The development of gas condensate reservoirs with a large gas cap,thin oil rim,strong bottom water,and natural barriers faces numerous challenges,including reservoir heterogeneity,coning effects,phase changes,and mult...The development of gas condensate reservoirs with a large gas cap,thin oil rim,strong bottom water,and natural barriers faces numerous challenges,including reservoir heterogeneity,coning effects,phase changes,and multiphase flow dynamics.The influx of gas and water may lead to a low recovery of the oil rim,while reservoir heterogeneity and natural barriers further exacerbate the uneven distribution of reservoir fluid,complicating development strategies.This paper aims to investigate innovative and effective development strategies for this type of reservoir.A detailed,proportionally scaled numerical simulation is performed based on the experimental results of an artificial sand-filled model,providing novel insights into the dynamic behavior of these reservoirs.By understanding the phase behavior and fluid flow characteristics of the reservoir,the study simulates various strategies for the rational and efficient development of the gas condensate reservoir.These strategies include well patterns and completions,the decision to develop the oil rim or gas cap,depletion rates,the bottom water control,and gas injection.The results show that horizontal wells or highly deviated wells are more suitable for the development of the oil rim,as they provide larger control ranges.The presence of strong bottom water is advantageous for displacement energy supply and pressure maintenance,but it intensifies water coning effects,leading to an earlier breakthrough and a sharp production decline.Therefore,it is preferable to apply highly deviated wells at the oil-gas contact,developing the oil rim at lower rates and smaller pressure gradients,followed by developing the gas cap.This approach can reduce water coning effects and improve recovery,with oil and gas recovery reaching 24.4%and 67.95%,respectively,which is an increase of 16.74%and 17.84%compared to direct depletion development of the gas cap.Due to the strong water bottom,continuous gas injection at the top of the reservoir becomes challenging.This study introduces gas assisted gravity drainage with water control technology,a novel and highly effective approach that addresses the impact of bottom water coning effects on the oil and gas zones and overcomes the limitations of gas flooding in reservoirs with strong bottom water.This method can significantly improve oil and gas recovery,achieving recovery of 39.74%and 84.50%,respectively.Compared to the conventional depletion strategy of sequential oil rim and gas cap development,this method achieves additional improvements of 15.33%and 16.55%in oil and gas recovery,respectively.展开更多
Oil reservoirs with secondary bottom water in Ng33 members (in Guantao formation, Paleogene system) of Lin2-6 fault block in Huimin depression (Bohai Bay Basin) have entered the late stage of ultra-high water-containi...Oil reservoirs with secondary bottom water in Ng33 members (in Guantao formation, Paleogene system) of Lin2-6 fault block in Huimin depression (Bohai Bay Basin) have entered the late stage of ultra-high water-containing-exploitation. Oil exploitation from vertical wells is becoming more and more inefficient. The reservoir type, with water displacing oil and the remaining oil distribution are specifically studied in order to improve the efficiency of the recovery ratio. An integrated scheme for adjusting horizontal wells has been designed and the key technique of the scheme optimized. The study shows that: 1) the positive rhythm of fluvial depositional features is the internal cause of the flooding of oil reservoirs while water injection, injection-production patterns and accumulative petroleum production are the external causes; 2) oil-water driving patterns have transferred from edge water advancing to bottom-water-coning; distribution of the remaining oil mainly concentrates in the upper rhythm and top of the middle rhythm in Ng33 members; 3) a great deal of remaining oil is enriched in high positions of faults, in axes of tiny structures, in stagnation areas among water-injection wells and oil-wells and in tectonic saddle areas with sparse wells. Compared with vertical wells, horizontal wells have advantages such as high recovery, high off-take potential, high critical output, large controlling areas and long time of bottom-water breakthrough.展开更多
It is known that there is a discrepancy between field data and the results predicted from the previous equations derived by simplifying three-dimensional（3-D） flow into two-dimensions（2-D）.This paper presents a ne...It is known that there is a discrepancy between field data and the results predicted from the previous equations derived by simplifying three-dimensional（3-D） flow into two-dimensions（2-D）.This paper presents a new steady-state productivity equation for horizontal wells in bottom water drive gas reservoirs.Firstly,the fundamental solution to the 3-D steady-state Laplace equation is derived with the philosophy of source and the Green function for a horizontal well located at the center of the laterally infinite gas reservoir.Then,using the fundamental solution and the Simpson integral formula,the average pseudo-pressure equation and the steady-state productivity equation are achieved for the horizontal section.Two case-studies are given in the paper,the results calculated from the newly-derived formula are very close to the numerical simulation performed with the Canadian software CMG and the real production data,indicating that the new formula can be used to predict the steady-state productivity of such horizontal gas wells.展开更多
Horizontal wells are commonly used in bottom water reservoirs,which can increase contact area between wellbores and reservoirs.There are many completion methods used to control cresting,among which variable density pe...Horizontal wells are commonly used in bottom water reservoirs,which can increase contact area between wellbores and reservoirs.There are many completion methods used to control cresting,among which variable density perforation is an effective one.It is difficult to evaluate well productivity and to analyze inflow profiles of horizontal wells with quantities of unevenly distributed perforations,which are characterized by different parameters.In this paper,fluid flow in each wellbore perforation,as well as the reservoir,was analyzed.A comprehensive model,coupling the fluid flow in the reservoir and the wellbore pressure drawdown,was developed based on potential functions and solved using the numerical discrete method.Then,a bottom water cresting model was established on the basis of the piston-like displacement principle.Finally,bottom water cresting parameters and factors influencing inflow profile were analyzed.A more systematic optimization method was proposed by introducing the concept of cumulative free-water production,which could maintain a balance（or then a balance is achieved）between stabilizing oil production and controlling bottom water cresting.Results show that the inflow profile is affected by the perforation distribution.Wells with denser perforation density at the toe end and thinner density at the heel end may obtain low production,but the water breakthrough time is delayed.Taking cumulative free-water production as a parameter to evaluate perforation strategies is advisable in bottom water reservoirs.展开更多
