Lithologic Reservoirs

Flooding river discharges a sediment-water mixture having a bulk density that often exceeds that of the water in the receiving water body. Consequently,when these flows enter a marine or lacustrine basin they plunge and move basinward as a land-derived underflow or hyperpycnal flow. Deposits related to hyperpycnal flows are hyperpycnites. Some fine hyperpycnites are composed of an inversely graded(waxing flow)basal unit,followed in transition by a normally graded(waning flow)unit.Three main facies families related to the three main elements that govern the movement of almost all sustained hyperpycnal discharges in marine settings:bedload,suspended load and lofting. These facies categories are here termed as B(bedload related sedimentary facies),S(suspended-load related sedimentary facies)and L(lofting related sedimentary facies). Hyperpycnites include three kinds of depositional elements:channel fill,lobes and levee deposits. Although hyperpycnites display typical and diagnostic characteristics that allow a clear recognition,these deposits are often misinterpreted in the literature as sandy debrites,shoreface,estuarine of fluvial deposits.

Review on oil and gas seismogeology models

LIU Zhenfeng

2018, Vol.30(1): 19–29 Abstract ( 439 ) PDF (1255 KB) ( 705 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2018.01.002

Oil and gas seismogeology is more quantitative than other branches in geology for its employing seismic prospecting in petroleum industry and the need of quantitative research of underground objects in oil & gas exploration and development. Oil and gas seismogeology model plays an important role in corresponding quantitative researches. There are many seismogeology models with the research development of oil and gas seismogeology and its applications in petroleum industry. Oil and gas seismogeology models are often referred as the results of integrated seismogeology research,for this reason,it can be divided into four categories:geological structure model,strata sedimentary model,reservoir geological model and fluid distribution model. Based on these categories, this paper elaborated seismic migration,seismic sedimentology,seismic inversion imaging,seismic reservoir characterization methods driven by physical or datum model and seismic fluid identification,and all these technologies are linked closely with all kinds of seismogeology models mentioned above. In view of the integrality and systematicness of integrated seismic geology research,the scale difference and coupling pattern between seismogeology models should be taken seriously. Combined with the recent development of seismic exploration,this paper discussed reverse time migration,seismic inversion imaging marked by full waveform inversion,seismic reservoir characterization methods driven by physical or datum model,seismic fluid identification based on seismic frequency and phase variation,and their influence on seismogeology model research.

Hydrocarbon accumulation conditions and main controlling factors of Chang 7-Chang 9 oil reservoirs of Yanchang Formation in Donghan region,Ordos Basin

CAO Yue, LIU Yanzhe, CHEN Yiguo, MENG Wangcai, GAO Pengpeng

2018, Vol.30(1): 30–38 Abstract ( 493 ) PDF (1539 KB) ( 552 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2018.01.003

The exploration degree is still low in Chang 7-Chang 9 oil reservoir of Upper Triassic in Donghan region of Ordos Basin. Based on the drilling and logging data from 87 wells and thin section observation,physical property analysis and oil test for 15 wells,under the guidance of geology theory of tight hydrocarbon accumulation,the source rocks,sedimentary microfacies,reservoir properties and cap rock were studied,and the main controlling factors of reservoir were discussed in terms of reservoir distribution,source rocks,sedimentary microfacies, structure and cap rock. The results show that:(1)Two sets of hydrocarbon source rocks are developed in Chang 7 and Chang 9 oil reservoirs,with Chang 7 source rock being the main source rocks. Subaqueous distributary channel and subaqueous interdistributary bays are developed,the fine sandstone in subaqueous distributary channel is the main reservoir,and lithic feldspathic sandstone is the main rock type,with poor physical properties. Mud shale deposited during the lake flooding period and mudstone in distributary bay are the main cap rocks; (2)The effective matching among hydrocarbon source rocks,sedimentary microfacies,superimposed contiguous lithologic changing zones of subaqueous distributary channel in delta front,and nose uplift zones,is the key for reservoir-forming and exploration breakthrough of tight sandstone.(3)There are two types of hydrocarbon reservoir assemblage,the type of self-generation and self-storage is dominated in Chang 7 oil reservoir,and the type of upper-generation and lower storage is dominated in Chang 8 oil reservoir. The results are helpful for guiding the deep exploration and deployment in this area,and also have reference significance for similar areas.

Geochemistry of hydrocarbon source rocks of Chang 7 in Ganquan-Fuxian area,Ordos Basin

YUAN Yuan, DU Kefeng, GE Yunjin, WU Feng, SONG Jian

2018, Vol.30(1): 39–45 Abstract ( 465 ) PDF (1133 KB) ( 544 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2018.01.004

Ganquan-Fuxian area is a main enrichment area of tight oil in Yanchang Oilfield,Ordos Basin,however, the resource potential and enrichment law are unclear,and the exploitation risk is large. The data of cores and logging were used to study the distribution of Chang 7 source rocks,and the total organic carbon,pyrolysis,chloroform bitumen "A" and vitrinite reflectance(Roc)were analyzed to evaluate the hydrocarbon-generating potentials of Chang 7 source rocks. The results show that the organic matter is mainly of Ⅰ and Ⅱ 1 type and in a maturate oil generation stage,with great hydrocarbon-generating potential,which is determined to be relatively good source rocks. The thickness and organic matter abundance of Chang 7 source rocks are controlled by sedimentary environment. The Chang 7 source rocks are mainly distributed in northwestern deep to semi-deep lake sedimentary area near the center of the lake basin,with the thickness of 50-70 m,which can be the key area for the next tight oil exploration. The research result is helpful for guiding the evaluation of hydrocarbon geochemical characteristics and hydrocarbon generation potential and the prediction of favorable oil and gas areas.

