In oil and gas well cementing processes,accurately predicting the bottom hole circulating temperature(BHCT)is critical to ensuring effective zonal isolation.Overestimating the temperature can lead to excessive retarda...In oil and gas well cementing processes,accurately predicting the bottom hole circulating temperature(BHCT)is critical to ensuring effective zonal isolation.Overestimating the temperature can lead to excessive retardation issues,while underestimation can cause cementing accidents.Current methods for calculating the BHCT of cement slurry typically simplify the cementing processes to a single-fluid circulation and ignore the impact of pre-cementing processes on temperature,leading to significant discrepancies between calculated and actual results.In this study,the wellbore and formation are simplified into a two-dimensional axisymmetric structure,and a mathematical model of the temperature field under multi-fluid and multi-step conditions is established based on the law of energy conservation.The finite volume method was used to discretize the model,and a transient temperature field solver for the entire cementing process was developed,which can numerically calculate the temperature of any fluid at any time,any location.For an actual well example,the temperature distribution of the wellbore and formation after casing running is taken as the initial condition.Numerical calculations were performed sequentially to calculate the temperature fields of circulation flushing,wellbore preparation,and cementing,as well as the BHCT of the cement slurry.The study reveals that during the circulation flushing stage,the maximum temperature point in the wellbore is located at a distance of about 366 m above the bottom of the well.In the wellbore preparation stage,due to static heat exchange,the maximum temperature point gradually shifts to the bottom of the well.The BHCT of cement slurry changes continuously under cementing processes with multi-fluid and multi-step,making it a transient value.The BHCT of the lead slurry and tail slurry are not equal,with the maximum BHCT of the tail slurry being 2.46°C higher than that of the lead slurry.If circulation flushing and wellbore preparation are not considered,the calculated BHCT of the cement slurry will have errors of+6.8%and-1.9%.The study highlighted that considering thermal effects of all cementing stages,such as circulation flushing and wellbore preparation,in BHCT calculations can help improve prediction accuracy.展开更多
Ultrasonic cement bond logging is a widely used method for evaluating cementing quality. Conventional ultrasonic cement bond logging uses vertical incidence and cannot accurately evaluate lightweight cement bonding. O...Ultrasonic cement bond logging is a widely used method for evaluating cementing quality. Conventional ultrasonic cement bond logging uses vertical incidence and cannot accurately evaluate lightweight cement bonding. Oblique incidence is a new technology for evaluating cement quality with improved accuracy for lightweight cements. In this study, we simulated models of acoustic impedance of cement and cementing quality using ultrasonic oblique incidence, and we obtained the relation between cementing quality, acoustic impedance of cement, and the acoustic attenuation coeffi cient of the A0-mode and S0-mode Lamb waves. Then, we simulated models of different cement thickness and we obtained the relation between cement thickness and the time difference of the arrival between the A0 and A0′ modes.展开更多
Coalbeds are characterized by high organic matter content,presence of joints and smooth joint surface,which lead to weak bonding between coal and set cement and poor cementing quality of coalbeds,and consequently the ...Coalbeds are characterized by high organic matter content,presence of joints and smooth joint surface,which lead to weak bonding between coal and set cement and poor cementing quality of coalbeds,and consequently the economic and effective development of coalbed methane(CBM)is restricted seriously.In this paper,components,compositions and wetting characteristics of coal were analyzed in order to improve the water wettability of coal,the effects of different surfactants and their concentration and soaking time on the surface wetting angle of coal and interfacial bonding strength were tested and measured.The high-efficiency hydrophilic wettability modifier was optimized.The strengthened coalbed bonding prepad fluid system was developed and applied practically in the Qinshui Basin,Shanxi province.The results of laboratory tests and field applications show that the compact adsorption of surfactant containing ether and sulfate radical on the surface of coal can convert the surface wettability into strong hydrophilicity at the concentration of 0.3%within 30 s,thus improving significantly the interface bonding strength(up to 65.5%)between coal and set cement.The field application in CBM well cementing shows that the strengthened coalbed bonding prepad fluid can improve the cementing quality from unqualified level to high level,and play a significant role in improving CBM hole interval cementing quality.It is concluded that this technology provides an effective guarantee for coalbed cementing quality improvement and smooth implementation of stimulation measures like fracturing.展开更多
Determining reasonable fracturing stage spacing is the key to horizontal well fracturing.Different from traditional stage spacing optimization methods based on the principle of maximum stimulated reservoir volume,in t...Determining reasonable fracturing stage spacing is the key to horizontal well fracturing.Different from traditional stage spacing optimization methods based on the principle of maximum stimulated reservoir volume,in this paper,by considering the integrity of the wellbore interface,a fracture propagation model was established based on displacement discontinuity method and the competition mechanism of multifracture joint expansion,leading to the proposal of an unequal stage spacing optimization model.The results show that in the first stage,the interfacial fractures spread symmetrically along the axis of the central point during that stage,while in the second and subsequent stages,the interfacial fractures of each cluster extend asymmetrically along the left and right sides.There are two kinds of interface connectivity behaviour:in one,the existing fractures first extend and connect within the stage,and in the other,the fractures first extend in the direction close to the previous stage,with the specific behaviour depending on the combined effect of stress shadow and flow competition during hydraulic fracture expansion.The stage spacing is positively correlated with the number of fractures and Young’s modulus of the cement and formation and is negatively correlated with the cluster spacing and horizontal principal stress difference.The sensitivity is the strongest when the Young’s modulus of the cement sheath is 10-20 GPa,and the sensitivity of the horizontal principal stress difference is the weakest.展开更多