Dimensional analysis and numerical simulations were carried out to research prediction method of breakthrough time of horizontal wells in bottom water reservoir. Four dimensionless independent variables and dimensionl...Dimensional analysis and numerical simulations were carried out to research prediction method of breakthrough time of horizontal wells in bottom water reservoir. Four dimensionless independent variables and dimensionless time were derived from 10 influencing factors of the problem by using dimensional analysis. Simulations of horizontal well in reservoir with bottom water were run to find the prediction correlation. A general and concise functional relationship for predicting breakthrough time was established based on simulation results and theoretical analysis. The breakthrough time of one conceptual model predicted by the correlation is very close to the result by Eclipse with less than 2% error. The practical breakthrough time of one well in Helder oilfield is 10 d, and the predicted results by the method is 11.2 d, which is more accurate than the analytical result. Case study indicates that the method could predict breakthrough time of horizontal well under different reservoir conditions accurately. For its university and ease of use, the method is suitable for quick prediction of breakthrough time.展开更多
It is well-known that barriers have a significant impact on the production performance of horizontal wells developed in a bottom water drive reservoir. In most cases, reservoir barriers are semi-permeable. Based on pr...It is well-known that barriers have a significant impact on the production performance of horizontal wells developed in a bottom water drive reservoir. In most cases, reservoir barriers are semi-permeable. Based on previous research on impermeable reservoir barrier, a mathematical flow model was derived for a horizontal well of a bottom water drive reservoir with a semi-permeable barrier. Besides, analytical equations were also presented to calculate critical parameters, such as production rate,pressure and potential difference. The effects of barrier, well and reservoir parameters on our model results were further investigated.The results show that the larger the barrier size is or the higher the barrier location is, the higher the critical production rate and potential difference of a horizontal well are. When the barrier permeability equals the formation permeability or the barrier width equals zero, the critical production rates converge to the values same to that of the case with no barrier. When the barrier permeability equals zero, the problem is regarded as a case of impermeable barrier. This model can be applied to predicting horizontal wells' critical production parameters in reservoirs with semi-permeable barriers.展开更多
To understand the effects of the Yellow Sea Cold Bottom Water （YSCBW） on the diel vertical migration （D- VM） of the copepod Calanus sinicus, we surveyed vertical distribution of C. sinicus at a fixed station in th...To understand the effects of the Yellow Sea Cold Bottom Water （YSCBW） on the diel vertical migration （D- VM） of the copepod Calanus sinicus, we surveyed vertical distribution of C. sinicus at a fixed station in the Yellow Sea before （spring） and during （summer） formation of the YSCBW. Cold water （〈10℃） was observed in the bottom layer when the water column was thermally stratified in summer, but the water column was thermally well-mixed in spring 2010. Samples were collected from five different layers at 3-h intervals using an opening-closing net. Adult females （1-155 ind./m3） showed a clear normal DVM pattern throughout the entire water column in spring, whereas adult males did not migrate. DVM of copepodite V （CV） individuals was not clear, but the maximum abundance of CI-CIV occurred consistently in the upper 10-20 m layer, where there was a high concentration of chlorophyll-a （Chl-a） （0.49-1.19μg/L）. In summer, weak DVM was limited to cold waters beneath the thermocline for adult females （〈30 ind./m3）, but not for adult males. The maximum abundance of CI-CIV also occurred consistently in the subsurface layer （20-40 m） together with high concentrations of Chl-a （0.81-2.36 μg/L）. CV individuals （1-272 ind./m3） moved slightly upward noc- turnally to the near-surface layer （10-20 m）, where the average temperature was 25.74℃, but they were not found in the surface layer （0-10 m; 28.31℃）. These results indicate that the existence of the YSBCW affected food availability at depth and the vertical temperature distribution, leading to variation in the amplitude and shape of stage-specific vertical distributions （CI to adults） in C. sinicus before and during the formation of cold waters in the Yellow Sea during the study period.展开更多
Antarctic Bottom Water(AABW)plays an important role in the meridional overturning circulation and contributes significantly to global heat transport and sea level rise(SLR).Based on the Global Ocean(1/12)°Physica...Antarctic Bottom Water(AABW)plays an important role in the meridional overturning circulation and contributes significantly to global heat transport and sea level rise(SLR).Based on the Global Ocean(1/12)°Physical Reanalysis(GLORYS12V1)products and conductivity-temperature-depth instrument data from the World Ocean Circulation Experiment hydrographic program,we analyzed the trends in the thickness,volume,temperature,salinity,and neutral density of the AABW in the Amundsen Sea from 1993 to 2017.Over the past 25 years,the volume has decreased by 3.45×10^(12) m^(3)/a,thinning at a rate of 5 m/a.In the vertical direction,the contraction of the AABW is compensated by the volume expansion of the Circumpolar Deep Water.As the volume of AABW decreases,the temperature of the AABW increases by about 0.002℃/a.This warming is equivalent to a heat flux of 0.27 W/m^(2).A local SLR is produced due to thermal expansion of 0.35 mm/a.During the study period,the neutral density decreased by 0.0003 kg/(m^(3)·a)due to warming.In the horizontal direction,the volume of AABW flowing from the Ross Sea into the Amundsen Sea gradually decreases and the temperature of the AABW increases continuously.The horizontal transport loss of the AABW volume is 4.07×10^(14) m^(3) and the horizontal heat transport results in a 0.03℃ increase in the temperature of the AABW.展开更多
X oilfield is located in Bohai Sea area, in which G oil formation is a typical drape anticline structure, which is composed of multiple sets of thick sandy conglomerate and multiple sets of argillaceous intercalation....X oilfield is located in Bohai Sea area, in which G oil formation is a typical drape anticline structure, which is composed of multiple sets of thick sandy conglomerate and multiple sets of argillaceous intercalation. From the perspective of development effect, muddy interlayer has a great impact on the oilfield. In this paper, through core identification and well logging identification, the electrical discrimination standard is summarized to identify the interlayer. Through statistics and analysis of the production performance of actual wells, the influence of muddy interlayer on the development performance of oil wells is summarized. This study provides guidance for the development of strong bottom water reservoirs with interlayer.展开更多
