Lithologic Reservoirs

In order to solve the glutenite reservoir distribution of the third member of Paleogene Dongying Formation(Ed3) in the Shinan steep slope zone of Bozhong Depression,using 3D seismic interpretation,drilling, experimental data,the key factors(parent rock,valley system,fault active rate,sedimentary paleo-terrain,lakelevel change) in the source-sink system were quantitatively characterized. The results show:(1) The reservoirs in the Ed3 are mainly fan delta facies. The lithologies of their parent rock are composed of Mesozoic volcanic rocks in the south and volcanic rocks,carbonate rocks and granites in the northwest.(2) Five large and long valley systems are identified,which carry larger volume of glutenite from the provenance zone to the sink zone.(3) The Ed3 sedimentary palaeogeography is dominated by faults,which are characterized by segmented activities. The difference in activity results in the difference between the source and the sink zone.(4) The extension distance of the gravel is positively related to the decline of the slop. The closer the lake surface is to the source,the shorter the gultenite extends;conversely,the longer the glutenite extends. The scale of the glutenite is affected by the influence of source system,fault activity and lake level. The erosion of the source and the paleogeomorphology of the sink zone are mainly controlled by the fault activity. This rule provides a reference for the evaluation of glutenite reservoir in steep slope of faulted basin.

Storage space and gas content law of Longmaxi shale in Changning area,Sichuan Basin

SHEN Rui, HU Zhiming, GUO Hekun, JIANG Baicai, MIAO Sheng, LI Wuguang

2018, Vol.30(5): 11–17 Abstract ( 447 ) PDF (10471 KB) ( 687 )

doi: https://doi.org/10.12108/yxyqc.20180502

The shales of the lower Silurian Longmaxi are widely developed in Changning area of Sichuan Basin. The micro pore structure and full-scale pore size distribution characteristics of shale reservoirs in this area are not yet clear. The pore structure of lower Longmaxi shale reservoir was researched by field emission scanning electron microscope(FE-SEM),high pressure mercury intrusion,low temperature nitrogen adsorption and low temperature CO2adsorption. Taking the Ning 203 well as an example,a set of analysis method about nanometer-micrometer full scale pore size distribution was established. The first pore size distribution was obtained by gas adsorption, and the second pore size distribution was obtained by high pressure mercury intrusion in this method. The difference between the data of the pore size distribution obtained by the two kinds of tests was judged. According to the result of the judgment,the pore size distribution data of 3.7-200.0 nm were obtained after treatment. The pore size distribution data of the non-repeated pore size were obtained by the two methods combined. The micropores,mesopores and macropores for core samples in proportion were calculated,so the full-scale pore size distribution data of core samples were obtained. Results show the lower part of Longmaxi shale pore structure is very complex. Micropores are connected in series with mesopores and macropores. The pore throat is small,so the connectivity is poor. Mesoporous and microporous accounted for the percentage of pore volume is more than 80%. Pore throats of the diameter above 15 nm mainly contain free gas,and the ones below 2 nm mainly contain adsorbed gas.

Sedimentary characteristics and controlling factors of sublacustrine fans in backbulge zone of foreland basin: Triassic in Lunnan area,Tarim Basin

ZHONG Mihong, TANG Wu

2018, Vol.30(5): 18–28 Abstract ( 453 ) PDF (11908 KB) ( 537 )

