• 中国科学引文数据库(CSCD)来源期刊
  • 全国中文核心期刊
  • 美国《化学文摘》(CA)收录期刊
  • 俄罗斯《文摘杂志》(AJ)收录期刊
  • EBSCO学术数据库收
Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
Experimental study on the wellbore stability of tight sandstone under gas drilling
ZHANG Wen, LIU Xiangjun, LIANG Lixi, XIONG Jian
 doi: 10.11911/syztjs.2022094
Abstract(10) FullText HTML(5) PDF (3498KB)(1)
Abstract:

Wellbore instability is a state instability driven by energy. Based on the principle of energy dissipation, the triaxial compression experiments were used to study the mechanism of wellbore instability in sandstone formation during gas drilling. The conclusions are as follows: the energy evolution of sandstone can be divided into a first stage of stable accumulation of elastic energy, a second of slow accumulation of dissipated energy and a third stage of elastic energy release with a rapid accumulation of dissipated energy; as the confining pressure decreases, the dissipated energy index required to destroy the sandstone decreases, yet the elastic energy storage limit decreases linearly. When the loading rate increases, the dissipation energy required to destroy the sandstone decreases first and then increases, which means a critical loading rate exists. The conversion rate of dissipated energy in sandstone is positively correlated with confining pressure and loading rate. The higher conversion rate of dissipated energy in sandstone causes weakening of cohesive force and strengthening of friction. Too fast gas drilling rate will increase the instability area of wellbore, which is more serious in the case of high formation pressure. Therefore, reducing the drilling rate appropriately and giving the formation sufficient time to depressurize is beneficial to wellbore stability during gas drilling. The research results are of great significance for optimizing the gas drilling rate.

Optimized and Fast Drilling Technology for Deep Shale Gas Horizontal Wellsin Luzhou Block
LI Tao, YANG Zhe, XU Weiqiang, YANG Qiang, YANG Zhaoliang
 doi: 10.11911/syztjs.2022036
Abstract(22) FullText HTML(7) PDF (1624KB)(16)
Abstract:

The Longmaxi shale gas reservoirs in Luzhou are deeply buried and have a high temperature. During the drilling process, technical problems such as frequent lost circulation, low rate of penetration (ROP), high failure rate of steering instruments due to high temperature, and long drilling period are frequently encountered. Therefore, on the basis of analyzing the actual formation conditions and technical challenges, the research on optimization of casing program and wellbore trajectory, plugging treatment improvement for lost circulation, selection of efficient bits, surface cooling of oil-based drilling fluid and underbalanced drilling technologies were conducted. As a result, an optimized and fast drilling technology for deep shale horizontal well in Luzhou Block was developed. This technology was applied to 34 shale gas horizontal wells in Luzhou Block. Average drilling depth of the wells was 5 760 m and the average length of horizontal sections was 1 890 m. In addition, the average ROP was increased from 5.61 m/h to 7.03 m/h. The inclined and horizontal sections were completed in one trip and the drilling footage of a single trip reached 2 330 m, which created a new record. The optimized and fast drilling technology for deep shale gas horizontal wells in Luzhou Block has ensured the safe drilling of deep shale gas, improved ROP and efficiency. It can provide a technical reference for ROP improvement of deep shale gas horizontal wells in other regions.

Liner Cementing Techniques for Complicated Deep Wells in Sun Basin, North Yellow Sea
HU Jinjun, HAN Guanghai, ZHANG Haifeng, SHI Weiji
 doi: 10.11911/syztjs.2022098
Abstract(13) FullText HTML(13) PDF (1854KB)(3)
Abstract:

The complex geology of Sun Basin in North Yellow Sea including loss and falling cuttings which caused poor cementing quality in liner. Improve wellbore condition before cement job, choose slips-embedded liner hanger with packer to expand annular flow area, develop matrix flow restriction cement slurry mixing with fiber to reduce risk of leakage. Finally, a set of anti-blocking and anti-leakage narrow annular liner cementing technology suitable for complicated deep wells of Sun Basin in North Yellow Sea has been formed. That have been applied in 4 wells, no loss and annular blocking took place and all the cementing reached effective sealing. The applying result shows that this technology can effectively improve cementing quality and benefits further exploration.