During the development of carbonate reservoirs,the risk of bottom water invasion is a frequent concern.Pore-scale simulation methods are commonly acknowledged as effective tools for investigating the dynamics involved...During the development of carbonate reservoirs,the risk of bottom water invasion is a frequent concern.Pore-scale simulation methods are commonly acknowledged as effective tools for investigating the dynamics involved in water invasion mechanisms.Despite extensive research on gas-water two-phase flow,few studies have investigated reservoirs with interlayers,which can remarkably affect assessments of water invasion.Three models were designed to study the effects of different interlayer distributions on flow behavior.A mathematical model based on the volume of fluid(VOF)method was employed to describe variations in water saturation.The four primary influencing factors(interlayer distribution,gravity,pressure difference,and wettability)were studied based on simulations.The accuracy of the model was validated through comparisons with microfluidic visualization experiments.Compared to the model without interlayers,the models with semi-permeable and semi-sealed interlayers reduced the risk of water invasion,resulting in slower upward water saturation rates and delayed water breakthrough times.Neglecting gravity would introduce errors of up to 5.6%in water saturation and 24.2%in water breakthrough time for the models with interlayers.Controlling the pressure difference within 1.5 MPa/100 m would effectively reduce the produced water-gas ratio and delay the water breakthrough time.The water invasion behavior in the models with interlayers was highly sensitive to contact angles in the range of 50°-60°,while its effect on the model without interlayers was relatively small.Field-scale water invasion dynamics with examples from the Yuanba(YB)gas field in the Sichuan Basin,China,were consistent with the pore-scale simulation results.This work provides fundamental support for and valuable insights into the development of similar gas reservoirs,offering a strong foundation for future endeavors in this field.展开更多
The segmented water control technology for bottom water reservoirs can effectively delay the entry of bottom water and adjust the production profile.To clarify the impact of different methods on horizontal well produc...The segmented water control technology for bottom water reservoirs can effectively delay the entry of bottom water and adjust the production profile.To clarify the impact of different methods on horizontal well production with different reservoir conditions and to provide theoretical support for the scientific selection of methods for bottom water reservoirs,a numerical simulation method is presented in this study,which is able to deal with wellbore reservoir coupling under screen tube,perforation,and ICD(Inflow Control Device)completion.Assuming the geological characteristics of the bottom-water conglomerate reservoir in the Triassic Formation of the Tahe Block 9 as a test case,the three aforementioned completion methods are tested to predict the transient production characteristics.The impact of completion parameters,reservoir permeability,bottom-water energy,and individual well control on the time to encounter water in horizontal wells(during a water-free production period)is discussed.A boundary chart for the selection of completion methods is introduced accordingly.The results show that the optimized ICD completion development effect for heterogeneous reservoirs is the best,followed by optimized perforation completion.Permeability is the main factor affecting the performances of completion methods,while bottom water energy and single well controlled reserves have a scarce impact.The average permeability of the reservoir is less than 500 mD,and ICD has the best water control effect.If the permeability is greater than 500 mD,the water control effect of perforation completion becomes a better option.展开更多
X oilfield is an offshore strong bottom water reservoir with water cut up to 96% at present, and liquid extraction has become one of the main ways to increase oil production. However, the current liquid production of ...X oilfield is an offshore strong bottom water reservoir with water cut up to 96% at present, and liquid extraction has become one of the main ways to increase oil production. However, the current liquid production of the oilfield reaches 60,000 m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">/d due to the limitation of offshore platform, well trough and equipment, the oilfield is unable to continue liquid extraction. In order to maximize the oil production of the oilfield, it is necessary to study the strategy of shut in and cone pressure. Through numerical simulation, this paper analyzes the influence of different factors, such as crude oil density, viscosity, reservoir thickness, interlayer, permeability and so on, on the drop height of water cone and the effect of precipitation and oil increase after well shut in. At the same time, the weight of each factor is analyzed by combining the actual dynamic data with the fuzzy mathematics method, and the strategy of well shut in and cone pressure is formulated for the offshore strong bottom water reservoir. It provides the basis and guidance for the reasonable use of shut in pressure cone when the reservoir with strong bottom water meets the bottleneck of liquid volume.展开更多
X oilfield is a typical strong bottom water reservoir in Bohai Sea. It is developed by single sand body horizontal well. The edge and bottom water of the reservoir is active and natural energy development mode is adop...X oilfield is a typical strong bottom water reservoir in Bohai Sea. It is developed by single sand body horizontal well. The edge and bottom water of the reservoir is active and natural energy development mode is adopted. At present, the comprehensive water cut of the oilfield is more than 96%, and has entered the stage of high water cut oil recovery. At present, fluid extraction from old wells and new adjustment wells are the main ways to increase oil production. With the deepening of development, the distribution of underground remaining oil is becoming more and more complex. In order to further improve the implementation effect of adjustment wells, the study of residual oil distribution law is increasingly important, and the study of water ridge morphology of horizontal wells in bottom water reservoir has an important guiding role in the study of remaining oil distribution. The main contents of this paper are as follows: the influence of horizontal well spacing, vertical and horizontal permeability ratio, single well liquid production, vertical position of horizontal well, oil-water viscosity ratio, water cut and interlayer on water ridge morphology. These understandings can effectively guide the deployment and optimization of adjustment wells. It provides technical support for the prediction of watered out thickness and optimization of adjustment well layout scheme in X oilfield, and guides the further development and production of the oilfield.展开更多
