Lithologic Reservoirs

Quantitative prediction of organic pores in shale with low to moderate maturity is significant for shale oil resources assessment. Theoretical models of the conversion rate and hydrocarbon generation rate were established to predict the organic porosity of shale quantitatively based on genetic mechanism of organic pores in shale. Both models can efficiently predict the upper limit for organic porosity of shale. Moreover,the statistic model for prediction of organic porosity of shale with low to moderate maturity was built with surface porosity observed through scanning electron microscope,which can be used to calculate the approximation of the organic porosity. The statistical analysis reveals findings in two aspects. Firstly,for the lacustrine shale in China,the surface porosity has an exponential relationship with Ro,and it increases slowly at the stages of low to moderate maturity. Secondly,for the marine shale in North America,the surface porosity has a logarithmic relationship with Ro,and it increases rapidly at the stages of low to moderate maturity. In addition,differences of organic pores between shale with low to moderate maturity and shale with high to over maturity were discussed. It is indicated that the lacustrine shale with low to moderate maturity in China contains less organic pores than the marine shale in North America,which provides references for study on organic pores in shale and assessment and exploration of shale oil resources.

Microscopic pore structure and seepage characteristics of different pore assemblage types in ultra low permeability reservoir:a case of Chang 6 reservoir in Tang 157 well area,Ganguyi Oilfield

ZHAO Xisen, DANG Hailong, PANG Zhenyu, SHI Pitong, CAO Shang, DING Lei, BAI Pu

2017, Vol.29(6): 8–14 Abstract ( 398 ) PDF (1249 KB) ( 527 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.002

Aiming to overcome reservoir heterogeneity influence in water injection development,it is the first that high mercury injection,constant mercury injection,nuclear magnetic resonance have been applied to make an accurate quantification of reservoir characteristics in the stage of water injection from the angle of pore combination. In this paper main current throat radius and moveable fluid saturation have been defined for the sake of understanding the features of water flooding and residual oil for different pore assembly types. Dissolved/intergranular pores developing in the favorable sedimentary faces of the lowest compaction and cementation make its reservoir have the highest value of porosity,permeability,oil saturation and moveable fluid saturation,which makes the apparent apartment of oil and is the easiest to form preponderant permeable paths of 0.963-1.494 μm main current throat radius and fingering flooding results in residual oil of large area. Secondly by the sequence of intergranular-dissolved,dissolved-micro and micro pores,main current throat radius range is respectively 0.432-1.071 μm, 0.364-0.411 μm and its flooding type changes from finger-net, net to immovable flooding.

Division of Carboniferous volcanic rock mass in eastern Junggar Basin

KONG Chuixian, QIU Zigang, LU Zhiyuan, JIA Junfei, CHANG Tianquan

2017, Vol.29(6): 15–22 Abstract ( 380 ) PDF (4649 KB) ( 514 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.003

In recent years, volcanic rock reservoir exploration has become a hot spot in Junggar Basin, and breakthrough progresses have been made in different areas of Junggar Basin. The fact that the volcanic rock masses are stacked on each other increases the difficulty of identification and brings great difficulty in the prediction of effective reservoirs and oil and gas development. Under the guidance of "one rock mass,one reservoir" reservoir model, the data of geology, core, logging curves, analytical test, seismic and development dynamics,were used to confirm the fissure eruption mode and volcanic eruption periods. Six types of volcanic rock mass consisting of twelve sets of lithologic section were classified according to lithologic cycles and seismic reflection characteristics. The testing result further confirms that there are two main volcanic reservoir rock masses,and single volcanic reservoir rock mass has the characteristics of wide area,big thickness and large scale. The volcanic rock masses are inclined to the southeast direction overall,and constitute the ridge-like fault-stratigraphic trap reservoir together with the overlying sedimentary strata under the control of the faults. These results have great significance for the prediction of effective reservoirs and improvement of oil and gas production.