doi: https://doi.org/10.12108/yxyqc.20180503

In order to discuss the sedimentary characteristics and controlling factors of sublacustrine fans in backbulge zone of foreland basin,based on the cores,analysis assay,well logs and 3D seismic data,combined with the method of "point-line-surface",the characteristics of sublacustrine fan of T Ⅱ oil group of Middle Triassic Karamay Formation in Lunnan area of Tarim Basin were analyzed. The results show that sand-rich sublacustrine fans were developed in the study area, which are mainly composed of gravelly coarse sandstone,conglomeratic sandstone and medium-coarse sandstone,with Bouma sequence vertically developed,and grading bedding,massive bedding as well as deformed bedding could be recognized. In addition,the logging curves show a combination of micro linear dentalization and block or bell shaped. On seismic profiles,they are responded to middlehigh amplitude and high continuity refection or lenticular or short axial refection,and incised sinuous channels are identified on RMS(root-mean-square) amplitude attribute. Meanwhile,three subfacies and five microfacies were recognized,among which feeder channel and levee microfacies were developed in inner fan,braided channel and interchannels were developed in middle fan,and distal source turbidite were developed in outer fan. The sublacustrine fans located below the south slope break belt,with several distinct feeder channels developed,and compared with separated interchannels,the braided channels were continuously distributed. Caused by gravity flows,the sublacustrine fans were formed as a result of that a large amount of sandstone were transported to deepwater environment through feeder channels, and the development of sublacustrine fans were controlled by episodic tectonic activities of foreland basin, paleogeomorphology,and provenance supply. The development of sublacustrine fans was induced by tectonic activities,and the planar distribution characteristics were influenced by paleogeomorphology,with lithology,physical properties,and scale determined by provenance supply.

Gas-bearing property and main controlling factors of Lower Cambrian shale in complex tectonic area of northwestern Hunan province: a case of well Ciye 1

MENG Fanyang, CHEN Ke, BAO Shujing, LI Haohan, ZHANG Cong, WANG Jinzhu

2018, Vol.30(5): 29–39 Abstract ( 593 ) PDF (11104 KB) ( 628 )

doi: https://doi.org/10.12108/yxyqc.20180504

The lower Cambrian marine shales with large thickness and high organic content are widely developed in southern China,however the main controlling factors affecting shale gas-bearing property are still not clear. The shale of the Lower Cambrian Niutitang Formation in the complex tectonic area of northwestern Hunan province has a large thickness and medium depth,and the shale gas parameter well Ciye 1,which was drilled in the selected Cili Jinglongqiao syncline,has a thick shale thickness of 149 m. The core samples were taken to analyze total organic carbon(TOC) content,vitrinite reflectance,mineral composition and reservoir properties,revealing that the average TOC content of Niutitang Formation is 4.83%,the bottom high quality shale with TOC content more than 3% has a thickness of 37 m,and the average vitrinite reflectance of shale is 3.28%. The total shale gas content of Niutitang Formation measured by core direct desorption method reaches 0.859 m3/t,and the average methane content in natural gas composition is 78.23%. By analyzing the tectonic evolution characteristics of Cili area in northwestern Hunan,and comparing the key parameters of the Lower Cambrian shale in the surrounding drilling wells with well Ciye 1,the main controlling factors affecting the gas-bearing property of the Lower Cambrian shale in northwestern Hunan are tectonic preservation conditions and shale evolution degree. The palaeo uplifts in southern China such as Xuefeng uplift,Huangling anticline and Hannan old land with stable basement, good preservation conditions and low shale maturity,are the key areas for the further shale gas exploration in complex tectonic areas.

Reservoir pore structures of Jianquanzi member in Laojunmiao structure,Jiuxi Basin

ZHANG Shiming, ZHANG Xiaojun, ZHENG Lianyong, WANG Pu, GOU Yingchun, WU Liangyu

2018, Vol.30(5): 40–50 Abstract ( 423 ) PDF (47354 KB) ( 713 )

doi: https://doi.org/10.12108/yxyqc.20180505

Since the formation of Juanquanzi member in Laojunmiao structure has the features of high water cut and low displacement efficiency,the study of pore structure becomes the key to enhanced oil recovery. A variety of experimental test methods were used to study the pore structure and influencing factors of Paleogene Oligocene clastic reservoir in Juanquanzi member of Baiyanghe Formation,such as casting thin section observation,SEM analysis,capillary pressure testing and so on. The result shows that the reservoir lithologies are mainly lithic sandstone and feldspathic lithic sandstone,with high debris content,low maturity of composition and texture. Reservoir spaces are mainly residual intergranular pores and intergranular dissolved pores. The reservoirs can be divided into four types according to pore structure characteristics,and type Ⅰand type Ⅱhave relatively good reservoir property,with permeability above 10 mD. The capillary curves have significant platforms,and coarse skewness. There is a positive correlation between reservoir properties and the concentration of pore throat and the proportion of rough throat. The layer analysis shows that the layer L was in alkaline diagenetic environment,there were a large amounts of clay minerals and calcite cements contained in intergranular pores,and the well sections with weak cementation have good reservoir properties. The acid diagenetic environment of layer M inhibited the cementation,parts of primary pores were preserved,and the dissolution effect by acidic fluids promoted the formation of high quality reservoirs in M layer. The research results can provide geological basis for later effective exploitation.