The bottom water heavy oil reservoir has high natural energy, and the bottom water body multiple of the reservoir is 300 times or even higher. The natural energy of the reservoir can keep the superior condition that t...The bottom water heavy oil reservoir has high natural energy, and the bottom water body multiple of the reservoir is 300 times or even higher. The natural energy of the reservoir can keep the superior condition that the formation energy does not decrease under the condition of large liquid volume and high recovery rate. In view of this reservoir condition, we take C oilfield as an example to carry out the oilfield development effect under the condition of large liquid volume and high-speed production, and analyze the influence of high-speed production and medium low-speed production on recovery rate of similar heavy oil bottom water-reservoir. The results show that the rising trend of water cut in oilfield is the same whether high-speed development with large liquid volume or conventional low-speed development is adopted. Under the condition of high liquid production, the sweep efficiency of water flooding is high in the same period of time, which has certain advantages of enhanced oil recovery. The development mode of early large liquid production is explored, which provides certain guidance for the efficient development of heavy oil reservoir with bottom water.展开更多
Carbonate gas reservoirs with edge and bottom water contain abundant reserves,making them key production targets in the Tarim Basin,Sichuan Basin,Ordos Basin,and other petroleum provinces.Water invasion may occur in t...Carbonate gas reservoirs with edge and bottom water contain abundant reserves,making them key production targets in the Tarim Basin,Sichuan Basin,Ordos Basin,and other petroleum provinces.Water invasion may occur in the middle and late development stages of such reservoirs,leading to reduction of gas displacement efficiency and gas recovery.In this paper,a pore-scale water-gas immiscible flow model is established by coupling the fluid flow equation and the gas-water contact(GWC)tracking equation.The process of gas displacement with water is simulated in the heterogeneous porous media generated by the quartet structure generation set(QSGS).Finally,the mechanisms of remaining gas distribution and formation are analyzed,and the variation mechanism of microscopic gas displacement efficiency is discussed.The results are obtained in three aspects.First,the remaining gas is distributed at the blind end,in the pore-throat and as clusters,with their proportions and scales jointly controlled by microscopic pore structures,wettability and capillary number.The remaining gas can be further produced by changing the production pressure differential to disturb the original pressure system and gas expansion,so as to improve the microscopic gas displacement efficiency.Second,the microscopic gas displacement efficiency is closely related to the gas flow process.Formation or expansion of each water flow path may cause rapid increase of water cut and slows down the increase of gas displacement efficiency.Third,the microscopic pore structure and wettability are the inherent features of the gas reservoir,so the capillary number can be optimized to change the mode of GWC advancement,and then to effectively improve the microscopic gas displacement efficiency.It is concluded that for real gas wells,the evolution of mechanical mechanisms of GWC advancement should be revealed depending upon the microscopic pore structure and wettability of the reservoir,and then the optimal capillary number can be determined.Furthermore,clarifying the pore-scale water-gas flow characteristics and physical mechanism of microscopic gas displacement provides guidance for the planning of enhanced gas recovery.展开更多
The methane concentration of water samples at five stations collected by the CTD rosette water sampler in the areas of southwest Dongsha Islands and the Xisha Trough was analyzed by the gas-stripping method on aboard ...The methane concentration of water samples at five stations collected by the CTD rosette water sampler in the areas of southwest Dongsha Islands and the Xisha Trough was analyzed by the gas-stripping method on aboard ship. It shows abnormal high methane concentrations in near bottom water samples at three stations. In the southwest Dongsha Islands area, the methane conc.entration of 4. 25 and 10. 64 nmol/dm3 occurs in near bottom water samples at Stas E105A and El06, respectively. In the Xisha Trough area, the high methane concentrations of 5. 17, 8.48 and 8.70 nmol/dm3 in water depths of 1 750, 1 900 and 2 050 m, respectively, have been observed at Sta. F413. It is believed that the abnormal high methane concentrations are generated from the leakage of methane from sediments. Combining with previous geophysical and geochemical data from these two areas, this was probably related to the submarine gas hydrates decomposition and cold seep system. In May 2007, gas hydrate samples were successfully obtained by the drilling in the Shenhu Sea area located in the southwest Dongsha Islands area. It is called for further drilling surveys to confirm the existence of gas hydrate and cold seep system in the Xisha Trough as early as possible.展开更多
Aiming at the complex flowing environment including the buried hill of Metamorphite, the active bottom water and the fracture at Budate Reservoir within Beir Depression of the Hailar Basin, combining the laboratory st...Aiming at the complex flowing environment including the buried hill of Metamorphite, the active bottom water and the fracture at Budate Reservoir within Beir Depression of the Hailar Basin, combining the laboratory studies and based on analysis of its drive mechanism, field wells’ parameters were used to analyze the effects of different conditions of the fractured metamorphic reservoir with bottom water on its law of wa-ter-cut variation and the waterflooding efficiency. The results show that for the Budate buried hill reservoir with bottom water, the gravity should be taken into consideration to determine reasonable perforation ratio and production pressure difference. And because of the acid sensitivity of the buried hill reservoir, application of proper clay stabilizer will enhance the field oil recovery to a satisfactory extent.展开更多
X oilfield has successfully adopted horizontal wells to develop strong bottom water reservoirs, as a typical representative of development styles in the Bohai offshore oilfield. At present, many contributions to metho...X oilfield has successfully adopted horizontal wells to develop strong bottom water reservoirs, as a typical representative of development styles in the Bohai offshore oilfield. At present, many contributions to methods of inverting relative permeability curve and forecasting residual recoverable reserves had been made by investigators, but rarely involved in horizontal wells’ in bottom water reservoir. As the pore volume injected was less (usually under 30 PV), the relative permeability curve endpoint had become a serious distortion. That caused a certain deviation in forecasting residual recoverable reserves in the practical value of field directly. For the performance of water cresting, the common method existed some problems, such as no pertinence, ineffectiveness and less affecting factors considered. This paper adopts the streamlines theory with two phases flowing to solve that. Meanwhile, based on the research coupling genetic algorithm, optimized relative permeability curve was calculated by bottom-water drive model. The residual oil saturation calculated was lower than the initial’s, and the hydrophilic property was more reinforced, due to improving the pore volume injected vastly. Also, the study finally helped us enhance residual recoverable reserves degree at high water cut stage, more than 20%, taking Guantao sandstone as an example. As oil field being gradually entering high water cut stage, this method had a great significance to evaluate the development effect and guide the potential of the reservoir.展开更多
