Lithologic Reservoirs

Sulige Gas Field is a typical tight gas reservoir in China. There are some controversies in research conclusion of sedimentation types and diagenesis process. According to the core data, this paper studied the general geological characteristics of tight sand reservoir, illuminated the differences of reservoir properties from two aspects of sedimentation and diagenesis, and pointed out that strong compaction, ferroan calcite replacement and siliceous cementation are the main factors for reservoir densification. Based on the analysis of sedimentary microfacies, it is defined that distributary channel sand body is high quality reservoir in eastern Sulige Gas Field, and four kinds of vertical combination models and three kinds of lateral contact models of single sand body for the delta plain distributive channel were established.

A new evaluation method of well productivity

LI Chuanliang， ZHU Suyang

2014, Vol.26(3): 7–10 Abstract ( 615 ) PDF (387 KB) ( 722 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.002

Productivity evaluation of wells is completed through productivity test of wells. Conventional productivity tests are accomplished at well bottom through measuring production rate and flowing pressure of well bottom in order to determine the productivity index of wells. Productivity index is a parameter to evaluate productivity of wells. However, some wells are difficult to measure their bottom pressure and the productivity index cannot be obtained. In order to evaluate the productivity of wells effectively, productivity evaluation method was improved with measurement at wellhead other than at well bottom. Test of well productivity at wellhead is completed through the determination of nozzle flow equation, which can determine the nozzle productivity index to evaluate the productivity of wells. The nozzle productivity test is completed through measuring flow rate of wells and the size of choke nozzle, which can calculate the nozzle productivity index. The nozzle productivity test can be done simultaneously with the production of wells without any negative effect on the production of oil and gas and any additional cost. Nozzle productivity test is quite simple and practical to the conventional test at well bottom.

Characteristics and origin of low permeability reservoir of the third member of Shahejie Formation in Bozhong 25-1 oilfield

SUN Haitao， LI Chao， ZHONG Dakang， ZHOU Junliang

2014, Vol.26(3): 11–16 Abstract ( 644 ) PDF (799 KB) ( 672 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.003

The third member of Shahejie Formaiton in Bozhong 25-1 oilfield is consisted of lithic arkose and feldspathic litharenite, with the current burial depth of 3 300～3 800 m, and the diagenetic evolution reached the middle diagenetic stage. During the diagenetic process, the reservoir physical properties were mainly changed by compaction, cementation and dissolution, and became medium porosity and low permeability reservoir. The reservoir properties were mainly controlled by sedimentary background and diagenetic evolution. Firstly, the gravity flow sedimentary background caused the less primary pores and plenty matrix; secondly, the intense compaction and cementation and weak dissolution caused the medium porosity and low permeability. The relatively high quality reservoir mainly developed in proximal deposited sand bodies, where the reservoir physical properties are high.

Analysis method of sedimentary microfacies by combining three facies

LIU Baoguo， CHEN Shan

2014, Vol.26(3): 17–21 Abstract ( 587 ) PDF (633 KB) ( 572 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.004

Traditional sedimentary microfacies of third-order sequence is too large to guide the reservoir prediction. A method of combining ancient landform, seismic attributes and sand percentage was proposed to analyze sedimentary microfacies and describe the advantageous thin reservoir distribution. The high-frequency sequence boundary can be interpreted on frequency division section by referring to the high-frequency sequence division on single well. Seismic facies of high-frequency sequence was chosen under the control of ancient landform graph. By analyzing the sandstone percentage figure, the sedimentary microfacies figure was obtained. In this figure, the sedimentary microfacies boundary is controlled by boundary of seismic attributes, and the interior of the sedimentary microfacies is described by contour of sandstone percentage. Comparing with traditional sedimentary facies ideograph, this figure is more quantitative for having the external form and internal structure. It can be used to analyze the possible location of advantageous reservoir and indicate the dessert area. It makes reservoir prediction more real and believable.