Features of liquid hydrocarbon in different states in oil shale during hydrous pyrolysis

SUN Lina, ZHANG Mingfeng, WU Chenjun, WANG Zixiang, TUO Jincai

2017, Vol.29(6): 23–31 Abstract ( 312 ) PDF (1419 KB) ( 587 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.004

In order to understand the components and change features of liquid hydrocarbons in different states, a series of simulation experiments were conducted on source rocks using WYMN-3 high temperature and pressure simulator. These pyrolysis experiments were conducted on the columned oil-shales samples from Yanchang Formation in Ordos Basin and Lucaogou Formation in Junggar Basin under semi-open system,and the temperatures were set on 250℃, 300℃, 350℃, 375℃, 400℃, 450℃ and 500℃. The hydrodynamic pressures were all carried on 50 MPa,and the experiments were all kept on the target temperatures for 48 hours. The liquid hydrocarbons products were separated into expelled oil,wash-out oil and residual oil,and the sum of the three components was defined as total oil. Based on the analysis about the features of expelled,wash-out,residual and total oil,what we have found were listed as below:(1)with the temperature increasing,the tendency of expelled oil and total oil is the same,which shows the importance of expelled oil for the yields of total oil; (2)the trend of wash-out and residual oils with different temperatures is the same, which could be related to the evolution of organic matters; (3)from the changing stages of expelled,wash-out and residual oils,the three thermal evolution stages are the thermal cracking of soluble organic matter in original source rocks,the thermal cracking of kerogens,and the second cracking of oil to gases; (4)the stages of expelled oil are always later than washout oil, which indicates that the expelled oil would be retained on the surface of source rocks before the second migration; (5)the maximum yields of residual oil are occurred at 350℃ in both samples,thus the beginning of oil generation window is the maximum point of residual oil; (6)the higher total organic carbon content may be resulted in the higher generation of hydrocarbons during thermal evolution, and the higher contents of saturated hydrocarbons and aromatic hydrocarbons could be also resulted in the higher yields of hydrocarbons. Therefore, these researches could provide some theoretical foundations for the studies of liquid hydrocarbons evolution.

Characteristics of Chang 8 reservoir in Zhengning area,Ordos Basin

ZENG Yuan, CHEN Shijia, LI Shixiang, LU Jungang

2017, Vol.29(6): 32–42 Abstract ( 503 ) PDF (1788 KB) ( 487 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.005

In order to promote the exploration and development of tight oil and gas in Zhengning area, Ordos Basin, based on core slice,scanning electron microscope and mercury injection data, reservoir characteristics, reservoir densification and relationship between physical properties and oil-bearing property were analyzed. The Chang 8 sandstone is mainly composed of feldspar lithic sandstone and lithic feldspar sandstone,with high content of interstitial matter, which is mainly composed by ferroan calcite, hydromica, chlorite membrane, kiesel, and kaolinite. The Chang 8 sandstone is low in clastic structure maturity, which is mainly medium-sorted subangular particles. Matrix pores and natural fractures jointly form reservoir pore system,and matrix pores are mainly small pores with fine throat. Compaction and cementation are main densification origins for Chang 8 tight reservoir. Natural fractures are main percolation pathway,and together with dissolution,they improved reservoir physical properties. Physical properties of Chang 81 reservoir are obviously better than that of Chang 82 reservoir. Oil-bearing is relative with physical property. Better physical property is the key for high oil production.

Paleo-tectonic restoration in southern Qinshui Basin and its hydrocarbon significance

YIN Shuai, ZHAO Wei, Fan Ziyi

2017, Vol.29(6): 43–50 Abstract ( 438 ) PDF (4845 KB) ( 496 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.006