基金the support from the National Natural Science Foundation of China(NSFC Grant No.:52004032)。
文摘The development of gas condensate reservoirs with a large gas cap,thin oil rim,strong bottom water,and natural barriers faces numerous challenges,including reservoir heterogeneity,coning effects,phase changes,and multiphase flow dynamics.The influx of gas and water may lead to a low recovery of the oil rim,while reservoir heterogeneity and natural barriers further exacerbate the uneven distribution of reservoir fluid,complicating development strategies.This paper aims to investigate innovative and effective development strategies for this type of reservoir.A detailed,proportionally scaled numerical simulation is performed based on the experimental results of an artificial sand-filled model,providing novel insights into the dynamic behavior of these reservoirs.By understanding the phase behavior and fluid flow characteristics of the reservoir,the study simulates various strategies for the rational and efficient development of the gas condensate reservoir.These strategies include well patterns and completions,the decision to develop the oil rim or gas cap,depletion rates,the bottom water control,and gas injection.The results show that horizontal wells or highly deviated wells are more suitable for the development of the oil rim,as they provide larger control ranges.The presence of strong bottom water is advantageous for displacement energy supply and pressure maintenance,but it intensifies water coning effects,leading to an earlier breakthrough and a sharp production decline.Therefore,it is preferable to apply highly deviated wells at the oil-gas contact,developing the oil rim at lower rates and smaller pressure gradients,followed by developing the gas cap.This approach can reduce water coning effects and improve recovery,with oil and gas recovery reaching 24.4%and 67.95%,respectively,which is an increase of 16.74%and 17.84%compared to direct depletion development of the gas cap.Due to the strong water bottom,continuous gas injection at the top of the reservoir becomes challenging.This study introduces gas assisted gravity drainage with water control technology,a novel and highly effective approach that addresses the impact of bottom water coning effects on the oil and gas zones and overcomes the limitations of gas flooding in reservoirs with strong bottom water.This method can significantly improve oil and gas recovery,achieving recovery of 39.74%and 84.50%,respectively.Compared to the conventional depletion strategy of sequential oil rim and gas cap development,this method achieves additional improvements of 15.33%and 16.55%in oil and gas recovery,respectively.
基金Projects 2003CB214603 supported by the National Basic Research Program of ChinaDMSM200803 by the Open Fund of Key Laboratory of Deposi-tional Mineralization & Sedimentary Mineral, Shandong Province
文摘Oil reservoirs with secondary bottom water in Ng33 members (in Guantao formation, Paleogene system) of Lin2-6 fault block in Huimin depression (Bohai Bay Basin) have entered the late stage of ultra-high water-containing-exploitation. Oil exploitation from vertical wells is becoming more and more inefficient. The reservoir type, with water displacing oil and the remaining oil distribution are specifically studied in order to improve the efficiency of the recovery ratio. An integrated scheme for adjusting horizontal wells has been designed and the key technique of the scheme optimized. The study shows that: 1) the positive rhythm of fluvial depositional features is the internal cause of the flooding of oil reservoirs while water injection, injection-production patterns and accumulative petroleum production are the external causes; 2) oil-water driving patterns have transferred from edge water advancing to bottom-water-coning; distribution of the remaining oil mainly concentrates in the upper rhythm and top of the middle rhythm in Ng33 members; 3) a great deal of remaining oil is enriched in high positions of faults, in axes of tiny structures, in stagnation areas among water-injection wells and oil-wells and in tectonic saddle areas with sparse wells. Compared with vertical wells, horizontal wells have advantages such as high recovery, high off-take potential, high critical output, large controlling areas and long time of bottom-water breakthrough.
基金financial support from the Open Fund(PLN1003) of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(Southwest Petroleum University)the National Science and Technology Major Project in the l lth Five-Year Plan(Grant No.2008ZX05054)
文摘It is known that there is a discrepancy between field data and the results predicted from the previous equations derived by simplifying three-dimensional（3-D） flow into two-dimensions（2-D）.This paper presents a new steady-state productivity equation for horizontal wells in bottom water drive gas reservoirs.Firstly,the fundamental solution to the 3-D steady-state Laplace equation is derived with the philosophy of source and the Green function for a horizontal well located at the center of the laterally infinite gas reservoir.Then,using the fundamental solution and the Simpson integral formula,the average pseudo-pressure equation and the steady-state productivity equation are achieved for the horizontal section.Two case-studies are given in the paper,the results calculated from the newly-derived formula are very close to the numerical simulation performed with the Canadian software CMG and the real production data,indicating that the new formula can be used to predict the steady-state productivity of such horizontal gas wells.
文摘Horizontal wells are commonly used in bottom water reservoirs,which can increase contact area between wellbores and reservoirs.There are many completion methods used to control cresting,among which variable density perforation is an effective one.It is difficult to evaluate well productivity and to analyze inflow profiles of horizontal wells with quantities of unevenly distributed perforations,which are characterized by different parameters.In this paper,fluid flow in each wellbore perforation,as well as the reservoir,was analyzed.A comprehensive model,coupling the fluid flow in the reservoir and the wellbore pressure drawdown,was developed based on potential functions and solved using the numerical discrete method.Then,a bottom water cresting model was established on the basis of the piston-like displacement principle.Finally,bottom water cresting parameters and factors influencing inflow profile were analyzed.A more systematic optimization method was proposed by introducing the concept of cumulative free-water production,which could maintain a balance（or then a balance is achieved）between stabilizing oil production and controlling bottom water cresting.Results show that the inflow profile is affected by the perforation distribution.Wells with denser perforation density at the toe end and thinner density at the heel end may obtain low production,but the water breakthrough time is delayed.Taking cumulative free-water production as a parameter to evaluate perforation strategies is advisable in bottom water reservoirs.