Diagenetic characteristics of tight sandstone of Chang 4+5 reservoir in Longdong area, Ordos Basin

ZHU Shifa，XU Liming，ZHU Xiaomin，LIANG Xiaowei，LI Panpan，NIU Xiaobing

2014, Vol.26(3): 22–27 Abstract ( 608 ) PDF (946 KB) ( 478 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.005

Based on the observations of rock thin sections, casting thin sections and scanning electron microscope, this paper summarized the diagenesis characteristics of the tight sandstone reservoir of Chang 4+5 reservoir in Longdong area, and studied the origin of the tight reservoirs in Zhenyuan-Huanxian Region and Huachi-Baibao area. The result show that the rock types of Chang 4+5 reservoir mainly are very fine grained-fine grained lithic arkose, feldspathic lithic sandstone and the transition between the two types. The rock debris is mainly plastic and soluble. And the content of flexible mica fragments is high. The compressive strength of the reservoir rocks is very weak. The chlorite coating can effectively inhibit quartz and feldspar overgrowth in Huachi-Baibao area. The cementation of iron carbonate is intensive, and the feldspar dissolution is relatively weak. In different areas, the characteristics of diagenesis are obvious different. The tight sandstones of Chang 4+5 reservoir are contributed by genetic types of rock, sediment size, rock composition, late diagenetic reconstruction and so on. The high-quality reservoir rocks are those massive sandstones of the underwater distributary channels, with slight quartz overgrowth in Zhenyuan-Huanxian area and proper chlorite coating in Huachi-Baibao area.

Formation of low permeability reservoir and typical case analysis in Kuqa Depression

LIU Fen， ZHU Xiaomin， PAN Rong， LI Yang， XUE Mengge， DI Hongli

2014, Vol.26(3): 28–37 Abstract ( 535 ) PDF (1142 KB) ( 407 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.006

With the development of oil and gas exploration, the low permeability reservoirs have been a significant target of oil and gas exploration and development. Based on the study on Cretaceous low-porosity and low-permeability reservoir of Kelasu tectonic zone in Kuqa Depression, Tarim Basin, we summarized the characteristics of low permeability reservoir, and discussed its formation mechanisms and controlling factors. The result shows that low permeability reservoirs can be divided into 3 types accorded to the genetic differences: primary low permeability reservoir, secondary low permeability reservoir and fractured low permeability reservoir. The origin of the low permeability reservoir is impacted jointly by deposition, diagenesis and later tectonism. Deposition is the most fundamental reason for the low permeability reservoir, and strong compaction and cementation account mainly for it. Dissolution and later tectonic fractures increase the porosity and permeability of the reservoir, and that are the key factors for the low permeability in deep reservoir.

Sedimentary characteristics of turbidite fan in upper submember of Es₃ in the third area of Shanghe Oilfield, Huimin Sag

WANG Ning， HE Youbin， WANG Siwen， ZHANG Zhulin

2014, Vol.26(3): 38–44 Abstract ( 522 ) PDF (868 KB) ( 430 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.007

Based on core observation, log data, thin section analysis and regional geological background, this paper studied the rock types, grain size characteristics and sedimentary structures of turbidite fan of upper sub-member of the third member of Shahejie Formation in the third area of Shanghe Oilfield. The result shows that the rock types mainly include siltstone, fine sandstone and argillutite. Erosion surface, gloove cast, grading bedding, convolute bedding, flame structure and small-sized contemporaneous fault are mainly developed. The granularity analysis result shows typical features of turbidite deposit. Middle fan which is dominant and outer fan are recognized, which can be further divided into channel, interchannel, channel lateral margin, and outer fan mud. The vertical sedimentary sequence, sedimentary facies distribution and evolution and the controlling factors were analyzed.

Microscopic morphology and formation mechanism of lacustrine source rocks of Hetaoyuan Formation in Biyang Sag

LI Miaomiao，MA Suping，XIA Yanqing，ZHANG Xiaobao

2014, Vol.26(3): 45–50 Abstract ( 482 ) PDF (751 KB) ( 440 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.008

The study on the lacustrine source rocks of Hetaoyuan Formation in Biyang Sag was carried out by using backscattered electron imaging technology. The study results show that the shape of organic matter mainly denominated in trip, oval biological detritus. The organic matter in source rocks distributed in different forms, so according to the distribution characteristics of organic matters, the source rocks in Biyang Sag can be subdivided three types, including lamination source rocks, scattering organic matter source rocks and intermediate forms source rocks. Meanwhile, according to the analysis of geochemical data, the lamination source rocks is with high organic carbon content, formed in high salinity saltwater environment, with fewer external runoff, the main source of sedimentary organic matter is aquatic organisms, and the kerogen is mainly typeⅠ; scattering organic matter source rocks is with low content of organic carbon, deposited in low salinity freshwater environment, with more external runoff, the main source of sedimentary organic matter are terrestrial and aquatic organisms, and the kerogen is mainly type Ⅱ ; while the sedimentary environment of intermediate forms source rocks is intermediate between the lamination source rocks and the scattering organic matter source rocks.

