Abstract:Over the past decade， unconventional oil and gas exploration and development expanded considerably worldwide. Continuous technological progress and innovations in horizontal drilling and multi-stage hydraulic fracturing enabled extended-reach lateral wells， which coupled with high intensity multi-stage completions allowed operators to maximize both reservoir contact area and stimulated reservoir volume （SRV）. However， challenges in completion optimization still remain and operators continue experimenting with various combinations of completion and stimulation parameters to ensure economic viability of developing unconventional reservoirs. Selecting optimal fit-for-purpose completion and stimulation parameters is a highly critical and field specific task.This paper summarizes the 2014 - 2020 fracture stimulation trends in 9 major North American unconventional plays： Marcellus， Haynesville， Barnett， Utica， Bone Spring， Bakken， Wolfcamp Midland， Eagle Ford， Scoop/Stack. The overall evolvement and trends of several key completion and stimulation parameters have been analyzed for each play. In addition， the influence of individual completion and stimulation parameters， such as stimulated lateral length， proppant intensity， stage spacing etc.， on well productivity has been evaluated. The initial post frac well productivity （average 90-day initial production rate） was analyzed to evaluate the impact of each completion parameter on well performance and determine the optimal range for each completion parameter leading to best well performance.

Abstract:Fiber is one of the key factors for successful fracturing of high conductivity fractures in oil and gas wells. In order to optimize the fracturing technology and operation parameters for high conductivity fractures， laboratory physical model experiment with fiber as the main influencing factor was carried out to analyze the influence of fiber on proppant placement and channel occupancy in high conductivity fractures. The experimental results show： Adding fiber can significantly improve the sand carrying capacity and efficiency of fracturing fluid. The higher the fiber concentration is， the closer the proppant is placed to the middle and front of the fracture， which promotes the formation of long fractures in the fracturing process. The larger the constant adding proportion of fiber， the larger the occupancy rate of the fracture channel. However， the non-constant addition proportion of fiber provides the highest channel occupancy in the wedge-shaped way. In fracturing， the wedge-shaped addition method with high fiber proportion is helpful to form high conductivity fractures； over large or over small displacement will lead to less channel occupancy； and under the experimental conditions， the optimal displacement is 5.0 m³/h. The channel occupancy increases first and then decreases along the fracture extension direction with the maximum value in the middle of the fracture， and the minimum value at the crack opening. The fiber proportion and pumping rate do not affect the distribution trend of channel occupancy in high conductivity cracks.

Abstract:The exploitation of deep oil and gas resources has become an important strategy of national oil and gas development， and borehole instability in mudstone and shale formations is the technical bottleneck restricting the safe and efficient development of deep oil and gas resources. This paper analyzes the mechanical and chemical mechanisms of deep mudstone shale borehole failure with the focus on the research status and development trend of wellbore stability prediction models for shale hydration， weak structural plane， anisotropy and multi-field coupling. Improper mud density is the major cause for mechanical wellbore failure， while mudstone and shale hydrations are the major causes for chemical wellbore failure. Investigation of the effects of the weak plane and anisotropy on the safe density window of drilling mud is the major method to study the wellbore stability in deep mud and shale formations under the action of the fluid-solid-chemical-thermal coupling behavior on the wellbore.

Abstract:In order to maximize reservoir contact and improve reservoir productivity， highly deviated wells are used in Chang-7 reservoir， Ba-19 block of Huanjiang Oilfield. In the earlier frac treatment， negligence of the influence of the calcic interbed on fracture height led to a very different actual fracture geometry from the design， resulting in the problems of fracture channeling between wells and high water cut production. With examination of reservoir profile logging characteristics， analysis of the vertical stress distribution based on the subdivision layers， and investigation of the key factors of “the composite layer effect” affecting fracture height extension， the multi-stage fracturing scheme was optimized which produced a better hydraulic fracture geometry and size. The technical modification improved fracturing treatment quality with the good rate of fracture stimulation in Chang-7 reservoir up 100%； Thus， greatly improving the development level in the area.

