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Optimization of hydraulic parameters and structure parameters of rotary jetting tools
HU Qiangfa, GU Ziang, FANG Wei, SHI Huaizhong, LIU Jiawei, ZHANG Xueming, HUANG Zhigang
 doi: 10.13639/j.odpt.2022.03.015
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The jet tool with rotary nozzles can generate a high-speed jet flow, and under the action of the recoil force from the jet flow, the nozzles will be driven to rotate to form a complex rotating jet flow, which can achieve efficient cleaning of oil pipes and casings. Taking the Ø73 mm oil tubing under the condition of 7 000 m well depth as an example, a Ø54 mm series jet tool with rotary nozzles matched with Ø44.5 mm coiled tubing was designed. Then, the hydraulic parameters of the jet tool with rotary nozzles were optimized, and the structural parameters of the tool were also optimized by using computational fluid dynamics method. The research shows that: when the displacement is 270 L/min, the jet flow velocity of the jet tool with rotary nozzles is about 170 m/s, which can and the total pressure consumption of the system is about 42 MPa, meet the cleaning requirements; as the offset radius of the lateral nozzles increases, the back impact moment generated by the lateral nozzles increases approximately linearly, and the impact pressure on the wall decreases first and then increases; with the increase of the inclination angle, the impact pressure of the inclined nozzles on the inner wall of the oil tubing increases; when the rotation speed is within the range of 60-360 r/min, the impact pressure of the inclined nozzles on the wall surface does not change much; the optimal combination of structural parameters is the lateral nozzle offset radius of 12 mm, the inclined nozzle inclination angle of 75°, and the forward inclined nozzle angle of 15°. This research can provide a guidance for on-site construction and parameter optimization of the jet tools with rotary nozzles.
Nano-gel temporary plugging for high-temperature high-pressure gas wells of the Suqiao gas storage
SONG Changwei, LI Jun, LI Haochen, ZHONG Liguo, LIU Jianbin, ZHU Yu, LUAN Zhengxuan
 doi: 10.13639/j.odpt.2022.03.013
[Abstract](0) [FullText HTML](0) PDF 2086KB(0)
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In the Suqiao storage, the average reservoir depth of gas wells is near 5000 m, the formation temperature is 140°C–150°C, and the reservoir pressure under the injection-production condition is typically 35–45 MPa. The workover of gas wells requires a temporary well kill. However, conventional polymer gel-based plugging agents are intolerant of high temperature and prone to leak-off, which leads to unsatisfactory well-kill performance. Given this, the 150°C-tolerant nano gel was developed and the gelation performance, thermal tolerance, and rheology of such nano gel were evaluated. Furthermore, the nano gel temporary well kill testing was performed in two high-temperature high-pressure (HPHT) wells in the Suqiao storage. It was shown that this temporary plugging technique presents the advantages of simple operation, fast effects, and low costs, and can be extensively applied to temporary plugging of HTHP wells and profile control and water plugging of high-temperature oil and gas reservoirs.
Inter-fracture asynchronous periodic injection-production energy supplement technology for horizontal wells in ultra-low permeability reservoirs
SHEN Rui, XIONG Wei, WANG Shouhu, WANG Juntao, WANG Long, HE Jibo, PING Yi, GAO Shusheng
 doi: 10.13639/j.odpt.2022.03.008
[Abstract](0) [FullText HTML](0) PDF 2037KB(0)
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Since horizontal wells in ultra-low permeability sandstone reservoirs lack effective means of energy supplement, an alternate injection-production process between fractures in same horizontal well was proposed. The process string is composed of release sub, Y445 packer, Y341 packer, one-way injection dispenser, one-way production dispenser, and card stripper, which can realize water injection in partial fractures and oil production in other partial fractures. Therefore, the staged asynchronous injection-production energy supplement can be realized in a same horizontal well. Asynchronous injection-production and oil-increasing between fractures is the result of the combined action of multiple driving mechanisms, including water flooding, elastic flooding, and imbibition. Compared with the traditional area water injection well pattern, it is easier to achieve more effective flooding effect. The research shows that: for the inter-fracture asynchronous periodic injection-production energy supplement method in the same well, the water in injected in to the hydraulic fracturing fractures, which greatly increases the water absorption area in the reservoir; the shape of the flow field changes from radial flow to linear flow; the distance between the injection end and the production end is shortened, which increases displacement pressure gradient and effective permeability. The combined effect of these mechanisms plays an important role in increasing oil production. Field tests show that the inter-fracture asynchronous periodic injection-production energy supplement method in same horizontal well can effectively improve single-well production, and can be popularized to ultra-low permeability sandstone reservoirs on a large scale.
Failure analysis of completion test string for deep high-temperature and high-pressure gas well: A case study on a well in Shunnan area
WANG Yanbin, SHI Xiaolei, GAO Deli, ZHANG Jinshuang, CHEN Junhai
 doi: 10.13639/j.odpt.2022.03.006
[Abstract](0) [FullText HTML](0) PDF 1700KB(0)
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The safety and reliability of the completion test string for deep high-temperature and high-pressure oil and gas wells is of great significance to ensure the safe and efficient development of deep oil and gas. Considering the comprehensive influence of factors such as temperature and pressure changes, pipe end constraints, and buckling friction during the test, the force analysis model of the test pipe string was established, and the mechanical analysis software of the completion test pipe string for deep high-temperature and high-pressure gas wells was developed. Then, the temperature and pressure analysis, stress deformation calculation, and mechanical strength check of the test string in a well in Shunnan area were performed, which revealed the reasons for the failure of well completion test string. The results show that: the developed software can more accurately analyze the temperature and pressure environment for the test string in the high-temperature and high-pressure wells, and can perform stress deformation analysis and strength check, which can be used in engineering practice; the local corrosion damage and the generated cracks on the surface of the test string in the well will reduce the strength of the pipe string, which is the main reason for its failure; special attention should be paid to the effect of corrosion on the mechanical strength of the pipe string in high-temperature and high-pressure wells in this area. This research can provide a theoretical basis for the optimal design and safety control of the completion test string in high-temperature and high-pressure wells.