Optimization method of deflection angle of wedge tooth of single cone bit
CHEN Lian, SONG Zhaohui, WANG Xindong, ZHANG Wutao, CHEN Xu, XIE Zhengsen, SU Zihua
 doi: 10.11911/syztjs.2022026
Abstract(20) FullText HTML(10) PDF (2119KB)(1)
Abstract:

The tooth orientation of single-cone bit directly affects the scraping of teeth. How to determine the proper tooth orientation is the key to improve the rock breaking efficiency and ROP. According to the moving characteristic of single-cone bit and the working characteristic of teeth, the numerical calculation method is used to simulate the tooth scraping, and the optimal calculation method of tooth orientation is established. Meanwhile, the comparative experiments of rock-breaking drilling with different tooth orientation are carried out. The simulation results show that the tooth working face and scraping amount are constantly changing in the process of breaking rock by scraping. The optimal calculation method of tooth orientation can accurately and quickly calculate the scraping volume of teeth and find out the best orientation. It is found that the best orientation of teeth is around 90 through the optimal calculation. The accuracy of the calculation method is verified by the comparative experiment of rock-breaking drilling. And there is still room for improvement in tooth orientation of the existing bit. The optimized analysis method of orientation can provide a useful means for the optimization of single-cone bit tooth arrangement, and has obvious practical significance for improving rock-breaking efficiency and drilling speed of single-cone bit.

Application Status and Prospect of Artificial Intelligence in Reservoir Stimulation
ZHANG Shikun, CHEN Zuo
 doi: 10.11911/syztjs.2022115
Abstract(19) FullText HTML(18) PDF (1738KB)(5)
Abstract:

In recent years, with the rapid development of artificial intelligence (AI) theory and computer technology, intelligence and digitalization have become an important force to promote the transformation and upgrading of the oil and gas industry. The research status of AI technology in reservoir geologic parameter prediction, the optimization of fracturing design, the real-time control of fracturing operation parameters, the fracturing tools and materials optimization are introduced. The main problems existing in the current AI reservoir stimulation technology as well as the key development trend are analyzed. In general, AI technology for reservoir stimulation is still in the stage of exploration and development. Foreign countries have taken the lead in intelligent identification of “sweet spot”, optimization of fracturing parameters, and intelligent control of field construction, which has been successfully applied in fracturing services in several fields in North America, and achieved good results. China has only carried out early exploration in fracturing big data machine learning, intelligent fracturing materials and other aspects, and has not seen the achievements and field application of intelligent fracturing equipment and tools. There is a gap between China and foreign countries. The main problems affecting the development of AI reservoir stimulation technology are pointed out, including the poor reliability of data samples, the lack of AI fracturing methods and the lack of interdisciplinary talents. It is also predicted that with the development of the Internet of everything technology, an intelligent completion and fracturing system will be formed, which can complete reservoir evaluation, “sweet spot” identification, fracturing parameter optimization design, field control, post-pressure evaluation and other work without human intervention. That truly realizes the integration of intelligent reservoir stimulation.

Development and Analysis of Force on Blade and Drilling Pressure Distribution of Multistage Diameter Changing while Drilling Reamer
WANG Zhanwen, ZHANG Hong, SHI Lei, FENG Yun, TU Yiliu
 doi: 10.11911/syztjs.2022044
Abstract(9) FullText HTML(8) PDF (2389KB)(1)
Abstract:

Aimed at the problems of fixed reaming aperture and low reaming efficiency in reaming operations of reamer while drilling at home and abroad, based on the working principle of reamer while drilling structure and the application of new diameter changing structure, a multistage hydraulic reamer while drilling tool was developed. The functional relationship between the reamer size and the axial displacement of the active piston was established, the force analysis of reamer blade was also carried out, and the weight distribution of the tool was analyzed by using the two-factor calculation method, and the influence law of the weight distribution ratio of the reamer with the reamer size, drilling tool sharpness and formation compressive strength was obtained. The analysis showed that the drilling pressure ratio of the reamer was positively proportional to the formation compressive strength, positively proportional to the size of the reamer, and inversely proportional to the sharpness of the reamer. The theoretical diameter expansion rate of the reamer was 7%−20%. It was concluded that the weight distribution analysis of reamer can guide the design of reamer and the selection of lead bit, and the designed multistage reamer tool can provide effective technical support for improving reaming efficiency.

