Abstract:Fuling shale gas field is the first national shale gas demonstration area for commercial development. Compared with North America, the surface conditions, geological conditions and shale gas reservoir characteristics are more complex, the reservoir buried deeper with low ROP, long drilling cycle and high cost. Therefore the research on optimal and fast drilling technology for horizontal wells in Fuling shale gas was carried out, with engineering design optimization for horizontal wells drilling, optimal and fast drilling, domestic low-cost oil base drilling fluid, well cementing technology for long horizontal section for the requirement of massive hydraulic fracturing, mountain features well factory drilling technology and green environmental protection drilling technology, a fast drilling technology system for shale gas horizontal wells. This system has been applied in 290 wells in Fuling shale gas field with completion of 256 wells. The average ROP increased by 182%, average drilling cycle shortened by 55% and average drilling cost decreased by 34% in each well. This provides a strong technical support for first phase production capacity of 5 billion m3 in Fuling field gas, and plays important leading role for the scale development of shale gas in China.

Abstract:To minimize the impact of shale gas drilling on environment to the lowest level, the key technologies for drilling is formed in Fuling shale gas field by technology program optimization and field practice exploration. This paper analyzes the impact of shale gas drilling on the environment in Fuling area starting with horizontal drilling characteristics and environmental features there. On this basis, “green” drilling technical system is constructed with core of oil-based drilling fluid recycling, harmless treatment of oil-based cuttings, converting oil to electricity, drilling design and construction technology optimization as well as “well factory” pattern drilling. This technology was popularized and applied in the first phase production of Fuling shale gas field, carban dioxide emission is reduced 209 thousand tons, well site area is reduced 30% with zero pollution and zerp emission.

Abstract:In view of the development of unconventional oil and gas reservoirs and safety drilling in complex formations, the research and application of oil-based drilling fluids are carried out to solve wall stability of horizontal well, friction, cuttings carrying and formation pollution. Oil-based drilling fluid formula with diesel and white oil as base oil, circulation loss control technique and on-site operation process were formed by the study and selection of emulsifier, organic bentonite, filtrate reducer, plugging agent and some other treatment agents, which met the construction requirements in the application in more than 100 wells in Fuling with favorable technical and economic effects. Combined with the specific conditions of Fuling block, intensive study was continued, field tests of powder emulsifier and non-bentonite oil-based drilling fluid were made in 2015.

Abstract:Fuling shale gas field is in high steep fold zone Baoluan-Jiaoshiba anticlinal zone Jiaoshiba texture in the southeast of Sichuan. Upper Ordovician Wufeng formation-the lower Silurian Longmaxi formation was mainly explored, the main lithology are limestone, mudstone and shale, it was prone to leak, slough and blowout in drilling construction. The well was designed to be three-section horizontal structure, water-based drilling fluid was used in the first and second sections. By the technical research, the water-based drilling fluid system is established; taking potassium chloride and polyamine inhibitor as main material, series of water-based drilling fluid technology is formed, which is suitable for Fuling shale gas field exploration and development in shallow gas control, borehole wall stability, friction drag reducing, leakage control and plugging.

Abstract:Shale beds of Fuling area contain abundant natural gas resources with good exploration prospect. The main target strata in this block is shale gas bed in upper Ordovician Wufeng formation-the lower part of lower Silurian Longmaxi formation. In the upper shale formation, borehole wall stability is poor and formation pressure bearing capacity is low with karst development as well as collapse and leakage; fluid distribution of marine sedimentary formation is complex, lithology changes in some formations with poor drillability and low ROP. Cluster wells were adopted, but the horizontal wellbore trajectory is complex with large displacement, it was difficult for large directional borehole rectified azimuth and back pressure was serious. New technologies and new tools were used in field experiment, such as rotary steering drilling technology, tortion impacter, rotary impaction motor and hydraulic oscillator, the penetration rate was greatly improved and the drilling cycle was shortened. In this paper, these new technologies and new tools are elaborated in the working principles and field application and the economic effects are evaluated.

