Lithologic Reservoirs

In order to improve the architecture classification scheme of clastic reservoir and better apply it to oilfield development,based on the study of reservoir architecture of different sedimentary types in Dagang Oilfield,by establishing three-dimensional geological model and numerical simulation based on reservoir architecture research, the residual oil distribution controlled by architecture was recognized,and the accuracy of reservoir architecture research was required. The classification scheme of reservoir architecture was redefined by combining and corresponding stratigraphic classification with sedimentary microfacies classification. On this basis,the ideas,contents and methods of reservoir architecture research system were put forward. The results show that this reservoir architecture classification scheme is much more explicit,the sixth-order architecture interface corresponds to the composite sedimentary formation unit. On the plane,it corresponds to composite meandering zone or composite braided flow zone,which is composed of more than two single complexes;on the profile,it is composed of small layers or sand layers,and the interior is composed of multiple single sand layers,and mudstone interlayer is developed between the single sand layers. The scheme was applied to Zao Ⅱ and Zao Ⅲ oil formations in Guan 80 fault block of Dagang Oilfield,and the architecture units 7,8 and 9(composite channel,single sedimentary unit and accretion body)were divided and characterized,which have obvious advantages in the study of the archi-tecture of dense well pattern development oilfield in ultra-high water cut stage.

Characteristics and hydrocarbon significance of lacustrine turbidite of Early Cretaceous Pointe Indienne Formation in Lower Congo Basin

YU Ye, CAI Linghui, YIN Taiju, WANG Li, ZHANG Xingqiang, XU Jifeng

2020, Vol.32(6): 12–21 Abstract ( 217 ) PDF (6564 KB) ( 266 )

doi: https://doi.org/10.12108/yxyqc.20200602

In order to define the key subsalt exploration layer in the Lower Congo Basin,the characteristics and hydrocarbon significance of lacustrine turbidite of Early Cretaceous Pointe Indienne Formation in the Lower Congo Basin were investigated by using the relevant theories and methods of sedimentology and petroleum geology,combined with regional geological background, drilling and logging data and the test analysis results, and the development model of large turbidite fan of Pointe Indienne Formation was established. The results show that the turbidite was formed in the deep lake sedimentary environment,and its superimposed sandbody has typical turbidite sedimentary characteristics,such as typical Bauma sequence and characteristic sedimentary structure. The turbidite sandstone is feldspathic detrital quartz sandstone or greywacke with low component maturity and poor structural maturity,which is characterized by rapid accumulation of gravity flow sedimentation. A number of complete and incomplete Bauma sequences have been identified in the turbidite sandstone,showing the combination of thick massive turbidite and thin or micro turbidite,indicating the sedimentary characteristics of the inner,middle and outer fans of the turbidite fan. The turbidite sandstone is a medium porosity and low permeability reservoir,which is in contact with the thick and high-quality source rocks developed in the upper and lower part of Pointe Indienne Formation. It has good source reservoir cap assemblage,and is the key layer for the subsalt oil and gas exploration in the Lower Congo Basin.

Relationship between multifractal characteristics of pore size and lithofacies of shale of Shahezi Formation in Changling fault depression，Songliao Basin

LIANG Zhikai, LI Zhuo, LI Lianxia, JIANG Zhenxue, LIU Dongdong, GAO Fenglin, LIU Xiaoqing, XIAO Lei, YANG Youdong

2020, Vol.32(6): 22–35 Abstract ( 253 ) PDF (6105 KB) ( 291 )

doi: https://doi.org/10.12108/yxyqc.20200603

In order to analyze the heterogeneity of pore size distribution of different shale lithofacies and its influencing factors,the pore structure of eight types of shale lithofacies of Shahezi Formation in Changling fault depression was characterized by CO2 and N2 adsorption experiments,and the heterogeneity of pore size distribution was studied by multifractal theory. The results show that:for micro pores,organic-rich clay shale has the largest pore volume and specific surface area,and organic-rich mixed shale has the smallest pore volume and specific surface area;for meso-macropores,organic-rich mixed shale has the largest pore volume,and organic clay shale has the smallest pore volume and specific surface area. With the increase of q,the generalized fractal dimension Dq of gas adsorption curve decreases,the multifractal singular spectral function α-f (α)presents a continuous distribution, indicating that the shale pore size distribution has multiple fractal features. In the micropores, the organicrich siliceous shale has the smallest dispersion of pore size distribution,however,the heterogeneity of organic-rich mixed shale is the largest. In the meso-macropores, organic-rich siliceous shale lithofacies has the strongest heterogeneity and the smallest dispersion of pore size distribution. Micropores have a lower overall heterogeneity, comparing with meso-macropores. Based on partial least squares regression analysis,there are significant differences in the influence of different rock components on lithofacies,and TOC content is the main factor affecting pore heterogeneity. Based on the multifractal theory,the research results can reveal the difference of pore size distribution characteristics from different lithofacies,and can provide guidance for shale reservoir development of Shahezi Formation in Changling fault depression, Songliao Basin.