Recoverable coefficient calibration of shale gas in Yanchang Oilfield,Ordos Basin

LIU Gang, ZHAO Qianping, LIU Chao, SUN Jianbo, YIN Jintao

2018, Vol.30(5): 51–58 Abstract ( 355 ) PDF (1602 KB) ( 472 )

doi: https://doi.org/10.12108/yxyqc.20180506

The recoverable coefficient calibration of shale gas is the preferred method of shale gas resources evaluation for the area of low exploration degree. To take the shale gas zone in Yanchang Oilfield as the target,three fitting methods(analogy method,parameter weighting method and isothermal adsorption method) were used to calibrate the shale gas recoverable coefficient. Delphi weighting method was used to get accurate result in the actual block. With the exploration achievements of shale gas in Yanchang Oilfield,the method in this paper was used to calibrate the shale gas recoverable coefficient. The results show that the value of Triassic Yancheng Formation is 0.132,and the value of Upper Paleozoic Shanxi Formation and Benxi Formation is 0.201. The result could be important guidance for further exploration and development of shale gas in Yanchang Oilfield,it can also provide associated technical reference for the shale gas evaluation research in the other basins.

Method for high-resolution sequence stratigraphy division based on Ensemble Empirical Mode Decomposition

YANG Ying, YANG Wei, ZHU Shijun

2018, Vol.30(5): 59–67 Abstract ( 452 ) PDF (4881 KB) ( 484 )

doi: https://doi.org/10.12108/yxyqc.20180507

Dividing sequence boundary of different levels and identifying internal types of sedimentary cycle are important bases of sequence stratigraphic analysis. Logging signals are the superposition of sedimentary cycles in different periods. It can be applied to classify the sequence boundaries of different levels,and identify the types of cycles by time-frequency analysis which can expand the information of stratigraphic cycle hidden in the well logging data into different frequency bands. Ensemble Empirical Mode Decomposition(EEMD) was applied to decompose well logging data into Intrinsic Mode Functions of different frequency banks,then the frequency information of each components can be obtained by Hilbert transform. Stratigraphic sequence was divided according to the relationship between the periodic fluctuation of each components and the different types of sedimentary cycle, as well as the relationship between the frequency characteristics of each components and sequence boundaries of all levels. The application in the third member of Shahejie Formation of Dongying Sag shows that this method is suitable for the cycle division of short-term,medium-term and long-term. It provides a new idea for division of high-resolution sequence stratigraphy.

Stratified constrained near-surface model building method and its application in complex surface area

WANG Xiao, LIU Wenqing, ZENG Huahui, YANG Wei

2018, Vol.30(5): 68–73 Abstract ( 395 ) PDF (2901 KB) ( 520 )

doi: https://doi.org/10.12108/yxyqc.20180508

With the development of petroleum exploration,lithologic and low-relief structure reservoirs become more and more important. For low-relief structure,besides the inherent factor of stratigraphic lithology,the key factor that influences low-relief structures is the long-wavelength statics. The main reasons resulting in the longwavelength statics are the relative low precision of the near-surface velocity model and the inaccurate space depiction of low-velocity bottom interface in complex surface area. The near-surface velocity model was built using stratified constrained model building method. Firstly,the accurate low-velocity layer model was built using micrologging data,and then the descending-velocity layer model was built using short-refraction and vertical seismic profile(VSP) data,so as to obtain the initial model of global optimization nonlinear near-surface tomography. Nearsurface velocity model with high precision can be built by using the stratified constrained tomography method. Based on the VSP and measured well depth constraints,the space morphology of the interface of the descending-velocity layer was optimized by cokriging method. Through the above two strategies,the long-wavelength static correc tion problems in complex surface area were well solved,and good application results were achieved in litho-logic reservoir exploration in X area of Mahu Sag,Junggar Basin.