Sedimentary system of Tendi Formation to AG Formation in the western slope of X block, Muglad Basin

TAO Wenfang， ZHU Xiaomin， FAN Leyuan， CHEN Hehe

2014, Vol.26(3): 51–58 Abstract ( 727 ) PDF (1307 KB) ( 588 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.009

Based on the paleontology, cores, logs and seismic data, this paper analyzed the types and evolution of sedimentary systems from Tendi Formation in Tertiary to AG Formation in Cretaceous in the western slope of X block in Muglad Basin. The result shows that influenced by the source of the south part of western Matelige uplift, the study area is with rift lake basin sedimentary characteristics in Early Cretaceous, Late Cretaceous, and Eocene; the distribution from delta facies to shallow lake facies extends from west to east; in addition, （semi-） deep lake facies develops in the eastern part of the study area in the early stage of Early Cretaceous. The depression lacustrine deposition is manifested in the late period of Early Cretaceous, Paleocene and Oligocene-Pliocene. The fluvial facies promote to the west of the study area and comes into being delta, and a small range of shallow lake occurs in the east of the study area. In conclusion, the regional tectonic activities significantly control the sedimentary filling in the western slope of X block in Muglad Basin, and the sedimentary evolution shows obvious regularity.

Characteristics and controlling factors of dolomite reservoirs of Lower Ordovician Penglaiba Formation in Yubei area

L IN Xin，JIANG Haijun，Y UE Yong，WU Liming

2014, Vol.26(3): 59–66 Abstract ( 677 ) PDF (1080 KB) ( 402 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.010

Penglaiba Formation of Lower Ordovician in Yubei area becomes the target stratum for oil and gas exploration of marine carbonate rocks in Tarim Basin, and it developed large amounts of dolomite reservoirs. Due to the deep burial and low degree of exploration of dolomite, the cognition of its origin is not perfect and need further studying. Based on field geological inspection, core observation, identification of thin section, physical properties analysis, combined with SEM and the results of isotope geochemistry of carbon, oxygen and strontium, this paper analyzed the characteristics and controlling factors of dolomite reservoirs of Penglaiba Formation in Yubei area. The dolomites of Penglaiba Formation consist of replacement dolomite and recrystallization dolomite, which can be further subdivided into three categories, silty crystalline dolomite, medium grained dolomite and coarse crystalline dolomite in terms of grain size, and the most important reservoir rock is medium grained dolomite. The reservoir space in dolomites is subject to intercrystal pores, intercrystal dissolved pores, intracrystal dissolve pores, dissolved pores and fractures as migration channels. Dissolved pores and fractures are the most important reservoir space. The most common reservoir space is mainly the overlapped complex of cracks and cavities. Fracturing and its associated fractures and karstification are the keys for the development of dolomite reservoir of Lower Ordovician Penglaiba Formation. Fault activities control the development of associated fractures, which makes fresh surface water or deep hydrothermal infiltrate or upwell along faults and fractures, and then dissolution occurs. Atmospheric fresh water karstification effectively improves the dolomite reservoir properties at the top of Penglaiba Formation, while the hydrothermal karstification results in poor development of the lower reservoir of Penglaiba Formation, owing to filling with silica in the most holes and crakes.

Comparative study on geochemical characteristics of shale oil between China and U. S. A

WANG Min，SHI Lei，WANG Wenguang，HUANG Aihua，CHEN Guohui，TIAN Shansi

2014, Vol.26(3): 67–73 Abstract ( 919 ) PDF (1077 KB) ( 1050 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.011

Inspired by the development of shale gas and the decrease of natural gas price, the investors kicked off shale oil exploration and development. U. S. A has been obtained huge benefit from shale oil, and the shale oil resource potential is also huge in China. Based on the previous study on shale oil resource potential of basins in eastern China, the comparative study on geochemical characteristics of shale oil between U. S. A and China has been done. The research results indicate that the oil saturation index（OSI） can be used as an effective index for judging the shale oil intervals, combined with the carbonate mineral content, brittle mineral content and the interbed. The results also show that the OSI values of Jiyang Depression are similar with that of Monterey, Barnett and Eagle Ford shale. At present, the shale oil exploration of China should be aiming at the hybrid type.

