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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](21) PDF 1669KB(1075)
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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.
Optimization of cable-controlled intelligent separate-layer water injection technology in Daqing Oilfield
JIN Zhendong, TONG Yin, WANG Fengshan, GAO Guanglei, LI Jinghui, WANG Jiechun
[Abstract](0) [FullText HTML](11) PDF 1153KB(3)
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The cable-controlled intelligent separate-layer water injection technology realizes the continuous monitoring and real-time measurement and adjustment of downhole parameters, and provides sufficient data for reservoir analysis. However, due to the application of multidisciplinary downhole tools and the complexity of the technology, it is found in the previous field test that the number of wells with cable-controlled intelligent separate-layer water injection wells operating for more than 2 years accounts for only 51.9% of the total, which cannot meet the requirement of large-scale application. Through the fault analysis of the previous test wells, this paper finds the key factors affecting the process reliability. To solve the main affecting issues found in the fault analysis, the flow control valve of the cable-controlled intelligent water distributor, the cable sealing connection process and the structure of the well-flushing valve of cable-through packer are improved and optimized, and the smooth opening and closing of the flow control valve of the cable controlled intelligent water distributor under the pressure difference of 10 MPa is realized, with the leakage less than 1 m3/d. The connection between the cable and the cable-controlled intelligent water distributor is reliable, and the cable can be feed through smoothly through the upper and lower connectors of the cable-through packer. After the optimization and improvement, by April 2022, this technology has gone through field tests in 223 wells, and the proportion of wells running smoothly for more than 2 years increased from 56.1% to 91.9%.After optimization, the reliability of the cable-controlled intelligent separate-layer water injection process has been improved, laying a foundation for large-scale application of the technology in oilfields.
Intelligent operation control system of pumping unit
SUN Yan’an, LI Qiang, LEI Yu, QIAN Kun, WANG Xinmin, ZHENG Dongzhi
[Abstract](0) [FullText HTML](6) PDF 949KB(1)
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Currently, after years of development of oilfields in China, the liquid production of many oil wells has decreased year by year, and the phenomenon of insufficient hydrocarbon supply is becoming more and more common in medium and low production wells. The unbalanced supply and production of these oil wells is the main reason for the high energy consumption and low efficiency of pumping wells. To solve the key problem of supply-production balance, this paper develops a new intelligent control system of pumping unit based on electrical control devices and digital technology, which can regulate the operation parameters of the pumping unit according to the data characteristics of the collected pumping mechanical and electrical parameters without introducing high-cost sensors and complex on-site transformation, maintain the oil well production under reasonable flow pressure in real time, which in turn, maximize production capacity of the oil well and improve the efficiency of the pumping production system. In the field test of 11 wells, after the application of the intelligent operation control system of pumping units, the average liquid level of the oil wells increased by 36 m, the average daily liquid output increased by 2.22 t, and the system efficiency increased by 2%. The system improves the intelligence level of the pumping production system, saves energy consumption, and reduces the maintenance workload, which is of great significance for improving the level of information management and reducing the operating cost of the pumping production system.
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](11) PDF 1943KB(24)
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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.
Application of water-blocking and oil-permeable proppant in the high water-cut reservoir
ZHOU Wanfu, LI Qingsong, HAN Zhonglian, WANG Li, FU Hairong, LI Shengli
[Abstract](0) [FullText HTML](10) PDF 1266KB(1)
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Considering that the conventional proppant quartz sand fails in control the water cut of the produced fluid in fracturing stimulation Daqing Oilfield at the ultra-high water cut stage, the water-blocking and oil-permeable proppants were developed. The quartz sand was coated by organosilicon compound with active groups, and the lyophobic and lipophilic property was imposed on the surface of quartz sand to improve the water control ability of proppants. The laboratory evaluation shows that the oil wettability index of the proppant is greater than 0.75, and the permeation capacity of oil is more than 10 times that of water under a certain pressure difference. The success rate of water control is 100%, which is 54 percentage points higher than that of conventional proppant. This proppant provides a new method for reducing the development cost and increasing the recoverable reserves.
Analysis of friction upon drill string for 3D horizontal wells ontight oil platform in Daqing Oilfield
SHAO Shuai
[Abstract](0) [FullText HTML](26) PDF 1138KB(15)
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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.