Key techniques for seismic evaluation of lithologic reservoirs in southwestern Qaidam Basin

CHEN Guowen, SHEN Ya, YUAN Yunchao, HAN Bing, LI Yanming, YANG Tai

2018, Vol.30(5): 74–81 Abstract ( 281 ) PDF (8348 KB) ( 451 )

doi: https://doi.org/10.12108/yxyqc.20180509

With tremendous remaining oil and gas resources,the southwestern Qaidam Basin is an important area for the exploration of lithologic reservoirs. However,due to the late start of lithologic exploration,the studies on geological settings of hydrocarbon accumulation and the key hydrocarbon accumulation factors are not conducted thoroughly enough,which restricts the progress of lithologic exploration. This paper carried out the research works, such as the identification of geological settings and lithologic traps,comprehensively by enhancing the basic research,the overall understanding and the fine evaluation in recent years focusing on the rich hydrocarbongenerating depressions in western Qaidam Basin. 3D large-area contiguous seismic data from the southwestern Qaidam were used to carry out fine structural interpretation and reservoir prediction. Zhahaquan area was clearly identified as a favorable exploration zone,the favorable zones were delineated,the distribution of high-quality sand bodies were confirmed and the distribution of "sweet" was predicted accurately,and the first 100-millionton level lithologic reservoir reserve area was delineated and verified in Qaidam Basin. Based on the lithologic reservoir exploration practices in Zhahaquan area,a set of evaluation ideas and technical methods applicable for the lithologic reservoir exploration in southwestern Qaidam Basin was formed. This research plays an important guiding role in deepening the lithologic reservoir exploration in southwestern Qaidam Basin.

Inversion of rock physics parameters based on KT model fluid substitution

PENG Da, XIAO Fusen, RAN Qi, XIE Bing, CHEN Xiao, ZHANG Fuhong, CHEN Kang, XU Xiang

2018, Vol.30(5): 82–90 Abstract ( 474 ) PDF (2723 KB) ( 565 )

doi: https://doi.org/10.12108/yxyqc.20180510

There are many rock physics parameters in rock physics model,some parameters are directly obtained from log data or lab data,and the others are indirectly obtained by inversion,such as mineral matrix elastic modulus and pore geometry. It's important to investigate estimation methods for these rock physics parameters. For the sandstone reservoir,three different pore aspect ratios were used to describe the pore structure of sandstone,Biot's coefficient was used to determine the variation range of mineral matrix elastic modulus,and combined with simulated annealing simulated annealing algorithm,an inversion method for estimating rock physics parameters based on KT model fluid substitution was proposed. The mineral matrix bulk and shear modulus of 42 sandstone samples were inversed,and their pore aspect ratio spectrum were inversed simultaneously. The results show that:pore aspect spectrum has a great effect on rock elastic properties;pore aspect spectrum can be used to depict pore structure and diagenesis;using KT model with three pore aspect ratios to carry out fluid substitution simulation has a good adaptability;percentages of crack pores have a high sensitivity to rock elastic modulus.

Control effect of pore structure modality on remaining oil in glutenite reservoir: a case from lower Karamay Formation in block Qidong 1 of Karamay Oilfield

YIN Senlin, CHEN Gongyang, CHEN Yukun, WU Xiaojun

2018, Vol.30(5): 91–102 Abstract ( 312 ) PDF (20503 KB) ( 446 )

doi: https://doi.org/10.12108/yxyqc.20180511

The control effect of complex pore structure of glutenite reservoirs on remaining oil is very complicated and not clear. In this paper,based on the analysis data of 325 experimental samples,the control effect of complex pore structure modality on residual oil in water/polymer flooding is examined by means of large casting thin section,nuclear magnetic complex pore structure resonance and CT three-dimensional pore structure scanning. The results show that:(1) The distribution of remaining oil in water/polymer flooding follows some obvious patterns. The reservoirs with oil saturation in the range of 50% to 100% are displaced first, seeing quick decline in proportion.(2) In the middle and late stages of polymer flooding,some of the fluid advantage channels formed at the stage of water flooding, and the piston-type drive results in a large part of reservoirs with oil saturation in the range of 37.5% to 50.0% to be produced;the remaining oil is mainly in isolated distribution, and only in connected pieces in local parts.(3)Different pore structure modalities result in quite different oil displacement effects in water flooding/polymer flooding. The flooding efficiency in cores with single modality and dual modalities is higher,and the oil displacement efficiency of polymer is 9.30% to 18.38% after water flooding. Water flooding efficiency of single-modality core is the highest,while water flooding efficiencies of the dual-modality and complex modality cores are similar. The displacement efficiency with polymer is the highest in dual-modality cores, followed by single modality cores. The water content decreases by 20% after the cores with single-modality and dual-modality are injected with polymer.