The paleohighs are generally favorable accumulation areas for tight gas,so paleo-tectonic restoration is particularly important. Taking southern Qinshui Basin as an example,paleo-tectonic restoration was carried out for key tectonic stages of early Yanshanian(J1-J2), late Yanshan(J3-K1)and middle Himalayan(E-N)periods based on drilling,log and logging data. The results show that the whole area has been uplifted and eroded since the Late Triassic,and the strong erosion area distributed along the NE-SW direction. During the period of Yanshan movement, the paleouplift was inherited, the Permian strata were deformed strongly, and the paleo-tecnonic shows "multi-highs and multi-lows" features. Deplanation occurs during the middle Himalaya movement,and the paleo-tecnonic is gradually close to the current feature. Some of the paleo uplifts gradually become wide and gentle,and their tectonic forms are characterized by wide anticline and closed syncline. The paleo-tectonic units during the middle period of Himalayan movement were divided into highs,ramp and lows. It is suggested that paleo highs should be exlpored for tight sandstone gas in coal measure.

Tight sandstone reservoir characteristics and diagenesis evolution of Taiyuan Formation in Shenmu-Fugu area,Ordos Basin

LIU Zaizhen, LIU Yuming, LI Yangbing, LIU Xueqing, WANG Yuesheng, WANG Haiyan

2017, Vol.29(6): 51–59 Abstract ( 407 ) PDF (1404 KB) ( 436 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.007

In order to elucidate sandstone reservoir characteristics of Taiyuan Formation and its genesis of the densification in Shenmu-Fugu area,Ordos Basin,based on the data of cast thin section,scanning electron microscope,cathodoluminescence and high-pressure mercury,cementation and metasomatism between the cement and its relation with clastic particles,the diagenetic sequence and porosity evolution process were analyzed. The results show that the reservoir is dominated by medium-coarse lithic sandstone and feldspathic lithic sandstone. The reservoir porosity is 0.20%-12.00%, with average of 6.95%, and the permeability is 0.10-5.00 mD, with average of 0.91 mD,which belongs to typical low-porosity and extra-low-permeability tight sandstone reservoir.The pore structure is mainly small pore with fine throat and small pore with micro throat. The porosity evolution shows that the porosity decreased 15.5% by compaction,reduced about 10.4% by cementation,and increased about 4.41% by dissolution. The calculated reservoir porosity of Taiyuan Formation is 7.17%,which is similar to the analyzed porosity of 6.95% in the laboratory. Early compaction and late carbonate cementation are the main causes for the reservoir densification,while dissolution is beneficial to develop secondary pores for improving reservoirs properties.

Sandbody genesis and distribution regularity of Central Canyon in deepwater area of Qiongdongnan Basin

MAO Xuelian, ZHU Jitian, YAO Zhe, XU Shouli, TANG Lishan

2017, Vol.29(6): 60–68 Abstract ( 325 ) PDF (1523 KB) ( 631 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.008

Lingshui A-2 gas field was discovered in deepwater area of Qiongdongnan Basin. Well drilling reveals that multi-period high quality thick layer of turbidity channel sandstone developed in Huangliu Formation in Central Canyon. The filled channel standstone was cut by the late muddy channel and reformed by MTDs. The stacked relationship of multi-period sandbodies is very complex. So,the genesis and distribution regularity of the Central Crayon filling sandbody in Qiongdongnan Basin were studied using 3 Dseismic and the latest drilling data. The results show that the Central Canyon at least developed four sets of thick and high-quality reservoirs which are sand of turbidite deposits and the lithologies are primarily grey fine sandstone and siltstone. The accumulation styles of sandbody are vertical isolation and lateral accretion,and it is segmented in the distribution of sandbody. Vertically,Ⅰ and Ⅱ sand groups developed throughout the entire canyon,but Ⅲ and Ⅳ sand groups only developed in the middle and lower of the canyon. Horizontally,sandbodies developed contiguously in the straight-low bending section of the canyon and were independent block developed in the medium-high bending section. In addition,it is of important significance for exploration to establish a pattern which is longitudinal overlap and horizontal continuous distribution of sandbody to predict similar sandbody distribution in the Central Canyon.