Research on logging evaluation method of TOC content of shale gas reservoir in A area

X IONG Lei，ZHANG Chaomo，ZHANG Chong，X IE Bing，DING Yi，HAN Shumin

2014, Vol.26(3): 74–78 Abstract ( 505 ) PDF (843 KB) ( 897 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.012

Total organic carbon（TOC） content of shale gas reservoir reflects the hydrocarbon generation potential of shale rocks. It has an important guiding significance for shale gas development to obtain the TOC content accurately by use of conventional logging data which has characteristics of continuousness and high vertical resolution. Therefore, it is especially important to establish highly precise model of the organic carbon content evaluation. Combining the limiting factors of TOC content evaluation methods with the reality of complex lithological changes of A area, we established three kinds of TOC content models to evaluate shale rocks from X well in A area. They are BP neural network, uranium and kerogen. It is concluded that the BP neural network model is with the highest precision to forecast the total organic carbon content, and provide technical support to TOC content evaluation in complex lithology areas.

Microscopic characteristics of Chang 7 tight sandstone reservoir in Ordos Basin

WANG Xiujuan， WANG Minglei， ZHAO Aibin

2014, Vol.26(3): 79–83 Abstract ( 688 ) PDF (773 KB) ( 603 )

According to the characteristics of tight reservoir in Ordos Basin, based on FESEM, nanometer CT, rate controlled mercury penetration and NMR, this paper systematically studied the characteristics of reservoir pore, throat and the relationship between pore and throat. The result shows that the size of pores determines the reservoir capacity of tight oil reservoir, the average pore radius ranges from 15 μm to 20 μm, and the average pore volume is 0.05. The throat size is the main restricted factor for development cutoffs. The throat size ranges from 0.3 μm to 0.5 μm, and the throats ranging between 0.1 μm and 0.5 μm control 60% of movable fluid of reservoir. The reservoir with better physical properties exists in 30% to 40% big throat with better connectivity and the radius of throat is over 5 μm. The throat with radius of below 0.1 μm account for about 60% and connectivity is poor.

Application of seismic sedimentology to the analysis of sedimentary system in Fudong area

GUO Huajun， CHEN Nenggui，X U Yang， ZOU Zhiwen， LI Chang， WANG Libao

2014, Vol.26(3): 84–88 Abstract ( 628 ) PDF (992 KB) ( 476 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.014

Based on the comparison of traditional sedimentary system analysis methods, this paper proposed seismic sedimentology method to carry out sedimentary system analysis. On the basis of sequence stratigraphic classification, this paper carried out seismic data to 90° phase conversion, 3D seismic attribute analysis, extraction and analysis of stratigraphic section, established the corresponding relationship between seismic attribute characteristics and sedimentary facies by calibrating the seismic sedimentary facies through the observation of core and outcrops, well logging and modern sedimentary analysis, and analyzed the sedimentary system. It is considered that the seismic sedimentology sedimentary system analysis method is based on the sequence stratigraphic framework, and it can ensure the isochronous stratigraphic correlation, make full use of the lateral seismic resolution to recognize the thin layer of sand body which is difficult for the seismic vertical resolution, and combined the seismic attribute processing with sedimentology, it can predict sand body space distribution and evolution characteristics.

Application of capillary pressure curves and fractal theory to reservoir classification

LIU Yikun， WANG Yongping， TANG Huimin， WANG Fengjiao， CHEN Lingyun

2014, Vol.26(3): 89–92 Abstract ( 1044 ) PDF (856 KB) ( 625 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.015

This paper used the MIFA method to calculate the fractal dimension of 21 samples of an inspection well in M block of Daqing Oilfield, and applied the fractal dimension to divide the reservoir into three types, meanwhile used the capillary pressure curves to carry out the reservoir classification. The results show that the reservoir types classified by the two methods are similar. For the same type of reservoir, not only the capillary pressure curve is similar, but also the micro reservoir parameters are similar. The higher the fractal dimension is, the poorer the reservoir properties of reservoir are, and especially the reservoir heterogeneity is stronger. Through the statistical research of the washing degree of 21 samples, we found that the higher the fractal dimension is, the weaker the washing degree is. And it also further verified the previous conclusion that the higher the fractal dimension is, the poorer the reservoir properties are and the stronger the heterogeneity is.