Organic rich dark shale of Q Formation can be found in many areas(e.g.,in the North of S Basin).The shale target stratum is easy to hydrate and often undergoes spallation.Therefore,centering the casing in the horizont...Organic rich dark shale of Q Formation can be found in many areas(e.g.,in the North of S Basin).The shale target stratum is easy to hydrate and often undergoes spallation.Therefore,centering the casing in the horizontal section of the irregular borehole is relatively difficult.Similarly,achieving a good cementflushing efficiency under complex borehole conditions is a complex task.Through technologies such as centralizer,efficient preflushing,multi-stageflushing and ductile cement slurry,better performances can be achieved.In this study,it is shown that the cementing rate in the DY2H horizontal section is 97.8%,which is more than 34%higher than that of adjacent wells.This cementing matching technology for sidetracking horizontal wells can be used to improve the cementing quality of continental shale and provides a reference for future applications in thisfield.展开更多
Optimization of the content of tricalcium silicate（C 3 S）of high cementing clinker was investigated.The content of free-CaO（f-CaO）,mineral composite,the content of C 3 S in the clinker and the hydration product we...Optimization of the content of tricalcium silicate（C 3 S）of high cementing clinker was investigated.The content of free-CaO（f-CaO）,mineral composite,the content of C 3 S in the clinker and the hydration product were analyzed by chemical analysis and X-ray diffraction（XRD）.＂K Value＂method of QXRD was selected as a quantitative analysis way to measure the content of C 3 S,and the strength of cement paste was determined.The results show that at a water cement ratio of 0.29,the strength of cement paste with 73%C 3 S can be up to 97.5 MPa at 28 days age.The strength at 28 d of cement with 73%C 3 S is 16%higher than that with 78%C 3 S at water requirement for normal consistency.The relationship between the strength of high cementing Portland cement and the content of C 3 S in the clinker is nonlinear.According to the strength of cement paste,the optimal content of C 3 S in cement clinker is around 73%in this paper.展开更多
The precise managed pressure drilling(MPD)technology is mainly used to deal with the difficulties encountered when oil and gas open hole sections with multiple pressure systems and the strata with narrow safety densit...The precise managed pressure drilling(MPD)technology is mainly used to deal with the difficulties encountered when oil and gas open hole sections with multiple pressure systems and the strata with narrow safety density window are drilled through.If its liner cementing is carried out according to the conventional method,lost circulation is inevitable in the process of cementing while the displacement efficiency of smallclearance liner cementing is satisfied.If the positive and inverse injection technology is adopted,the cementing quality cannot meet the requirements of later well test engineering of ultradeep wells.In this paper,the cementing operation ofØ114.3 mm liner in Well Longgang 70 which was drilled in the Jiange structure of the Sichuan Basin was taken as an example to explore the application of the cementing technology based on the precise MPD and pressure balancing method to the cementing of long open-hole sections(as long as 859 m)with both high and low pressures running through multiple reservoirs.On the one hand,the technical measures were taken specifically to ensure the annulus filling efficiency of slurry and the pressure balance in the whole process of cementing.And on the other hand,the annulus pressure balance was precisely controlled by virtue of precise MPD devices and by injecting heavy weight drilling fluids through central pipes,and thus the wellbore pressure was kept steady in the whole process of cementing in the strata with narrow safety density window.It is indicated thatØ114.3 mm liner cementing in this well is good with qualified pressure tests and no channeling emerges at a funnel during the staged density reduction.It is concluded that this method can enhance the liner cementing quality of complex ultradeep gas wells and improve the wellbore conditions for the later safe well tests of high-pressure gas wells.展开更多
The aim of this study is to create a fast and stable iterative technique for numerical solution of a quasi-linear elliptic pressure equation. We developed a modified version of the Anderson acceleration(AA)algorithm t...The aim of this study is to create a fast and stable iterative technique for numerical solution of a quasi-linear elliptic pressure equation. We developed a modified version of the Anderson acceleration(AA)algorithm to fixed-point(FP) iteration method. It computes the approximation to the solutions at each iteration based on the history of vectors in extended space, which includes the vector of unknowns, the discrete form of the operator, and the equation's right-hand side. Several constraints are applied to AA algorithm, including a limitation of the time step variation during the iteration process, which allows switching to the base FP iterations to maintain convergence. Compared to the base FP algorithm, the improved version of the AA algorithm enables a reliable and rapid convergence of the iterative solution for the quasi-linear elliptic pressure equation describing the flow of particle-laden yield-stress fluids in a narrow channel during hydraulic fracturing, a key technology for stimulating hydrocarbon-bearing reservoirs. In particular, the proposed AA algorithm allows for faster computations and resolution of unyielding zones in hydraulic fractures that cannot be calculated using the FP algorithm. The quasi-linear elliptic pressure equation under consideration describes various physical processes, such as the displacement of fluids with viscoplastic rheology in a narrow cylindrical annulus during well cementing,the displacement of cross-linked gel in a proppant pack filling hydraulic fractures during the early stage of well production(fracture flowback), and multiphase filtration in a rock formation. We estimate computational complexity of the developed algorithm as compared to Jacobian-based algorithms and show that the performance of the former one is higher in modelling of flows of viscoplastic fluids. We believe that the developed algorithm is a useful numerical tool that can be implemented in commercial simulators to obtain fast and converged solutions to the non-linear problems described above.展开更多