Research and application of macro management chart on working condition of water injection well based on K-means-SVM algorithm
ZHANG Jiang, YANG Xuefeng
 doi: 10.13639/j.odpt.2022.03.019
[Abstract](0) [FullText HTML](3) PDF 4246KB(4)
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The macro management chart on the working condition of water injection wells is an important map that reflects the working condition of water injection wells. The construction of digital oil field provides massive data for the dynamic monitoring of water injection wells. Based on the massive data samples from water injection wells, by using the K-means clustering algorithm, macro working conditions of water injection wells, that is, the macro management chart composed the area to be reformed, the under-injection area, the normal injection area, the over-injection area, and the pending area was established. The regional boundary line was determined by using the support vector machine (SVM), and a control chart model on working condition management of injection wells was established. Using this model, the drawing method and application process of block macro management chart and single well dynamic management chart were formed. The field application shows that the macro control chart model constructed based on the big data method can reflect the relationship between the production dynamic characteristics, water injection intensity, water absorption capacity and injection completion rate of the research block and single well, which provides a decision-making basis for the next implementation of measures on water injection wells.
Progress in key technologies of scaling prevention and treatment in ASP flooding
CHENG Jiecheng
[Abstract](0) [FullText HTML](15) PDF 1579KB(6)
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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](13) PDF 2521KB(4)
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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](777) PDF 1629KB(2738)
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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(3).  
[Abstract](0) PDF 1172KB(67)
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2022, 44(3): 1-4.  
[Abstract](1) [FullText HTML](53) PDF 1447KB(48)
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DRILLING AND COMPLETION
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
2022, 44(3): 269-275.   doi: 10.13639/j.odpt.2022.03.001
[Abstract](0) [FullText HTML](84) PDF 1244KB(86)
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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
2022, 44(3): 276-282.   doi: 10.13639/j.odpt.2022.03.002
[Abstract](0) [FullText HTML](59) PDF 2216KB(56)
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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.
Research progress of intelligent fluid and its application to drilling fluids
HUANG Zhiyang, ZHAO Xionghu, MIAO Liujie, JIA Xiangru
2022, 44(3): 283-290.   doi: 10.13639/j.odpt.2022.03.003
[Abstract](0) [FullText HTML](51) PDF 1111KB(35)
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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.
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
2022, 44(3): 291-296.   doi: 10.13639/j.odpt.2022.03.004
[Abstract](0) [FullText HTML](40) PDF 1962KB(25)
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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.
Risk assessment and control technology for deep water and shallow gas drilling
YU Guimin, GU Chunwei, SONG Yu, ZHAO Yuhang, LI Lei, LIU Hexing, DU Wei, ZHAO Shaowei
2022, 44(3): 297-301.   doi: 10.13639/j.odpt.2022.03.005
[Abstract](0) [FullText HTML](42) PDF 1260KB(27)
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Shallow gas is often encountered during the development of deep-water oil and gas fields. Shallow gas is an overpressure gas accumulated on the seabed. Due to the prediction difficulty and few control methods, the area where shallow gas exists is usually avoided by changing well positions. This restricts the site selection of drilling wellheads, and even fails to achieve the purpose of reservoir exploration. Based on ANSYS Fluent software, by using VOF model and k-ε turbulence model, a calculation model for transient multiphase fluid flow when shallow gas blowout was established, and the shallow gas blowout features under the conditions of different pressure coefficients, reservoir scales, and wellbore sizes were obtained. Based on the gas flow characteristics and the reservoir scale, a numerical model of shallow gas blowout was established, and a prevention and control method of adopting active blowout technology for shallow gas at medium and high-risk level was put forward. This research has theoretical guiding significance for actively responding to potential geological disasters caused by shallow gas.
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
2022, 44(3): 302-308.   doi: 10.13639/j.odpt.2022.03.006
[Abstract](0) [FullText HTML](42) PDF 1703KB(26)
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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.
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
2022, 44(3): 309-320.   doi: 10.13639/j.odpt.2022.03.007
[Abstract](0) [FullText HTML](39) PDF 2310KB(25)
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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.
OIL AND GAS PRODUCTION
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
2022, 44(3): 321-327.   doi: 10.13639/j.odpt.2022.03.008
[Abstract](0) [FullText HTML](17) PDF 2066KB(12)
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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.