Flow unit combination and water flooding model of distributary channel sand body in eastern Xing-6 block

LYU Duanchuan, LIN Chengyan, REN Lihua, SONG Jinpeng, DI Xifeng

2018, Vol.30(5): 103–108 Abstract ( 278 ) PDF (12153 KB) ( 532 )

doi: https://doi.org/10.12108/yxyqc.20180512

In order to quantitatively analyze the flooding degree of ASP(alkaline surfactant polymer) flooding layers in shallow water delta distributary channel sand body in eastern Xing-6 block in Xingshugang oilfield, which belongs to Daqing placanticline,the vertical distribution characteristics of remaining oil saturation were determined. Through the observation of coring wells and the calculation results of relative change rate of permeability, and combining with oil saturation test data,different seepage units and their combination types were classified within the single sand body level,and the flooding degree were calculated quantitatively in different combination types of seepage units. A total of five types of fine-grained sediments and three combinations types of seepage units were identified in distributary channel. The understanding of flooding characteristics of different combination types of seepage units can provide geological basis for trapping potential of remaining oil in the later stage.

Development potential classification evaluation for water-flooding in conglomerate reservoir

WANG Zhenpeng, CHEN Minfeng, YIN Chengzhe

2018, Vol.30(5): 109–115 Abstract ( 556 ) PDF (4735 KB) ( 536 )

doi: https://doi.org/10.12108/yxyqc.20180513

In conglomerate reservoir,the lithology is complex and its heterogeneity is strong,which results in great differences of the utilization of reserves during water-flooding and so on. To solve these problems,based on the geological and development features of the conglomerate reservoir,the water-flooding development potential evaluation indicators system was set up considering heterogeneity,remaining reserve and flowing capacity of fluid. Then,on account of the characteristics of development performance in the actual oilfield,by taking the areal unit as the study object,development potential of different units can be classified in an unsupervised way through fuzzy C mean clustering method,which helps set up a subjective and reasonable evaluation method. This method was used to evaluate the development potential of BH oilfield in Xinjiang,and the results are consistent with the characteristics of the geological and development condition distributed regionally in BH oilfield,it is useful for implementing different adjustments in different regions. Furthermore,combined with different features of different potential regions,the corresponding development adjustment advice can be proposed.

Reasonable pattern well spacing deployment of lens lithologic reservoirs with low permeability

TAO Shuai, HAO Yongmao, ZHOU Jie, CAO Xiaopeng, LI Xiaozhou

2018, Vol.30(5): 116–123 Abstract ( 447 ) PDF (29856 KB) ( 499 )

doi: https://doi.org/10.12108/yxyqc.20180514

The lens lithologic reservoir with low permeability is characterized by scattered distribution and strong heterogeneity of sand body. During the process of development,the core is seriously flooded and the water flooding effect in fan edge is poor. Therefore,based on the method and theory of reservoir engineering,the calculation methods of ring spacing of annular wells and well spacing of oil well were established,and the calculation chart was drawn. At the same time, the rational pattern well spacing for lens lithologic reservoir with low permeability was studied by numerical simulation method. The results show that the well pattern of core injection wing production based on the phase control residual oil can effectively alleviate the problem of water injection pressure in the form of square water injection well pattern,and then reduce the difficulty of water injection and improve the efficiency of water flooding. Compared with the positive well pattern,when the injection to producing well ratio is 1:2 in the cross annular well pattern of core injection wing production,the streamline distribution of the oil and water wells is more uniform,and the development effect is better. For the annular well pattern with the injection and production wells number of 3 and 6 or 4 and 8,when the ring distance is 200 m,the optimum well spacing of production wells is 300 m and 250 m,respectively. This study can provide a theoretical basis and reference for continuous and efficient development of lens lithologic reservoirs with low permeability.