Abstract:Based on the in-depth analysis on the factors that restrict the drilling rate in Fuling shale gas field, National Oilwell Varco put forward a scheme aiming at improving the drilling efficiency in this area. A large number of field practices based on this scheme have been carried out so far. This paper gave a full description of the assembly of NOV-made drilling tools of rotary impactor, hydraulic oscillator and POB（power-plus oil-based mud） downhome motor as well as the related technical principles. The performances and advantages of these tools in the application in Fuling block are elaborated comprehensively and some technical shortages are presented. The implementation effects show that the drilling rate improving scheme of NOV is practical and has important guiding significance for the selection of drilling technology in the late stage of the optimized and fast horizontal well drilling.

Abstract:Before the operation of shale gas production well, large-scale should be carried out, the production casing must be able to bear the construction pressure of ≥90MPa. In 2013, unsteady pressure happened in 2 wells of testing well group in Fuling working area, which resulted in the subsection fracturing technology being confined in long horizontal for reservoir reconstruction, this problem sometimes became the bottleneck that resticted Fuling shale gas drilling production and quality. Therefore, the technical measures of leakage proof and plugging were studied in production casing design, construction and treatment with some progress to meet the requirement of efficient shale gas development. This paper introduces the countermeasures and practice achievements in leakage proof and plugging of casing in the first phase of Fuling shale gas, whi

Abstract:Various types of lost circulation occured frequently in Fuling shale gas well drilling, which seriously impacted the engineering quality, especially the oil-based drilling fluid leakage happened in the third segment of long horizontal section and even in cementation stage, both cementation quality and late shale gas exploitation were affected. In view of the characteristics of absorption well, a series of borehole preparation techniques, high performance fiber, spacer fluid plugging, optimal outside pipe slurry column structure, wall stability under pressure for absorption well cementation were studied to improve plugging performance and cementation quality. With enlargement of the exploitation area, the geological conditions will be more complicated, the paper puts forward the further research direction and the suggestion.

Abstract:With the development of Fuling shale gas exploration and development, the complex accidents become more prominent during long horizontal well drilling process. In Longmaxi formation, fracture developed, lithology was complex with serious breaking; mud density window was narrow, so it was prone to collapse with overflow and leakage and the lost circulation of oil-based mud was serious in the horizontal wells section. In order to quickly and safely drill through the complex shale layer, MPD technique（managed pressure drilling）was applied in Fuling shale gas field. MPD technique was used in Jiaoye well 33-4HF, some leakage loss display layers with different pressure coefficients were drilled in the long horizontal section, the final depth was reached successfully, the leakage of oil-based mud and the adverse effects were greatly reduced; as a result, economic loss was also reduced with distinct application effects.

Abstract:As the first national shale gas demonstration area, Fuling shale gas productivity demonstration area was started in 2012. Through continuous technological research and innovation, a perfect domestic horizontal well drilling technology series has been formed. With blocks transfer in 2015, the geological conditions became more complex, new technical difficulties were encountered in directional construction. On the basis of the existing mature technologies, by the technology optimization and the application of advanced friction and torsion reducing tools, the construction difficulties in new blocks have been effectively solved, which promotes the construction of shale gas productivity zone.

Abstract:Jiaoye 60-5HF is a horizontal shale gas well in southeast wing of Jiaoshiba structure with designed depth of 5290m, inclination angle 69.30° , vertical depth of 3945.04m and closed displacement 2513.99m. Several adjustments were made to overcome high temperature, large friction drag, backing pressure and well trajectory intersection to ensure the horizontal section extension along the reservior during the construction; the drilling depth was 5235.00m. It was a horizontal well with the deepest vertical depth in Fuling work area with inclination angle 81.8°, vertical depth 3820.56m, horizontal displacement 2509.53m and horizontal section length 1775.00m.

Abstract:In order to improve the plugging success rate when drilling to faults, large cracks, caves which lead mud loss, a new type of swelling pipe plugging tool was developed. The tool can be sent directly to the leakage layer and the plugging material solidifies in the confined spaces, the formed plug with required volume and intensity through the channel in the well trajectory will solve the no-return loss problems. The paper introduces this plugging tool about its structure composition, material selection, manufacture technology and the using methods.

