Abstract:Based on the theoretical study and field practices in magnetic ranging in well drilling， a model has been constructed for determination of the relative distance and direction between the downhole drill bit and target with the distance correction method and the Kalman filtering method for weak magnetic signals proposed； thus solving the problem with long distance and high precision magnetic ranging in CBM horizontal well drilling in the complex operation environment. The field test and application results showed that the calculation method for distance correction can obtain the value well approximate to the one measured in the interference-free environment； thus eliminating effectively the measurement error caused by downhole magnetic moment. The noise and clutter had a significant influence on the value of single measurement； however， through Kalman filtering， the measurement value was more accurate than the one from single positioning calculation with the measurement error reduced from 1.9m to 0.14m at the distance of 40.06m. In magnetic ranging for the “U” type CBM horizontal well intersection， the effective target can be controlled within 177.8mm of the vertical extraction well.

Abstract:Solution mining with intersected wells by horizontal drilling technology has always been the most commonly used and economic and effective means for mining salt resources. However， the salt mining well set is prone to the channel blockage in the process of brine extraction due to the complex formation conditions， saturated brine crystallization， casing damage and other factors，which restricts the service life of the horizontally connected salt well set. In recent years， the commonly used methods for the repair and treatment of blocked well sets are pressurizing， scraping， and window milling. Among them， window milling from horizontal wells is widely used for workover in many salt field blocks. During workover of Well Set Y2-Y4 at Shiyantian， Ningjin， Hebei province， it was found the existing mining cavern can not be reused， and was an obstacle for the second-time intersection of the well set. It was the first time that the two wells were switched in type （changing horizontal well into vertical well and vertical well into horizontal well） to by-pass the existing cavern to realize the reuse of the old well set in this block.

Abstract:At present， sustained casing pressure （SCP） occurs frequently in the development of high temperature and high pressure gas wells， indicating that leakage happens along the well， and the well integrity is damaged. The basic cause for sustained casing pressure is failure of the well barrier， which leads to abnormal annular pressure in gas wells and hence threatens safe production of gas wells. It makes sense to analyze the annular pressure build up test data to evaluate the leakage rate of cement sheaths and control the risk of SCP. Five SCP modes were analyzed， with the mathematic model established for gas infiltration flow in the two cases where both cement returns and doesn’t returns to surface. The cement integrity was evaluated using the annulus pressure diagnosis test data， which could not only predict the trend of the annulus pressure， but also obtain the equivalent leakage rate of the cement sheaths. The results of this paper can be used to conduct the cementing design and provide references for management and control of sustained casing pressure.

Abstract:Coral islands and reefs in the South China Sea have great resource potential and scientific research value. From 2013 to 2017， 115 Geological Team， Bureau of Geology and Mineral Exploration and Development of Guizhou Province， under auspices of the Chinese Academy of Sciences， drilled hundreds of boreholes for scientific research on various islands and reefs in the South China Sea. With properly tackling of the special difficulties in the secluded environment far away from the mainland during drilling， many important technical difficulties have been solved， including “Pumping test and well completion screen pipe placement for loose coral sand formation at coral island reef ”， “Quaternary overburden core drilling at island reef”， “Lagoon sand core drilling at coral island reef”， “Prevention and treatment of drilling accidents at coral island reef”； and a complete proven drilling technology system suitable for island and reef exploration has been formed. The geological brigade is the pioneer in the practice and theoretical research of island reef drilling engineering in China. The drilling technology system can guarantee the safety and quality of island and reef drilling projects， and has important guiding significance for the future exploration of island and reef in China.

Abstract:Natural gas hydrate is an important strategic exploitation resource in the future， which has been widely concerned by all countries in the world. Therefore， large-scale exploitation of subsea natural gas hydrate is inevitable. At present， the exploitation of subsea natural gas hydrate is still in the trial production stage， and so far no mature mining method has been formed. Starting from the problems caused by non-diagenetic that people are worried about during the exploitation of marine natural gas hydrate， such as large-scale gasification of subsea hydrate， destruction of marine ecological environment and submarine geological disasters， this paper analyzes the safety of the exploitation of marine natural gas hydrate， investigates the present situation of the exploitation of marine natural gas hydrate in the world， points out that reservoir stimulation is the only way for large-scale exploitation of marine natural gas hydrate in the future， and explores the feasibility of reservoir stimulation with modifying foamed cement slurry by hydraulic jet while drilling horizontal wells with hydraulic jet micro hole technology， which lays a foundation for the commercial exploitation of gas hydrate in China.

Abstract:In order to study optimization and application of testing technology for high-production and high-waxy well offshore， the causes of the problems with the test of the high-production and high-waxy reservoir in the West Lake were analyzed and the technology at home and abroad was investigated in light of the problems with a well test in the West Lake Sag， East China Sea. At the same time， the research on the fluidity support technology for the test string and the surface test process， and the research on the crude oil combustion guarantee technology were carried out. The results showed that the main causes that affect the test were the wax formation in the surface flow， large particles of backflow debris from the large choke and the damage of the combustion head due to burning of large volume of crude oil. The test string， the surface test flow and the combustion support technology were optimized so as to solve the problems related to high-production and high-waxy well tests.