基金Project(2011ZX05009-004)supported by the National Science and Technology Major Projects of China
文摘Dimensional analysis and numerical simulations were carried out to research prediction method of breakthrough time of horizontal wells in bottom water reservoir. Four dimensionless independent variables and dimensionless time were derived from 10 influencing factors of the problem by using dimensional analysis. Simulations of horizontal well in reservoir with bottom water were run to find the prediction correlation. A general and concise functional relationship for predicting breakthrough time was established based on simulation results and theoretical analysis. The breakthrough time of one conceptual model predicted by the correlation is very close to the result by Eclipse with less than 2% error. The practical breakthrough time of one well in Helder oilfield is 10 d, and the predicted results by the method is 11.2 d, which is more accurate than the analytical result. Case study indicates that the method could predict breakthrough time of horizontal well under different reservoir conditions accurately. For its university and ease of use, the method is suitable for quick prediction of breakthrough time.
基金Project(51404201)supported by the National Natural Science Foundation of ChinaProject(2011ZX05024-003)supported by the National Science and Technology Major Project of China+1 种基金Project(14ZB0045)supported by the Scientific Project of Sichuan Provincial Education Department,ChinaProject(2015JY0076)supported by Basic Application Research of Science and Technology Department of Sichuan Province,China
文摘It is well-known that barriers have a significant impact on the production performance of horizontal wells developed in a bottom water drive reservoir. In most cases, reservoir barriers are semi-permeable. Based on previous research on impermeable reservoir barrier, a mathematical flow model was derived for a horizontal well of a bottom water drive reservoir with a semi-permeable barrier. Besides, analytical equations were also presented to calculate critical parameters, such as production rate,pressure and potential difference. The effects of barrier, well and reservoir parameters on our model results were further investigated.The results show that the larger the barrier size is or the higher the barrier location is, the higher the critical production rate and potential difference of a horizontal well are. When the barrier permeability equals the formation permeability or the barrier width equals zero, the critical production rates converge to the values same to that of the case with no barrier. When the barrier permeability equals zero, the problem is regarded as a case of impermeable barrier. This model can be applied to predicting horizontal wells' critical production parameters in reservoirs with semi-permeable barriers.
基金The study on the impact of the Yellow Sea Bottom Cold Water Mass to the ecosystem(YES Coldwater:PE99165)part of the Korea-China cooperative project on the Yellow Sea Cold Water Mass
文摘To understand the effects of the Yellow Sea Cold Bottom Water （YSCBW） on the diel vertical migration （D- VM） of the copepod Calanus sinicus, we surveyed vertical distribution of C. sinicus at a fixed station in the Yellow Sea before （spring） and during （summer） formation of the YSCBW. Cold water （〈10℃） was observed in the bottom layer when the water column was thermally stratified in summer, but the water column was thermally well-mixed in spring 2010. Samples were collected from five different layers at 3-h intervals using an opening-closing net. Adult females （1-155 ind./m3） showed a clear normal DVM pattern throughout the entire water column in spring, whereas adult males did not migrate. DVM of copepodite V （CV） individuals was not clear, but the maximum abundance of CI-CIV occurred consistently in the upper 10-20 m layer, where there was a high concentration of chlorophyll-a （Chl-a） （0.49-1.19μg/L）. In summer, weak DVM was limited to cold waters beneath the thermocline for adult females （〈30 ind./m3）, but not for adult males. The maximum abundance of CI-CIV also occurred consistently in the subsurface layer （20-40 m） together with high concentrations of Chl-a （0.81-2.36 μg/L）. CV individuals （1-272 ind./m3） moved slightly upward noc- turnally to the near-surface layer （10-20 m）, where the average temperature was 25.74℃, but they were not found in the surface layer （0-10 m; 28.31℃）. These results indicate that the existence of the YSBCW affected food availability at depth and the vertical temperature distribution, leading to variation in the amplitude and shape of stage-specific vertical distributions （CI to adults） in C. sinicus before and during the formation of cold waters in the Yellow Sea during the study period.
基金The Impact and Response of Antarctic Seas to Climate Change Program under contract No.RFSOCC2020-2022-No.18the National Key Research and Development Program of China under contract No.2016YFA0601301。
文摘Antarctic Bottom Water(AABW)plays an important role in the meridional overturning circulation and contributes significantly to global heat transport and sea level rise(SLR).Based on the Global Ocean(1/12)°Physical Reanalysis(GLORYS12V1)products and conductivity-temperature-depth instrument data from the World Ocean Circulation Experiment hydrographic program,we analyzed the trends in the thickness,volume,temperature,salinity,and neutral density of the AABW in the Amundsen Sea from 1993 to 2017.Over the past 25 years,the volume has decreased by 3.45×10^(12) m^(3)/a,thinning at a rate of 5 m/a.In the vertical direction,the contraction of the AABW is compensated by the volume expansion of the Circumpolar Deep Water.As the volume of AABW decreases,the temperature of the AABW increases by about 0.002℃/a.This warming is equivalent to a heat flux of 0.27 W/m^(2).A local SLR is produced due to thermal expansion of 0.35 mm/a.During the study period,the neutral density decreased by 0.0003 kg/(m^(3)·a)due to warming.In the horizontal direction,the volume of AABW flowing from the Ross Sea into the Amundsen Sea gradually decreases and the temperature of the AABW increases continuously.The horizontal transport loss of the AABW volume is 4.07×10^(14) m^(3) and the horizontal heat transport results in a 0.03℃ increase in the temperature of the AABW.