Abstract:Shale gas mainly deposits in marine, continental and transitional facies in mud shale with adsorption and free state, the different deposition process, time and type of the rocks show the anisotropic of physical and chemical properties of strata or rocks. The formations of shale gas drilling mainly include mudstone, sandstone, argillaceous sandstone, sandy mudstone and so on in different times and these rocks have strong sensitivity to water molecules in drilling fluid, therefore a lot of time was spent to deal with difficult tripping, large amount of sentiments, repeated breaking and pipe sticking during the drilling process, the pure drilling time was reduced. The basic reasons of these problems were the diameter shrinkage and oversize caused by rock expansion and wall collapse respectively. This paper describes the formation characteristics of Zhongmou shale gas block firstly, and then the research and analysis on the drilling problems of Mouye well No.1 are made in borehole diameter shrinkage and oversize, the principled suggestions are put forward for drilling fluid and drilling technology selection.

Abstract:Shale gas is an unconventional gas resource produced from hydrocarbon rich shale, the investigation and evaluation of resource reserves mainly rely on drilling technology. Shale has strong water sensitivity, collapse and spalling often happen, which cause wall instability of diameter shrinkage and oversize in shale gas exploration drilling construction. Based on the technical requirements of shale gas drilling, the selection, design and optimization are made in drilling equipments, wellbore structure, drilling parameters, drilling tool assembly, drilling fluid, deviation control and accident prevention. Yanjin well 1-2 is successfully completed with the final depth of 1554.06m and becomes the deepest well in Yunnan shale gas resource investigation construction. This paper summed up the experience and existing problems in the well construction.

Abstract:Friction drag reduction is one of the key technologies in long horizontal shift well drilling. By optimizing the parameters of well track, a well track with low frictional coefficient is obtained. By the establishment of friction/torque analysis model, the influence of viscous force of drilling fluid and buckling of drill string on frictional drag was analyzed and friction/torque calculating formula was derived and a method to predict drag/torque was also presented. By using low friction coefficient oil-based drilling fluid, the friction coefficient was decreased by 65.2%. With casing floating technology, friction in casing running was significantly reduced. The above technologies were applied in well—YYP3, the friction in drilling process was accurately predicted to solve backing pressure in long horizontal shift well drilling and realize casing running in place in one time. The application in well-YYP3 show that these above technologies can be widely used in long horizontal shift well and can provide reference in long horizontal shift well drilling in other parts of China.

Abstract:The final hole depth of ChangYe parameter well-1 is 3204.72m with complex formation and long coring section. The drilling construction is elaborated in well structure, drilling tools assembly, drilling equipment, bit drilling parameters and drilling fluid. This paper mainly introduces the methods of ensuring the high coring rate and the application of potassium chloride mud system and composite drilling technologies in shale gas drilling.

Abstract:Shale gas is an invaluable clean and efficient new energy in the 21 century; the requirements on its exploration drilling construction technology have certain changes than they were before. The final hole diameter is large because of the larger core diameter, and the equipment driving power should be one or two levels higher than that for those geological survey holes of the same depth. Besides, flushing fluid is needed in gas logging as a medium, so there are limitations of affecting gas logging for flushing fluid; and measures to prevent poisonous & harmful gases and fire accident are also required for safety management. Timely adjustment of drilling parameters is one of the effective measures to ensure the core recovery rate in soft and broken formations. Good installation quality, good drilling tool conditions and complying with operation norm of wire-line core drilling are very important to ensure the quality of drilling construction.

Abstract:Shale gas exploration development and utilization are of importance for optimizing China's energy structure, promoting the rapid development of energy industry, improving self-sufficiency ability and level of the clean energy quality as well as reducing air pollution. By optimizing the casing program for shale gas drilling in broken formation, drilling efficiency will be greatly improved with lower drilling cost and shorter exploration cycle, so as to promote the large-scale development of shale gas resources utilization. Combined with the production practice of shale gas drilling, the discussion is made on the optimal design of casing progress for shale gas drilling in broken formation, especially in the borehole sections, borehole diamter selection, casing specifications and its running depth.

Abstract:Shallow drilled Qiangzi well-14 is a geological parameter well with designed depth of 1200m, the whole coring was required. There were difficulties of coring in broken formation, drilling in karst formation and construction in winter and what’s more, the high altitude unmanned environment also brought difficultie to the construction logistics supply. By taking special coring tools, cement grouting plugging, heating suction pipe with winding resistance wire as well as targeted construction management measures, the above difficulties have been effectively solved.