Technology policy limitation of subdivision water injection in ultra-high water cut stage: a case from Shengli uncompartmentalized reservoirs

LAI Shumin

2018, Vol.30(5): 124–130 Abstract ( 469 ) PDF (1528 KB) ( 565 )

doi: https://doi.org/10.12108/yxyqc.20180515

At present,the geological factors are still only considered in subdivision water injection technology policy limitation study,which can not reflect dynamic difference of reservoir. Considering both static and dynamic parameters,subdivision water injection optimal hierarchical models were established. The results show that the three-fourth class is better,and saturation ratio should be smaller than 1.2. Then the optimal permeability,numbers of layer and sandstone thickness model with different saturation ratios in 1.00-1.05,1.05-1.10,1.10-1.15 and 1.15-1.20 were established. Based on the results,the optimal permeability,numbers of layer and sandstone thickness curve plates were drawn,and regression equations were formed. The results show that the larger the saturation ratio is, the stricter policy limitation of subdivision water injection will be. The application of this policy limitation of subdivision water injection makes a huge impact in Shengli oilfield. So the research can provide an important theoretical basis of water injection development in middle-high permeability late extra-high water cut stage.

Application on HV high-strength gel water plugging system

REN Xiaojuan, LI Xiaoxiao, LU Yonghui, WANG Ning

2018, Vol.30(5): 131–137 Abstract ( 406 ) PDF (18711 KB) ( 422 )

doi: https://doi.org/10.12108/yxyqc.20180516

In the light of the disparity for spot applied effects and laboratory evaluation of the HV high-strength gel plugging technology in Yan 10 reservoir in block Wuqi,the influence of dynamic pressure in the pipe string after closing the well on the effect of gel plugging was analyzed. A kind of modified HV high-strength gel water plugging system was optimized by adding fortifier agent LCR,and the properties were characterized by gelling time,gelling strength,ageing stability,the influence of dynamic pressure and safety. The results show that short gell time can overcome the influence of dynamic pressure on the stability. Besides,the modified HV highstrength gel water plugging system was composed by 0.8% modified polymer +5.5% cross-linking agent of oligomerization phenolic resin +0.03% accessory ingredient +0.012% fortifier of LCR. Gelling time,strength,ageing stability,and construction safety meet the requirements of plugging and well application,and the stability and resistance to shearing can keep constant with the dynamic pressure. Meanwhile,remarkable results of increasing oil and decreasing water have been given by field application and have produced very good effect. The measure well of application has reduced water content of 37.78% at most,increased output of oil about 2.89 t in average,and have been validly work up to 9 months.

Forming mechanism and monitoring of horizontal hydraulic fracture: a case from Qilicun oilfield

ZHANG Hong, MENG Xuangang, SHAO Changjin, DAI Xiaoxu, YU Hao, LI Xiangfang

2018, Vol.30(5): 138–145 Abstract ( 120 ) PDF (1884 KB) ( 511 )

doi: https://doi.org/10.12108/yxyqc.20180617

To set up the reasonable development plans and judge the production,it is very important to know the hydraulic fracture geometry of the low permeability reservoir. Theoretical calculation,the Kaiser tests as well as the microseismic and production data monitoring were used to test the forming mechanism,forming conditions, and forming possibility of the horizontal hydraulic fracture. The results show that in the shallow reservoir,the vertical principal stress is the smallest one and it will be horizontal fracture after hydraulic fracturing,and it will be vertical fracture in deep reservoir. The production increases obviously after fracturing,the microseismic monitoring shows the horizontal fracturing characteristics,and there is no flowback of fracturing fluid during the secondary fracturing,which all verify the horizontal fracture after hydraulic fracturing in shallow reservoir in Qilicun oilfield. The horizontal fracture can be judged and monitored by combining the results of formula calculation,laboratory experiment and microseismic monitoring with the changes of the output before and after the fracturing and the field construction results. The research results are applicable to the monitoring of fractured horizontal fractures in similar low permeability reservoirs.

