enhancing the recovery of low and ultra-low per permeability gas fields has become an importance subject in the exploration and development of oil and gas fields. Horizontal branch well technology， which has been deployed and proven to be fruitful in enhancing gas field recovery at home and abroad， plays a significant role in increasing the recovery of low and ultra-low per permeability gas fields. Horizontal branch well technology， a fusion of multiple drilling technology including horizontal well and side-tracking， is a hot technology in oil development industry. It has been implemented in several fields in the E Sea， and proven to be an effective means to develop low permeability gas fields. As a result， it is of much importance to conduct in-depth study and summarization of the technology. This paper has analyzed the technology in depth and summarized its key application points in the E Sea X field， which can assist in further promotion and application of this technology in low permeability oil and gas fields in the E Sea.

Abstract:In order to understand the environmental pollution of groundwater around the landfill site， the soil， groundwater and downstream reservoir water quality around the solid waste disposal site in Changsha City were taken as the research objects. The single factor pollution index method and Nemerow pollution comprehensive index method were used to analyze the heavy metal content characteristics and risk assessment of the surrounding environment of the landfill site. The results showed that as， Cr（Ⅵ）， Ni， Pb， Zn and Cu were the main pollutants in the surrounding environment of the landfill site. The average content of heavy metals in the regional sampling points and the downstream reservoirs was lower than that in the groundwater quality standard class Ⅲ， and the pollution status of the landfill site was good. The content of Cr （Ⅵ） in ZK1 and R1 samples was higher than that in the groundwater quality standard class Ⅲ， which was the main risk pollutant of groundwater around the landfill site in ZK1~ZK4， Pb and Cr（Ⅵ） are the main heavy metal elements in the soil， which are moderately polluted and should be paid attention to.

Abstract:The percussive drilling of large diameter rock socketed inclined piles is very complicated. During the drilling process， common percussion bits have some shortages such as low hole forming efficiency， fast wear， short service life， and poor hole forming quality etc.， while the type of impact teeth on bits’ bottom， as well as its arrangement are key factors to solve the aforementioned problems. Based on this， the impact process of three kinds of impact teeth， i.e. triangular prism teeth， wedge teeth and double conical teeth were analyzed under different impact strokes and varied tensile strengths of sandstone. Results show that wedge-shaped teeth can be selected preferentially to drill soft formation， while triangular prism teeth should be selected if short impact strokes have to be used to drill relatively harder formations. The results in this study is meaningful to the teeth selection of impact bits in large diameter rock-socketed inclined piles construction by percussion drilling.