Research status and progress of artificial lifting of shale gas wells abroad
YE Changqing, MA Huiyun, CAI Daogang, GAO Xiang, YANG Zhenzhou, LIU Qing
2022, 44(3): 328-334, 365.   doi: 10.13639/j.odpt.2022.03.009
[Abstract](0) [FullText HTML](41) PDF 1959KB(32)
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Rapid production decline after fracturing is a prominent characteristic of shale gas wells and it is hard to deliver beneficial recovery without appropriate intervention. One of the critical tasks of high-efficiency recovery of shale gas is to optimize the artificial lifting of shale gas wells so as to drain wellbore liquid loading, stabilize gas production, and increase recoverable reserves per well. It analyzed the application performance of various artificial lifting techniques in North America and pointed out the constraints of applications and present technical disadvantages. With the fracturing fluid flowback, slug flows, early and late wellbore conditions of production wells and production characteristics through the lifecycle of shale gas wells taken into consideration, the optimization plan of artificial lifting was developed and the factors, to which extra attention shall be paid, during the optimization process were clarified. Finally, two novel technical mechanisms to boost shale gas production via pressurization and their application performance were introduced. This research provides references for the high-efficiency cost-effective development of shale gas in China.
Optimization and effect analysis of drainage gas recovery technology in Kela 2 gas field
YE Zhengrong, QIU Zhichao, ZHOU Xiang, YI Ran, LIU Xiang, ZHAO Zhihong
2022, 44(3): 335-340.   doi: 10.13639/j.odpt.2022.03.010
[Abstract](0) [FullText HTML](36) PDF 1347KB(19)
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The Kela 2 gas field is the main gas field for the West-East natural gas transmission project. Due to geological reasons, some gas wells in Kela 2 gas field have already produced water, which seriously affects the productivity and ultimate recovery of the gas wells. It is urgent to take drainage gas recovery measures to maintain the stable production of gas wells and the uniform advancement of edge and bottom water. The adaptability of the commonly used drainage gas recovery technologies was analyzed, and found that the most suitable drainage gas recovery technology in the Kela 2 gas field was wellhead pressurization and pipe string optimization, then the application effect of which was evaluated. The results show that: the pipe string optimization and wellhead pressurization can be used as the drainage gas recovery process in Kela 2 gas field; for water-producing gas wells, the optimal size of the running tubing is 62 mm, which can effectively carry liquid and prolong natural flow production. The wellhead pressurization process can effectively reduce the wellhead pressure and release the formation energy. When the wellhead pressure was reduced by 6 MPa, the corresponding formation pressure can be reduced by about 10 MPa after natural flow production, which greatly prolongs the gas well flowing production period. The research results show that wellhead pressurization can be used as the preferred drainage gas recovery process in the Kela 2 gas field, and the pipe string optimization process can be used as an alternative one.
Research and application of high-viscosity friction reducer
ZHOU Hongtao, SONG Zongxiao, QIU Xiaohui, ZHANG Jingchun, MA Shou, ZHENG Boxuan, WU Xiaotong
2022, 44(3): 341-347.   doi: 10.13639/j.odpt.2022.03.011
[Abstract](0) [FullText HTML](32) PDF 931KB(13)
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In recent years, high-viscosity friction reducer (HVFR) has gradually replaced guar gum and its derivatives, becoming mainstream chemicals for fracturing fluid, and has gradually been applied in the field successfully. Based on this background, the development history, performance evaluation, strengthening and field application of HVFR are described in this paper. Compared with traditional fracturing fluids, the low-concentration HVFR has more stable drag-reduction performance, and it exhibits excellent sand-carrying performance, which poses lower damage to reservoirs, showing a great development potential.
Practice of air foam flooding in the Lukeqin deep heavy oil reservoir
ZHU Yongxian, ZHANG Mingmin, ZHANG Kai, XIE Dianhe, WANG Xiaotao, ZHOU Hongtao
2022, 44(3): 348-353.   doi: 10.13639/j.odpt.2022.03.012
[Abstract](0) [FullText HTML](16) PDF 1144KB(7)
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The Lukeqin Triassic heavy oil reservoir is recovered via normal-temperature water flooding. However, due to the viscous fingering of injected water, the recovery performance was degraded year by year. To improve the overall development efficiency of the oilfield, the field testing of foam flooding-based EOR of deep heavy oil reservoirs was performed. The high temperature-tolerant high salinity-resistant foaming agent was selected according to the reservoir conditions and the foaming gas and injection parameters were optimized. Then, the field testing of the oxygen-reduced air foam flooding was performed in the YD203 well district in a slug alternating injection pattern. For 19 wells of the YD203 well district, the effective rate for 4 years was 89%, the overall water cut decreased by 39.5%, the cumulative oil production increment exceeded 20000 tons, and the estimated recovery factor of the oilfield was 6.8%. The findings of this research provide important guidance for further improving the recovery factor of the Lukeqin deep heavy oil reservoir and achieving the sustainable development of the oilfield.