Abstract:Improving the sealing ability of drilling fluids is the primary technical way to effectively solve the borehole instability in hard and brittle shale and coal. With the filtration loss for 30 minutes under specific temperature and pressure as the evaluation standard， the plugging characteristics of several plugging materials are experimentally studied. The results showed that the sealing effect of the materials increased with the addition amount except for ultra-fine calcium carbonate. The plugging effect of emulsified asphalt， emulsified paraffin， and oil-soluble phenolic resin deteriorated with increase of temperature， while the plugging effect of polythene glycol and polyester first deteriorated and then had a certain degree of recovery. Polyester and ultra-fine calcium carbonate can quickly plug micro-cracks. These plugging materials had a significant impact on the rheological properties of drilling fluids. Analysis of the plugging mechanism of each plugging material shows that different plugging materials have different plugging characteristics and are suitable for different temperature and pressure conditions. The plugging capacity of the water-based drilling fluid can be effectively improved only if the plugging material is selected depending on specific downhole conditions.

Abstract:The Luobusa Chromite Mine in Tibet is characterized by high altitude， thick overburden， complex geological conditions， broken rock strata， developed fractures， local water dissolution， water erosion and water sensitivity， leading to some drilling problems such as formation leakage and borehole shrinkage. This paper summarizes the drilling experiences from 28 medium and deep boreholes in this area in respect of drilling structure， drilling technology， drilling fluid， wall protection and plugging technology， technical measures taken in complex situations， etc. Good results have been achieved with all index meeting the design requirements. The core recovery rate is more than 90%， the rig-month efficiency is 555m， and all quality indicators meet the design requirements.

Abstract:In view of low success rate and slow speed in RIH of over-long casing in underground directional boreholes in coal mines， technical improvement measures are put forward， such as straight-maintaining drilling in the early section， control of curvature in the deflecting section， lowering of the kelly bar with drill rig， centralization of casing. Field test was carried out in Xinjing Coal Mine of Yangquan， where over-long casing was run in three directional boreholes for underground hydraulic fracturing with the maximum depth up to 168m. The success rate of casing running reached 100%， and the average casing running efficiency increased from 5.5m/h to 13.1m/h， eliminating effectively the limitation of over-long casing running in underground directional boreholes in coal mines.

Abstract:During drilling operations， circulation of drilling fluid has to be stopped in make-up and break-up of drill rods， which will cause the cuttings to settle downhole and the equivalent circulation density （ECD） of the drilling fluid to fluctuate； thus affecting the borehole safety. In order to avoid the above situation， the concept of uninterrupted drilling fluid circulation drilling technology is proposed. Drilling fluid is diverted through a continuous circulation system （CCS） or continuous circulation joint （CCJ）， by-passing the section of the drill pipes being worked to maintain mud circulation in the well， and stabilizing the equivalent circulation density （ECD） of drilling fluid. According to the technical principle， an automatic drilling fluid uninterrupted circulation wellhead is proposed. Through the cooperation of back-up tongs， the automatic drilling fluid switching system and torque-transfer power slips， uninterrupted circulation of drilling fluid can be realized during the disassembly and assembly of single drill rods in drilling to avoid effectively the drilling safety problems caused by drilling fluid standstill and excessive settlement of cuttings .

Abstract:In the process of deep water exploration and sampling， the swing or up and down movement of the drill pipe will be caused by the action of ocean current， which is one of the reasons leading to the distortion of obtained samples. The subsea frame is one of the key equipment to improve exploration and sampling offshore through clamping the drill pipe stably in exploration operations to ensure the samples quality. According to the size of the HYSY708 drilling ship and the requirement of exploration operation， a cable-free subsea frame was developed. So far， it has been employed in survey and sampling in the South China Sea and the East China Sea for more than 30 months， providing great support for the marine geological survey in China. In this paper， the working parameters and the principle of the subsea frame， the underwater hydraulic system， and the communication and control system are introduced with focus on analysis of the development of the deep water battery. The battery can ensure the operation time of the subsea frame up to 70h； thus， improving the survey operation efficiency. The product provides a foundation for the future research and development of relevant offshore drilling equipment.

Abstract:The drilling mast equipped with the imported DMH90 blasting hole drill is featured of strong integrity， quick and convenient erection， proper drill mast height to allow completion of the hole in one trip without changing rods （e.g.， the effective height of the drilling mast is slightly greater than the borehole depth）， resistance to large vibration impact force， and adaptability to adverse construction environment. Owing to these characteristics and difficulties， the blasthole drilling mast has been relied on imports since long before， leading to higher drilling cost and longer drilling duration； therefore， research on the substitute for the imported drill mast for the imported DMH90 blasting hole drill was carried out. This paper introduces the development of ZT27-45 blasting hole drill mast for DMH90 blasting hole drill， mainly covering the design points， mast material selection， welding technology， deformation prevention， stress relief and quality inspection. Field practice shows that the manufacturing quality of ZT27-45 drill mast meets the design requirements， and satisfies the needs of blasting hole drilling； thus， it realizes the substitution of import， reduces the cost， shortens the construction period and improves the mechanical properties.