As a byproduct of water treatment,drinking water treatment aluminum sludge(DWTAS)has challenges related to imperfect treatment and disposal,which has caused potential harm to human health and the environment.In this p...As a byproduct of water treatment,drinking water treatment aluminum sludge(DWTAS)has challenges related to imperfect treatment and disposal,which has caused potential harm to human health and the environment.In this paper,heat treatment DWTAS as a supplement cementitious material was used to prepare a green cementing material.The results show that the 800℃ is considered as the optimum heat treatment temperature for DWTAS.DWTAS-800℃ is fully activated after thermal decomposition to form incompletely crystallized highly activeγ-Al_(2)O_(3) and active SiO_(2).The addition of DWTAS promoted the formation of ettringite and C-(A)-S-H gel,which could make up for the low early compressive strength of cementing materials to a certain extent.When cured for 90 days,the compressive strength of the mortar with 30% DWTAS-800℃ reached 44.86 MPa.The dynamic process was well simulated by Krstulovi′c-Dabi′c hydration kinetics model.This study provided a methodology for the fabrication of environmentally friendly and cost-effective compound cementitiousmaterials and proposed a“waste-to-resource”strategy for the sustainable management of typical solid wastes.展开更多
Gaoshiti-Moxi structure belt of An-Yue Sinian gas reservoir, which was China’s largest monomer Marine carbonate gas reservoir up to now, located in vying-dragon female temple structure group that belong to the ancien...Gaoshiti-Moxi structure belt of An-Yue Sinian gas reservoir, which was China’s largest monomer Marine carbonate gas reservoir up to now, located in vying-dragon female temple structure group that belong to the ancient uplift slope of the middle of Sichuan. With the exploration and development of high temperature and high pressure carbonate reservoir, a large number of challenges and problems, such as long isolation section, active oil-gas show, large temperature difference, prone to super retarding cement slurry and gas channeling at flare position, have been encountered in the cementing of 177.8 mm hang-liner. In order to solve these problems, numerous measures and methods have been put into use for reducing the safety risk of cementing and improving cementing quality. The large temperature difference channeling cement slurry system, effective anti-pollution spacer and high-pressure packer type liner hanger were developed and applied for field tests in the early stage of development. In addition, equilibrium pressure cementing technology, optimizing of centralizer placement and plasma column structure, improvement of pump displacement and hold pressure while waiting on cement were used to ensure nice displacement efficiency and cementing quality. As Moxi X well for example, the cementing quality factor of merit was 40.29% and the qualification rate was up to 78.87% after adopting the cementing measures and methods above. The cementing quality was much higher than previous level and provided technical support for Gaoshiti-Moxi area.展开更多
The jetting and cementing bucket platform （JCBP） is a new type offshore oil-drilling platform. This paper aims to establish an analysis method for calculating the dynamic response of this platform. Based on the theo...The jetting and cementing bucket platform （JCBP） is a new type offshore oil-drilling platform. This paper aims to establish an analysis method for calculating the dynamic response of this platform. Based on the theory of elastic half space, the dynamic stiffness and damping of the platform＇ s foundation were obtained and attached to the end of the platform＇ s main jackets as a boundary condition. Then using finite element method （FEM）, the dynamic response of the platform due to wave and current loading was calculated. Furthermore, the whole platform＇ s finite element model was established and the dynamic response of the platform was calculated. The numerical results demonstrate that the present method by the usage of elastic half space theory and FEM is simple and it is reliable and efficient to calculate dynamic behavior of the platform in response to wave and current loading.展开更多
Considering the complicated interactions between temperature,pressure and hydration reaction of cement,a coupled model of temperature and pressure based on hydration kinetics during deep-water well cementing was estab...Considering the complicated interactions between temperature,pressure and hydration reaction of cement,a coupled model of temperature and pressure based on hydration kinetics during deep-water well cementing was established.The differential method was used to do the coupled numerical calculation,and the calculation results were compared with experimental and field data to verify the accuracy of the model.When the interactions between temperature,pressure and hydration reaction are considered,the calculation accuracy of the model proposed is within 5.6%,which can meet the engineering requirements.A series of numerical simulation was conducted to find out the variation pattern of temperature,pressure and hydration degree during the cement curing.The research results show that cement temperature increases dramatically as a result of the heat of cement hydration.With the development of cement gel strength,the pore pressure of cement slurry decreases gradually to even lower than the formation pressure,causing gas channeling;the transient temperature and pressure have an impact on the rate of cement hydration reaction,so cement slurry in the deeper part of wellbore has a higher rate of hydration rate as a result of the high temperature and pressure.For well cementing in deep water regions,the low temperature around seabed would slow the rate of cement hydration and thus prolong the cementing cycle.展开更多
Microbial contamination and bacteria growth in the cementing makup water impact cementing operation and integrity.To avoid the premature cement setting caused by microbial growth,the water is usually treated with bioc...Microbial contamination and bacteria growth in the cementing makup water impact cementing operation and integrity.To avoid the premature cement setting caused by microbial growth,the water is usually treated with biocides for microbial control before mixing.This treatment will also prevent biodegradation of the added polymers and stabilize the slurry rheological properties.Make-up water and cementing mix samples were collected from active drilling rigs in the field.In 12 hours biocide addition program,the tested biocide at 50,100,250,and 500 ppm for cementing operations revealed acceptable control of both GAB and SRB numbers in one Field,but not in another Field.In 24 hours biocide addition program,revealed varying levels for control microbial contamination in cementing operations,with higher efficiency with Field B samples opposed to field A,and with better control at higher concentrations of tested biocide at 250,and 500 ppm.As a recommendation therefore,usage of another biocide with a different chemistry at Field A is encouraged once a new biocide is selected.展开更多
Well cementing is an important step in petroleum engineering territory. Through many years study and research, China Nation Petroleum Corporation(abbreviated as CNPC) has made many good progresses in cementing process...Well cementing is an important step in petroleum engineering territory. Through many years study and research, China Nation Petroleum Corporation(abbreviated as CNPC) has made many good progresses in cementing process, and a series of cementing materials, cementing tools, and associated cementing techniques to them have been developed. Over the recent years, there have been significant improvements in application of single slurry system to super deep well, horizontal well, large displacement well and wells with large temperature span between cementing top and well bottom. Favorable results have been gained in field application of super high density cement slurry system and super low density cement slurry system. Application of conventional cementing tools and accessories has been the matured techniques, and breakthroughs have been made in liner hanger and swellable material.展开更多