Sedimentary characteristics and distribution regularities of Ordovician carbonate grainstone shoals in Tabei area,NW China

SONG Qian, MA Qing, LIU Ying, TENG Yiwei

2018, Vol.30(1): 46–54 Abstract ( 449 ) PDF (1790 KB) ( 514 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2018.01.005

The data of seismic,logging,core and thin sections were used to analyze the petrology characteristics, sedimentary characteristics,vertical depositional combination and distribution regularities of Ordovician Yijianfang Formation and Lianglitage Formation in northern Tarim Basin,and the main controlling factors of carbonate shoals development and the possibility about effective reservoir development of Lianglitage Formation were discussed. The results show that the sedimentary microfacies of Yijianfang Formation can be divided into four types:intraclastic shoal,algaeclastic shoal,bioclastic shoal and oolitic shoal. Tabei area was shallow and width platform during the Yijianfang Formation depositional stage,thick-layer grainstone shoal and reefs were developed vertically. The platform grainstone shoals present plate-like with good lateral continuity,and the reefs scattered among high-energy zones. The sedimentary microfacies of Lianglitage Formation can be divided into five types:intraclastic shoal,algae clastic shoal,bioclastic shoal,oolitic shoal and oncolite shoal. Tabei area turned into weak rimmed platform during the Lianglitage Formation depositional stage. The water was deep and less high-enegry facies developed. Medium-thick layer grainstone shoals and reefs were developed vertically. The grainstone shoals distributed as plate-like among the depression,and around the paleo-uplift as circle-type distribution. The development of grainstone shoals was mainly affected by relative sea level change,hydrodynamic conditions and paleogeomorphology. The development scale of grainstone shoal during Lianglitage Formation depositional stage is less than that of Yijianfang Formation depositional stage,however,the grainstone shoals in platform margin still could develop into effective reservoir,which is potential oil-gas reservoir.

Pore structure and fractal characteristics of Longmaxi shale in southern Sichuan Basin

CHEN Jukai, ZHU Yanming, CUI Zhaobang, ZHANG Chuanghui

2018, Vol.30(1): 55–62 Abstract ( 420 ) PDF (1344 KB) ( 568 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2018.01.006

The pore development characteristics of Longmaxi shale in the southern Sichuan Basin have influence on shale gas occurrence and flow process. To scientifically evaluate the influence,the high-pressure mercury intrusion,low-temperature nitrogen and carbon dioxide adsorption were comprehensively used to characterize the pore structure,and the fractal fitting of pores in different size was made to calculate the integrated fractal dimensions,and combined with geochemistry and mineral composition,the influencing factors of the integrated fractal dimensions were discussed. The results indicate that the pore diameter distributions of the samples are multi-modal. The pores in different stages account for the pore volume to some extent,whereas micropores and mesopores account for the pore specific surface area. The pores of Longmaxi shale have self-similarity according with fractals laws,and compared with mesopores and micropores,the structure of macropore is more complex. Considering the pore volume of different pore diameters as the weighted value,the calculated integrated fractal dimensions are from 2.491 to 2.623,with an average of 2.560. The organic carbon content and mineral composition have an obvious controlling effect on the integrated fractal dimension which becomes larger with higher organic carbon content and more complex pore structure. The brittle mineral content is negatively correlated with the integrated fractal dimension,while the maturity and clay minerals have a positive influence on it.

Dolomite reservoir types and development models of Middle-Upper Cambrian in Tarim Basin

WANG Xiaoli, LIN Changsong, JIAO Cunli, HUANG Lili

2018, Vol.30(1): 63–74 Abstract ( 335 ) PDF (2007 KB) ( 451 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2018.01.007

Dolomite reservoirs are extensively developed in Tarim Basin,however,the types,characteristics and genesis have not been research thoroughly and are debated. Based on the data of outcrop,cores,loggings and seismic,the sedimentology,reservoir sedimentology and sedimentary geochemistry were applied to study the reservoir space characteristics and controlling factors of the main dolomite reservoirs in the Middle-Upper Cambrian. The result shows that there are five types of dolomite reservoirs are developed in the Middle-Upper Cambrian,including evaporative tidal flat,reef shoal,hydrothermal fluid fracture,epigenetic karst-hydrothermal superposition and burial type. The reservoir spaces,development and distribution were controlled by depositional setting,dolomitization,karstification,deep fluid reformation. Three favorable types of dolomite reservoir development models were established,such as reef shoal type,epigenetic karst-hydrothermal superposition type and evaporative tidal flat type,and the favorable developmental areas were predicted. The research results have reference significance for the oil and gas exploration of the Middle-Upper Cambrian dolomite reservoirs in Tarim Basin.