Sandy debris flow of middle Banna Formation in Lizhou area of Baise, Guangxi province

LIZhuan， HE Youbin， XIAO Bin， WANG Zhenqi

2014, Vol.26(3): 93–100 Abstract ( 530 ) PDF (1192 KB) ( 380 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.016

A set of thick turbidite was found in the Middle Triassic in Baise area of Guangxi Province, where incoordinate massive sandstone which has not been aroused concern is also partially developed. Therefore, the origin of the massive sandstone is still unclear. Based on the observation of several field geological sections and integrated with the precious research, we put emphasis on the detailed description and sample analysis of the strata which outcrops well in Lizhou area. According to the lithology characteristics, the middle part of Banna Formation in Lizhou area includes four lithofacies: sliping collapse conglomerate（lithofacies 1）, thin to medium siltstone interbedded and thin to medium mudstone interbed（lithofacies 2）, medium to thick fine sandstone intercalated with thin bedded mudstone（lithofacies 3） and massive fine sandstone intercalated with thin bedded mudstone （lithofacies 4）. These lithofacies may represent that the middle part of Banna Formation formed in the continental slope environment and it is proximal channel deposition. According to the rock textures, sedimentary structures and sedimentary sequence features, the lithofacies 4 is supposed to be sandy debris flow deposition which occurred as lenses in the channel, superimposing with the migration of the channel. Then, through the research above, a sandy debris flow depositional model of the middle part of Banna Formation in the study area has been built up, which reflects the evolution of the channel including erosion, migration and abandonment.

Geochemical characteristics and source rocks and oil-source correlation of the Lower Cretaceous in Aer Sag, Erlian Basin

LU Xuejun， GAO Ping， DING Xiujian， CHEN Zhelong， LIU Guangdi

2014, Vol.26(3): 101–108 Abstract ( 549 ) PDF (998 KB) ( 489 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.017

Aer Sag is one of the sub-structural units in Erlian Basin, with a lower exploration degree. The Lower Cretaceous is proved the major source rocks and oil-producing intervals in Erlian Basin, which is also widely developed in Aer Sag. The organic geochemical analysis indicates that the Lower Cretaceous source rocks in Aer Sag possess high contents of organic matter, its organic matter type is mainly type Ⅰ and type Ⅱ, and its source rock maturity ranges from low-mature to mature indicating the phase of large amounts of hydrocarbon generating. Among them, the first member of Tenger Formation （K1bt1） has the greatest potential of hydrocarbon generation, and followed by the fourth member of Aershan Formation （K1bt4）. The Lower Cretaceous source rocks were mainly deposited in the freshwater to brackish water environment. The redox of K1bt4 preferred to a strongly reducing-weakly oxidizing environment, butK1bt4 tended to a weakly oxidizing environment. The distribution characteristics of regular steranes of the Lower Cretaceous source rocks is “C29>C27>C28”. It is shown that the biogenic sources are dominated by algae input, secondly by terrestrial input. In addition, the correlation of biomarker characteristics of oil sands and source rocks from the Lower Cretaceous suggest that K1bt1 oil originated from K1bt1 itself, but Aershan Formation oil might come from K1bt1 and mixed with the oil from K1bt4 source rocks.

A high-accuracy automatic identification and self-adaptive suppression method for single-frequency interference

CHEN Keyang， CHEN Shumin， LI Lailin， WANG Jianmin，WU Qingling， FAN Xingcai

2014, Vol.26(3): 109–113 Abstract ( 415 ) PDF (885 KB) ( 481 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.018