Research on solidification conservation and preparation method of high-temperature and high-pressure set cement for deep wells in deep water
LIU Shujie, WU Zhiqiang, WU Yi, HOU Duo, ZHANG Zhi
 doi: 10.13639/j.odpt.2022.03.004
[Abstract](0) [FullText HTML](0) PDF 2203KB(0)
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Deep wells in deep water are facing with special geological conditions such as super depth, ultra-high temperature, ultra-high pressure, and complex reservoirs, which put forward higher requirements for the comprehensive mechanical properties of cementing cement. Thus, there is an urgent need for solidification conservation and preparation methods of set cement under high-temperature and high-pressure working conditions, so as to evaluate and optimize the cement slurry system accurately and reliably. A solidification conservation device for high-temperature and high-pressure cement slurry and a method for preparing set cement were established to simulate the cement slurry solidification conservation process under high temperature and high pressure (150 MPa, 250 ℃) in deep wells in deep water. Besides. The mechanical properties such as uniaxial compressive strength and tensile strength of set cement prepared under different temperature and pressure conditions were analyzed and compared. The results show that the established cement solidification conservation and preparation method under high-temperature and high-pressure conditions can accurately simulate the high-temperature and high-pressure wellbore conditions of deep wells in deep water, and at the same time, the high-temperature and high-pressure conditions can also give full play to the performance advantages of the additives in cement slurry system. The set cement prepared by this method shows significant advantages in mechanical properties such as compressive strength and tensile strength compared with the set cement prepared by conventional methods. The proposal of this method is conducive to promoting the development of solidification conservation of high-temperature and high-pressure cement slurry system in deep wells in deep water, as well as the development of set cement preparation technology, which provides an experimental method and technical support for the optimization of cement slurry system formulations.
Research progress of intelligent fluid and its application to drilling fluids
HUANG Zhiyang, ZHAO Xionghu, MIAO Liujie, JIA Xiangru
 doi: 10.13639/j.odpt.2022.03.003
[Abstract](0) [FullText HTML](0) PDF 1113KB(0)
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Intelligent fluid, as a smart material with “controllable” physical properties, has extensive industrial applications in aerospace, bio-engineering, the medical industry, and micro-electronics. By response conditions, intelligent fluids were divided into the external-field controllable intelligent fluid (represented by magneto- and electro- rheological fluids) and stimuli-driven controllable intelligent fluid (represented by the smart hydrogel). The rheological mechanism and research progress of intelligent fluids were systematically reviewed and it was pointed out that the current hot spot of relevant research is to introduce nano-materials into intelligent fluids. Furthermore, the laboratory research progress of intelligent fluids applicable to drilling fluids was summarized to demonstrate the feasibility of intelligent fluids as drilling fluids. At last, given the development requirement of smart oilfields, it was proposed that inventing intelligent drilling fluids and developing smart drilling equipment, in particular, smart drilling fluid operation systems, are the development orientations of future smart drilling.
Drilling and completion technology for 5-multilateral sulfur-bearing gas wells with high temperature and high pressure in Sichuan Basin
LI Tao, XU Weiqiang, SU Qiang, ZENG Zhihao, YANG Zhaoliang
 doi: 10.13639/j.odpt.2022.03.001
[Abstract](0) [FullText HTML](0) PDF 1271KB(0)
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Well MX023-H1 is a 5-multilateral well in the gas reservoir in Longwangmiao formation, Sichuan Basin, and the purpose of drilling this well is to verify the adaptability of multilateral well technology in the efficient development of deep carbonate gas reservoirs. As the first level five multilateral sulfur-bearing gas well with high temperature and high pressure in China, the drilling and completion operation of the multilateral borehole is facing with many technical difficulties, such as high completion level, superabundant operation procedures, strict wellbore quality requirements, difficulty in running complex casing strings, and high-performance requirements for cementing sheath to prevent gas channeling. For this reason, in order to ensure the stability of the connection between the multilateral wellbore and the main wellbore during the later production period, the measures such as increasing the window strength and selecting stable formation windows were taken. Designing smooth borehole trajectory and improving the anti-slump performance of drilling fluid can ensure an inerratic well diameter and reduce the difficulty in running casing. By using the new designed Ø177.8 mm curved casing, the drafting operation of Ø215.9 mm multilateral borehole with a length of nearly 5 000 m has been completed, meeting the re-entry and drafting requirements for multilateral borehole, and creating good wellbore conditions for the smooth running of multilateral casing. The gap of the opening groove at the front end of the wall hook of the wall-mounted hanger was increased from 21.66 mm to 25.66 mm, which improves the success rate of wall-hanging. The three-set cement slurry system combined with the pressure-controlled balance cementing technology ensures the cementing quality under the condition of coexistence of overflow and leakage in the multilateral wellbore, with the qualified rate of the first interface reaching 97.6%, and the qualified rate of the second interface reaching 100%. Field application shows that the supporting technology can meet the drilling and completion requirements for the 5-multilateral sulfur-bearing deep gas wells with high temperature and high pressure, and the successful implementation of the drilling and completion operation for this multilateral well can provide reference for the subsequent popularization and application of 5-multilateral well technology.
Evaluation of rock-clearing effect and structure optimization design of cuttings bed breaker
PENG Shuo, HUANG Wenjun, GAO Deli
 doi: 10.13639/j.odpt.2022.03.002
[Abstract](0) [FullText HTML](0) PDF 2216KB(0)
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During the drilling of extended-reach wells and long horizontal wells, broken cuttings easily accumulate on the low side of the wellbore annulus to form a cuttings bed, which can easily lead to drill pipe buckling, increased drilling tool friction and torque, abnormal equivalent circulating density, or even drilling accident. The cuttings bed breaker can effectively agitate the deposited cuttings bed and improve wellbore cleaning. Taking the cuttings bed beaker as the research object, the research on quantitative evaluation of rock cleaning effect and structure optimization design were carried out. The rock-clearing mechanism of the cuttings bed beaker was revealed by using computational fluid dynamics, and a set of methods on evaluating the rock-clearing effect of the cuttings bed beaker were established. Based on quantitative evaluation, the blade structure with best rock cleaning effect was determined, the influence of the blade structure parameters on the rock clearing effect was analyzed, and then the structure parameters were optimized. The research shows that among the three types of blade structures, the anti-spiral blade cuttings bed beaker has the best rock-clearing effect, and its rock-clearing effect can be significantly improved by increasing the helix angle and optimizing the number of blades. This research provides a theoretical basis for the structure optimization design of cuttings bed beaker.
Application and progress of oil and gas well monitoring techniques based on distributed optical fiber sensing
LI Xiaorong, LIU Xufeng, ZHANG Yi, GUO Fang, WANG Xindong, FENG Yongcun
[Abstract](0) [FullText HTML](2) PDF 2308KB(0)
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To facilitate the real-time life-cycle full-length monitoring of oil and gas wells, distributed optical fiber acoustic sensing is proposed. Distributed optical fiber sensing is divided into two techniques, namely distributed temperature sensing (DTS) and distributed acoustic sensing (DAS), according to fundamental technical principles. The two techniques were compared, which pointed out the advantages of the DAS, such as high precision, long-distance monitoring, and high signal strength. The monitoring mechanism, optical fiber structure, and installation method were introduced, and a literature review was performed for research and applications of the DAS in fields of the seismic survey, well production and injection, hydraulic fracturing, sand production, pipe leakage, and wellbore integrity. Our research showed that the DAS is a cost-effective promising technique that enables full-lifecycle real-time monitoring of oil and gas wells and it can provide technical support for formulating appropriate development plans, improving operation safety, and reducing development costs.