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
2022, 44(3): 354-359.   doi: 10.13639/j.odpt.2022.03.013
[Abstract](0) [FullText HTML](35) PDF 2089KB(10)
Abstract:
In the Suqiao storage, the average reservoir depth of gas wells is near 5000 m, the formation temperature is 140 ℃–150 ℃, 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 ℃-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.
Experimental study on formation process of methane hydrate in PAM-AA hydrogel system
SHI Haolin, XU Jiafang, CHEN Jie, YANG Xiaolong, DING Tingji
2022, 44(3): 360-365.   doi: 10.13639/j.odpt.2022.03.014
[Abstract](0) [FullText HTML](14) PDF 1646KB(5)
Abstract:
As a clean energy with huge reserves and a widely used industrial raw material, natural gas hydrate has attracted more and more attention from scholars and industry. The formation process of methane hydrate in the reactor containing polyacrylamide-acrylic acid (PAM-AA) salt solution was experimentally studied, and the effect of PAM-AA hydrogel system on the formation of methane hydrate was revealed. The results show that the hydrogel system promotes the formation of methane hydrate at 2 ℃ and 8 MPa; the hydrogel system inhibits the formation of methane hydrate at 2 ℃ and 4.5 MPa; the PAM-AA hydrogel system can disrupt the normal formation of methane hydrate, manifesting as shortening the time for massive formation of methane hydrate (promoting) and hindering mass transfer between gas and liquid (inhibiting); the experimentally generated methane hydrate forms are divided into two types, namely loose and containing a lot of pores or hard and dense, which correspond to the systems that inhibit/promote the formation of methane hydrate, respectively. Exploring the generation process of methane hydrate in the PAM-AA hydrogel system can provide a reference for the generation, prevention, storage, and transportation of methane hydrate in industrial field.
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
2022, 44(3): 366-375.   doi: 10.13639/j.odpt.2022.03.015
[Abstract](0) [FullText HTML](31) PDF 2445KB(20)
Abstract:
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 and the total pressure consumption of the system is about 42 MPa, which can 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.
INTELLIGENCE COLUMN
Digital technology energizes offshore oilfield development:
LI Jinman, ZHOU Shouwei, SUN Jinsheng, LIN Yang, HUO Hongbo, CHENG Linsong
2022, 44(3): 376-382.   doi: 10.13639/j.odpt.2022.03.016
[Abstract](0) [FullText HTML](48) PDF 1458KB(23)
Abstract:
Energizing the oilfield development with digital technology is the megatrend of the advancement of the future petroleum industry. By building the site-scale Internet of Things (IoT), applying artificial intelligence and big data, and creating the three-dimensional digitalized working platform, the Bohai oilfield preliminarily delivered the digital technology-boosted offshore oilfield development mode. Nerve endings of the edge IoT were built to promote full sensing and reliable transfer of the IoT, facilitate data-driven closed-loop smart management of the reservoir, injector-producer, safety, and equipment and facilities, and realize smart operation and maintenance of active offshore production facilities. The onshore-offshore connectivity and operation efficiency were greatly enhanced and the digital technology considerably contributed to the high-quality development of the Bohai oilfield. Moreover, the construction of the smart offshore oilfield was clarified and the outlook of the smart oilfield techniques such as the intelligent digital twin and edge-cloud coordination was presented. This successful trial on building the smart offshore oilfield with the help of digital technology has delivered preliminary achievements and demonstrates tremendous space for future application promotion.