Logging identification of effective source rocks in salt-lake facies in western Qaidam Basin

LI Yanli, WANG Jiangong, SHI Yajun, ZHANG Ping, XU Li

2017, Vol.29(6): 69–75 Abstract ( 349 ) PDF (1232 KB) ( 427 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.009

In recent years,a big salt-lake facies self-generation and self-storage reservoir was discovered firstly in upper Xiaganchaigou Formation(E32)in western Yingxiong Mountain of southwestern Qaidam Basin. In order to clear hydrocarbon accumulation mechanism and effectively estimate resources,it is very important to identify and evaluate effective hydrocarbon source rock in salt-lake facies. Based on core observation, geochemical analysis, logging correlation of typical wells,an overlap method of natural gamma ray-resistivity logging curve was established to identify hydrocarbon source rocks and to determine the lithology of hydrocarbon source rock based on geochemical parameters calibration. The logging qualitative and quantitative identification standards in the saltlake facies were determined and applied in Hongshi Depression. The salt-lake facies source rocks in the western Qaidam Basin have strong heterogeneity,only calcareous mudstone with high gamma and high resistivity is effective hydrocarbon source rock. It is simple,effective and accurate to identify source rocks by natural gammaresistivity overlap method. It is of great significance for rapid evaluation and exploration deployment of oil and gas resources in complex lithologic area.

Logging evaluation for permeability of tight sandstone gas reservoirs based on flow unit classification:a case from Xujiahe Formation in Guang' an area,central Sichuan Basin

CHEN Zhiqiang, WU Siyuan, BAI Rong, LEI Gang

2017, Vol.29(6): 76–83 Abstract ( 385 ) PDF (1831 KB) ( 710 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.010

Strong heterogeneity exists in the tight sandstone gas reservoirs of Xujiahe Formation in Guang' an area, central Sichuan Basin, which leads to poor correlation between porosity and permeability. It is difficult to calculate the permeability directly by using a single regression model. Therefore,physical property data from 859 standard plunger cores,the reservoir was divided into five types of flow unit according to Flow Unit Index(FZI)from small to large,the corresponding regression models were established,and there was a good correlation between porosity and permeability in each type of Flow Unit. In order to make the established models for every type of flow unit available in estimating permeability in the whole intervals in field application,the consecutive FZI should be first obtained to classify formation. Therefore,20 typical samples were selected to carry out Nuclear Magnetic Resonance(NMR)and mercury injection experiment. On the basis of experiment data, conversion models between T2 geometric mean(T2 lm)and Swanson parameter, Swanson parameter and reservoir quality index (RQI),RQI and FZI were established. Models of calculating the key factor of RQI in expression of FZI estimation formula were established,and then a credible technique of extracting FZI consecutively from NMR logs was proposed, which ensures the credibility of formation classification by using the predicted FZI. Finally, continuous division of flow unit and logging evaluation for permeability of tight sandstone gas reservoirs in the study area were succeeded. Application results show that the FZI calculated by NMR log calculation is consistent with core analysis FZI, and NMR log can effectively solve the problem of continuously quantitative evaluation of FZI. Compared with single regression model and NMR Coates model,permeability value calculated by the classification of flow unit is more consistent with core analysis,this method can effectively improve the accuracy of permeability logging evaluation. This method can be used in tight gas reservoir evaluation and deliverability prediction directly.

Formation mechanism and log evaluation methods of marine low resistivity reservoir in Oriente Basin

YANG Ruixiang, WANG Xianggong, BAI Songtao, WAN Jinbin, CAI Chengding

2017, Vol.29(6): 84–90 Abstract ( 301 ) PDF (1208 KB) ( 570 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.011

It is difficult to calculate the bound water saturation and water saturation directly by using Archie method in the low contrast of oil and water layers in marine reservoirs. In order to solve the problem,based on geologic factors,core and logging data,combined with logging response characteristics of low resistivity reservoir,the formation mechanism of marine low resistivity reservoir was studied,and the fine evaluation model of reservoir saturation was established by analyzing the main controlling factors. The results show that the bound fluid and additional conductivity characteristics of glauconite are the main cause of the formation of low resistivity reservoir. The low resistivity reservoir saturation calculated by bound water saturation calculation model based on the main controlling factors and the corrected water saturation calculation model based on conductive factor are consistent with bound water saturation analyzed by core mercury injection experiment. Applied to marine low resistivity reservoir evaluation in Oriente Basin,the corrected water saturation calculation model based on conductivity factor improved the coincidence rate of interpretation and reservoir parameter interpretation accuracy,and achieved good application effect, verifying its effectiveness.