Analysis of friction upon drill string for 3D horizontal wells ontight oil platform in Daqing Oilfield
SHAO Shuai
[Abstract](0) [FullText HTML](10) PDF 1138KB(9)
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Platform horizontal wells are the main form to develop tight oil in Daqing Oilfield. The way placing wells on platform leads to 3D well sections in some horizontal well trajectories. During drilling process, compared with 2D horizontal wells, 3D horizontal wells have greater friction upon drill string, which limits the extension limit of horizontal wells. On the basis of the soft string theoretical model, by analyzing the contact form between the drill string and the borehole wall in the 3D well section, the model calculating shifting of the drill string was given, which was verified by integrating Landmark software simulation with actual drilling situation. The simulation results show that the contact area between the drill string and the borehole wall in the 3D well section is larger than that of the 2D well section, that the deviation angle is positively correlated with the friction upon drill string when adjusting orientation, and that the overall friction coefficient of 3D horizontal wells is above 0.4. During design process or drilling process, it is necessary to reduce the friction upon drilling string according to the friction generation law in the 3D well section, and some means may help, such as optimizing horizontal well trajectory and wellbore structure, reasonably allocating the position of the heavier drill pipe in drilling tool assembly, improving the lubricity of drilling fluid, and selecting friction reduction tools. Reducing the friction upon drilling string can effectively lengthen platform horizontal wells, which will ensure efficient development of tight oil platforms.
Technology of production enhancement by fracturing of multiple branch fracture in vertical well in low permeability oilfields in the periphery of Daqing
WANG Xianjun, HU Zhifan, ZHANG Hongtao, CHEN Xidi, WANG Wei
[Abstract](0) [FullText HTML](5) PDF 1921KB(1)
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Conventional fracturing in low-permeability oilfields in the periphery of Daqing creates the small scale double-wing fracture, and the small fracture controlled volume and the poor stimulation effect were obtained. Increasing the fracture length promotes communication with offset wells and fails in improving the controlling degree of sand body between well arrays, and the development cost increases. The fracturing technology of multiple branch fractures in the vertical well creates multiple branch fractures on both sides of the major fracture under the condition of well pattern, increases the fracture controlled volume, improves the controlling degree of sand body between well arrays, and enhances the stimulation effect. Through physical and numerical simulation, the formation mechanism of branch fractures was obtained. Based on variation of rock mechanical parameters and the characteristics of branch fracture initiation, an optimization design method integrating computation of in-situ stress evolution and optimization of fracture parameters was formed. The fiber temporary plugging agent inside the fracture was optimized, the temporary plugging process of fiber + proppant in the fracture was formed, and the field diagnosis and control method was developed. The technology has been applied in 310 wells. The increase in daily oil production per well at the initial stage is 1.9-4.8 t, which is 2.1-4.0 times that of conventional fracturing, and the return on investment is 1:2.5, providing technical support for efficient development of low-permeability reservoirs in Daqing Oilfield.
Key technologies of multi-stage fracturing string in Sichuan-Chongqing high-pressure tight gas reservoirs
WANG Jinyou, XU Yongquan, GONG Leilei, ZHAO Yize, YAO Jinjian
[Abstract](0) [FullText HTML](2) PDF 1664KB(2)
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The potential of the old wells in the tight gas reservoirs in Sichuan-Chongqing area needs to be further tapped by multi-stage fracturing process, however, the existing process string cannot meet the complex requirements of high pressure, large-sand-volume erosion, setting under slurry conditions, and removable after fracturing, therefore, researches on multi-stage fracturing technology in high-pressure tight gas reservoirs were carried out. Y344 pressure-steering sand blasting packer was developed independently. This packer integrates blasting and packing functions, reducing tool size, and improving the passability of multi-layer fracturing strings. The structure of the sandblasting body and rubber cylinder of the packer was optimized by finite element analysis software, and 42CrMo high-strength material was selected to improve the pressure bearing performance. Researches on erosion and abrasion resistance of materials were carried out, the flow state was analyzed by using numerical simulation method, the layout of cemented carbide parts was optimized, and the problem of large wear in areas such as sandblasting ports was solved. Hydraulic anchors and other tools were designed with liquid inlet sand control structure to meet the requirements under slurry environments. Laboratory experiments show that the technical string meets the high-pressure requirement of 90 MPa, and the sand volume added into a single layer on site reaches 160 m3, which provides an effective technical means for solving the problem of high-pressure multi-stage tubing fracturing in similar reservoirs.
Progress in key technologies of scaling prevention and treatment in ASP flooding
CHENG Jiecheng
[Abstract](0) [FullText HTML](5) PDF 1579KB(2)
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In application of enhanced oil recovery in Daqing Oilfield, ASP flooding increases the oil recovery by about 20 % and 6%-10% compared with water flooding and polymer flooding respectively. Nevertheless, existence of alkali causes serious scaling in the mechanically pumping wells, which increases the difficulty in oil production and the intensity of maintenance, and it is a factor restricting industrial application of ASP flooding. Pilot in ASP flooding and research on dynamics of scaling and the long-term interaction between the ASP system and the reservoir rock have been carried out in Daqing Oilfield. The mechanism of calcium-silicon composite scaling was revealed, and the method of qualitative and quantitative prediction of scaling was established. The anti-scaling artificial lifting equipment was developed through structural design and nano-spraying modification of low surface energy materials. A composite anti-scaling agent with the scale-cleaning and anti-scaling rate above 85% was developed based on the scaling mechanism. Through combination of physical and chemical prevention, the pump inspection period of oil wells is greatly extended, and the problem of short continuous production period due to scaling is resolved. This promotes large-scale application of ASP flooding.