Industrial electrical interference in seismic data has the characteristics of single-frequency, which can be expressed with sine or cosine function. Therefore, this paper presented a new method of automatic identification and self-adaptive suppression of the single-frequency interference based on normalized cross correlation coefficient. We combined the sine function and cosine function to depict the single-frequency interference within the deep time-window, which can approximate the single-frequency interference that may be contained within the practical seismic data, and then minimized the square difference target function between the practical seismic data and the predicted single frequency interference, and finally computed the amplitude, frequency and phase of single-frequency interference. We carried out the normalized cross correlation computation between the predicted single-frequency interference and the practical seismic data, the larger the normalized cross correlation coefficient is, the more possibility the seismic data contains the single-frequency interference. On the contrary, this seismic trace does not contain single frequency interference or contains single frequency interference with week amplitude that can be ignored. Consequently, we presented a threshold value which is used to select the seismic trace containing single-frequency interference, which is subtracted from the original seismic data. With above processing stages, we finished the automatic identification and selt-adaptive suppression of single-frequency interference from the seismic data. The practical seismic data verifies the effectiveness and accuracy of the proposed method, which is better than conventional band pass filter square energy identifying method and the industrial software over the identification accuracy and suppression effect. In a summary, the proposed method can provide an effective method for the practical seismic data amplitude-preserved processing.

Carbonate reservoir characterization based on low-frequency shadow method by matching pursuit algorithm

SHI Zhanzhan， PANG Su， TANG Xiangrong， HE Zhenhua

2014, Vol.26(3): 114–118 Abstract ( 534 ) PDF (856 KB) ( 529 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.019

This paper focused on the low-frequency shadow caused by the attenuation by absorption of seismic waves in viscous media, which can be used as a hydrocarbon indicator. It is very difficult to detect the low-frequency shadow in deep carbonate reservoir by conventional time-frequency analysis methods, due to the poor seismic resolution resulted by the complex inner structure in stratigraphic and lithologic traps. A new matching pursuit algorithm based low-frequency shadow method for carbonate reservoir characterization was introduced. This paper described the low frequency shadow and the principle of matching pursuit algorithm based on spectral decomposition of seismic signal, and showed that the method has high time-frequency resolution compared with others and it can be used to predict the deep carbonate reservoir. The well drilling data proved the good prediction efforts.

Research on reservoir flow units of Triassic in block-1, Tahe Oilfield

WANG Ke， DAI Junsheng， JIA Kaifu， LIU Hailei

2014, Vol.26(3): 119–124 Abstract ( 593 ) PDF (1143 KB) ( 355 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.020

The research of flow units is the key of deepening and developing reservoir characterization, and it has important theoretical intention and practical value on revealing distribution of remaining oil. Based on establishing classification standard and discriminant of flow units in fluvial and delta facies, this paper classified the reservoir flow units of Triassic in block-1 of Tahe Oilfield, and analyzed the spatial distribution of flow units and its relationship with reservoir architectural structure and remaining oil. The result shows that flow units of the study area can be classified into E（excellent）, G （good）, M（medium） and P（poor） types, while E and G types have the most extensive distribution, and M and P types have smaller distribution area. Meanwhile, the interlayer and interwell flow units have distinct discrepancy. The E type flow unit has consistent distribution with lateral sandbar, and G type flow unit is corresponding to channel deposit and lengthwise sandbar that are sand reservoir bodies with high porosity and permeability, which means that reservoir architecture has favorable correspondence with flow units. E and G types of flow units are the main digging orientation of remaining oil, while M type is the secondary digging orientation. P type of flow unit has limited geological reserves of remaining oil, therefore has less digging potential.

Study on enhancing heavy oil recovery mechanism of antiscaling alkali

TANG Mingguang， LIU Qinghua， ZHANG Guicai， CHEN Lifeng

2014, Vol.26(3): 125–130 Abstract ( 551 ) PDF (932 KB) ( 415 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.03.021

The content of calcium and magnesium ions in the formation water in Xiaba block is relatively high, so scaling problem will occur when use conventional alkali agent such as sodium hydroxide and sodium carbonate. This paper investigated the alkaline which has antiscaling effect, and chose NaBO2 which has strong chelating capacity for calcium and magnesium ions to do indoor research and used sandpacks to evaluate its displacement efficiency. The results show that although the dynamic interfacial tension is high, the displacement efficiency during the sandpacks tests is good. During the displacement process, a large differential pressure response appeared when the alkali concentration is high, and the incremental oil recovery increased with the increase of alkali concentration. Microscopic mechanism shows that the alkaline solution penetrates into the crude oil to form water drops inside the oil phase, and those water drops turn into W/O emulsions subsequently, which could block the water channel and inhibit the viscous fingering, leading to the improvement of sweep efficiency.