Application of reverse-time migration technology to complex structural imaging in Daqing exploration area

CHEN Keyang

2017, Vol.29(6): 91–100 Abstract ( 337 ) PDF (1604 KB) ( 578 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.012

The conventional seismic migration methods are difficult to solve complex structure accurate imaging of Daqing seismic data. The key factors on reverse-time migration precision were analyzed, such as finite difference method's order, absorbing boundary conditions, reverse-time imaging condition, wavelet phase correction, background noise suppression,reverse-time parameter optimization. A set of high-precision reverse-time migration techniques is improved in key algorithm and imaging results, which is applied to practical seismic data reverse-time migration in Daqing exploration area. The high-precision reverse-time migration technology is better than that of conventional Kirchhoff pre-stack depth imaging technology and conventional correlation reverse-time ima-ging technology. The results are of some reference to the theory,method,and practical application of reverse-time migration technology.

Wide-frequency prospecting technology and its application on deep-seated Jurassic exploration in northern margin of Qaidam Basin

WANG Yongsheng, HU Jie, ZHANG Jing, WANG Chuanwu, ZHU Bo, WU Yongguo

2017, Vol.29(6): 101–107 Abstract ( 376 ) PDF (1374 KB) ( 474 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.013

The targets are located in the deep Jurassic and basement in northern margin of Qaidam Basin. Under the influence of complex seismic geological conditions,the signal-to-noise ratio and resolution of seismic data are low, so it is difficult to implement favorable structural trap. Based on wide-frequency prospecting, a set of integrated seismic exploration technology of acquisition,processing and interpretation were carried out. The results show that deep imaging quality of the new acquisition seismic data is improved,and the reflection of Jurassic structure, fault and bedrock is clear, while the low frequency information is rich, effective bandwidth is broadened, and resolution is significantly improved. The integrated technology uses the low frequency vibroseis seismic excitation to enhance wave signal energy and broaden the original data bandwidth. High density wide azimuth observation ensures continuous, symmetric and uniform sampling of the wave field, and improves the signal-to-noise ratio. The precision of the complex structure imaging is improved by high precision chromatography first-break refraction static correction. The wide frequency inversion reservoir prediction accurately depicts the favorable sand body. The application results show that broadband seismic exploration technology can effectively solve the deep imaging problems in this area, and it is an effective technical support for oilfield exploration and development.

Establishment of apparent permeability model and seepage flow model for shale reservoir

ZHANG Liehui, SHAN Baochao, ZHAO Yulong, GUO Jingjing, TANG Hongming

2017, Vol.29(6): 108–118 Abstract ( 433 ) PDF (1965 KB) ( 696 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.014

Multi-scaled effects of gas seepage behavior,such as slippage effect,Knudsen diffusion and surface diffusion, can lead to non-Darcy flow in shale formation. A flow chart considering real gas effects was plotted according the value of Knudsen number,and a comprehensive apparent permeability model was established considering different flow mechanisms. Flux contribution of slip viscous flow,Knudsen diffusion and surface diffusion were discussed under different pore radii and pressure conditions. Using the apparent permeability model,a comprehensive flow continual equation was built considering adsorption/desorption effect and dissolved gas diffusion in Kerogen. The results show that nonlinear flow effect is obvious in low pressure and small pore conditions. The main mass transfer mechanism is different under different conditions. Knudsen and surface diffusion mainly affect the middle flow period through changing the apparent permeablity. Dissolved gas in Kerogen and adsorbed gas are important occurrence of shale gas and supplement of free gas during reservoir development,and they have a significant influence on unstable productivity during middle-later flow period. Dissolved gas and adsorbed gas can increase the cumulative gas production, slow down gas reservoir pressure drop.