Abstract:Air DTH hammer drilling technology can not only improve drilling efficiency， but also does not damage geothermal reservoirs； therefore， it is widely used in geothermal well drilling. However， it is limited by drilling depth and water output. During drilling of deep geothermal wells in the Shunhuang Mountain of Yongzhou， Hunan， air down-the-hole hammer drilling technology was used to achieve a breakthrough in the drilling depth with the drilling depth up to 1820m， and the actual water output of 400m³/day at surface temperature of 43℃， meeting the design index. The relevant drilling measures are summarized so as to promote application of the technology in geothermal deep wells.

Abstract:Diamond drilling is one of the main drilling methods in China. It is applied widely in geological explotation， and oil and gas drilling. In order to improve technical and economical index of the method， research on the stress-strain state of rock to be drilled， the rock fragmentation process and its relationship with drilling parameters is very necessary. Russian drillers have done a lot of relevantwork： they studied the optimal relationship between penetration rate and drilling parameters， proposed the concept about the combination of critical drilling parameters， and recommented measures guaranteeing normal drilling and prevening abnormal wear of drill bits， etc.， which can provide some reference for the Chinese counterparts.

Abstract:In deep geothermal mining， granite formation encountered in the drilling process will lead to low ROP， high bit consumption， and long drilling time due to its poor drillability， high density and hardness， and strong abrasiveness. In order to improve drilling efficiency， and reduce drilling time and cost， jet-type fluid hammer drilling was used with roller cone bits to efficiently break hard rock formations in geothermal resources survey. At the same time， various drilling process parameters such as displacement， weight on bit， rotation speed， were optimized and field tested for multiple times. Application results showed that for the same footage drilled in hard rock formations， jet-type fluid hammer drilling increased drilling efficiency by 30% over conventional drilling， which greatly increases the mechanical drilling speed in hard rock formations， and effectively increases drilling efficiency， achieving high-efficiency rock breaking. It can provide important technical support for drilling speeding up and increasing drilling efficiency in granite and other hard rock formations.

Abstract:The Jianshui Puxiong rare earth deposit in southeast Yunnan is a super-large weathered crust ion adsorption rare earth deposit discovered and identified by the No.209 Geological Team，Geological Bureau of Yunnan Nuclear Industry. The ore body occurs in the fully weathered layer and semi-weathered layer of the Changlinggang alkaline rock body. The ore has high grade and large thickness which is different from the ion-adsorbed rare earth ore in the weathered granite crust； thus， conventional shallow wells and the Gannan drills cannot be used to expose the rare earth ore body. In this paper， the split tube core barrel and the construction of shallow wells in adjacent locations are used to compare the grade changes of the ore body in the Jianshui Puxiong mining area for the same sampling layer and sample length with calculation of the relative error， and positive and negative deviation of the grade. The results show that the relative error qualification rate of a single corresponding sample is 100%； the samples with grade positive deviation <0.07% account for 78.57% of the total number of samples，while those with grade negative deviation account for 21.43% of the total number of samples. The samples with grade positive deviation ≥0.07% account for samples 52.17% of the total，while those with negative deviation account for 47.83% of the total number of samples， indicating positive and negative deviations within the controllable range. The single project average grade relative error qualification rate is 100%. It shows that the split tube core barrel can be effectively applied to the exploration of weathered crust ion-adsorbed rare-earth minerals to realize resource evaluation.

Abstract:The multilayer goafs and a large number of accumulated tailing strata in Luanchuan molybdenum mine in Luoyang lead to hole wall failure during drilling， which is generally exhibited as collapse， block falling； meanwhile， the detection equipment can not be lowered to the bottom of the hole and the construction period is delayed. In view of this situation， this paper summarizes two new exploration techniques： （1） A new process of strengthening the hole wall with loess is adopted during drilling， by which loess forms a protective layer on the hole wall through compaction. （2） a new type of tapered bit is designed， which can be stricken down to the bottom of the goaf with a heavy hammer； thus， the borehole television and other detection equipment can be run down hole with protection of the central hollow drill string. Field use has proven that the techniques are feasible by repeated field practice， and the hole wall remained stable and no longer appeared unstable with progress of the construction period， providing guarantee for the subsequent geological exploration of goafs. They have ensured the smooth implementation of the operations economically and safely， and also provide reference for the exploration of complex strata in the future.