Establishment of Pressure Profile and Optimization of Well Structure in the Southern Shunbei No. 5 Fault Zone
LI Shuanggui, LUO Jiang, YU Yang, TANG Ming, YI Hao, ZENG Dezhi
 doi: 10.11911/syztjs.2022037
Abstract(14) FullText HTML(23) PDF (1942KB)(3)
Abstract:

The southern part of the Shunbei No. 5 fault zone is affected by the fault tectonic movement, and problems such as malignant leakage and low drilling efficiency are common during the drilling process. Therefore, based on the imaging logging data and drilling data of adjacent wells, a new leakage pressure calculation model was established, and the prediction results of four pressure profiles in the southern formation of No. 5 fault zone were obtained; according to the four pressure profile and the analysis results of geological difficulties, the undeveloped area of the intrusion is optimized from the original five spuds to four spuds, and the borehole size is reduced to shorten the drilling cycle; a conventional four-spud casing program suitable for strong formation pressure-bearing capacity and a conventional five-spud specially sealed casing program to reduce the size of the wellbore are designed for the development area of the intrusive body, which improves the wellbore stability. The field test shows that the prediction results of the established leakage pressure calculation model have high accuracy. By using the optimized conventional five spud special sealing well structure, the average drilling cycle is shortened by 44 to 55 days, and the cementing quality qualification rate is increased by 37%. The research shows that the optimized well bore structure in Shunbei No. 5 fault zone can effectively improve the drilling efficiency, and provide a technical reference for the design of ultra-deep well structure in complex formation.

Research of Guar Gum Drilling Fluid in CBM Horizontal Wells in Qinnan Area
GENG Xueli, ZHENG Xiaobin, SU Yanhui, JING Qian, SHI Bin, LI Jian
 doi: 10.11911/syztjs.2022038
Abstract(12) FullText HTML(9) PDF (1800KB)(1)
Abstract:

Based on the analysis of reservoir characteristics and drilling technical difficulties, guar gum drilling fluid and bio enzyme gel breaking fluid were developed to solve the problems of wellbore collapse and reservoir damage when clean brine and conventional polymer drilling fluid were used in horizontal well drilling of No. 15 coal seam in Qinnan area. Guar gum drilling fluid is formed by optimizing the dosage of guar gum and evaluating the salt resistance, and matching other treatment agents; Through the optimization of biological enzyme type and dosage, and the study of drainage performance, a biological enzyme gel breaking solution was formed. The indoor test shows that guar gum drilling fluid has good rheological and salt resistance properties, can greatly improve the compressive strength of coal and rock, is easy to break at low temperature, the residue after breaking is less than 300 mg / L, and the permeability recovery rate of coal and rock is more than 85%. After the application of guar gum drilling fluid in the horizontal wells of coalbed methane in Qinnan area, it shows good stability of the well wall. In combination with the biological enzyme gel breaking fluid, the daily productivity of a single well can be increased by more than 15% while achieving low-temperature gel breaking, which has good reservoir protection effect. After the application of guar gum drilling fluid in the horizontal wells of coalbed methane in Qinnan area, it shows good stability of the well wall. In combination with the biological enzyme gel breaking fluid, the daily productivity of a single well can be increased by more than 15% while achieving low-temperature gel breaking, which has good reservoir protection effect. The research shows that guar gum drilling fluid can realize the smooth drilling of long horizontal section in coal seam, and can break the gel at low temperature after drilling, which provides a new reservoir protection method for the drilling of horizontal well in collapsible coal seam.