Large-scale hydraulic fracturing combined with horizontal well drilling is the key technology in shale gas development.But poor cementing quality is a crucial bottleneck restricting well completion and reservoir stimu...Large-scale hydraulic fracturing combined with horizontal well drilling is the key technology in shale gas development.But poor cementing quality is a crucial bottleneck restricting well completion and reservoir stimulation.In this paper,the shale gas development blocks in the Sichuan Basin were taken as the examples to explore the process and support measures that can be used to keep the mechanical integrity of cement sheath under the effect of hydraulic fracturing.It is indicated that the near-bit three-centralizer drifting BHA used for casing stiffness simulation can decrease the casing running difficulty in the long horizontal section of a shale gas well and increase the time efficiency and safety of casing running;that the flushing efficiency of high-efficiency oil flushing spacer fluid system is higher than 90%from room temperature to 120℃,so it can guarantee the displacement efficiency of cement slurry to the oil-based drilling fluid and the effective cementing of borehole wall;that the performance of anti-channeling ductile cement slurry used in the cementing of long horizontal sections in this area after it is set is confirmed,with the elastic modulus of set cement being lower than 7 GPa and triaxial strength being higher than 40 MPa,so as to alleviate or avoid the damage to cement sheath in the process of fracturing;and that cementing quality is improved by applying the support technologies,e.g.drilling fluid adjustment,pre-stress cementing and ground high-pressure pumping.During 2015e2016,these cementing technologies were applied in 85 wells in the Sichuan Basin.The average well depth of these wells is 4832 m,the average length of horizontal sections is 1560 m and the quality rate of well cementing is 89.58%.During the waiting-on-cement(WOC)time after well cementing,there is no sustained casing pressure.And gas channeling in the annulus during well drilling,completion and test is improved remarkably.It is concluded that this suite of technologies can guarantee and improve the cementing quality of long horizontal sections in shale gas wells and provides good cementing conditions for shale gas development.展开更多
When well cementing is conducted in horizontal shale gas wells in Weiyuan block of the Weiyuan-Changning State Shale Demonstration Area,Sichuan Basin,the oil-based drilling fluid is not compatible with cement slurry,i...When well cementing is conducted in horizontal shale gas wells in Weiyuan block of the Weiyuan-Changning State Shale Demonstration Area,Sichuan Basin,the oil-based drilling fluid is not compatible with cement slurry,is difficult to be displaced because of its high density,and cement sheath tends to be broken in the situations of large-scale stimulated reservoir volume fracturing.In view of these problems,a series of studies were carried out specifically on the theoretical basis of cement sheath sealing mechanical parameters,oil-displacement preflush improving the interface cementation quality,toughness set cement satisfying large-scale fracturing requirements and cementing technology conducive to the wellbore integrity.The following achievements were made.First,the theoretical model of cement sheath mechanical integrity taking into account the plastic characteristics and interface cementation strength of cement sheath is instructive to the mechanical design of set cement for horizontal shale gas wells,avoiding the micro-annulus as much as possible.Second,oil-displacement preflush is developed and it is well compatible with oil-based drilling fluids and cement slurry with the flushing efficiency on oil-based drilling fluids higher than 90%.Third,the tough set cement which is developed based on the theoretical model of cement sheath sealing integrity not only guarantees higher compressive strength,but decreases Young's modulus by 30%.Forth,it is confirmed that water displacement cementing technology suitable for shale gas wells is conducive to improving the wellbore seal integrity.These research findings were applied in 12 horizontal wells.It is indicated that the quality cementing ratio of horizontal segment reaches 92%and the post fracturing effect is very good,which guarantees the sealing integrity of wellbores and provides a technical support for the highly efficient development of shale gas reservoirs.展开更多
In the Sichuan Basin,the drilling of complex deep and ultradeep wells is restricted by the casing sequence.Multiple pressure systems are usually encountered in the same open hole section,and narrow safety density wind...In the Sichuan Basin,the drilling of complex deep and ultradeep wells is restricted by the casing sequence.Multiple pressure systems are usually encountered in the same open hole section,and narrow safety density window is observed in vertical strata.The application of managed pressure drilling(MPD)technique which is often used in well drilling ensures the safe and efficient drilling,but it also brings about great challenges to the small-gap liner cementing at the lower part.Therefore,it is of great practical significance to research a cementing technology that can not only satisfy the quality requirement of small gap liner cementing,but also ensure the safe cementing in the strata with narrow safety density window.In this paper,a cementing technology based on precise managed pressure balancing method was proposed by referring to the successful application of MPD technique.According to the cementing design,the hydrostatic column pressure of annulusfluid is under-balanced(slightly lower than the formation pore pressure),and then a precise managed pressure drilling device is adopted to produce back pressure through wellhead restriction or apply wellhead compensation pressure,so that the balanced pore pressure can be reached in the process of cementing via the wellhead pressure and theflow friction offluid in the annulus.After the cementing is completed,a certain compensation pressure is applied to the annulus continuously to prevent annulus channeling during waiting on cement caused by insufficient static pressure and slurry weight loss.After this technology was applied to an ultradeep exploration well in the Sichuan Basin,the qualification rate of borehole cementing quality reached 97%,and the well sections with good cementing quality accounted for 76%.In conclusion,this technology needs no additional equipment,and only by virtue of the MPD equipment,it can achieve safe cementing construction and cementing quality improvement under high displacement efficiency.展开更多