Abstract:Deep formations in the Xihu area of East China Sea are characterized by strong abrasiveness， poor drillability， low ROP and abnormal high temperature and pressure. Through continuous exploration and practice of casing program optimization technology， a relatively fixed exploration casing program has been formed for the East China Sea in recent years. However， further increasing of drilling rate for 444.5mm surface hole has encountered a bottleneck， and there is still room for optimization of casing program for atmospheric deep wells. With the continuous progress on drilling technology and the need for oil and gas exploration and development in the East China Sea， the number of highly deviated wells and horizontal wells is increasing， while it is difficult to run 177.8mm liner in 215.9mm horizontal section of the development well. Therefore， it is necessary to further optimize the casing program in Xihu Sag of East China Sea. To overcome these difficulties， the surface hole size optimization technology， the liner size optimization technology of the development well and the casing program simplification technology of the deep well have been studied and formed. The field application indicated that the drilling speed was improved significantly， which lays a foundation for further optimization of the casing program in subsequent wells. It also reduced the probability of complex conditions in the deep well section， increased the annulus clearance of exploration wells between casing and wellbore， and provided convenience for subsequent operation； meanwhile， it can feed new thought for the well structure design of deep and ultra-deep wells under complex geological conditions.

Abstract:In deep water oil and gas exploration and development， the operation environment is complex and changeful. In order to avoid the damage of typhoon and other bad weather to offshore drilling， the emergency release of the blowout preventer and the riser has become the key to avoid offshore drilling accidents. In order to explore the recoil law of the riser in emergency release， the causes and recoil process of emergency release of the riser were analyzed. The axial mechanical analysis model was established for the riser system under emergency release condition by using OrcaFlex method. Taking a 1520m deep water well in the South China Sea as an example， the effects of tensioning force， wave movement， drilling fluid density and platform drift on riser recoil were studied. The results showed that the larger the top tensioning force was， the larger the recoil displacement of the riser and the change of the stroke of the expansion joint were. With the increase of wave height， the recoil response of the riser tended to strengthen. The wave direction had no effect on riser recoil response. Different drilling fluid densities in the pipe had obvious influence on riser recoil. With the increase of platform drift distance， the recoil response of the riser became more intense. The research results have certain guiding significance for the safety of the riser in recoiling.

Abstract:As environment protection and mud property maintenance in geological exploration are becoming increasingly important， higher requirements have been put forward for drilling mud purification in uranium exploration. In view of the characteristics of short construction period per borehole， frequent equipment movement and small mud handling capacity in uranium drilling， two mud treatment while drilling processes have been proposed each for sandstone uranium deposit and hard-rock exploration； besides， two sets of compact， modular and intelligent mud treatment while drilling equipment also have been developed for sandstone and hard-rock uranium green exploration. Field test has verified that the equipment provided good environmental protection benefits and economic benefits， achieving the goal of one mud formula for multiple holes and zero mud discharge with increase in in drilling efficiency while saving materials； thus it has solved fundamentally the problem of environmental pollution caused by mud discharge during drilling. The drilling mud treated by the equipment contained much less harmful solid phase with lower density and improved rheology； thus， it maintained good performance， leading to reduced downhole incidences such as bit burial， drilling string sticking， and ensuring the downhole safety with drilling quality. The modular structure leads to convenient movement and transportation and is suitable for all kinds of terrain and traffic conditions. It can be popularized and applied in uranium drilling.