Pressure transient analysis on CO₂ huff and puff in low permeability reservoir

LI Youquan, HAN Xiuhong, YAN Yan, ZHANG Dezhi, ZHOU Zhiwei, MENG Fankun

2017, Vol.29(6): 119–127 Abstract ( 346 ) PDF (1687 KB) ( 632 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.015

CO2 huff and puff are important way to improve oil recovery in low permeability reservoir. However, the recognition of the pressure response performance is not clear. After the injection of CO2 in low permeability reservoir,the fluid properties such as viscosity vary with the CO2 concentration,resulting in the phenomenon of plane heterogeneity. In order to characterize the pressure transient, the CO2 concentration distribution was obtained based on Fick's law to characterize the fluid property. The permeability modulus and starting pressure gradient were introduced in Darcy flow equation to characterize the low permeability characteristics. The pressure response model for CO2 huff and puff in low permeability reservoir was established by viscosity coupling concentration equation and flow equation,and it was solved by numerical method. The reliability of the model was verified by analytical method and numerical simulation, and finally the influences of low permeability properties and CO2 concentration on the pressure response curve were analyzed. The results show that the increase of starting-up pressure gradient leads to higher CO2 injection pressure and the rise of pressure and pressure derivative curve slope. The pressure and pressure derivative curve slope become smaller with the increase of the permeability modulus. The diffusion of CO2becomes faster while increasing the injection rate of CO2,and the injection pressure becomes larger,at the same time,the boundary between swept area and unswept area is clearer. As the diffusion efficient of CO2 increases,the difference of fluid properties in difference place becomes smaller and the boundary between swept area and unswept area is not clear. This model can be applied to well testing of CO2 huff and puff process in low permeability reservoir, the prediction of reservoir parameter and analysis of CO2 concentration distribution.

Interlayers of meandering river reservoir:a case from Qinhuangdao 32-6 oilfield

GAN Liqin, SU Jinchang, XIE Yue, LI Chao, HE Kang, LAI Youchun

2017, Vol.29(6): 128–134 Abstract ( 416 ) PDF (1977 KB) ( 870 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.016

To reveal the distribution rules of remaining oil and water flooded reservoir influenced by the meandering river reservoir interlayer, the interlayers' upper limit of physical property was obtained through the analysis of the physical parameters and the relation between the productivity index per-meter,and the choice of natural gamma,resistivity and thickness as the main sensitive parameters,calculate weight coefficients are obtained by using the grey correlation method,interlayer and comprehensive index discriminant chart. The application of the oil zone in the lower Minghuazheng Formation in the south area of Qinhuangdao 32-6 oilfield proves that the coincidence rate of the discrimination plate is upmost 96%. The adjustment is carried out at the bottom of the remaining oil retention zone and the top of the water flooded layer of the reservoir,and the production effect is obvious. In the meandering river reservoir interlayer development zone,the interlayer retards water cut rising rate of the production well;the formation of water flooding zone is easy to form in the interlayer non-developed area,which leads to the formation of remaining oil retention zone in the adjacent interlayer growth zone. The understanding will guide the potential tapping of productivity in the middle and late stages of oilfield development.

Water production laws and controlling factors of gas reservoir in Xihu Sag

LIAO Hengjie, YANG Zhixing, LI Yuansheng, CHENG Junyang, CHENG Chao

2017, Vol.29(6): 135–141 Abstract ( 304 ) PDF (3952 KB) ( 600 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.017

The water drive gas reservoirs are principal types in Xihu Sag, in which most of wells produce water after several production years, so a correct understanding of the effluent characteristics and controlling factors of edge and bottom water reservoir is the key to the successful development of the gas reservoirs. Based on the production dynamic data, dynamic production water invasion identification method and unstable test water invasion identification method were used to study the water production characteristics and water gas ratio rising law, and the law of water cut rising and main controlling factors of different types of water drive gas reservoirs were defined. The results show that the water production characteristic curves were classified into three types,which are vertical spike type, ladder step type and concave slow type. The vertical spike type is mainly controlled by the size of water,which is dominated by strong edge water gas reservoir. The ladder step type is mainly controlled by the development degree and rhythm characteristics of interlayer,which is dominated by bottom water gas reservoirs. The concave slow type is mainly controlled by reservoir and the size of the water,which is dominated by weak water flooding gas reservoirs. This study result is helpful for the technical policy of further development of water drive gas reservoir.