Abstract:Oil-based drilling fluid is mainly used for horizontal sections drilling of shale gas horizontal well in China. Due to the expensive cost of cutting treatment, it is urgent to develop and apply a high performance water-based drilling fluid system with environmental protection characteristics. By the laboratory experiments, main treatment agents of plugging agent and filtration-reducing agent were optimizingly selected, and the formula of potassium ammonium chloride based film-forming drilling fluid system was developed with evaluation experiments on temperature resistance, lubrication, anti-collapse and inhibition, plugging and anti-pollution properties. The experimental results show that this drilling fluid has good rheology with excellent temperature resistance up to 150℃, it is also featured by good lubrication performance, strong resistance to salt and calcium pollution, leakage proof and plugging as well as strong anti-collapse and inhibition.

Abstract:For plugging lost circulation in high temperature formations, normal gels with lower thermal stability are unable to be applied. To solve the problem, a novel two-step crosslinking gel containing thermal stable polymer GN-1 was developed, which performed high temperature resistance. The optimized gel system is fresh water 1.5%GN-1 0.15% ground crosslinkers 1% downhole crosslinkers 0.2% antioxidant. Thermal stability of the gel was evaluated via hot rolling and high temperature rheological measurement. After hot rolling at 180℃ for 24h, the shear viscosity of the gel at the rate of 7.34s-1 was above 10000mPa?s. The viscoelasticity of the high-density gel system remained good after aging for 24h under 180℃. The results showed that the gel had excellent heat-resisting property. The influence of environmental temperature and pH value to gelling performance and the compatibility with polysulfonate drilling fluid system was also discussed, which was very helpful to operation in future.

Abstract:Yanchang oilfield shale gas reservoir is deeply buried with complex geological conditions, foliation structure development, poor physical properties of rock and shale easily expanses and disperses. Because of the coexistence of pores and cracks, the characteristics of the shale reservoir are worse than the sandstone oil reservoir, such as the particle movement damage, reservoir stress sensitivity damage, water blocking damage and so on. In view of Yanchang oil shale reservoir is too dense, the permeability measuring can not be made by conventional methods. The artificial fracture method was used to determine the pollution degree of drilling fluid to characterize the damage rate of drilling fluids to the reservoir. Measured by the artificial fracture method, the return pollution permeability rate is up to 91.060% with the use of white oil-based drilling fluids system in Yanchang oil field. It is preliminarily confirmed that this drilling fluids system has good effect in reservoir protection and can be further promoted and used in Yanchang oil field.

Abstract:Wuye-1 is a shale gas basic geological survey well to identify the distribution of shale beds. The lithology is mainly mudstone, sandstone, shale, carbonaceous slate and limesone with large inclination, poor cementation, fracture and low wall strength in shallow layer. Low solid film-forming flushing fluid system was used in construction site to solve difficulties of formation中国地质调查局地质矿产调查评价项目“重点成矿带钻探冲洗液关键技术研究与示范”(编号：12120113097400 broken, collapsing and water sensitive drilling construction. The application of this system has good effects in wall protection, inhibition and cementation to ensure the smooth construction of the project.

Abstract:The mainly of shale gas development are horizontal wells, due to fracture and bedding developed in shale formation, collapse and other wellbore stability problems can easily occur in the process of drilling long horizontal sections, as well as carrying rocks, friction and other issues; A lot of research work surface silicate drilling fluid inhibition is closer to the oil-based drilling fluid system, but it can be used during drilling horizontal wells in shale gas is worth exploring. On the basis of silicate drilling fluid system and shale stability analysis, the establishment of a potassium silicate drilling fluid system, beside a good suppression performance outside, the drilling fluid system having lower fluid loss (high temperature and high pressure loss is less than 6mL), and easy to control rheology, good lubrication, analysts believe that the system can meet shale gas horizontal drilling requirements.

Abstract:In order to solve the technological problems of high cost of oil-based drilling fluids, cuttings with high oil content and difficult late environmental treatment and speed up the progress of shale gas development to ease the shortage of oil and gas resources, by the laboratory experiments, an oil-based drilling fluid system with low oil-water ratio was successfully developed. This system has good rheological property, electrical stability and inhibitory property with low filtration, by which drilling fluid cost is reduced through effectively wellbore stability control and friction & torque reducing. The application of this system met the construction requirements and ensured construction safety in Baoye well-3.