Expert Viewpoint
Abstract:

As the main carbon emission stage of oil & gas exploration and development, drilling and completion are important fields for achieving net zero emission. In this paper, the carbon emission footprint of the whole oil & gas industry chain and the trend of mitigating carbon emission of major oil service companies were summarized, and the development direction for carbon emission reduction during drilling and completion was analyzed. Specifically, it is necessary to upgrade the power system of drilling rigs and fracturing pump trucks, improve the automation level of equipment power management, strengthen the application of energy storage technology in drilling and completion, promote automatic drilling and completion and remote decision-making systems, and explore the coupling between drilling and completion and marine new energy,etc. Then, suggestions for carbon emission reduction during drilling and completion were proposed based on the carbon peak and carbon neutralization targets of China and oil & gas enterprises, as well as the technical level of drilling and completion. The suggestions include focusing on the carbon emission footprint of oil & gas exploration and development, strengthening the carbon emission management and promoting the low-carbon transformation during the whole drilling and completion process, improving the efficiency of drilling and completion, and exploring the utilization of marine new energy.As a result, these suggestions are of great significance to accelerate the carbon emission reduction of drilling and completion and meet China’s commitment to low-carbon transformation.

Special Report of Remote Detection Technology
Abstract:

In order to detect changes in stratigraphic structures in time, and accurately evaluate formation while avoiding drilling risks, logging while drilling (LWD) instruments are required with adequate depth of detection (DOD) and higher resolution. However, the measurement results of a single scale LWD cannot simultaneously satisfy the stated requirements. Therefore, the detection characteristics of ultra-deep azimuthal electromagnetic wave LWD and a conventional one were simulated and investigated, and the boundary detection ability and resolution of the system were analyzed as well. Meanwhile, the detection effect of undrilled formation interface was also explored. Moreover, the quasi-Newton method was used to perform accurate and fast inversion of data from LWD with multi-scale azimuthal electromagnetic waves. The study results showed that by increasing the coil spacing and reducing the frequency, the LWD with ultra-deep azimuthal electromagnetic waves could have a boundary detection ability of tens of meters. Combined with a small-scale azimuthal electromagnetic wave LWD, the real-time resistivity profile of reservoirs through inversion could be obtained, so as to bring about geological prediction, geosteering, and reservoir characterization in the vicinity of wellbore and farther away.

Abstract:

In order to detect of risky formations in advance and in front of the bit during gas drilling, a downhole impact source tool suitable for gas drilling environment was designed. Based on the gas drilling environment, the key structure of the impact source tool was designed. Through the indoor impact test, the vibration-absorbing structure and impact energy of the impact source tool were optimized. The RecurDyn simulation software was used to analyze impact block movements and optimize the parameters of the key structure. The impact resistance of the bottom vibration-absorbing disc and the tensile strength of the limit structure of the transmission rod were simulated to analyze the mechanical properties of the impact source tool. The field operation plan was made and the main advantages of the tool was analyzed. The results showed that polytetrafluoroethylene (PTFE) could significantly attenuate drill collar waves and coda waves, helpful in pinpointing weak reflection wave signals in the time domain. When the impact energy was 50 J, the propagation distance of impact vibration waves was 18.61 m, which could achieve advanced detection of gas drilling. The maximum impact force on PTFE was 1 796.88 N, and its relative deformation was not more than 0.03%. In addition, the weight of bottom hole assembly (BHA) borne by the limit structure of the transmission rod cannot exceed 1 150 kN. As a result, the structural design and mechanical property simulation of the impact tool for advanced detection while drilling for gas drilling could provide a theoretical basis for the development and application of near-bit impact source tools.

Abstract:

In order to prevent drilling collision in significantly unconsolidated formations and describe borehole trajectories, a dipole P-wave imaging method for adjacent boreholes was developed based on acoustic remote detection logging technology. First, scattered full-wave fields of adjacent wells that were excited by dipole acoustic sources from wells were simulated based on the finite difference method, and the amplitude and azimuth characteristics of different scattered waves were analyzed. Then, the influence of non-coplanar wells on the amplitude and arrival time of scattered waves was studied. Finally, the reliability of dipole P-wave imaging for adjacent wells was verified by a model test of two wells and actual logging data measured in the field. The results indicated that the dipole P-wave was superior to S-wave in adjacent well imaging in significantly unconsolidated formations, and the clearest azimuth after four-component rotation was the azimuth of the target well. In addition, adjacent well imaging was not affected by non-coplanar wells. It was shown by the study results that the dipole P-wave imaging method for adjacent boreholes can provide a new technical tool to prevent drilling collision in shallow unconsolidated formations and describe borehole trajectories.

