Abstract:The study of application of portable fully hydraulic drill is carried out in the exploration of Maoniuping rare earth mining area， and the performance and advantages under complex geological conditions are explored. The modular design improved the environmental adaptability of the drill. Advanced drilling technologies such as thin wall series drill rods and low solid flushing fluids are adopted to form a set of drilling technical parameters suitable for the fractured strata in the mining area， and the drilling efficiency and core recovery rate are successfully improved. Based on the engineering practice， the construction situation and application effect of portable drill have been discussed， and the existing problems and the countermeasures are summarized and proposed. The research shown that portable fully hydraulic drill have demonstrated significant applicability in drilling complex strata of rare earth minerals， which provides important references for the exploration and construction for this type of mineral.

Abstract:In view of the coring problem for the China-led IODP349、367、368/368X voyage， through analyzing the coring data， the coring tools and factors affecting the core recovery， core quality and cored efficiency in sedimentary rock and hard rock are researched， the causes and degree of the influence factors such as lithology， technical tools and external environment etc. which affect the ocean drilling coring are classified and summarized. The corresponding improvement measures are put forward.

Abstract:The exploration and drilling of the Nalinggou uranium deposit in the Ordos Basin has some technical problems， such as low heart rate of loose sandstone core， slow drilling efficiency of core-gravel layer， low drilling efficiency of mudstone formation and easy deviation of drilling hole. The project team adopts various technical measures， such as various core mining methods， mud maintenance， optimized use of drill bit and reasonable drilling tool grading. Good results have been achieved in the aspects of keeping straight and preventing deviation， improving the adoption rate， and improving the drilling efficiency of gravel and mudstone， which better solves the above difficulties encountered in the construction， improves the drilling efficiency and drilling quality， and accumulates more valuable experience in sandstone drilling construction， which provides construction experience for the future drilling construction of sandstone type uranium ore in the north of the Ordos Basin.

Abstract:In order to solve the problem of insufficient core recovery in broken formation in Yongshun， Hunan Province， this paper investigates the geological structure characteristics of the exploration area with respect to Well Yongye-2， and analyzes the stratum characteristics based on the core samples from different strata. On the premise of strictly following the drilling design and quality requirements， different drilling fluids were adopted for each section to eliminate collapse and leakage. To deal with insufficient core recovery in broken formations， we developed and used a bladder multi-section bundled wireline core drilling tool. The unique bladder structure， equipped with a leading side jet drill bit， can protect the core from erosion by drilling fluid. Field results showed that when drilling deeper well sections with the well depth from 1055.76m to 1108.96m， core recovery increased to more than 90% from the existing lowest 79%， and the cores were well protected. The author believes that the above method can effectively solve the problem of insufficient core recovery in broken formations， and can provide guarantee and reference for follow-up work and similar projects.

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:To effectively solve the southern Songliao Basin oil and gas reservoir core bit selection difficulties， low rate of penetration and unstable core recovery， the core barrel and the core lifter were compared and matched， the core bit type was selected and the case-dependent core bit was investigated through the analysis of the geological characteristics of the coring interval， the XRD element component proportion， and the formation drillability. The coring assembly and coring parameters were optimized， and the coring process for different reservoirs was improved. The selected coring tool and the new coring bit were used in multiple wells with the average core recovery more than 98.98%， and the highest mechanical drilling speed up to 6.03m/h. The application of the optimized series of coring bits and the complete key technologies has solved the technical difficulties in coring in the southern Songliao Basin reservoir， which can provide reliable reference and technical support for subsequent coring.

Abstract:The artificially filled coral islands and reefs have a special stratigraphic structure， mainly of coral sand and coral debris， which makes it difficult to core and form holes. Taking the geological drilling and coring project on an island and reef in the South China Sea as an example， a series of corresponding technical measures were adopted according to the lithological characteristics of the formation： casing while drilling and dry core drilling for the upper loose or weakly cemented sand and gravel； a sand-bailing tool designed for complete circulation loss formation to ensure a clean borehole in reef limestone； drill bits with advance side nozzles for the soft and hard alternate beds； small-diameter dry core drilling for the silt-sand layer. The technology has achieved good results in drilling of 18 boreholes， which can provide a reference for subsequent coring in coral reef formations.

Abstract:Experts and scholars at home and abroad have conducted lots of research on coring in broken formation for many decades, leading to notable resultsin terms of decreasing core entry resistance, increasing core recovery, extending footage per run, increasing ROP, etc. However, less research has been made on solutions to core jamming incidents. To some extent the jam-releasing coring tools represented by JamBuster alleviated the core plugging problem, and extended the footage per round by adding liners, but the problem of core jamming hasn’t been fundamentally solved. This paper summarizes the research state of the special coring tools and technologies for broken formations in the past, analyses their shortcomings, and puts forward some suggestions for improvement.

Abstract:The requirement on the quality control in the technical specifications is very strict for drilling of the solution mining intersected well sets at Kazan Trona Mine. The vertical wells were easily deviated, with low core recovery and poor cement bonding due to the complex geology, the high dip angle of the formation, and presence of several aquifers; meanwhile, for the horizontal well, it was very difficult to control the trajectory. After a thorough analysis of data obtained from previously drilled wells and a study of related issues and optimization of solutions, several measurements were put forward and applied. The results showed that all the drilling problems were effectively solved, the drilling process was improved, and the construction period was reduced. The experience acquired from the project could be used as reference for the similar works.

Abstract:In order to cope with the difficulty in maintaining the borehole verticality and core recovery due to great alternation of strata, liquefaction of soft strata and sand, poor cementation and loose structure of sand encountered in drilling of the standard 200m geo-technical investigation boreholes in the Xiongan New Area, comprehensive measures such as proper configuration of the drilling string, optimization of drilling parameters have been adopted to prevent drilling deviation. At the same time, effective technical measures such as dry core drilling in loose strata, isolation in core barrels, diversion of the mud pump discharge for core ejection have been adopted to ensure the drilling quality, leading to very obvious technical results.