Impact of authigenic clay minerals on micro-heterogeneity of deep water tight sandstone reservoirs: a case study of Triassic Chang 6 oil reservoir in Heshui area，southwestern Ordos Basin

CAO Jiangjun, CHEN Chaobing, LUO Jinglan, WANG Xi

2020, Vol.32(6): 36–49 Abstract ( 333 ) PDF (7731 KB) ( 326 )

doi: https://doi.org/10.12108/yxyqc.20200604

The intense development of authigenic clay minerals of the gravity flow reservoir in Chang 6 oil reservoir in Heshui area resulted in its complex pore throat structure,strong micro-heterogeneity,thus relatively poor physical properties. Based on the previous research results, the influence of authigenic clay minerals on the microheterogeneity of Chang 6 reservoir was studied by means of casting thin section,image grain size,scanning electron microscope,mineral X-ray diffraction,high-pressure mercury injection,physical properties and laser scanning confocal microscope. The results show that:(1)As the main product of diagenesis,authigenic clay minerals have an important influence on the micro-heterogeneity of Chang 6 oil reservoir,which is one of the major factors caused reservoir densification.(2)The authigenic clay mineral in the reservoir are mainly chlorite,illite and kaolinite. Among them,the content of chlorite is basically as same as that of kaolinite in sandy clastic flow and turbidity flow reservoirs,while illite content is higher in the turbidity flow reservoir.(3)Illite is the most important authigenic clay mineral that controls the percolation ability of the reservoir,and has an important influence on the micro-heterogeneity of the reservoir. The reservoir began to be affected by illite cementation and its heterogeneity became intense as a whole after 102 Ma.(4)Three zones can be divided at the study area based on the illite content and permeability of the reservoir. The first zone is the illite weak cementation area where the reservoir is of weak micro-heterogeneity and is mainly located in the northeastern of the study area,which is the priority exploration target area of the "sweet spot". The second zone is the illite moderate cemented area,where the reservoir is of moderate micro-heterogeneity and is mainly located in the central part of the study area,which is the secondary "sweet spot" exploration target. The third one is the illite intensively cemented zone,where the reservoir is of strong micro-heterogeneity and is mainly located in the southwestern of the study area,which is a "nonsweet spot area". The research results can provide a reference for the integrated research on the micro-heterogeneity of Chang 6 oil reservoir in Ordos Basin.

Division of sedimentary cycle of sandy conglomerate body and its relationship with physical properties: a case study from the upper submenber of the fourth member of Shahejie Formation in Y920 block of northern steep slope zone in Dongying Sag

QING Fan, YAN Jianping, WANG Jun, GENG Bin, WANG Min, ZHAO Zhenyu, CHAO Jing

2020, Vol.32(6): 50–61 Abstract ( 283 ) PDF (8821 KB) ( 316 )