Optimization of fracture morphology and parameters in Songbei tight gas reservoir
ZHANG Yongping, QI Shilong, TANG Pengfei, ZHANG Xingya, YANG Chuncheng, SONG Jingyang
[Abstract](0) [FullText HTML](11) PDF 2521KB(2)
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The Songhezi formation in Songbei is in an ultra-deep tight gas reservoir, with multiple thin sublayers distributed vertically. In order to improve single-well production, in view of the unfavorable conditions such as large horizontal stress difference and lack of natural fractures in Shahezi formation, the basic research based on physical simulation and related mathematical simulations for Shahezi formation was carried out. A chart for judging complex fractures in Shahezi formation in the tight gas reservoir and the corresponding technology for choosing fracturing process optimally were established, which could help to realize targeted reservoir reformation under different lithologies and different blocks. 14 wells were tested in the field, among which 5 wells were tested with a gas production exceeding 10×104 m3. Furthermore, the wells producing an industrial gas flow after fracturing accounted for 71%, which improved the overall development effect of deep gas wells in Songbei. The research results provide strong technical support for the submission and effective development of exploration reserves in Daqing Oilfield, and have reference and guiding significance for other similar oilfields in China.
Experimental law of well scaling in the production process of deepwater gas well
LIU Wenyuan, HU Jinqiu, YAO Tianfu, OUYANG Tiebing, LI Xiangfang
 doi: 10.13639/j.odpt.2020.03.021
[Abstract](4) [FullText HTML](764) PDF 1629KB(2733)
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Offshore gas wells are characterized by large depth, complex scale removing operation and high operation cost, so it is imperative to predict and control the scaling in the wells of deepwater gas wells. In this paper, laboratory experiment and theoretical calculation were combined to evaluate the scaling risks in the wells during the production of four typical deepwater gas wells in the South China Sea Gasfield, predict scaling velocities and scaling positions in the wells of gas wells in the process of production and analyze the scaling characteristics and laws. It is indicated that the scaling type of gas well is controlled by the compositions of formation water and the scaling velocity in the production process of gas well is mainly dependent on the deposition velocity of stable scale after the surface deposition period. The scaling difference at different well depths in the production process of deepwater gas well is mainly dominated by the temperature distribution along the well, and the scale control shall focus on the middle and lower parts of the well and the conditions of high gas production rate and high water/gas ratio. Compared with onshore gas wells, deepwater gas wells are affected more by the scaling in wells, so to keep the efficient and safe production of deepwater gas wells, it is quite important to take the scale control measures in time to prevent the formation of scale and control the scale deposition in the allowable range.
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2022, 44(2).  
[Abstract](0)
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2022, 44(2): 1-4.  
[Abstract](0) [FullText HTML](10) PDF 1451KB(7)
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DRILLING AND COMPLETION
Prediction and analysis of build-up rate during sliding drilling
WANG Ge, HUANG Wenjun, GAO Deli
2022, 44(2): 139-144, 160.   doi: 10.13639/j.odpt.2022.02.001
[Abstract](0) [FullText HTML](13) PDF 1532KB(5)
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The drilling engineering is facing difficulties in accurately predicting the build-up rate during the sliding drilling operation. First, this research developed the three-dimensional mechanical model of the steering bottomhole assembly (BHA), based on the weighted residual method, and calculated the mechanical load of the bit and friction distribution in the steering BHA during sliding. Moreover, given the build-up characteristics of the tool during sliding, the sliding build-up rate prediction model with a zero side penetration rate and the inversion method of the conversion coefficient were developed. At last, the build-up rate conversion coefficient of a shale gas horizontal well was inverted from its drilling data and this application confirms the precision of the proposed sliding build-up rate prediction model. Besides, the effects of drilling parameters, trajectory parameters, cutting characteristics of the bit, and tool structure on the build-up rate and friction of the tool are investigated. It is shown that during the sliding steering, it is in favor of improving the build-up performance of the tool and the sliding drilling efficiency to properly increase the structural bend angle of the tool, lower the weight on bit, and enhance the side cutting performance of the bit. The findings of this research provide vital references for optimizing the steering drilling parameters, tool structure design, and well trajectory control.
Key technology and practice of horizontal drilling for marine deep shale gas in southern Sichuan Basin
JIA Lichun, LI Zhilin, ZHANG Jichuan, TAO Huaizhi, LI Lei, HUANG Chongjun, WEI Xiao
2022, 44(2): 145-152.   doi: 10.13639/j.odpt.2022.02.002
[Abstract](0) [FullText HTML](9) PDF 1482KB(8)
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The southern Sichuan Basin has abundant marine deep shale gas resources, which is a critical replacement for the current and future shale gas development. However, drilling of deep shale gas faces numerous challenges, such as inadequate thermal tolerance of steering instruments and drilling fluids, high difficulties in well trajectory control and clean-up of wells and tools, low penetration rate, and high risks of downhole complex issues, due to the geologic characteristics of deep shale gas (numerous sequences, high formation temperature, high formation pressure, and thin high-quality reservoirs). Given this, we managed to develop the key technology for horizontal drilling of deep shale gas through multiple efforts. The 165ºC-tolerant rotary steerable system was selected to reduce runs and facilitate time-efficient drilling, and moreover, the drilling fluid surface cooling system was deployed to ensure the normal functioning of downhole tools. The PDC bit with efficient rock-breaking was developed to raise the penetration rate. The managed pressure drilling was adopted to reduce the drilling fluid density. The dynamic weighting device of cuttings and degradable cutting-laden fibers were developed for efficient well clean-up. At last, the geology-engineering-integrated steering mode was introduced to accurately identify the lithology and stratigraphy of formations at the bit. The field application shows the drilling cycle of a well in the L203 well district is shortened from 199 d to 82.6 d; that of the Z201 well district, from 239.5 d to 118 d; the encounter ratio with the platinum target averages 92.8%. The proposed key technology for the deep shale gas horizontal drilling provides guidance and demonstration for future ROP-enhancing and efficiency-improvement of deep shale gas drilling.
Difficulties and countermeasures for ROP improvement of horizontal drilling in the conglomerate oil reservoir of the Mahu sag: A case study of the Jinlong-2 well district
HUANG Honglin, LI Jun, GAO Reyu, YANG Hongwei, LIU Kai, JIANG Zhenxin
2022, 44(2): 153-160.   doi: 10.13639/j.odpt.2022.02.003
[Abstract](0) [FullText HTML](23) PDF 1879KB(13)
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The drilling interval of the Upper Wuerhe Formation of the Mahu conglomerate oil reservoir has high heterogeneity and is prone to collapse. Moreover, the drilling interval of the Jimuhe Formation suffers from low drillability and frequent lost circulation caused by well-developed microfractures. The rate of penetration (ROP) is low, the casing program is complex, and the cycle of drilling and well completion is rather long. Given the above technical difficulties, with the Jinlong-2 well district in the Mahu sag as an example, the plans to optimize the drilling fluid performance and casing program and introduce impregnated PDC hybrid bits were proposed after comprehensive analysis of the geology, lithology, formation pressure system, drilling complexities, and drilling cost. The field application shows that, in the Upper Wuerhe Formation mudstone in the Jinlong-2 well district, the average reaming ratio of wells is reduced from 45.2% to 13.8%, and the drilling/completion period per well is shortened by 50.5%; in the Jiamuhe Formation, the average lost circulation count of wells in horizontal section is decreased by 73.7%, the average volume of lost circulation is reduced by 94.3%, and the ROP is improved by 55.4%. This research provides theoretical support for safe and efficient drilling/completion of horizontal wells in the Mahu conglomerate oil reservoir, and it is highly valuable for building the production capacity of 5 million tons in the Mahu area.