基金supported by the National Natural Science Foundation of China(No.U22B6003 and No.52274010)the China Scholarship Council(No.202008080235)。
文摘In oil and gas well cementing processes,accurately predicting the bottom hole circulating temperature(BHCT)is critical to ensuring effective zonal isolation.Overestimating the temperature can lead to excessive retardation issues,while underestimation can cause cementing accidents.Current methods for calculating the BHCT of cement slurry typically simplify the cementing processes to a single-fluid circulation and ignore the impact of pre-cementing processes on temperature,leading to significant discrepancies between calculated and actual results.In this study,the wellbore and formation are simplified into a two-dimensional axisymmetric structure,and a mathematical model of the temperature field under multi-fluid and multi-step conditions is established based on the law of energy conservation.The finite volume method was used to discretize the model,and a transient temperature field solver for the entire cementing process was developed,which can numerically calculate the temperature of any fluid at any time,any location.For an actual well example,the temperature distribution of the wellbore and formation after casing running is taken as the initial condition.Numerical calculations were performed sequentially to calculate the temperature fields of circulation flushing,wellbore preparation,and cementing,as well as the BHCT of the cement slurry.The study reveals that during the circulation flushing stage,the maximum temperature point in the wellbore is located at a distance of about 366 m above the bottom of the well.In the wellbore preparation stage,due to static heat exchange,the maximum temperature point gradually shifts to the bottom of the well.The BHCT of cement slurry changes continuously under cementing processes with multi-fluid and multi-step,making it a transient value.The BHCT of the lead slurry and tail slurry are not equal,with the maximum BHCT of the tail slurry being 2.46°C higher than that of the lead slurry.If circulation flushing and wellbore preparation are not considered,the calculated BHCT of the cement slurry will have errors of+6.8%and-1.9%.The study highlighted that considering thermal effects of all cementing stages,such as circulation flushing and wellbore preparation,in BHCT calculations can help improve prediction accuracy.
基金partially supported by the National Natural Science Foundation of China(Nos.11204380,11374371,61102102,and 11134011)National Science and Technology Major Project(No.2011ZX05020-009)+1 种基金Petro China Innovation Foundation(No.2013D-5006-0304)Chinese Petroleum Corporation Project(Nos.2011A-3903 and 2011B-4001)
文摘Ultrasonic cement bond logging is a widely used method for evaluating cementing quality. Conventional ultrasonic cement bond logging uses vertical incidence and cannot accurately evaluate lightweight cement bonding. Oblique incidence is a new technology for evaluating cement quality with improved accuracy for lightweight cements. In this study, we simulated models of acoustic impedance of cement and cementing quality using ultrasonic oblique incidence, and we obtained the relation between cementing quality, acoustic impedance of cement, and the acoustic attenuation coeffi cient of the A0-mode and S0-mode Lamb waves. Then, we simulated models of different cement thickness and we obtained the relation between cement thickness and the time difference of the arrival between the A0 and A0′ modes.
文摘Coalbeds are characterized by high organic matter content,presence of joints and smooth joint surface,which lead to weak bonding between coal and set cement and poor cementing quality of coalbeds,and consequently the economic and effective development of coalbed methane(CBM)is restricted seriously.In this paper,components,compositions and wetting characteristics of coal were analyzed in order to improve the water wettability of coal,the effects of different surfactants and their concentration and soaking time on the surface wetting angle of coal and interfacial bonding strength were tested and measured.The high-efficiency hydrophilic wettability modifier was optimized.The strengthened coalbed bonding prepad fluid system was developed and applied practically in the Qinshui Basin,Shanxi province.The results of laboratory tests and field applications show that the compact adsorption of surfactant containing ether and sulfate radical on the surface of coal can convert the surface wettability into strong hydrophilicity at the concentration of 0.3%within 30 s,thus improving significantly the interface bonding strength(up to 65.5%)between coal and set cement.The field application in CBM well cementing shows that the strengthened coalbed bonding prepad fluid can improve the cementing quality from unqualified level to high level,and play a significant role in improving CBM hole interval cementing quality.It is concluded that this technology provides an effective guarantee for coalbed cementing quality improvement and smooth implementation of stimulation measures like fracturing.
基金This work was supported by the Natural Science Foundation of Heilongjiang Province of China(YQ2021E005)the National Natural Science Foundation of China(No.51774094)+2 种基金the Youth Fund Project of National Natural Science Foundation of China(52004065)the Heilongjiang Natural Science Foundation Project(excellent youth project)(YQ2021E006)"Reveal the top"Science and Technology Project of Heilongjiang Province(2021ZZ10-04).
文摘Determining reasonable fracturing stage spacing is the key to horizontal well fracturing.Different from traditional stage spacing optimization methods based on the principle of maximum stimulated reservoir volume,in this paper,by considering the integrity of the wellbore interface,a fracture propagation model was established based on displacement discontinuity method and the competition mechanism of multifracture joint expansion,leading to the proposal of an unequal stage spacing optimization model.The results show that in the first stage,the interfacial fractures spread symmetrically along the axis of the central point during that stage,while in the second and subsequent stages,the interfacial fractures of each cluster extend asymmetrically along the left and right sides.There are two kinds of interface connectivity behaviour:in one,the existing fractures first extend and connect within the stage,and in the other,the fractures first extend in the direction close to the previous stage,with the specific behaviour depending on the combined effect of stress shadow and flow competition during hydraulic fracture expansion.The stage spacing is positively correlated with the number of fractures and Young’s modulus of the cement and formation and is negatively correlated with the cluster spacing and horizontal principal stress difference.The sensitivity is the strongest when the Young’s modulus of the cement sheath is 10-20 GPa,and the sensitivity of the horizontal principal stress difference is the weakest.