doi: https://doi.org/10.12108/yxyqc.20200605

The sandy conglomerate reservoirs have complex lithology and strong heterogeneity,and the fan bodies are stacked in multiple stages,making it difficult to divide the sedimentary cycle. Based on core and FMI images, with the well logging information wavelet transform technology as the core,and with 3D seismic as the constraint,the method of sedimentary cycle division of sandy conglomerate fan body was established by taking the upper submenber of the fourth member of Shahejie Formation in Y920 block of the northern steep slope zone in Dongying Sag as the research object. Based on core and FMI images,the interface of sedimentary cycle can be identified intuitively,and then conventional logging data can be calibrated. The wavelet coefficient curve showing oscillation characteristics after the wavelet transform of logging information can reflect the response characteristics of the sedimentary interface,and the sedimentary period of a single well can be divided quantitatively by combining the scale factor of power spectrum screening. Through the well-seismic combination,the isochronic comparison of the cycle interfaces in the entire region was achieved,and the sandy conglomerate body in Y920 block was divided into 8 sedimentary cycles. The development of the sedimentary cycle controls the distribution of sedimentary facies and lithology,which is also closely related to the distribution of physical properties. The results show that the strata in the study area show good physical properties in the middle and upper part of sedimentary cycle in the initial stage of retrograde deposition(root-middle fan)from the bottom to the top(8 to 1 sedimentary cycle),and the strata show good physical properties in the entire sedimentary cycle of the intermediate deposition stage(middle fan)and the middle and lower parts of sedimentary cycle in the final deposition stage(middle-bottom fan). Furthermore,the thickness of the effective reservoirs in each cycle of a single well was counted,and the planar distribution characteristics of the effective reservoirs were described in cycles. It is found that the northwest of 3,4 and 5 sedimentary cycles is the favorable reservoir distribution range of Y920 block. The research results provide a basis for fine exploration and development of sandy conglomerate reservoirs in the northern steep slope zone of Dongying Sag.

Spatio-temporal distribution of soft-sediment deformation structures on slope: a case study of Chang 7 oil reservoir in Zhenyuan area，Ordos Basin

HE Weiling, LUO Shunshe, LI Yudong, WU You, LYU Qiqi, XI Mingli

2020, Vol.32(6): 62–72 Abstract ( 277 ) PDF (6445 KB) ( 373 )

doi: https://doi.org/10.12108/yxyqc.20200606

In order to study the spatio-temporal distribution of soft-sediment deformation structures of Chang 7 oil reservoir of Upper Triassic Yanchang Formation,the detailed observation and description of core from 20 wells in Zhenyuan area,southwestern Ordos Basin,were carried out. Combined with morphological characteristics and formation mechanism of the soft-sediment deformation structures,seven common types of soft-sediment deformation structures were recognized,including slump deformation,liquefied curled deformation,torn mud intraclasts,liquefaction sandstone dikes,sandy ball-pillow structures,flame structures and load casts. Vertically,softsediment deformation structures are most frequently observed in Chang 72 sublayer,followed by Chang 71 and Chang 73 sublayers. Horizontally,the soft-sediment deformation structures mainly distribute in the deep-water slope-break zone and semi-deep and deep lake where is located in the central and eastern of the study area. The formation mechanism and distribution of soft-sediment deformation structures on slope is that:(1)Basin-mountain coupling has activated triggers for the occurrence of soft-sediment deformation structures.(2)The transition period between the lake transgression and lake regression is the stage when the soft-sediment deformation structures are most concentrated.(3)The distribution of the soft-sediment deformation structures is closely related to the development of slope break zone. From the slope to the semi-deep lake-deep lake environment,various types of softsediment deformation structures have evolved regularly. The results of this study have important reference for the distribution pattern of sedimentary deformation structures,the prediction of gravity flow sand body distribution and the study of sedimentary events.

Sand body configuration and reservoir characteristics of large braided river delta: a case study of Ahe Formation in northern Kuqa Depression， Tarim Basin

YUAN Chun, ZHANG Huiliang, WANG Bo

2020, Vol.32(6): 73–84 Abstract ( 364 ) PDF (10389 KB) ( 390 )

doi: https://doi.org/10.12108/yxyqc.20200607

Large sand-gravel braided river delta was deposited in the Jurassic Ahe Formation in northern Kuqa Depression of Tarim Basin,which is an important target for oil and gas exploration. However,the rapid change of lithofacies, complex sand body architecture, relatively tight reservoir and strong heterogeneity restrict the exploration and development of oil and gas. Through the establishment of outcrop basal section,transverse sand body tracking,sand body configuration description,sampling and experimental analysis of sandstone with different lithofacies,the vertical construction,transverse distribution regularity and reservoir properties of different lithofacies were analyzed. The results show that there are three types of sedimentary formations formed on the longitudinal of Ahe Formation:large-scale sandy gravel braided channel-lateral accretion bar-longitudinal sand bar,mediumsized sandy gravel braided channel-transverse sand bar-lakeside composite sand body,and small-sized sandy braided channel-inclined sand bar. Among them,the reservoir performance of medium-sized channel-transverse sand bar is relatively better,and the favorable reservoirs are mainly trough cross bedding sandy fine conglomerate, tabular cross bedding medium sandstone and low angle parallel bedding fine sandstone. The lower braided river delta plain and front are favorable exploration directions.