Research and application of a high-temperature high-density drilling fluid system in Well Shunbei-4XH
DONG Xiaoqiang, FANG Junwei, LI Xiong, ZHANG Guo, ZHANG Yongfeng, WANG Congbo
2022, 44(2): 161-167.   doi: 10.13639/j.odpt.2022.02.004
[Abstract](0) [FullText HTML](8) PDF 1223KB(5)
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Well Shunbei-4XH is a key preliminary prospecting well for the No. IV fault zone of the Shunbei oilfield. The Ordovician Yijianfang formation and Yingshan formation of the production casing section of this well are well-developed with micro fractures and karst vugs and represent fracture-type carbonate gas reservoir with the formation temperature exceeding 170 ℃. To enhance the gel thermal stability, plugging and anti-collapse performance, and high-temperature settlement stability of the drilling fluid system and also avoid reservoir damage, the water-based drilling fluid system with thermal resistance to 200 ℃ and density of 2.00–2.25 g/cm3 was developed via development and optimization of key additives. The filter loss at 180 ℃ is 9.2 mL and the 7-day settlement stability coefficient at 200 ℃ is 0.513. The test results of the oscillatory rheometer and dynamic light scattering as well as the field application demonstrate that the presented system has premium flow and lubricating performance, favorable high-temperature settlement stability, and low filter loss at high temperature and high pressure (≤10 mL). It can immediately plug micro fractures of the reservoir to deliver desired temporary plugging.
Drilling fluid solutions to well instability in deep layers of Linhe block of the Bayan Hetao Basin
YAN Ruichang, ZHANG Yu, WU Hongling, CAO Bin, WANG Guanjun, FU Yuehua, CHENG Zhi
2022, 44(2): 168-172, 185.   doi: 10.13639/j.odpt.2022.02.005
[Abstract](0) [FullText HTML](10) PDF 3963KB(9)
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Deep drilling in the Linhe block of the Bayan Hetao Basin suffers from severe well instability, which restrains the high-efficient development of the oilfield. The clay mineral composition and micro structure of the core samples of the troublesome layers were investigated via the X-ray diffraction analysis and scanning electron microscopy, respectively, which reveals that the well instability is mainly attributed to the high water sensitivity and well-developed micro fractures of the formations. Micro fractures are expanded by the water wedge of the invading mud filtrate and formation hydration raises the collapse pressure. These jointly lead to borehole wall caving. The key to solving well instability is to improve the inhibition and plugging performance of the drilling fluid system. Given this, the micro-nano plugging agents were introduced to improve the plugging performance of the drilling fluid system and the polyamine was added for synergy with KCl to enhance the inhibition performance. The laboratory experiments demonstrate that the optimized drilling fluid system presents a reduction of the shale swelling by 62% and rolling recovery of cuttings by over 90%. The field applications in three wells result in the average borehole enlargement ratio below 20% for the Palaeogene formations. The optimized drilling fluid system effectively improves deep well stability in the Linhe block of the Bayan Hetao Basin and technically supports the high-efficient development of the oilfield.
Practice of liner cementing facing both well kick and lost circulation in Well Shi-70 of Qaidam Basin
FEI Zhongming, DANG Donghong, KONG Zhe, HE Jianyong, JIANG Shiwei, GAO Fei, YANG Jie
2022, 44(2): 173-177.   doi: 10.13639/j.odpt.2022.02.006
[Abstract](0) [FullText HTML](3) PDF 889KB(2)
Abstract:
In Well Shi-70, drilling of the liner wellbore section encounters both the high-pressure brine layer and thief zone. The drilling fluid cannot balance the high-pressure aquifer. Meanwhile, internal circulation is present downhole and disturbs the annular pressure system. Consequently, cementing is prone to lost circulation, high difficulties are found in sealing the high-pressure brine layer, and cementing quality is associated with high uncertainty. Based on cement slurry performance tests and cementing practice analysis, the high-temperature-tolerant high-density thief-zone-plugging cement slurry system was designed. The system has a density of 1.88–2.40 g/cm3, with the stability below 0.03 g/cm3, SPN less than 3, adjustable thickening time, and 24 h comprehensive strength of above 18 MPa. The casing/linear injection-annulus squeeze method was adopted in field practices. The required thickening time was estimated from the operation parameters. By reducing the thickening time of the tail slurry and lowering the pump rate in the later stage of slurry displacement, the slurry was gradual thickened and set during the low-rate displacement to rapidly seal off the high-pressure aquifer. Then, cement squeeze through the annulus was performed to seal off intervals above the thief zone. Thus, the Ø273.05 mm liner cementing was successfully completed in this well. The cementing quality at the casing shoe and thief zone was tested to be premium and that at the brine aquifer was also acceptable. The practice provides successful experience for liner cementing in this area.
Application of formation testing while drilling in highly deviated wells with oil-based drilling fluid
WU Jinbo, CHEN Ming, SUN Dianqiang, WANG Feng, ZHOU Jiheng
2022, 44(2): 178-185.   doi: 10.13639/j.odpt.2022.02.007
[Abstract](0) [FullText HTML](5) PDF 1779KB(3)
Abstract:
Highly deviated well is deployed in the rolling exploration of western South China Sea oilfield to simultaneously probe into multiple layers, and high-density oil-based drilling fluid is used to maintain wellbore stability. Under such circumstances, the conventional wireline formation testing has high operation risks and difficulties, and the conventional sonic, density and resistivity sensors have trouble in accurately distinguishing formation oil and filtrate of oil-based drilling fluids. Therefore, the sampling-while-drilling technique is required to ensure the acquisition of qualified data. The FASTrak Prism, a tool for pressure measurement and sampling while drilling, can run in hole with the BHA and overcome the sticking and blockage issues of wireline well logging. The spectrometry-while-drilling technique enables accurately identifying the formation oil by measuring the (methane) gas content of fluids via the multi-channel density measurement. The field application of the FASTrak Prism-based pressure measurement and sampling while drilling in the reserves assessment for western South China Sea oilfield demonstrates how to rapidly differentiate filtrate of oil-based drilling fluids and formation oil with the help of the spectrometry-while-drilling sensor, and this technique can help to gain key data, such as formation pressure, reservoir physical properties, and fluid properties, for the exploration-development-integrated reserves assessment. The successful application validates the feasibility of the proposed technique in the integrated exploration and development of western South China Sea oilfield.