Abstract:

Accomplishing real-time detection and accurate imaging of a formation boundary is one of the current urgent and difficult points of logging while drilling (LWD). However, existing LWD technologies face problems such as overlong instruments, difficult signal synchronization, and large detection blind areas,etc. Therefore, in this paper, closed and open coils were employed as transmitter and receiver coils, respectively, and a new hybrid dipole antenna system was designed. In addition, the structure and the measurement principle of the system were explained, and the method of converting measured electric potential signals into geological signals was established. The response law and influencing factors of remote detection based on electric field signals were analyzed. Accordingly, the relationship of the real and imaginary parts of the geological signals with the coil spacing and working frequency of the hybrid dipole remote detection in typical laminated media was studied. The azimuth sensitivity of the geological signals to the formation interface, and the influencing law of resistivity and contrast on the boundary detection ability were investigated. Finally, with a single interface model, the maximum boundary detection distance of the hybrid dipole remote detection method under short coil spacing and multiple working frequencies was determined. The research results can provide a theoretical basis for the development of logging instruments with hybrid dipole remote detection.

Abstract:

In order to obtain azimuthal acoustic velocity information of formations around wells and evaluate the heterogeneity of the formations, a well model with different velocities in different directions was designed, and the performance of remote detection acoustic logging while drilling (LWD) in measuring azimuthal acoustic velocity was studied. The well model had four sectors, and the velocities of compressional and shear waves in adjacent sectors were different. In addition, acoustic wave propagation of the well model was numerically simulated, and an eccentric transmitter and an eccentric receiver were adopted for measurement. As a result, waveforms recorded by array receivers were obtained with their azimuth angle of 0°, 90°, 180°, and 270°, respectively. Furthermore, azimuthal acoustic velocity information of formations around wells was extracted from the waveforms, and changes in sectors with different azimuths were identified. According to the parameters of the well model with different velocities in different directions, a test device was designed. The tile-like azimuthal acoustic source was used to accurately measure the acoustic velocity of high-speed media in two sectors, and the acoustic velocity variation trend of low-speed media in the other two sectors was identified. The test results were in agreement with the simulation results. The research showed that it is feasible to evaluate acoustic velocity in different directions by the well model with different velocities in different directions, which provides a theoretical basis for geosteering and formation anisotropy analysis by remote detection acoustic LWD.

Abstract:

In order to understand the characteristics and influencing factors of geo-signals of ultra-deep electromagnetic wave logging while drilling through interfaces, the analytical solution of multi-component electromagnetic wave logging in layered anisotropic media was adopted. On this basis, geo-signals of three structures including the axial transmitting and tilt receiving coil system of PeriScope, the tilt transmitting and tilt receiving coil system of DWPR, and the symmetrical measurement of GeoSphere were numerically simulated under a low frequency and long spacing condition of ultra-deep electromagnetic wave logging while drilling. The response characteristics through interfaces, depth of investigation (DOI), and influence of anisotropy of the geo-signals of the three structures were compared, and their applicabilities in ultra-deep detection were discussed. The study found that the geo-signals of the three structures could indicate stratigraphic interfaces and their orientations, and the non-monotonicity of the responses was apparent under long spacing and high frequency. Specifically, the monotonicity of the geo-signals by dual tilt coil system of DWPR was the strongest. Under a stratigraphic model with a resistivity ratio of 100:1, the geo-signals from GeoSphere had the largest DOI, and those from dual tilt coil system of DWPR took second place. The amplitude ratio geo-signals of the dual tilt coil system of DWPR were not influenced by the anisotropy of strata, while other geo-signals were all affected by the anisotropy of strata. The results showed that the DOI of the geo-signals could be effectively improved by lowering the frequency and enhancing the spacing, which was also beneficial to the monotonicity of the geo-signal responses to the stratigraphic interfaces, with the result that the anisotropy had influences on almost all geo-signals.