Discussion on seismic identification characteristics and controlling factors of sediment bypass

SHANG Wenliang, XU Shaohua, CAI Molun, GAO Hongcan, LI Xiaogang, CHEN Cen, CAI Change, QIN Lei

2020, Vol.32(6): 85–96 Abstract ( 213 ) PDF (8319 KB) ( 327 )

doi: https://doi.org/10.12108/yxyqc.20200608

At present,most of researches on sediment bypass are focused on explaining the non-deposition that occur in continental shelves or slopes,but the main controlling factors of sediment bypass are still not clear. By collecting domestic and foreign cases of sediment bypass and making comparative analysis on different cases, the identification signs of sediment bypass on seismic profiles and the main controlling factors of sediment bypass have been ascertained. The result shows:(1)Sediment bypass represents depositional break,and appears as the merging of seismic events of the top and bottom formation in seismic profile. (2)Sediment bypass mostly occurs on above-graded slope,and the filling stages of different accommodation spaces(ponded-basin accommodation space,healed-slope accommodation space and slope accommodation space)in above-graded slope provide potential areas for sediment bypass.(3)Sediment grain size,concentration,fluid flow,and slope determine whether the sediment can pass by. Among them,sediment grain size and fluid flow are the main factors that affect the turbidity currents bypass. Sediment concentration is the main factor that affects the debris flow. (4)The controlling effect of slope on sediment bypass is reflected in two aspects:absolute gradient difference and relative slope ratio of adjacent formation. Relative slope ratio is an important condition for the start of sediment bypass. The absolute slope difference determines the distance of sediment bypass. The smaller the absolute gradient difference is,the shorter the bypass distance is;the larger the absolute gradient difference is,the longer the bypass distance is. This research is helpful to deepen the understanding and knowledge about the sediment transport process,and also has reference for future research of sediment bypass.

Tight oil accumulation conditions of the second member of Qiketai Formation in Shengbei sub-sag，Turpan-Hami Basin

FENG Yue, HUANG Zhilong, LI Tianjun, ZHANG Hua, LI Hongwei, ZHOU Yadong

2020, Vol.32(6): 97–108 Abstract ( 219 ) PDF (8465 KB) ( 316 )

doi: https://doi.org/10.12108/yxyqc.20200609

In order to analyze the conditions and main controlling factors of tight oil accumulation of the second member of Qiketai Formation(J2 q2)in Shengbei sub-sag of Turpan-Hami Basin,and effectively promote the scale effect of tight oil exploration,core and thin section observation,scanning electron microscopy(SEM), high-pressure mercury injection and organic geochemistry analyses were carried out. The results show that:(1)The J2 q2 source rock is a set of low-mature high-quality source rocks,which deposited in a slightly reduced brackish lake environment,the average TOC of source rock is 1.78%,and the organic matter is mainly of type Ⅰ and type Ⅱ1.(2)A set of tight mixed rock reservoir was developed in the middle of the second member of Qiketai Formation,with porosity ranging from 2.6 to 7.7% and the permeability less than 1.0 mD. The overall performance was characterized by medium reservoir pore structure and connectivity. The cut-off pore-throat radius and lower limit of porosity are 50 nm and 2.6%,respectively,and the mobility of tight oil is relatively strong. (3)The distribution of high-quality source rocks,oil-source faults and favorable sedimentary facies belts control the tight oil accumulation,which has the characteristics of "self-source hydrocarbon supply,fault-fracture transportation and reservoir control of favorable facies belt". According to the reservoir controlling factors,two kinds of favorable areas for tight oil exploration can be divided. The research results have important guiding significance for promoting the exploration of tight oil in Shengbei sub-sag of the Turpan-Hami Basin.

Sedimentary paleoenvironment of source rocks of Permian Lucaogou Formation in Jimsar Sag