Well logging-based anti-drilling property evaluation of igneous rock in Bozhong 34-9 oilfield
PENG Chao, DENG Jinhui, TAN Zhongjian, QIN Yanyan, YUAN Yadong, YAO Qiang
2022, 44(2): 186-190.   doi: 10.13639/j.odpt.2022.02.008
[Abstract](0) [FullText HTML](20) PDF 1353KB(2)
Abstract:
The igneous rock of the Dongying Formation in the Bozhong 34-9 oilfield is found with a low average penetration rate and the drilling time-efficiency is severely impacted. Given this, this research investigated the rock mechanical properties of igneous rock. The rock mechanical properties of the igneous rock interval were calculated using the well logging data. The correlation between the anti-drilling property and interval transit time of sonic logging of the igneous rock in the study area was modeled in a mathematical-statistical approach, for evaluating the anti-drilling characteristics. Our research shows that the formation profile of anti-drilling characteristic parameters, based on well logging and rock properties, can truly represent the igneous rock in the study area. The prediction accuracy of the rock drillability, compressive strength, and shear strength reaches about 90%. Based on the above analysis, the bit and bottomhole assembly were optimized and then applied in several ten wells, which were found to increase the average penetration rate of the igneous rock by about 20%. The drilling rate and efficiency of the study area are effectively improved.
OIL AND GAS PRODUCTION
Optimization and application of brittleness evaluation methods for continental organic-rich shale: A case study of the 2nd Member of Kongjiadian Formation, Cangdong Sag, Bohai Bay Basin
HAN Wenzhong, DOU Yu, LI Haodong, ZHANG Wei, SHI Zhannan, DONG Jiangchang
2022, 44(2): 191-198.   doi: 10.13639/j.odpt.2022.02.009
[Abstract](0) [FullText HTML](3) PDF 1466KB(0)
Abstract:
Shale brittleness is one of the key indexes affecting dimensions of hydraulic fractures and determining the producibility of trapped hydrocarbons in shale. Therefore, it is one of the major parameters for evaluation of the planar sweet-spot zone, horizontal drilling sweet-spot target, and sweet-spot hydraulic fracturing stage. The shale brittleness geological model was built on the framework of the felsic mineral, carbonate, clay, and organic matter, and five shale brittleness evaluation formulas based on mineral composition were developed, via the X-ray diffraction (XRD) mineral analysis, TOC measurement, and tri-axial rock mechanic tests of 17 shale samples collected from the 2nd Member of the Kongjiadian Formation in the Cangdong sag. The novel brittleness evaluation method that comprehensively incorporates TOC and brittleness of various minerals, and the simplified brittleness evaluation considering two key parameters (namely TOC and clays) were selected via the comparison with the brittleness formula based on rock mechanic parameters. The former applies to intervals with sufficient XRD mineral analysis data, while the latter applies to well logging evaluation. The mineral composition-based method was applied to the C6 interval of the 2nd Member of the Kongjiadian Formation in Well G108-8, which also considered the oil content, and the shale interval with high brittleness, and high or medium oil content was identified as the engineering-oil content dual sweet-spot. The formation testing results of Wells Z1608 and GX5 validated the effectiveness of the developed brittleness evaluation method for shale oil exploration and the vital guidance on sweet-spot stage identification and hydraulic fracturing design.
Effects of injected water quality on fractured oil reservoirs
SUN Tao, MENG Xiangjuan, WANG Jing, LI Zhen, WU Hongjun, AKEBAER Cadebai, ZHAO Jing
2022, 44(2): 199-203, 210.   doi: 10.13639/j.odpt.2022.02.010
[Abstract](0) [FullText HTML](3) PDF 1400KB(0)
Abstract:
This research investigated the reservoir damage of naturally fractured oil reservoirs caused by suspended solids and oil in injected water via laboratory core flooding tests. The results showed that the median diameter of suspended solid particles and oil content are the main factors controlling reservoir damage. With the permeability damage upper limit of 20%, the injected water quality requirements are that the median diameter and content of suspended solids should be no more than 10 μm and 10 mg/L respectively, and the oil content should be no more than 10 mg/L, for fracture widths ≤50 μm; the median diameter and content of suspended solids, no more than 20 μm and 10 mg/L respectively, and the oil content no more than 20 mg/L, for fracture widths of 50–100 μm; the median diameter and content of suspended solids no more than 50 μm and 50 mg/L respectively, and the oil content no more than 40 mg/L, for fracture widths of 100–200 μm; the median diameter and content of suspended solids no more than 60 μm and 80 mg/L, respectively, and the oil content no more than 50 mg/L. The findings of this research laid down the theoretical basis for high-efficiency water flooding of fractured oil reservoirs.
Experimental study on fracture propagation during in-fracture temporary plugging and diverting fracturing in carbonate rock
LI Yue, MOU Jianye, JIE Qiong, ZHANG Shicheng, MA Xinfang, ZHANG Jun
2022, 44(2): 204-210.   doi: 10.13639/j.odpt.2022.02.011
[Abstract](0) [FullText HTML](3) PDF 3191KB(1)
Abstract:
Karst caverns are the main storage space in the fractured-vuggy carbonate reservoirs in the Tahe oilfield, and many accumulations around wellbores are not located in the direction of the maximum horizontal principal stress. Therefore, the temporary plugging and diverting fracturing is demanded for stimuilation of reservoirs deviating from the maximum horizontal principal stress. The simulation experiments of in-fracture temporary plugging and diverting fracturing (ITPDF) were performed using 30 cm × 30 cm × 30 cm outcrop specimens of carbonate rock. The fracture morphology after conventional fracturing and ITPDF was observed via CT scanning to analyze the effects of the in-situ stress difference, natural fractures, and fracturing fluid viscosity on the fracture morphology, and the fracture initiation in ITPDF was theoretically investigated. The research shows that well-developed natural fractures or beddings in rock and sufficient temporary plugging pressure are essential for a successful ITPDF. ITPDF is workable under varied in-situ stress differences; the smaller the in-situ stress difference, the more complex the fracture morphology, and the larger the stimulated volume. Entry of temporary plugging agent into fractures is critical for diverting fracturing. A fracturing fluid with too low viscosity is less capable of sand carrying and may induce primary fractures with small aperture, hindering the smooth entry of temporary plugging agent. The research results provide a theoretical basis for the fracturing design of fractured-vuggy carbonate reservoirs in the Tahe oilfield.