Well test analysis method for polymer flooding after water flooding in triple-layer reservoir

ZENG Yang, KANG Xiaodong, TANG Engao, WEI Zhijie, CHENG Shiqing

2018, Vol.30(5): 146–153 Abstract ( 330 ) PDF (1554 KB) ( 477 )

doi: https://doi.org/10.12108/yxyqc.20180518

In the study of the current model of polymer well testing,the two conditions of multi-layer reservoir and non Newton-Newton composite reservoir were not considered simultaneously,which resulted in the fact that the fitting results of actual data of many offshore polymer flooding reservoirs were not ideal. By taking into account the actual situation of polymer flooding after water flooding in multi-layer offshore reservoirs,a well testing model for polymer flooding after water flooding in triple-layer reservoir was established based on the theory of fluid flow in porous media,type curves were plotted and its influencing factors were discussed by the numerical inversion method and this model was verified by the field examples. The result show that the type curves have six regimes,the typical feature which is different from the triple-layer non composite model is the end-stage upwarp segment,the initial concentration of polymer has little influence on the curve,the crossflow coefficient mainly affects the time of the concave,coefficient ratio and storativity ratio mainly affect the width and depth of the concave,and the composite radius mainly affects the down degree of the upper part of the pressure derivative curve.

Mechanism and influencing factors of foam mixed flowback of sand production

JING Ziyan, ZHANG Jia, LI Guobin, ZHU Biao, HAN Guoqing, LIU Shuangshuang

2018, Vol.30(5): 154–160 Abstract ( 796 ) PDF (1513 KB) ( 583 )

doi: https://doi.org/10.12108/yxyqc.20180519

With the increase of oil recovery,wellbore blockage in sandstone reservoir is becoming more and more serious. How to remove blockage and increase output has become a key issue of efficient development. From the angle of improving the permeability of oil layer to improve the production,many countries have generally adopted the methods of oil layer acidification and hydraulic fracturing to increase the oil recovery rate,but it also brings many negative problems,such as reservoir damage. Based on the mechanism of foam temporary support,state equation was used to deduce the change equation of formation pressure under the condition of foam compressibility,and study the influence of the main formation conditions and construction parameters under the condition of foam compressi-bility by combining the physical simulation experiment. The results show that gas liquid ratio, fracture,porosity and pressure drop are the main factors that affect the sand carrying capacity and the discharge of fine sand. This study can provide a theoretical and technical guidance for improving foam mixed flowback theoretical model and practical construction,and can help to improve single well recovery.

Calculation method for productivity of fractured horizontal well in tight gas reservoir

WANG Xinjie

2018, Vol.30(5): 161–168 Abstract ( 416 ) PDF (2471 KB) ( 640 )

doi: https://doi.org/10.12108/yxyqc.20180520

In order to accurately evaluate the productivity of fractured horizontal wells in tight gas reservoirs and determine the rational distribution of gas wells, and to achieve efficient development of gas wells, based on the theory of conformal transformation and gas water two-phase seepage theory,the effective permeability of the matrix was used as a variable to consider the effects of fracturing and gas well production on the effective permeability of the reservoir,and gas liquid two phase productivity equation of fracturing horizontal well was established and verified by actual production data. The reliability of the deliverability calculation results was verified. The results show that when the dimensionless discharge boundary is greater than 0.55,the production pressure drop of the gas well increases rapidly with the increase of production,and the higher the water-gas ratio is,the greater the pressure drop for the gas well is needed under the same gas well productivity. When the horizontal direction is parallel to the Ky direction,the greater the permeability anisotropy Ky/Kx is,the smaller the production pressure drop is needed in the same gas production. When the angle between the horizontal section and the main permeability direction is less than 30°,the production pressure drop of the gas well under the same gas production condition is almost unchanged.Therefore,from the view of reducing the pressure loss of reservoir pressure in fractured horizontal wells,the influences of permeability anisotropy and the direction of horizontal well horizontal section should be fully consi-dered,and the control of gas well production and necessary water control and drainage measures should be taken into consideration in order to achieve better development effect.