JIANG Zhongfa, DING Xiujian, WANG Zhongquan, ZHAO Xinmei

2020, Vol.32(6): 109–119 Abstract ( 337 ) PDF (2522 KB) ( 375 )

doi: https://doi.org/10.12108/yxyqc.20200610

In order to find out the sedimentary paleoenvironment evolution process of the source rocks of Middle Permian Lucaogou Formation in Jimsar Sag,Junggar Basin,the major element and trace element tests were carried out on 27 hydrocarbon source rock samples,and combined with biomarkers and δ18O data of carbonate rocks, the paleo-oxygen facies,paleo-salinity,paleo-climate and paleo-water depth evolution of the first and second members of Lucaogou Formation were studied. The results show that nC17 is the main peak carbon of n-alkanes in the first member of Lucaogou Formation in Jimsar Sag,and gammacerane,phytane,β-carotene,vanadium, uranium,ferrous oxide,strontian,magnesium and calcium are enriched,the δ18O of autogenic carbonate in it is higher,and the paleoenvironment is saline and anaerobic-anoxic environment under arid climate,with some strata brackish,and w(MnO)/w(TiO2)indicates that its paleo-water depth is deeper. nC21 and nC23 are the main peak carbon of n-alkanes in the second member of Lucaogou Formation in Jimsar Sag,and pristine,ferric oxide,aluminum,titanium and C24 tetracyclic terpene are enriched in it,and the paleoenvironment is generally brackish-saline and anoxic environment under humid climate,occasionally saline environment under arid climate,and its paleowater depth is shallower. The research results show that the first member of Lucaogou Formation can be regarded as the next exploration focus in the study area.

EXPLORATION TECHNOLOGY

Uncertainty analysis in AVO forward modeling for tight sandstone reservoirs

ZHANG Yan, GAO Shichen, MENG Wanying, CHENG Yuhong, JIANG Sisi

2020, Vol.32(6): 120–128 Abstract ( 242 ) PDF (2567 KB) ( 328 )

doi: https://doi.org/10.12108/yxyqc.20200611

Traditional AVO forward modeling usually uses constant parameters to construct the petrophysics model,however,these parameters have uncertainties in the exploration process,resulting in great uncertainty for the process of forward modeling. The petrophysical model was firstly established based on the wireline logs and the tools of probability density function(PDF)and information entropy(IE)were used to characterize the uncertainty of petrophysical parameters. Then based on the typical reflection interfaces,the parameters of AVO forward modeling,including the ratio of compressional wave velocity,shear wave velocity and density between the media above and below of reflection interfaces,are analyzed to the influence of AVO forward modeling. Finally,the Markov Chain Monte Carlo(MCMC)simulation method was used to model the reflection characteristics and AVO attribute response of different lithological interfaces. The IE was then used to analyze the uncertainty in AVO analysis. The results show that the PDF and IE indicate that petrophysical parameters are different in different lithologies,but there is a certain overlap for each other,which results in uncertain and multi-solution for the identification of lithology using petrophysical parameters. The AVO response indicates that the changes of the petrophysical parameters of the upper and lower media and the differences of lithology of the lower media result in different responses of AVO reflection coefficient. The attribute of AVO intercept(P)and the AVO gradient(G) shift to the type Ⅲ,as the gas saturation increases. The study effectively evaluates the uncertainty in the AVO forward modeling through statistical methods,which can provide a priori understanding for reservoir prediction and is helpful for the risk assessment and decision-making optimization of reservoir prediction.

Conventional logging evaluation method for carbonate fractured reservoir

REN Jie

2020, Vol.32(6): 129–137 Abstract ( 270 ) PDF (3488 KB) ( 347 )

doi: https://doi.org/10.12108/yxyqc.20200612

The reservoir of KT-Ⅱmember of Carboniferous in K oilfield of Kazakhstan is a limestone reservoir with medium low porosity and ultra-low permeability in open platform facies. Fractures are very important to improve the seepage capacity of the reservoir. The methods of using conventional logging data to evaluate fractures in carbonate reservoir studied by predecessors is of poor certainty and easy to be influenced by many factors such as fracture occurrence,saturation and mud invasion depth. Based on the limited coring and electrical imaging logging data of the target interval in the study area,combined with the study of logging response characteristics of pore reservoir and fracture-pore reservoir,a method was proposed to determine the resistivity of base block rock and acoustic time difference of base block by using compensated neutron logging. By comparing the difference characteristics of these two parameters with deep lateral resistivity and acoustic time difference respectively,fracture development sections with different occurrence in reservoirs were comprehensively identified,then the logging interpretation models of fracture porosity,secondary porosity,fracture permeability,total permeability were established,realizing and the fracture identification and parameter quantitative evaluation of carbonate reservoir by using conventional logging data. The comprehensive evaluation results of logging applied by this method can better match the coring physical property analysis and production performance,which provides a basis for reasonable and efficient development of this kind of reservoir.