文摘X oilfield is located in Bohai Sea area, in which G oil formation is a typical drape anticline structure, which is composed of multiple sets of thick sandy conglomerate and multiple sets of argillaceous intercalation. From the perspective of development effect, muddy interlayer has a great impact on the oilfield. In this paper, through core identification and well logging identification, the electrical discrimination standard is summarized to identify the interlayer. Through statistics and analysis of the production performance of actual wells, the influence of muddy interlayer on the development performance of oil wells is summarized. This study provides guidance for the development of strong bottom water reservoirs with interlayer.
基金supported by the National Natural Science Foundation of China(Grant No.52304044)the Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance(Grant No.2020CX010403)the Sichuan Science and Technology Program(Grant No.2022NSFSC0190).
文摘During the development of carbonate reservoirs,the risk of bottom water invasion is a frequent concern.Pore-scale simulation methods are commonly acknowledged as effective tools for investigating the dynamics involved in water invasion mechanisms.Despite extensive research on gas-water two-phase flow,few studies have investigated reservoirs with interlayers,which can remarkably affect assessments of water invasion.Three models were designed to study the effects of different interlayer distributions on flow behavior.A mathematical model based on the volume of fluid(VOF)method was employed to describe variations in water saturation.The four primary influencing factors(interlayer distribution,gravity,pressure difference,and wettability)were studied based on simulations.The accuracy of the model was validated through comparisons with microfluidic visualization experiments.Compared to the model without interlayers,the models with semi-permeable and semi-sealed interlayers reduced the risk of water invasion,resulting in slower upward water saturation rates and delayed water breakthrough times.Neglecting gravity would introduce errors of up to 5.6%in water saturation and 24.2%in water breakthrough time for the models with interlayers.Controlling the pressure difference within 1.5 MPa/100 m would effectively reduce the produced water-gas ratio and delay the water breakthrough time.The water invasion behavior in the models with interlayers was highly sensitive to contact angles in the range of 50°-60°,while its effect on the model without interlayers was relatively small.Field-scale water invasion dynamics with examples from the Yuanba(YB)gas field in the Sichuan Basin,China,were consistent with the pore-scale simulation results.This work provides fundamental support for and valuable insights into the development of similar gas reservoirs,offering a strong foundation for future endeavors in this field.
文摘The segmented water control technology for bottom water reservoirs can effectively delay the entry of bottom water and adjust the production profile.To clarify the impact of different methods on horizontal well production with different reservoir conditions and to provide theoretical support for the scientific selection of methods for bottom water reservoirs,a numerical simulation method is presented in this study,which is able to deal with wellbore reservoir coupling under screen tube,perforation,and ICD(Inflow Control Device)completion.Assuming the geological characteristics of the bottom-water conglomerate reservoir in the Triassic Formation of the Tahe Block 9 as a test case,the three aforementioned completion methods are tested to predict the transient production characteristics.The impact of completion parameters,reservoir permeability,bottom-water energy,and individual well control on the time to encounter water in horizontal wells(during a water-free production period)is discussed.A boundary chart for the selection of completion methods is introduced accordingly.The results show that the optimized ICD completion development effect for heterogeneous reservoirs is the best,followed by optimized perforation completion.Permeability is the main factor affecting the performances of completion methods,while bottom water energy and single well controlled reserves have a scarce impact.The average permeability of the reservoir is less than 500 mD,and ICD has the best water control effect.If the permeability is greater than 500 mD,the water control effect of perforation completion becomes a better option.
文摘X oilfield is an offshore strong bottom water reservoir with water cut up to 96% at present, and liquid extraction has become one of the main ways to increase oil production. However, the current liquid production of the oilfield reaches 60,000 m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">/d due to the limitation of offshore platform, well trough and equipment, the oilfield is unable to continue liquid extraction. In order to maximize the oil production of the oilfield, it is necessary to study the strategy of shut in and cone pressure. Through numerical simulation, this paper analyzes the influence of different factors, such as crude oil density, viscosity, reservoir thickness, interlayer, permeability and so on, on the drop height of water cone and the effect of precipitation and oil increase after well shut in. At the same time, the weight of each factor is analyzed by combining the actual dynamic data with the fuzzy mathematics method, and the strategy of well shut in and cone pressure is formulated for the offshore strong bottom water reservoir. It provides the basis and guidance for the reasonable use of shut in pressure cone when the reservoir with strong bottom water meets the bottleneck of liquid volume.
文摘X oilfield is a typical strong bottom water reservoir in Bohai Sea. It is developed by single sand body horizontal well. The edge and bottom water of the reservoir is active and natural energy development mode is adopted. At present, the comprehensive water cut of the oilfield is more than 96%, and has entered the stage of high water cut oil recovery. At present, fluid extraction from old wells and new adjustment wells are the main ways to increase oil production. With the deepening of development, the distribution of underground remaining oil is becoming more and more complex. In order to further improve the implementation effect of adjustment wells, the study of residual oil distribution law is increasingly important, and the study of water ridge morphology of horizontal wells in bottom water reservoir has an important guiding role in the study of remaining oil distribution. The main contents of this paper are as follows: the influence of horizontal well spacing, vertical and horizontal permeability ratio, single well liquid production, vertical position of horizontal well, oil-water viscosity ratio, water cut and interlayer on water ridge morphology. These understandings can effectively guide the deployment and optimization of adjustment wells. It provides technical support for the prediction of watered out thickness and optimization of adjustment well layout scheme in X oilfield, and guides the further development and production of the oilfield.
文摘The bottom water heavy oil reservoir has high natural energy, and the bottom water body multiple of the reservoir is 300 times or even higher. The natural energy of the reservoir can keep the superior condition that the formation energy does not decrease under the condition of large liquid volume and high recovery rate. In view of this reservoir condition, we take C oilfield as an example to carry out the oilfield development effect under the condition of large liquid volume and high-speed production, and analyze the influence of high-speed production and medium low-speed production on recovery rate of similar heavy oil bottom water-reservoir. The results show that the rising trend of water cut in oilfield is the same whether high-speed development with large liquid volume or conventional low-speed development is adopted. Under the condition of high liquid production, the sweep efficiency of water flooding is high in the same period of time, which has certain advantages of enhanced oil recovery. The development mode of early large liquid production is explored, which provides certain guidance for the efficient development of heavy oil reservoir with bottom water.