基金funded by the CNPC Science and Technology Department Project(2021ZZ10-03)。
文摘Organic rich dark shale of Q Formation can be found in many areas(e.g.,in the North of S Basin).The shale target stratum is easy to hydrate and often undergoes spallation.Therefore,centering the casing in the horizontal section of the irregular borehole is relatively difficult.Similarly,achieving a good cementflushing efficiency under complex borehole conditions is a complex task.Through technologies such as centralizer,efficient preflushing,multi-stageflushing and ductile cement slurry,better performances can be achieved.In this study,it is shown that the cementing rate in the DY2H horizontal section is 97.8%,which is more than 34%higher than that of adjacent wells.This cementing matching technology for sidetracking horizontal wells can be used to improve the cementing quality of continental shale and provides a reference for future applications in thisfield.
基金Funded by National Basic Research Program of China(No. 2009CB623100)National Eleventh Five-Year Scientific and Technical Support Plans(No.2006BAF02A24)+2 种基金Natural Science Fund for Colleges and Universities in Jiangsu Province(No.08KJB430006)Open Fund for the Key Laboratory of Inorganical and Composite Materials in Jiangsu Province(No. wjjqfhxc1200801)Innovation Fund of Doctoral Dissertation of Nanjing University of Technology(No.BSCX200705)
文摘Optimization of the content of tricalcium silicate（C 3 S）of high cementing clinker was investigated.The content of free-CaO（f-CaO）,mineral composite,the content of C 3 S in the clinker and the hydration product were analyzed by chemical analysis and X-ray diffraction（XRD）.＂K Value＂method of QXRD was selected as a quantitative analysis way to measure the content of C 3 S,and the strength of cement paste was determined.The results show that at a water cement ratio of 0.29,the strength of cement paste with 73%C 3 S can be up to 97.5 MPa at 28 days age.The strength at 28 d of cement with 73%C 3 S is 16%higher than that with 78%C 3 S at water requirement for normal consistency.The relationship between the strength of high cementing Portland cement and the content of C 3 S in the clinker is nonlinear.According to the strength of cement paste,the optimal content of C 3 S in cement clinker is around 73%in this paper.
文摘The precise managed pressure drilling(MPD)technology is mainly used to deal with the difficulties encountered when oil and gas open hole sections with multiple pressure systems and the strata with narrow safety density window are drilled through.If its liner cementing is carried out according to the conventional method,lost circulation is inevitable in the process of cementing while the displacement efficiency of smallclearance liner cementing is satisfied.If the positive and inverse injection technology is adopted,the cementing quality cannot meet the requirements of later well test engineering of ultradeep wells.In this paper,the cementing operation ofØ114.3 mm liner in Well Longgang 70 which was drilled in the Jiange structure of the Sichuan Basin was taken as an example to explore the application of the cementing technology based on the precise MPD and pressure balancing method to the cementing of long open-hole sections(as long as 859 m)with both high and low pressures running through multiple reservoirs.On the one hand,the technical measures were taken specifically to ensure the annulus filling efficiency of slurry and the pressure balance in the whole process of cementing.And on the other hand,the annulus pressure balance was precisely controlled by virtue of precise MPD devices and by injecting heavy weight drilling fluids through central pipes,and thus the wellbore pressure was kept steady in the whole process of cementing in the strata with narrow safety density window.It is indicated thatØ114.3 mm liner cementing in this well is good with qualified pressure tests and no channeling emerges at a funnel during the staged density reduction.It is concluded that this method can enhance the liner cementing quality of complex ultradeep gas wells and improve the wellbore conditions for the later safe well tests of high-pressure gas wells.
基金partial financial support from Gazpromneft Science and Technology Center。
文摘The aim of this study is to create a fast and stable iterative technique for numerical solution of a quasi-linear elliptic pressure equation. We developed a modified version of the Anderson acceleration(AA)algorithm to fixed-point(FP) iteration method. It computes the approximation to the solutions at each iteration based on the history of vectors in extended space, which includes the vector of unknowns, the discrete form of the operator, and the equation's right-hand side. Several constraints are applied to AA algorithm, including a limitation of the time step variation during the iteration process, which allows switching to the base FP iterations to maintain convergence. Compared to the base FP algorithm, the improved version of the AA algorithm enables a reliable and rapid convergence of the iterative solution for the quasi-linear elliptic pressure equation describing the flow of particle-laden yield-stress fluids in a narrow channel during hydraulic fracturing, a key technology for stimulating hydrocarbon-bearing reservoirs. In particular, the proposed AA algorithm allows for faster computations and resolution of unyielding zones in hydraulic fractures that cannot be calculated using the FP algorithm. The quasi-linear elliptic pressure equation under consideration describes various physical processes, such as the displacement of fluids with viscoplastic rheology in a narrow cylindrical annulus during well cementing,the displacement of cross-linked gel in a proppant pack filling hydraulic fractures during the early stage of well production(fracture flowback), and multiphase filtration in a rock formation. We estimate computational complexity of the developed algorithm as compared to Jacobian-based algorithms and show that the performance of the former one is higher in modelling of flows of viscoplastic fluids. We believe that the developed algorithm is a useful numerical tool that can be implemented in commercial simulators to obtain fast and converged solutions to the non-linear problems described above.
基金This work is supported by the National Key Research and Development Program of China(No.2022YFC3203203)the Outstanding Youth Science Foundation of Shaanxi Province(No.2023-JC-JQ-36)the National Natural Science Foundation of China(No.52300121).