Abstract:Mining water discharge and groundwater protection is at issue due to the limited water storage space in the goaf collapse zone due to the relatively soft overlying rock with high contents of clay in the south mining area of Mindong No.1 Mine. With analysis of the groundwater leakage causes， it was concluded that the overlying rock fractures produced by coal mining was the main source of groundwater leakage； meanwhile， the water channeling cracks in the overlying rock can be effectively blocked with artificial grouting via boreholes to block the groundwater discharge channel and curtain grouting reinforcement technology to seal off water channeling cracks in the roadway. Field application has proven that curtain grouting with in-hole screen pipes in the soft surrounding rock of the roadway to fully fill and reinforce the cracks in the soft surrounding rock is an important way to achieve “zero discharge” and groundwater protection of mining water in the mine through proper selection of the location of the grouting holes， spacing， grouting material and slurry ratio， borehole structure and drilling parameters according to the engineering geological conditions of the mining area.

Abstract:In view of the defects with the conventional casing running process with the cement buoyancy plug for coal mine large diameter wells， such as multiple steps， drilling fluid pollution， high amount of concrete settlement and residuals， research was carried out on the casing running process with the steel buoyancy plug in the case of a large diameter gas extraction well at a coal mine in Huozhou . This paper introduces the process principle， calculation of critical casing strength at elastic buckling deformation and material yield failure， the structure and assembly design and strength calibration for the steel buoyancy plug. This process was used to run gas extraction casing of 150t at ?836 mm diameter， and the field use has proven that this technique can reduce tripping of the drilling string during casing running operation， shorten the operation time， and eliminate concrete residue in casing； in addition， the process is feature of simple manufacture and convenient operation. It can provide experience and reference for future similar projects.

Abstract:The deep and large foundation pit project of an international financial building in Shanghai is adjacent to the operating rail line interval with the shortest distance of only 7.87m on the north side， and the clearance of 2.0 to 3.0m from the pipe ditch of World Expo on the south side. Because of the high sensitivity of the surrounding environment， the deformation control of the foundation pit is quite demanding； meanwhile， the project is located on the bank of the Huangpu River. The shallow layer at the site is a typical silty soft soil layer， while the lower part is a soil layer rich in confined ground water. Moreover， the micro-confined aquifer is connected to the first and second confined aquifers， and the sealing curtain cannot cut off the confined aquifers. All these factors constitute complex geological conditions. Considering the situation， the project adopted various technical measures. The final measurement results showed that the maximum deformation of the tunnel is 6.52mm， and the maximum deformation of the pipe ditch is 15.3mm， which meet the deformation control requirements， ensuring the safe operation of the tunnel and the pipe ditch.

Abstract:In order to solve the problems of high-frequency and high-amplitude vibration and easy deviation of drilling holes with rotary drilling at increased WOB under special working conditions， such as brittle rock， soft and hard alternate formation， this paper analyzes the rock crushing mechanism of rotary drilling rig to find out the causes of the drilling problems at increased WOB. Study was conducted on the drilling process at increased WOB with the implementation plan and applicable scope put forward. Field application of the process was performed to verify its feasibility， and the results showed that rotary drilling at reduced WOB was of great significance to reduce drilling vibration， improve the structural stability of equipment and ensure the borehole quality.

Abstract:Part of the foundation pit of the Zone A2 commercial and residential buildings of Taiyuan Wanda Plaza is composed of coarse sand and gravel stratum， where the deep mixing piles cannot be used effectively for the water cut-off curtain of the foundation pit； therefor， high pressure jet grouting piles were put forward for the water cut-off curtain in coarse sand and gravel stratum. With the jet grout technology， the double casing anchor drill pre-bored the grout hole with the single pipe high pressure jet grout process for grouting to complete the project successfully. Inspection indicated that the jet grouting elements interlocked well with each other with even cement content across the effective pile diameter and free of blocky inclusions； thus， providing good sealing effect.

Abstract:Karst geology has negative impact on subway tunnel construction， and may bring potential safety hazards and increase construction difficulty. Based on the exploration data of the Nanjing to Jurong intercity rail project， the karst caves in the interval are classified， the karst treatment experience of similar strong karst formations are summarized， and the relevant treatment principles are proposed. The three-dimensional finite element simulation is used to determine the karst treatment range with the corresponding treatment measures proposed. Sleeve valve tube grouting was used to treat caves within 3m of the outer contour of the tunnel with the deployment of the grout holes reaching the cave boundary as the criteria. The dual-fluid slurry of cement-water glass was injected from the peripheral holes， while plain cement slurry was injected from the central holes use. The grouting pressure and the grouting amount were taken as the final injection index， and grouting effect was checked by using the drilling core method to meet the requirements on strength， compactness and permeability. The core samples were found to be complete and continuous after treatment， and the cement-soil mixture was dense， which verified the feasibility of the grouting design.