基金Project supported by the National Natural Science Foundation Projects of China(NSFC)“Dynamic wetting mechanism and transport characteristics of waterdisplacing-gas in nano-pores of unconventional reservoirs”(No.52174041)“Research on fracturing fluid invasion/flowback/retentionmechanisms in shale reservoirs and their impacts on gas well productivity”(No.52104051)+1 种基金“Research on cross scale coupling flow and production law of effective shale gas reservoir pores”(No.51874319)the Natural Science Foundation Project of Beijing“Simulation study on the transfer mechanismand transfer of oil inmicro-nanopores of tight/shale reservoirs”(No.2204093).
文摘Carbonate gas reservoirs with edge and bottom water contain abundant reserves,making them key production targets in the Tarim Basin,Sichuan Basin,Ordos Basin,and other petroleum provinces.Water invasion may occur in the middle and late development stages of such reservoirs,leading to reduction of gas displacement efficiency and gas recovery.In this paper,a pore-scale water-gas immiscible flow model is established by coupling the fluid flow equation and the gas-water contact(GWC)tracking equation.The process of gas displacement with water is simulated in the heterogeneous porous media generated by the quartet structure generation set(QSGS).Finally,the mechanisms of remaining gas distribution and formation are analyzed,and the variation mechanism of microscopic gas displacement efficiency is discussed.The results are obtained in three aspects.First,the remaining gas is distributed at the blind end,in the pore-throat and as clusters,with their proportions and scales jointly controlled by microscopic pore structures,wettability and capillary number.The remaining gas can be further produced by changing the production pressure differential to disturb the original pressure system and gas expansion,so as to improve the microscopic gas displacement efficiency.Second,the microscopic gas displacement efficiency is closely related to the gas flow process.Formation or expansion of each water flow path may cause rapid increase of water cut and slows down the increase of gas displacement efficiency.Third,the microscopic pore structure and wettability are the inherent features of the gas reservoir,so the capillary number can be optimized to change the mode of GWC advancement,and then to effectively improve the microscopic gas displacement efficiency.It is concluded that for real gas wells,the evolution of mechanical mechanisms of GWC advancement should be revealed depending upon the microscopic pore structure and wettability of the reservoir,and then the optimal capillary number can be determined.Furthermore,clarifying the pore-scale water-gas flow characteristics and physical mechanism of microscopic gas displacement provides guidance for the planning of enhanced gas recovery.
基金Instrument Developing Project of the Chinese Academy of Sciences(YZ201136)National Natural Science Foundation of China(41106086,41474065,41376059,41376061,91428205,41576036,41076028,41476167,and 41606080)Chinese Academy of Sciences Scholarship,the Strat
基金The National "863" High Technology Research Foundation of China under contract No.2006AA09Z222the Fujian Province Natural Science Foundation of China under contract No.2005YZ1013
文摘The methane concentration of water samples at five stations collected by the CTD rosette water sampler in the areas of southwest Dongsha Islands and the Xisha Trough was analyzed by the gas-stripping method on aboard ship. It shows abnormal high methane concentrations in near bottom water samples at three stations. In the southwest Dongsha Islands area, the methane conc.entration of 4. 25 and 10. 64 nmol/dm3 occurs in near bottom water samples at Stas E105A and El06, respectively. In the Xisha Trough area, the high methane concentrations of 5. 17, 8.48 and 8.70 nmol/dm3 in water depths of 1 750, 1 900 and 2 050 m, respectively, have been observed at Sta. F413. It is believed that the abnormal high methane concentrations are generated from the leakage of methane from sediments. Combining with previous geophysical and geochemical data from these two areas, this was probably related to the submarine gas hydrates decomposition and cold seep system. In May 2007, gas hydrate samples were successfully obtained by the drilling in the Shenhu Sea area located in the southwest Dongsha Islands area. It is called for further drilling surveys to confirm the existence of gas hydrate and cold seep system in the Xisha Trough as early as possible.
文摘Aiming at the complex flowing environment including the buried hill of Metamorphite, the active bottom water and the fracture at Budate Reservoir within Beir Depression of the Hailar Basin, combining the laboratory studies and based on analysis of its drive mechanism, field wells’ parameters were used to analyze the effects of different conditions of the fractured metamorphic reservoir with bottom water on its law of wa-ter-cut variation and the waterflooding efficiency. The results show that for the Budate buried hill reservoir with bottom water, the gravity should be taken into consideration to determine reasonable perforation ratio and production pressure difference. And because of the acid sensitivity of the buried hill reservoir, application of proper clay stabilizer will enhance the field oil recovery to a satisfactory extent.
文摘X oilfield has successfully adopted horizontal wells to develop strong bottom water reservoirs, as a typical representative of development styles in the Bohai offshore oilfield. At present, many contributions to methods of inverting relative permeability curve and forecasting residual recoverable reserves had been made by investigators, but rarely involved in horizontal wells’ in bottom water reservoir. As the pore volume injected was less (usually under 30 PV), the relative permeability curve endpoint had become a serious distortion. That caused a certain deviation in forecasting residual recoverable reserves in the practical value of field directly. For the performance of water cresting, the common method existed some problems, such as no pertinence, ineffectiveness and less affecting factors considered. This paper adopts the streamlines theory with two phases flowing to solve that. Meanwhile, based on the research coupling genetic algorithm, optimized relative permeability curve was calculated by bottom-water drive model. The residual oil saturation calculated was lower than the initial’s, and the hydrophilic property was more reinforced, due to improving the pore volume injected vastly. Also, the study finally helped us enhance residual recoverable reserves degree at high water cut stage, more than 20%, taking Guantao sandstone as an example. As oil field being gradually entering high water cut stage, this method had a great significance to evaluate the development effect and guide the potential of the reservoir.