Application of initialization by enumeration equilibrium to reservoir numerical simulation

YUE Shijun, ZHENG Changlong, YANG Zhaoping, JING Ziyan, LIU Xiongzhi, JIN Baozhong

2017, Vol.29(6): 142–147 Abstract ( 366 ) PDF (1909 KB) ( 529 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.018

The initialization of reservoir numerical simulation mode is very important to the model. The equilibrium method commonly used may result in the same initial oil saturation for a large connectivity area, which is different to the real condition. For improving the accuracy of the simulation model,the initialization by enumeration equilibrium method was proposed. The initial saturation is enumerated from 3D geological model and no longer depends on the end point values of the relative permeability curves. Then the end point scaling method is used for the relative permeability curves,and the new curves are produced. The initial liquid equilibrium-requirements can be met by capillary pressure scaling. The results show that the initial oil saturation distribution gained by enumeration-equilibrium method is closer to the true condition,and the history match can be simplified. The approach works well in application on reservoir numerical simulation.

Pseudo-steady state deliverability for gas wells in thick gas reservoirs

HUANG Quanhua, TONG Kai, CHEN Chong, LU Yun, FU Yunhui

2017, Vol.29(6): 148–153 Abstract ( 316 ) PDF (1309 KB) ( 476 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.019

The deliverability evaluation is one of the main contents of natural gas engineering,which is crucial to the reasonable and efficient development of the gas reservoirs. The plane radial flow deliverability equation and semi-spherical flow deliverability equation are commonly used to evaluate the deliverability of gas wells. For the gas reservoirs with great thickness and high deliverability,the two methods are not so applicable. To derive a new method to evaluate the deliverability of gas well in thick reservoir,the model was improved,in which the layer was made up of perforated interval and unperforated interval. According to the percolation mechanics,pseudo-steady state deliverability equation of gas wells in semi-spherical flow model was deduced. Then the pseudosteady state deliverability equations of the two intervals and the whole gas layer were derived. A calculation example of a producing gas well in thick reservoirs was performed. The results show that the factors of perforating degree, skin effect and effect of non-Darcy flow can't be ignored and the pseudo-steady state deliverability equation based on the improved model is more accordant with the actual production. This study could provide a practicable method for the productivity evaluation for gas wells in thick gas reservoirs.

Fracture morphology and production performance of radial well fracturing

LI Xiaolong, XU Huaru, LIU Xiaoqiang, WANG Tao, ZHANG Kaiwen, QU Zhanqing

2017, Vol.29(6): 154–160 Abstract ( 268 ) PDF (1120 KB) ( 453 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2017.06.020

The technology of radial well fracturing combined with steam soak is suitable for the development of heavy oil reservoir with low permeability,but it is lack of mechanism research so far. The fracture morphology of radial well fracturing was studied by 3 D simulating experiment,and the thermal deliverability of radial well was researched by simulation. The results show that multi-cracks morphology is performed under the multi radial wells which could increases the drainage area,and the radial well can guide the fracture of hydraulic fracturing well. The steam soak stimulation assisted by radial well fracturing is very effective for the development of heavy oil reservoir with low permeability,and the productivity gets the best effect when the number of the radial wells is 4. The thermal deliverability in 3 years of radial well fracturing is 2.65 times larger than that of regular fracturing. The applicability of the combined technology was proved and the parameters of steam soak were optimized. The conclusion is significant and important for the development of heavy oil reservoir.