Abstract:Ice drilling technologies for the polar regions are the crucial means of obtaining the ice core to investigate the interaction of the polar ice sheet, ice shelf, and ocean; and obtaining subglacial bedrock core and water sample to explore the subglacial environment. At present, the difficulties and frontiers of polar ice drilling technology mainly include deep ice core drilling, ice shelf hot water drilling, subglacial bedrock drilling and subglacial environment sampling, observation technology. In view of the above four key technologies of polar ice drilling, this paper summarizes and sorts out the research progress and project development of related technologies in China and abroad. In general, the research on polar drilling technology started late in China, but the research on the key technologies and equipment of polar ice drilling in China is moving towards surpassing the polar drilling powers in the world, as China’s polar strategy continues to advance. And it will certainly provide a strong technical support for China’s polar scientific research.

Abstract:Natural gas hydrate(NGH) sedimentary bodies are shallow, soft and unconsolidated, where the mud window is narrow. It is time-consuming and expensive to drilling NGH with conventional riser drilling; meanwhile, NGH dissociation leads to changes in NGH saturation and wellbore pore pressure, causing the mud window to narrow down and the borehole be instability. This paper introduces the principle of deep water riserless mud recovery drilling (RMR) and analyzes its adaptability in marine NGH drilling. The results indicate that RMR can solve the problem of the narrow mud window. The real-time monitoring system can improve the maneuverability and completely eradicate the hydrothion leakage. It simplifies the wellbore configuration and reduces the well construction cost. It is safe and environment friendly without any discharge into the ocean.

Abstract:Continued growth in energy demand, prevention and control of environmental pollution, and response to climate change require accelerated energy structure adjustment. Marine geological surveys are urgently required to provide new target areas for oil and gas exploration and development, which provide basic support for the commercial exploration and development of natural gas hydrates. China’s independently designed and built Marine Geology-10 Ship fills the gaps in our country’s small tonnage and large deep marine geological drilling ships, which enhances our marine geological survey capabilities, and marks China’s comprehensive marine geological survey capabilities are among the best in the world and provides valuable experience for the future ocean drilling. The drilling system of Marine Geology-10 Ship uses different coring tools for different strata, and successfully completed drilling A and B holes for coring work in a South China Sea region. In view of the risks of marine drilling operations, the countermeasures formulated by Marine Geology-10 Ship have ensured the normal drilling operations. Practice has proved that the drilling system of Marine Geology〖KG-*8〗-〖KG-*8〗〖KG*9〗10 Ship successfully completed the coring work of marine geological drilling.

Abstract:In the post-petroleum era, natural gas hydrate has become the best energy source for exploitation. It has the characteristics of abundant reserves, cleanliness and high efficiency. Countries all over the world attach great importance to the investigation and exploitation of natural gas hydrate resources. In 2017, China successfully implemented the vertical well production test of marine natural gas hydrate, and achieved fruitful results. The hydraulic jet micro-wellbore technology is a new drilling technology that has been developed and applied in oil drilling; and its application to marine natural gas hydrate drilling has the advantages of low drilling cost, smooth drilling of the horizontal section, less difficulty in control of the well trajectory, small reservoir pollution, and reduced risk of large-scale seabed collapse. But there are still some key technical issues remained for solution, such as the length of the horizontal section, the stability of the borehole, the handling of stuck drills, the development of drilling tools, the short life of coiled tubing.

Abstract:Sidetracking from low performance wells in Bohai Oilfield is one of the important means to stabilize and increase production. Optimizing the sidetracking plan to achieve cost reduction and efficiency enhancement is the research focus of the refined sidetracking well design. This paper systematically introduces the sidetracking well design method. The sidetracking section is optimized through properly matching of the low-performance well location and the sidetracking well location; for the shallow sidetracking plan, several technical solutions are presented, including riser reentry, open hole sidetracking from under the riser shoe, sidetracking from surface casing by window-milling, as well as the applicable conditions and difficulties in open hole sidetracking from under the surface casing shoe; for the deep sidetracking plan, the optimal flow chart for sidetracking from the milled window on production casing and sidetracking from under production casing shoes is proposed. Taking two low-performance wells A and B in Bohai as an example, optimization of the drilling slots, the sidetracking well sections was performed. With interchange of the sidetracking target locations of the two wells, the drilling amount was reduced by 1428m. The field application results show that the sidetracking plan for the two low-performance wells are rational and can achieve the purpose of cost reduction and efficiency enhancement. The optimal method of low-performance well sidetracking proposed in this paper can provide some guidance for the sidetracking design for low-performance wells in Bohai Oilfield.

Abstract:Corrosion of the aluminum alloy drill pipe in the drilling fluid can affect the drilling performance and even cause serious downhole incidents. In order to improve the corrosion resistance of the aluminum alloy drill pipe, the organic corrosion inhibitor (C18H29NaO3S or SDBS) or rare earth corrosion inhibitor (La2(SO4)3) was added at some ratio to the polysulfonate drilling fluid at 10 pH and 70℃, and its effect on the 7075 aluminum alloy drill pipe corrosion was investigated through the mechanical test. The results show that both corrosion inhibitors can reduce aluminum alloy corrosion in alkaline drilling fluids, and improve the tensile strength of aluminum alloy drill pipe by up to 6.73%. The second phase particles of Cu, Mg, Si and other elements in the alloy are the corrosion-sensitive areas. Corrosion pits are formed where the second phase particles have fell off. The corrosion products mainly consist of Al, C, O and other elements.