Development and application of the emulsion polymer/ core-shell microsphere profile control system
LIU Guangpu, JU Ye, LI Jianye, LI Xiang, QIAO Qilin
2022, 44(2): 211-216.   doi: 10.13639/j.odpt.2022.02.012
[Abstract](0) [FullText HTML](6) PDF 2415KB(3)
Abstract:
Pathways for moderate–strong water channeling are gradually formed in deep zones of the medium–low permeability sandstone reservoirs in the Bohai Sea during during water flooding. The conventional polymer microsphere system cannot facilitate profile control and plugging and present desired injectivity in sandstone reservoirs. To solve this problem, the emulsion polymer + core-shell microsphere profile control system that can form network structures in deep formations was developed. Laboratory tests were performed to investigate the viscosity variation, particle size variation and dynamic transportation in porous medium of aggregates of the comoposite system. The results show that the comoposite system composed of emulsion polymer solution (hydrolysis degree = 30%) and core-shell polymer microspheres (core-shell charge ratio = 1∶3) with the mass ratio of 0.0646∶1 has the viscosity of 18 mPa·s and the particle size of 102 μm, and can rachieve the plugging efficiency up to 86.6%. The field application of this system in the S cluster of the Bohai B oilfield demonstrates that the oil production increment of the cluster exceeds 5 600 m3, the maximum decrease of water cut is up to 7%, and the effective duration lasts for more than six months, which indicate the good performance of water control and production enhancement.
Application of intelligent solid tracers in production profile testing of offshore horizontal wells
LIU Zimin, LI Haitao, YANG Jingwen, NIE Song, MA Xin, GAO Sujuan
2022, 44(2): 217-224.   doi: 10.13639/j.odpt.2022.02.013
[Abstract](0) [FullText HTML](0) PDF 1840KB(0)
Abstract:
Given the harsh testing conditions, high cost, and low accuracy of production profile testing of offshore horizontal wells, an production profile testing method based on intelligent solid tracers was proposed for offshore horizontal wells. The release pattern and influential factor of intelligent solid tracers were investigated. It is shown that the release rate of solid tracers is high upon the initial contact with fluids; it slows down and eventually reaches equilibrium, as the contact time lapses. Moreover, solid tracers have high tolerances to high temperatures and salinity. The release rate is directly proportional to temperature and inversely proportional to salinity. The release rate is independent of the flushing rate. Based on the release pattern of solid tracers and the single-phase steady flow model of horizontal wells, the horizontal well production profile interpretation method was developed and practiced in the field, together with the active switch water control technique and AICD water control technique. The field application demonstrates that before adjusting the water control tool, the liquid production contributions of the heel, middle, and toe sections of the tested well are 88.57%, 5.43%, and 6%, respectively; they change to 50%, 17.19%, and 32.81%, correspondingly, after the water control tool is adjusted. This validates the performance of the water control tool to balance the liquid production of each section. This technology is of great practical significance for promoting high-efficiency cost-effective recovery of offshore horizontal wells in China.
Drainage and production optimization of electric submersible pump for depressurization recovery of offshore natural gas hydrates
PING Xiaolin, HAN Guoqing, CEN Xueqi, ZHU Weitao, BAI Zhenqiang, WANG Qinghua, PENG Long
2022, 44(2): 225-232.   doi: 10.13639/j.odpt.2022.02.014
[Abstract](0) [FullText HTML](4) PDF 1465KB(1)
Abstract:
The pilot production of natural gas hydrates demonstrates that the electric submersible pump (ESP) is the most applicable tool to artificial lifting in depressurization recovery of natural gas hydrates. Based on a comprehensive analysis of multiple factors, such as the complex zonal production pipe string, the temperature field of the ambient seawater environment, ESP, and gas-liquid separator, the gas-liquid two-phase wellbore flow model was developed for ESP-assisted depressurization recovery of offshore natural gas hydrates. The heat transfer processes of different pipes were analyzed and the flow regime distribution, and temperature and pressure profiles of different pipes were predicted. Finally, the production operation was optimized using the proposed model. The results show that during depressurization recovery of natural gas hydrates, the working fluid level in the gas production pipe can be lowered by increasing the wellhead back pressure or decreasing the ESP frequency, to reduce the risks of continuous water production from gas production pipes. This research provides references for production optimization of ESP-based dewatering and gas recovery during depressurizing offshore natural gas hydrate reservoirs.
INTELLIGENCE COLUMN
Applications of Internet of Things in offshore well drilling/completion
LI Jinman, SUN Jinsheng, HUO Hongbo, TAO Lin, LIU Zhaonian, CHENG Linsong
2022, 44(2): 233-240.   doi: 10.13639/j.odpt.2022.02.015
[Abstract](0) [FullText HTML](8) PDF 1295KB(3)
Abstract:
Techniques of Internet of Things (IoT) have great advantages for offshore well drilling/completion in harsh environments with high risks. During intelligentization of offshore oilfields, the offshore well drilling/completion based on the Internet of Things was preliminarily developed by constructing the IoT core architecture for offshore well drilling/completion, deploying edge IoT acquisition nerve terminals, and improving the industrial Internet. With the IoT techniques, rapid progress of offshore well drilling/completion has been made in multi-disciplinary fields, which realized the information digitalization mutual communication of the bottomhole and wellbore, the information digitalization fusion of formation data and the well trajectory, and oil well lifecycle safety digitalization. The goods-and-materials tracking technique ensures efficient regional resource sharing and also personnel safety. Applications of Internet of Things in offshore well drilling/completion represent bold innovation and breakthroughs of the conventional petroleum industry, which has gained preliminary achievements and highlights wide application prospect.
Intelligent identification and time-efficiency analysis of drilling operation conditions
HU Zhiqiang, YANG Jin, WANG Lei, HOU Xutian, ZHANG Zhenxiang, JIANG Menglei
2022, 44(2): 241-246.   doi: 10.13639/j.odpt.2022.02.016
[Abstract](0) [FullText HTML](2) PDF 1205KB(3)
Abstract:
Currently, the operation condition identification and time-efficiency analysis for drilling are mostly dependent on the data transfer efficiency of on-site devices and empirical diagnosis of engineering operators, which suffer from the incapability of handling massive real-time operation data, slow decision making-feedback mechanism, and low prediction accuracy. To efficiently assist the optimization of decision-making of engineering personnel using mud logging data, the data transfer module based on the WITS and WITSML standards was developed, the algorithm integrating the threshold method and neural network method was constructed,the historic data sheet including wellsite information and operation condition identification results of an individual well was tabulated, and the time-efficiency analysis software based on mud logging historic data was programmed. The research showed that the intelligent drilling operation condition identification results of the case-study well are consistent with the actual operation conditions, with the prediction accuracy over 90% and calculation error less than 1% for the drilling time-efficiency, and the application performance is highly satisfactory. This research effectively improves the efficiency of identifying drilling operation conditions and analyzing drilling time-efficiency, and provides guidance for drilling practice.