Abstract:In the disaster of impact of buildings （structures） by rockfalls， the shape of the rockfall is often uncertain， and the surface shape of buildings （structures） is also different. When a rockfall impacts a structure， its impact dynamic response characteristics are also different due to the different shape of the rockfall. The Explicit dynamic finite element method in ABAQUS finite element software is used to carry out the numerical simulation of the impact of structures with different surface shapes by rockfalls with different shapes， and the cushioning energy dissipation characteristics of different buffer layers are compared and analyzed. The results show that under the initial conditions of the same mass and initial velocity， when rockfalls with different shapes impact flat wall structures， the peak value of impact force becomes from large to small in the order as cube>cylinder （bottom）>cylinder （side）>sphere>triangular pyramid； when the impacting surface shape of the rockfall changes from “sharp” to “blunt”， the damage degree of the structure impacted by the rockfall will decrease， but the overall deformation area will increase； when the structures with different surface shapes are subject to rockfall impact， the peak value of impact force is in the order of plane shape>convex shape>concave shape>wavy shape>inclined shape. The inclined structure has relatively better rockfall impact resistance. Through comparative analysis of the cushioning and energy dissipation characteristics of rockfall impact when different buffer layers are set in front of the structure， it is concluded that the EPS sand composite cushion has good cushioning and dissipation performance， and it has a broad application prospect in the actual rockfall disaster protection engineering.

Abstract:At 2 pm. on January 10，2021， an explosion occurred at 240m underground of Hushan gold mine of Shandong Wucailong Investment Co.， Ltd. in Qixia City， Yantai， Shandong， resulting in 22 workers trapped underground. The Accident Emergency Rescue Headquarters deployed four rescue boreholes in the first batch. The 6th Geological Brigade of Shandong Bureau of Geology and Mineral Exploration and Development undertook the construction task of No.3 rescue hole. The construction scheme of “DTH hammer drilling+high-precision inclinometer+casing wall protection and water stop” was adopted to quickly drill to 521m. Then， cooperate with the national mine emergency rescue geodetic survey team to complete the remaining 60m construction task by using directional drilling technology. The first one penetrated the roadway and received a response from the trapped miners underground. This successful rescue has created a new model of relay drilling rescue and provided reference ideas for mine rescue work.

Abstract:The SMW construction method has the advantages of simple construction process， economic reliability， high applicability and less environmental pollution. Since it was introduced from abroad， it has been widely used in the coastal soft soil areas of our country， but it is rarely used in the inland hard soil areas， and the standards and specifications are not well developed with some requirements remained controversial. This paper introduces the application and improvement of SMW piles in a foundation pit project in the complex surrounding environment in southwest Shandong， summarizes some problems that may be encountered in the process of design and construction， and puts forward corresponding solutions. It is more economical and reliable to use the method in the medium-sized foundation pit project where the surrounding environment is complex， the space for sloping is limited， and environmental protection requirements is strict. Since different software may lead to different calculation results in some degree， locally recognized software should be selected for the design stage with the appropriate model and parameters for calculation， and the calculation results are then optimized according to experience. The cement content and the water cement ratio for SMW piles directly affect the strength， uniformity and flow plasticity of cement-soil mixture， hence the difficulty and quality of steel construction， as well as the water sealing effect of the cement-soil curtain wall. But there is no unified standard for the hard soil area； thus， testing is necessary to obtain the optimum mixing ratio according to the actual site conditions.

Abstract:This article proposes a new combined supporting system—the slope protection pile and the compound soil nail wall with micro steel pipe piles， which successfully solved the technical difficulties such as necessity of vertical excavation around the foundation pit due to no grading space， great depth of the foundation pit， requirement for small displacement， and high support costs. In addition， the system provided convenient construction， and was beneficial to control of the displacement and deformation of the slope， and enhancement of the overall stability of the slope without impact on the surrounding environment during the excavation of the foundation pit. The design and construction with this support method was tested for a project in Beijing， and the monitoring results were good with great improvement in the safety and stability of the slope； thus， verifying the feasibility of the support form. It has technical and economic advantages that conventional soil nail walls and slope protection piles cannot compare to in deep foundation pit support. It can be used as a reference for other similar projects， and has high application and promotion value.