文摘As a byproduct of water treatment,drinking water treatment aluminum sludge(DWTAS)has challenges related to imperfect treatment and disposal,which has caused potential harm to human health and the environment.In this paper,heat treatment DWTAS as a supplement cementitious material was used to prepare a green cementing material.The results show that the 800℃ is considered as the optimum heat treatment temperature for DWTAS.DWTAS-800℃ is fully activated after thermal decomposition to form incompletely crystallized highly activeγ-Al_(2)O_(3) and active SiO_(2).The addition of DWTAS promoted the formation of ettringite and C-(A)-S-H gel,which could make up for the low early compressive strength of cementing materials to a certain extent.When cured for 90 days,the compressive strength of the mortar with 30% DWTAS-800℃ reached 44.86 MPa.The dynamic process was well simulated by Krstulovi′c-Dabi′c hydration kinetics model.This study provided a methodology for the fabrication of environmentally friendly and cost-effective compound cementitiousmaterials and proposed a“waste-to-resource”strategy for the sustainable management of typical solid wastes.
文摘Gaoshiti-Moxi structure belt of An-Yue Sinian gas reservoir, which was China’s largest monomer Marine carbonate gas reservoir up to now, located in vying-dragon female temple structure group that belong to the ancient uplift slope of the middle of Sichuan. With the exploration and development of high temperature and high pressure carbonate reservoir, a large number of challenges and problems, such as long isolation section, active oil-gas show, large temperature difference, prone to super retarding cement slurry and gas channeling at flare position, have been encountered in the cementing of 177.8 mm hang-liner. In order to solve these problems, numerous measures and methods have been put into use for reducing the safety risk of cementing and improving cementing quality. The large temperature difference channeling cement slurry system, effective anti-pollution spacer and high-pressure packer type liner hanger were developed and applied for field tests in the early stage of development. In addition, equilibrium pressure cementing technology, optimizing of centralizer placement and plasma column structure, improvement of pump displacement and hold pressure while waiting on cement were used to ensure nice displacement efficiency and cementing quality. As Moxi X well for example, the cementing quality factor of merit was 40.29% and the qualification rate was up to 78.87% after adopting the cementing measures and methods above. The cementing quality was much higher than previous level and provided technical support for Gaoshiti-Moxi area.
文摘The jetting and cementing bucket platform （JCBP） is a new type offshore oil-drilling platform. This paper aims to establish an analysis method for calculating the dynamic response of this platform. Based on the theory of elastic half space, the dynamic stiffness and damping of the platform＇ s foundation were obtained and attached to the end of the platform＇ s main jackets as a boundary condition. Then using finite element method （FEM）, the dynamic response of the platform due to wave and current loading was calculated. Furthermore, the whole platform＇ s finite element model was established and the dynamic response of the platform was calculated. The numerical results demonstrate that the present method by the usage of elastic half space theory and FEM is simple and it is reliable and efficient to calculate dynamic behavior of the platform in response to wave and current loading.
基金Supported by the National Natural Science Foundation of China(U1762216)China National Science and Technology Major Project(2016ZX05028-001-03)
文摘Considering the complicated interactions between temperature,pressure and hydration reaction of cement,a coupled model of temperature and pressure based on hydration kinetics during deep-water well cementing was established.The differential method was used to do the coupled numerical calculation,and the calculation results were compared with experimental and field data to verify the accuracy of the model.When the interactions between temperature,pressure and hydration reaction are considered,the calculation accuracy of the model proposed is within 5.6%,which can meet the engineering requirements.A series of numerical simulation was conducted to find out the variation pattern of temperature,pressure and hydration degree during the cement curing.The research results show that cement temperature increases dramatically as a result of the heat of cement hydration.With the development of cement gel strength,the pore pressure of cement slurry decreases gradually to even lower than the formation pressure,causing gas channeling;the transient temperature and pressure have an impact on the rate of cement hydration reaction,so cement slurry in the deeper part of wellbore has a higher rate of hydration rate as a result of the high temperature and pressure.For well cementing in deep water regions,the low temperature around seabed would slow the rate of cement hydration and thus prolong the cementing cycle.
文摘Microbial contamination and bacteria growth in the cementing makup water impact cementing operation and integrity.To avoid the premature cement setting caused by microbial growth,the water is usually treated with biocides for microbial control before mixing.This treatment will also prevent biodegradation of the added polymers and stabilize the slurry rheological properties.Make-up water and cementing mix samples were collected from active drilling rigs in the field.In 12 hours biocide addition program,the tested biocide at 50,100,250,and 500 ppm for cementing operations revealed acceptable control of both GAB and SRB numbers in one Field,but not in another Field.In 24 hours biocide addition program,revealed varying levels for control microbial contamination in cementing operations,with higher efficiency with Field B samples opposed to field A,and with better control at higher concentrations of tested biocide at 250,and 500 ppm.As a recommendation therefore,usage of another biocide with a different chemistry at Field A is encouraged once a new biocide is selected.
基金Part research results of"Cementing bond packing upgrading and bionic well wall consolidation drilling fluid techniques"of a key CNPC project"New technology and method of drilling"(No.2011A-4207)
文摘Well cementing is an important step in petroleum engineering territory. Through many years study and research, China Nation Petroleum Corporation(abbreviated as CNPC) has made many good progresses in cementing process, and a series of cementing materials, cementing tools, and associated cementing techniques to them have been developed. Over the recent years, there have been significant improvements in application of single slurry system to super deep well, horizontal well, large displacement well and wells with large temperature span between cementing top and well bottom. Favorable results have been gained in field application of super high density cement slurry system and super low density cement slurry system. Application of conventional cementing tools and accessories has been the matured techniques, and breakthroughs have been made in liner hanger and swellable material.
基金Project supported by the National Major Science and Technology Project“Development of large-scale oil/gas fields and CBM”0“New technologies for improving the cementing quality and wellbore integrity under the condition of large-scale volume fracturing”(No.2016ZX05022-005).