Gas-bearing property evaluation of tight sandstone reservoir based on Xu-White model

ZHANG Peng, YANG Qiaoyun, FAN Yiren, ZHANG Yun, ZHANG Haitao

2020, Vol.32(6): 138–145 Abstract ( 215 ) PDF (4160 KB) ( 364 )

doi: https://doi.org/10.12108/yxyqc.20200613

The tight sandstone reservoir in eastern Ordos Basin is a typical lithologic gas reservoir,with poor physical properties,limited reservoir space and complex pore structure. The conventional logging data is easily influenced by rock matrix, pore fluid makes little contribution to its response characteristics, and well logging curve is difficult to highlight the information of pore fluid effectively,which leads to gas identification difficultly. In order to solve this problem effectively,a new method for identifying gas-bearing tight sandstone gas reservoir was proposed by obtaining gas-bearing indicator factor and gas-bearing sensitive parameters such as P-S-wave velocity ratio difference,bulk modulus difference,which is based on Xu-White model,array acoustic logging data,BiotGassmann equation and fluid replacement model. The results show that array acoustic logging can get real acoustic information reflecting the real framework and fluid characteristics of the formation,so it is an effective method for gas-bearing property evaluation of tight sandstone reservoirs. The accuracy of identification of tight sandstone gas reservoir by bulk modulus difference and gas-bearing indicator factor is high,and the gas-bearing property evaluation effect is good,while the evaluation effect of P-S velocity ratio difference is poor. According to actual data processing and gas test data,this method achieved good results in gas-bearing property evaluation of tight sandstone reservoir in eastern Ordos Basin,meanwhile it can provide some technical support for gas-bearing property evaluation of similar tight sandstone reservoirs in other areas.

OIL AND GAS FIELD DEVELOPMENT

Quantitative characterization of sweep coefficient of water drive in horizontal well for offshore bottom water reservoir

ZHANG Yunlai, CHEN Jianbo, ZHOU Haiyan, ZHANG Jilei, ZHANG Wei

2020, Vol.32(6): 146–153 Abstract ( 240 ) PDF (3227 KB) ( 478 )

doi: https://doi.org/10.12108/yxyqc.20200614

In the middle and late stage of the development of offshore bottom water reservoir, there are some problems, such as unclear understanding of water drive oil law and difficulty in quantitative description of water drive sweep coefficient between horizontal wells. Taking Q oilfield in Bohai Sea as an example,the fine numerical model of bottom water reservoir was established by using indoor one-dimensional long core water flooding experiment and reservoir numerical simulation method, the variation law of flooding efficiency and cross-well water flooding sweep coefficient between horizontal wells after long-term water flooding in bottom water reservoir was carried out. The results show that the displacement multiple in the water displacement experiment was increased to 2 000 PV and the displacement speed was increased from 1 mL/min to 5 mL/min, and the displacement efficiency was increased by 15%-20% when the displacement efficiency is more than 100 PV. Based on the numerical simulation of horizontal well water drive sweep volume, the phase permeability curve after high-power water drive was introduced, and the grid accuracy of the model was improved to 10.0 m×10.0 m×0.3 m,realizing the fine characterization of water drive sweep volume. The calculated sweep coefficient was reduced from 66.7% of the original model to 54.6%, which improves the calculation accuracy of the model. The height and spacing of oil string in horizontal well distribution are the main control factors affecting cross-hole water drive sweep coefficient. The lower the oil column height in horizontal section is,the larger the well spacing is,and the lower the sweep coefficient of cross-hole water drive is. Based on the research results,the cross-well water drive sweep coefficient chart of offshore bottom water reservoir was established,and the boundary parameters of horizontal well layout in bottom water reservoir were defined. The well distance of the well is 100-150 m,the height of the oil column is 6-8m,the well control reserve is(15-25)×104m3,the maximum extraction of the horizontal well is 2 000 m3/d,the limit economic oil production is 10 m3/d,and the accumulated oil production of the horizontal well can reach more than 50 000 m3. The research results have successfully guided the implementation of 21 infill horizontal wells in bottom water reservoir of offshore Q oilfield,and can provide reference for high efficiency potential tapping in the middle and late stage of the bottom water reservoir.