Drilling & Completion
Abstract:

Well Shunbei 56X is a major ultra-deep wildcat well for the deployment of the Shunbei V Strip. While drilling this well, loss of circulation happened easily in the Permian and Silurian systems, with attendant technical problems, such as the poor stability of well walls in Ordovician fractured formations, well deviation in Ordovician Sangtamu Formation, difficulty in controlling the well trajectory, and gas kicks of fracture zones drilled in reservoirs, etc. Therefore, to remedy the geological characteristics tied to the Permian, Silurian, and Ordovician formations, an anti-leakage and plugging drilling fluid and the high-temperature oil-based drilling fluid with strong plugging properties were selected, and corresponding maintenance and treatment measures were formulated. It could effectively prevent loss of circulation in Permian and Silurian systems and ensure the well wall stability in the Ordovician system. The technology of “high-torque positive displacement drill (PDM) + vertical drilling system” was applied to achieve deviation prevention and fast drilling of the vertical sections of the well. Moreover, with a combination of well-path optimization, fast regulation of tool faces, matching technology of high-temperature measurement while drilling (MWD), and well trajectory design, the trajectory of the well was highly consistent with the well-path to achieve accurate target hits. The technology of “slightly overbalanced density design + simple managed pressure drilling” was utilized to solve the gas kick problem of fracture zones drilled in reservoirs. During the drilling of Well Shunbei 56X, no well control risks were identified, and targets were accurately hit. The well was smoothly drilled to the depth of 9300.00 m (a vertical depth of 8087.94 m),which makes it the deepest horizontal well in China and the deepest onshore horizontal well in Asia so far. The safe completion of this well shows that China is capable of drilling ultra-deep horizontal wells, and can provide a technical support for for exploration and development of ultra-deep Shunbei Oil & Gas Field.

Abstract:

Ultra-short radius horizontal wells play an important role in the stimulation of old oil and gas wells and the potential tapping of remaining oil. The commonly used ultra-short radius horizontal drilling technology with flexible bottom hole assembly (BHA), however, faces the problems of long tripping periods and high operation costs. In contrast, coiled tubing drilling tools feature high drilling efficiency with low costs and are safe and reliable. Hence, this study combined the advantages of coiled tubing and flexible BHA and developed key tools for ultra-short radius horizontal drilling, including large-torque positive displacement motors (PDM) at high and low rotary speed, optimized flexible BHA, stacking whipstock and build-up PDC bit, etc. Moreover, supporting operation processes were optimized. As a result, the ultra-short radius horizontal drilling technology combining coiled tubing and flexible BHA was preliminarily developed. The technology was first applied in a field test in Well Ling 72-5CZ of Jianghan Oilfield, and an ultra-short radius horizontal lateral well of 30.21 m was drilled, with an average rate of penetration of 0.8 m/h. The trajectory was in good agreement with the designed one, and the horizontal section has an average inclination angle of 88.17°. The field test results verify that the ultra-short radius horizontal drilling technology combining coiled tubing and flexible BHA is feasible, and it can provide a new technology for the potential tapping of remaining oil and efficient development of low-permeability oil fields.

Abstract:

To fully grasp the dynamic pressure variations during gas injection of underground gas storage (UGS) and resolve the difficulty in determining formation parameters caused by continuous gas injection, an integrated calculation method of pressure and formation parameters in gas injection process of UGS was developed according to on-site static and dynamic data. The method was based on an improved particle swarm optimization (PSO) algorithm and integrated the calculation methods of reservoir pressure, bottom-hole pressure, and wellhead pressure. The wellhead pressure was first calculated by these calculation methods, and improved PSO algorithm was then employed to continuously adjust and optimize pressure and formation parameters. In this way, the obtained wellhead pressure could be fitted with measured wellhead pressure to the optimal extent, which could further lead to the determination of formation parameters such as reservoir pressure, bottom-hole pressure, average permeability of reservoirs and investigation radius. The integrated method was used to calculate the wellhead pressure of three injection and production wells and the average permeability of reservoirs. The results show that the determination coefficients for calculated and measured wellhead pressure of the three wells were 0.9889, 0.9893, and 0.9784, and the calculated reservoir permeability was consistent with that obtained from well test interpretation. This indicates that the developed method can produce reliable results. The research results demonstrate that the integrated method can be used to learn the pressure variations during the gas injection process of UGS and is conducive to guiding the safe operation of UGS.

More+