文摘Large-scale hydraulic fracturing combined with horizontal well drilling is the key technology in shale gas development.But poor cementing quality is a crucial bottleneck restricting well completion and reservoir stimulation.In this paper,the shale gas development blocks in the Sichuan Basin were taken as the examples to explore the process and support measures that can be used to keep the mechanical integrity of cement sheath under the effect of hydraulic fracturing.It is indicated that the near-bit three-centralizer drifting BHA used for casing stiffness simulation can decrease the casing running difficulty in the long horizontal section of a shale gas well and increase the time efficiency and safety of casing running;that the flushing efficiency of high-efficiency oil flushing spacer fluid system is higher than 90%from room temperature to 120℃,so it can guarantee the displacement efficiency of cement slurry to the oil-based drilling fluid and the effective cementing of borehole wall;that the performance of anti-channeling ductile cement slurry used in the cementing of long horizontal sections in this area after it is set is confirmed,with the elastic modulus of set cement being lower than 7 GPa and triaxial strength being higher than 40 MPa,so as to alleviate or avoid the damage to cement sheath in the process of fracturing;and that cementing quality is improved by applying the support technologies,e.g.drilling fluid adjustment,pre-stress cementing and ground high-pressure pumping.During 2015e2016,these cementing technologies were applied in 85 wells in the Sichuan Basin.The average well depth of these wells is 4832 m,the average length of horizontal sections is 1560 m and the quality rate of well cementing is 89.58%.During the waiting-on-cement(WOC)time after well cementing,there is no sustained casing pressure.And gas channeling in the annulus during well drilling,completion and test is improved remarkably.It is concluded that this suite of technologies can guarantee and improve the cementing quality of long horizontal sections in shale gas wells and provides good cementing conditions for shale gas development.
基金Project supported by the National Key Basic Research Program of China(973 Program),“Basic Study on High-efficiency Development of Marine Shale Gas in South China(Part 3“Key Basic Study on Drilling and Completion of Horizontal Shale Gas Wells”)”(Grant No.2013CB228003).
文摘When well cementing is conducted in horizontal shale gas wells in Weiyuan block of the Weiyuan-Changning State Shale Demonstration Area,Sichuan Basin,the oil-based drilling fluid is not compatible with cement slurry,is difficult to be displaced because of its high density,and cement sheath tends to be broken in the situations of large-scale stimulated reservoir volume fracturing.In view of these problems,a series of studies were carried out specifically on the theoretical basis of cement sheath sealing mechanical parameters,oil-displacement preflush improving the interface cementation quality,toughness set cement satisfying large-scale fracturing requirements and cementing technology conducive to the wellbore integrity.The following achievements were made.First,the theoretical model of cement sheath mechanical integrity taking into account the plastic characteristics and interface cementation strength of cement sheath is instructive to the mechanical design of set cement for horizontal shale gas wells,avoiding the micro-annulus as much as possible.Second,oil-displacement preflush is developed and it is well compatible with oil-based drilling fluids and cement slurry with the flushing efficiency on oil-based drilling fluids higher than 90%.Third,the tough set cement which is developed based on the theoretical model of cement sheath sealing integrity not only guarantees higher compressive strength,but decreases Young's modulus by 30%.Forth,it is confirmed that water displacement cementing technology suitable for shale gas wells is conducive to improving the wellbore seal integrity.These research findings were applied in 12 horizontal wells.It is indicated that the quality cementing ratio of horizontal segment reaches 92%and the post fracturing effect is very good,which guarantees the sealing integrity of wellbores and provides a technical support for the highly efficient development of shale gas reservoirs.
基金supported by the National Major Science and Technology Project"Development demonstration project of large-scale carbonae gas fields in the Sichuan Basin-Research and application of large-scale deep carbonate gas reservoir drilling and production technology"(No:2016ZX05052-003)Pet roChina Major Science and Technology Project"Research and application of key technologies for maintaining 30billion cubic meters of natural gas production in Southwest Oil and Gas Field-Research and application ofdrilling,completion,and oil testing technologies for high temperature and high pressure sulfur-bearing deep wells in the Sichuan Basin"(No:2016E-0608)。
文摘In the Sichuan Basin,the drilling of complex deep and ultradeep wells is restricted by the casing sequence.Multiple pressure systems are usually encountered in the same open hole section,and narrow safety density window is observed in vertical strata.The application of managed pressure drilling(MPD)technique which is often used in well drilling ensures the safe and efficient drilling,but it also brings about great challenges to the small-gap liner cementing at the lower part.Therefore,it is of great practical significance to research a cementing technology that can not only satisfy the quality requirement of small gap liner cementing,but also ensure the safe cementing in the strata with narrow safety density window.In this paper,a cementing technology based on precise managed pressure balancing method was proposed by referring to the successful application of MPD technique.According to the cementing design,the hydrostatic column pressure of annulusfluid is under-balanced(slightly lower than the formation pore pressure),and then a precise managed pressure drilling device is adopted to produce back pressure through wellhead restriction or apply wellhead compensation pressure,so that the balanced pore pressure can be reached in the process of cementing via the wellhead pressure and theflow friction offluid in the annulus.After the cementing is completed,a certain compensation pressure is applied to the annulus continuously to prevent annulus channeling during waiting on cement caused by insufficient static pressure and slurry weight loss.After this technology was applied to an ultradeep exploration well in the Sichuan Basin,the qualification rate of borehole cementing quality reached 97%,and the well sections with good cementing quality accounted for 76%.In conclusion,this technology needs no additional equipment,and only by virtue of the MPD equipment,it can achieve safe cementing construction and cementing quality improvement under high displacement efficiency.