Reservoir architecture and remaining oil distribution of channel-bar: a case from lower Minghuazhen Formation in Bohai A oilfield

DENG Meng, SHAO Yingbo, ZHAO Junshou, LIAO Hui, DENG Qi

2020, Vol.32(6): 154–163 Abstract ( 222 ) PDF (4750 KB) ( 277 )

doi: https://doi.org/10.12108/yxyqc.20200615

The lower Minghuazhen Formation of Neogen in Bohai A oilfield is bird-foot shallow water delta deposition. Due to the frequent erosion and superimposition of channel-bar in different periods on the plane,its spatial structure pattern was extremely complex,which greatly restricted the development effect of the oilfield. Under the guidance of sedimentary theory,based on the data of core,well logging and production performance,the fine reservoir configuration was carried out by using the method of reservoir configuration factor analysis. Meanwhile the spatial structure pattern of single sand body configuration units were defined,the control of remaining oil distribution by different single sand body configuration was discussed,and four types of remaining oil distribution models were established. The results show that the single sand body configuration units in the study area mainly develop three vertical contact patterns(such as separation type,superposition type and cutting superposition type)and three lateral splicing patterns(such as separation type,splicing type and side cutting type). In addition,the controls of single sand body configuration on the distribution of remaining oil were analyzed. It is considered that the rhythm within the single sand body,contact model of channel-bar sand body and plane heterogeneity are the main control factors of the distribution of remaining oil. The study area mainly develops "top enrichment", "vertical seepage blocking type", "plugging" and "under injection type" remaining oil distribution models, and the responding remaining oil potential can be exploited by sidetracking horizontal wells,injecting in thick layers while producing in thin layers,infilling wells and well pattern optimization respectively. The research results have guiding significance for the exploration of remaining oil potential in the middle-high water cut stages of the old offshore oilfields.

Well placement optimization of coalbed methane based on hybrid particle swarm optimization algorithm

LIU Mingming, WANG Quan, MA Shou, TIAN Zhongzheng, CONG Yan

2020, Vol.32(6): 164–171 Abstract ( 231 ) PDF (3348 KB) ( 498 )

doi: https://doi.org/10.12108/yxyqc.20200616

The well locations directly influence the gas recovery factor and the economic benefit of coalbed methane development projects. Based on the disadvantage of particle swarm optimization and the advantage of simulated anneal algorithm,a hybrid particle swarm optimization algorithm was proposed. This algorithm took the net present value as the objective function,the single well control area and well location as variables,and combined the reservoir numerical simulation method to optimize the single well control area and well location with the largest net present value(NPV),which was realized by matlab programming. The results show that the well location optimization based on hybrid particle swarm optimization algorithm overcomes the disadvantage of the conventional well pattern which is experience-dependent. It needs less amount of computation to determine the optimal well location compared with exhaust algorithm. The optimal single well control area of coalbed gas field in Qinshui Basin is 0.2 km2. For the optimal control area of a single well,the optimal NPV obtained by hybrid particle swarm optimization algorithm is 12.55% higher than that of the conventional rectangular well pattern. The optimal well location is closely related to gas content and permeability,among which the permeability distribution is particularly important,and it is an optimal combination of gas content and permeability. The research results provide a new method for the well location optimization of CBM development.

PETROLEUM ENGINEERING

Practice of volume fracturing and microseismic monitoring technology in horizontal wells of shale oil

LIU Bo, XU Gang, JI Yongjun, WEI Lulu, LIANG Xueli, HE Jinyu

2020, Vol.32(6): 172–180 Abstract ( 271 ) PDF (3931 KB) ( 400 )

doi: https://doi.org/10.12108/yxyqc.20200617

In order to explore and solve the imaging problem of artificial fracture network during horizontal well volume fracturing and bench top zipper fracturing of shale reservoir in Jimsar block, Junggar Basin,high density dense cutting volume fracturing was adopted to carry out reservoir stimulation,large displacement construction can meet the requirements of full opening of multiple clusters and fractures,reverse mixed fracturing process of slick water and guar gum can realize high-efficiency fracture making and sand carrying, and combined with a variety of particle size proppant,it can effectively fill micro fractures and artificial fractures. The artificial fracture network of shale oil horizontal well was identified by microseismic monitoring technology. The results show that faults and natural fracture zones have influence on microseismic events attribute characteristics,and events attribute characteristics can also show the development degree of faults and natural fractures. Under large-scale volume fracturing,the artificial fractures of four wells in the study area were connected with each other horizontally, forming a complex fracture network. The daily oil production in the initial stage of production after fracturing has been greatly improved,and it can provide a technical basis for long-term and efficient development of shale oil in this area.