Application of knowledge-driven data mining in the complex reservoir evaluation
GUO Sujie, LI Jingwei, YU Weigao, LYU Jiangping, JIANG Weizhai, DAI Guangkuo, HU Lin
2022, 44(2): 247-252.   doi: 10.13639/j.odpt.2022.02.017
[Abstract](0) [FullText HTML](1) PDF 1409KB(2)
Abstract:
Several ten techniques were introduced and further developed for the complex oil and gas reservoir evaluation. However, these techniques are found with both consistency and differences/contradictions. Given this, knowledge-driven data mining, combined with the identified data response characteristics of multiple complex reservoirs in the study area, was used to search for sensitive parameters from mud logging and well logging data of target layers of formation testing. Subsequently, factor analysis, multivariate discriminant analysis, and grey correlation analysis were performed to build the multi-parameter reservoir fluid property evaluation model. The application results showed that the presented multi-parameter evaluation model is objective and effective. It delivers effective evaluations of the bio-degraded oil reservoir, heavy oil reservoir, and mixed-source oil reservoir in the study area, and provides inspiring experience for the fine evaluation of complex reservoirs. It can be further promoted to relevant oilfields and makes contributions to improving the efficiency of oilfield exploration and development.
Research progress of data-driven injection production optimization of complex oil reservoirs
SONG Laiming, WANG Chunqiu, LU Chuan, DING Zupeng, LI Guiliang, TAN Chaodong, CHENG Shiqing
2022, 44(2): 253-260.   doi: 10.13639/j.odpt.2022.02.018
[Abstract](0) [FullText HTML](2) PDF 956KB(1)
Abstract:
Due to the complicated injector-producer correlation and frequent variation of the displacement field, the mature oilfield after water flooding is found with drastic variation of the underground oil/water distribution pattern and requires refined recovery. To promote the intelligentization of the petroleum industry, the research and application of data-driven injection-production optimization of complex oil reservoirs were reviewed, which highlighted big data-driven models and artificial intelligence algorithms for injector-producer connectivity analysis and production optimization. This review indicates that precise modelling of complex oil reservoirs and rapid solving of relevant optimization problems are key to intelligentization of oilfield production and recovery and the crossing and fusion of data, mechanisms, and artificial intelligence algorithms is the development orientation of future research on smart oilfield recovery.
Working condition diagnosis of electric submersible pump based on machine learning
WANG Biao, HAN Guoqing, LU Xin, TAN Shuai, ZHU Zhiyong, LIANG Xingyuan
2022, 44(2): 261-268.   doi: 10.13639/j.odpt.2022.02.019
[Abstract](0) [FullText HTML](4) PDF 1333KB(3)
Abstract:
The working condition diagnosis model of the electric submersible pump (ESP) based on machine learning (ML) using real-time current data was established to reduce human error in the working condition recognition and analysis of ESPs with current cards. Firstly, the feature engineering (FE) method was used to acquire the eigenvalues of ESP current. Secondly, the principal component analysis (PCA) method was used for the unsupervised dimensionality reduction clustering of eigenvalues, and the results of clustering were compared with the actual working conditions to prove the effectiveness of clustering. Thirdly, the logistic regression (LR) model was established using the labeled data after dimensionality reduction. Finally, the untrained data was substituted into the established model for error analysis. The complete working condition diagnosis process based on ML using high-density real-time current data was conducted for 56 ESP wells in Oilfield A. The results show that the model successfully realizes the classification and recognition of four common working conditions, including normal, pump depletion, overload shutdown, and frequent short-cycle operation. The accuracy, precision, and recall of the diagnosis reach more than 80%, while the F1 score reaches 85%, which meets the requirement of classification. The feasibility and reliability of working condition diagnosis of ESPs based on ML using real-time current data are proved.
Current situation and future development of CNPC fracturing fluid technology
p class, CHENG Xingsheng, LU Yongjun, GUAN Baoshan, WANG Liwei, ZHAI Wen, MING Hua
2014, 36(1): 1-5.  
[Abstract](4756) [PDF 1271KB](5728)
The current research situation and development trend of particle profile-control plugging agents
ZHAO Xiutai, CHEN Zehua, CHEN Wenxue, MA Hanqing, ZHAI Dongqi, REN Zenglei
2015, 37(4): 105-112.   doi: 10.13639/j.odpt.2015.04.027
[Abstract](972) [PDF 1463KB](2745)
The status, challenge and prospect of shale oil exploration and development in China
FU Qian
2015, 37(4): 58-62.   doi: 10.13639/j.odpt.2015.04.016
[Abstract](853) [PDF 1404KB](2040)
Development status and trend of deepwater oil-gas exploration and development technology
LV Jianzhong, GUO Xiaoxia, YANG Jinhua
2015, 37(1): 13-18.   doi: 10.13639/j.odpt.2015.01.004
[Abstract](840) [PDF 2988KB](1404)
Common problems of pumping bridge plug and clustering perforation for horizontal shale gas well and countermeasures
LIU Zulin, YANG Baojun, ZENG Yuchen
2014, 36(3): 75-78.   doi: 10.13639/j.odpt.2014.03.019
[Abstract](1124) [PDF 1257KB](1206)
Research progress of wellbore stability in hard brittle shale
ZHAO Kai, FAN Yongjie, YU Bo, HAN Jiyong, XU Yonghua, GAO Shihui
2016, 38(3): 277-285.   doi: 10.13639/j.odpt.2016.03.001
[Abstract](1076) [PDF 7533KB](1816)
Rock fragmentation mechanism and application of near-bit torsion impacter
LI Wei, HE Xuanpeng, YAN Tie, WANG Shuchao
2014, 36(5): 1-4.   doi: 10.13639/j.odpt.2014.05.001
[Abstract](905) [PDF 1747KB](1439)
Analysis of factors affecting the formation of Effective Stimulated Reservoir Volume(ESRV)
CUI Mingyue, LIU Yuzhang, XIU Nailing, DING Yunhong, YAN Xuemei, DOU Jingjing, FU Haifeng
2014, 36(2): 82-87.   doi: 10.13639/j.odpt.2014.02.021
[Abstract](854) [PDF 2013KB](1083)