Oil reservoir-well-integrated intelligent diagnostic model based on ensemble learning
YANG Yaozhong, BING Shaoqiang, MA Chengjie, YU Jinbiao, WANG Xiang, LI Bingchao, JING Ruilin, SUN Zhaolong
2022, 44(3): 383-389.   doi: 10.13639/j.odpt.2022.03.017
[Abstract](0) [FullText HTML](39) PDF 1182KB(23)
Abstract:
At present,reservoir engineering and production engineering analyze anomalies separately, using specialized data and information systems of their disciplines. In such cases, the complex correlation between the reservoir and well systems is somewhat simplified and thus the resultant diagnosis of production anomalies is inadequate and the proposed treatment lacks pertinence. Given this, the oil reservoir-well-integrated intelligent diagnostic model, based on the ensemble learning consisting of the random forest and convolution neural network (CNN), was developed. For different oil reservoir and well anomalies such as ineffective water injection and pump leakage, the decision-making tree based on the random forest was used to investigate abnormal conditions of oil reservoirs, the CNN was adopted to diagnose well anomalies, and finally, the integrated diagnosis was produced by integrating the two classifiers via ensemble learning. The field validation of the diagnosis showed the presented method improves the performance and normalization capacity of the constituent classifier via ensemble learning and the integrated diagnosis of reservoir and well anomalies is delivered, with an application accuracy of over 90%. This invention can strongly support the intelligent management of oilfields.
Development and application of intelligent switch control system for layered oil production
TIAN Fangyong, CHEN Chuandong, LI Jinhong, LUO Dailiang, HAI Yongqiang
2022, 44(3): 390-395.   doi: 10.13639/j.odpt.2022.03.018
[Abstract](0) [FullText HTML](18) PDF 2034KB(10)
Abstract:
Layered oil production is an important means to solve the interlayer and plane contradiction and to tap the potential of remaining oil in high water-cut stage for oilfields. The intelligent switch is one of the core tools for layered oil production, while under high-temperature and high-pressure environment, the effective life of the intelligent switch is short, and the function of the intelligent switch acts unreliably. Using single chip control and low power consumption mode, the key components of the power supply module, motor drive module, and pressure monitoring module of the intelligent switch control system were optimized, and the circuit was designed. Furthermore, the control programs for timing alternating production, remote layer adjustment, and pressure monitoring were developed, which realized control functions, such as timing alternating production and pressure signal layer adjustment, for the intelligent switch. By using VB6.0 programming language, a set of man-machine interface was developed, realizing the functions of communication, parameter setting, and data playback. Indoor tests and field applications show that in the high-temperature and high-pressure environment, the timing alternating production and remote layer adjustment of the intelligent switch are stable and reliable, with effective life more than 1 year, which meets the needs of intelligent layered oil production process.
Slow-stroke displacement test method based on photoelectric pixel recognition
NI Guoqiang, LIU Pai, GAO Zhongxian, WU Qiang, LAI Xueyong, WANG Yumeng, CAI Haonan
2022, 44(3): 396-400.   doi: 10.13639/j.odpt.2022.03.020
[Abstract](0) [FullText HTML](21) PDF 1262KB(11)
Abstract:
When the pumping unit runs at low speed, the displacement of the suspension point changes slowly, which increases the difficulty in calculating the displacement amount and identifying the displacement direction during the displacement test process, resulting in an increase in the error rate of cable displacement and acceleration displacement data. In order to get rid of the influence of the running speed of the suspension point and realize fast, accurate and convenient slow-stroke displacement test, a slow-stroke displacement test method based on photoelectric pixel recognition was designed. Using the photoelectric mouse chip system as the probe, by irradiating, sampling, and analyzing the polished rod, with the help of the high resolution and fast scanning function of the mouse chip, the analog quantity detection for displacement was converted into the state quantity detection and the digital accumulation of trace displacement for the presence or absence of displacement, obtaining the displacement information consistent with the suspension point. The slow-stroke pumping unit well was tested with this method, and the displacement data that meets the engineering requirements were obtained. The field test has proved that it is feasible to apply the photoelectric pixel recognition and positioning technology to the displacement test of the polished rod of the pumping unit, which verifies that this technology is not affected by the operating speed of the pumping unit, is easy to process and use data, and produces accurate data.
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](4757) [PDF 1271KB](5759)
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](973) [PDF 1463KB](2768)
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](2063)
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](1425)
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](1208)
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](1078) [PDF 7533KB](1835)
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](1465)
Basic research progress and development suggestions on hydraulic fracturing
TONG Shaokai, GAO Deli
2019, 41(1): 101-115.   doi: 10.13639/j.odpt.2019.01.017
[Abstract](2642) [FullText HTML](1153) [PDF 977KB](144)