Abstract:Under the action of primary structural fractures and drilling induced fractures, well leakage is prominent in the Hangjinqi block, and conventional static plugging or bridge plugging is not effective. Based on the principle of “fiber bridging, filling up and standstill, cementing and curing”, a leak plugging slurry was developed through optimization of fibers and their length make-up ratio, sizing of floating beads and micro-silicon, and cement, and conditioning of expansion, thickening and toughness of the solidified solids. The plugging design method and process control measures were adopted to form a leak plugging technology suitable for fracture type leakage in Hangjinqi block. It has been used in 162 wells in the field and the success rate of one-time plugging is 93.7%, which can significantly improve drilling efficiency. It can also provide some reference for fracture type lost circulation in other areas.

Abstract:Because of geological structure development, large dip angle formation, and inter-bedded soft and hard formation at Hongliu Coalmine of Shenhua Ningxia Coal Industry Group, freezing wells were easy to deviate, and gyro and mud motors were needed to make correction drilling for a few times, delaying the project progress. To solve these problems, compound drilling was performed with combination of the PDC or cone bit and the 1° single bent motor, achieving good results in anti-deflection, and improving ROP. It may provide some reference for other similar projects.

Abstract:In the Shunbei block drilling work, there are many wells with complicate circulation loss in the Permian formation, such as large amount of leakage, second or multiple leakage. In some worse cases, it leads to collapse of the borehole and bit sticking, causing frequent down hole difficulties, bringing losses to the drilling project, and inhibiting the speed of exploration and development of the block. The down hole complex conditions exhibit mainly in the manner of leakage due to development of Permian igneous rock and strata fracture. In order to solve this problem, analysis of the complex Permian well leakage in the Shunbei area was carried out, and the Permian drilling difficulty in the area was analyzed in the light of the actual drilling situation in the Shunbei block and the characteristics of the Permian strata. This paper summarizes the concrete plugging-while-drilling measures and plugging schemes for leakage at different rates. Field results have proven that this comprehensive leak plugging strategy can effectively reduce complex leakage and improve the leak plugging efficiency.

Abstract:Using the conventional wire-line drilling tool in complex formation always leads to low core recovery. There are two main causes: firstly, because of poor waterproofness of the conventional wire-line drilling tool, the core is eroded by flushing fluid before entering the core barrel during drilling in loose soft formation; secondly, it has poor performance in preventing core loss in hard, brittle, broken formation since the core lifter cannot lock tightly the core, even though the core can enter into core barrel, leading to core falling off. A wire-line drilling tool is designed to solve these two problems for complex formation, and also exploit the advantages of wire-line drilling at best.

Abstract:The auxiliary back pulling device is a very important one among the optional auxiliary devices on the trenchless drilling rig, which directly determines the success of the trenchless project sometimes. Based on the analysis of the current mainstream motor-assisted device, a hydro-cylinder assisted device was designed. A two-degree-of-freedom mechanism is used to allow the tooth-shaped part automatically to engage the rack of the drill mast first and then the cylinder to provide assistance. Automatic switching can be realized remotely; thus reducing labor and costs.

Abstract:Aiming at the problem of low impact toughness of the impregnated diamond bit matrix, a method of adding stainless steel fiber net to the carcass to improve the impact toughness of the matrix is proposed. The impact toughness of matrix was tested at different combinations of the three variables: the placement, mesh and number of layers of the fiber net. It was obtained through experiments: (1)stainless steel fiber mesh can effectively improve the impact toughness of the matrix, and the X-axis placement position is better; (2)when the mesh number of the fiber web is the same, the impact toughness of the matrix decreases as the number of fiber mesh layers increases; (3)in the case of the same number of fiber net layers, the impact toughness of the matrix increases first and then decreases with the increase of the number of fiber net layers. With a single layer of 30 mesh net added, the impact toughness of the carcass reaches a maximum. Through the electron microscopy of the impact fracture and the mechanical analysis of the fiber net, the reasons for this law are explained, and the method of further optimizing the impact toughness of the matrix is proposed.

Abstract:Taking the deep foundation pit support project of Wuhan Renheng Park Century as the research background, design calculation and analysis is conducted with Tianhan Design Software on some support section of the project, where the foundation pit was supported by unequal double-row piles, that is, the front row piles were longer and the rear row piles were shorter. The results of calculation and analysis shows that the maximum displacement of the front row and rear row piles of the support section is 37.9mm, that occurs at 1.0m below the ground (at the top of the pile), and the elastic resistance safety factor in the passive zone is 3.90. The early warning control index for the foundation pit of this project is the horizontal displacement of the supporting structure not greater than 40mm, which can meet the design monitoring requirements and provide reference for the future application of unequal length double-row piles in the foundation pit.

Abstract:Bored piles of 600 and 1000mm diameter are designed for the Yantai Port Wanhua Industrial Park wharf upgrading project. The upper part is a thick layer of offshore backfilled stones, which is difficult to drill, prone to collapse, and difficult to form a hole. A large rotary drilling rig was used to drill the hole with the sim-casing process, where two layers of casing (inner and outer) were used to protective the wall. After drilling through the backfill layer and the mixed sand layer, the rotary drilling rig continued drilling with mud for wall protection, but the protection casing was no longer followed. In such a way, not only can the quality of the hole formation be ensured, but also the construction cost reduced. The outer casing can be pulled out after the completion of concreting and be re-used to reduce the project cost.

Abstract:Shield intervention is an inevitable process in shield tunnel construction. In reference with the practical experience on shield intervention in the tunnel between Zongbujidi Station and Feilong Road Station of Nanning Subway Line 4, this paper introduces the successful application of auxiliary intervention technology in shield tunneling at atmospheric pressure with the plain pile and dewatering in the Nanning subway. Based on the introduction of the engineering application background, the technical points for plain pile construction and dewatering in the auxiliary intervention method are described in detail, which can provide guidance for the selection of the intervention plan in shield tunneling in the Nanning area, and also provide reference for the selection of the intervention plan in shield tunneling under similar conditions.