Characteristics and main controlling factors of carbonate reservoirs of Longwangmiao Formation in eastern Sichuan Basin

HAN Bo, HE Zhiliang, REN Nana, TIAN Haiqin, MA Qiang

2018, Vol.30(1): 75–85 Abstract ( 364 ) PDF (2139 KB) ( 542 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2018.01.008

It is the Lower Cambrian Longwangmiao Formation in Sichuan Basin that has become an important reservoir rocks for oil and gas exploration with the discovery of Anyue gas field. Based on the investigation of the outcrops and the boreholes,the characteristics and major controlling factors of the Longwangmiao carbonate reservoirs in the eastern Sichuan Basin were studied by using optical,casting thin sections,X-ray diffraction,order degree of dolomite,carbon,oxygen isotopes analyses,as well as physical property analyses. The following conclusions can be drawn. The main sedimentary facies of Longwangmiao carbonates mainly include the restricted platform and open platform,followed by the tidal flat,grain bank,limestone flat microfacies,etc. Especially, there are many grain shoal and tidal flat groups or rhythms in a single sequence system tract. The lithology of reservoir rocks mainly consists of granular dolomite and the crystalline dolomite,followed by granular limestone with partly dolomitized. The reservoir physical property of granular dolomite is superior to powder and fine crystalline dolostones,the granular limestone with partly dolomitized has limited reservoir properties and the nondolomitization part has little reservoir space. The reservoir spaces are dominated by intergranular denudation pore,intercrystalline denudation pore and micro-fissure. It is revealed that the grain shoal microfacies with high degree of dolomitization is a prerequisite to reservoir rocks,the grain shoal microfacies is the material bases of developing the Longwangmiao formation reservoirs,penecontemporaneous and early stage of diagenesis dolomitization and penecontemporaneous dissolution are the key factors to form the reservoir.

Sedimentary characteristics and development model of fan delta in small faulted basin: a case of Shahezi Formation in northern Xujiaweizi Fault Depression,NE China

CAI Quansheng, HU Mingyi, CHEN Xiaohong, HU Zhonggui

2018, Vol.30(1): 86–96 Abstract ( 388 ) PDF (2086 KB) ( 528 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2018.01.009

The geological knowledge of fan delta in small-scale faulted basins will be of important significance for oil & gas exploration. Taking Shahezi Formation in the northern Xujiaweizi Fault Depression as an example, the data of core,logging and seismic were used to study the sedimentary characteristics and development model of fan delta in a small faulted basin formed during the intensive rifting stage. The results show that fan delta develops in Shahezi Formation within the study area,and the sediments of fan delta are mainly composed of brown to grey sandy conglomerate with low maturity,brown and black mudstone,and locally distributed carbonized mudstone. On the logging curves,the sandy conglomerate appears as zigzag shape with medium amplitude and zigzag box;on the imaging logging profiles,the conglomerates with high content of argillaceous sediments appear as bright spots with different size on black background. Furthermore,according to well-seismic calibrating,the sediments of fan delta typically show sphenoid progradation reflections,moundy and sphenoid disorder reflections on seismic profiles. By the analysis of fan delta distribution in Shahezi Formation,it indicates that the development of fan delta is closely related to basin scope and tectonic features. During the early sedimentary stage of the Shahezi Formation,not only the west steep slope but also the east gentle slope was dominated by fan deltas due to the small scope of the basin and sufficient sediments with short transportation distance. However,with the continuous activity of basin-controlling fault and the extension of basin,the fan delta on east gentle slope was gradually replaced with braided delta,and the differentiation characteristics of sedimentary facies on different tectonic belts become obvious. According to these features above,the development model of fan delta in a small fault basin formed during the intensive rifting stage was proposed,which will be very important for the oil and gas exploration in similar basins.

Description and distribution characteristics of Lower Carboniferous karst reservoir of Asa block in Marsel area,southern Kazakhstan

ZHAO Bozhi, LIN Changsong, LI Hao, WANG Yuan, SUN Yanda, HE Haiquan, WANG Qinglong

2018, Vol.30(1): 97–111 Abstract ( 381 ) PDF (2409 KB) ( 490 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2018.01.010

The Asa block located in Marsel exploration area at the north and middle of Kazakhstan has a good condition for natural gas deposits,and the Lower Carboniferous carbonate rocks have a rich gas display,which becomes a new breakthrough in recent exploration phase. As found in the related study,the favorable reservoir development is closely related with karstification. The imaging logging data,combined with cores,conventional logging curves and logging cross plots,were used to divide karst structural units for typical single wells in the study area. The results show that except Tournaisian(C1t),Karst developed in all the other layers of the Lower Carboniferous in Asa block,especially developed in Visean(C1v3)and Serpukhovian(C1sr). A fine description of the main karst section was conducted by using imaging logging and the result shows that karst in C1sr and in C1v3 has obvious different characteristics. Moreover,there are two sets of karsts developed in C1sr,and they are below the gypsum rocks which can indicate arid environment. Through horizontal well-tie section contrast,C1v3 has the features of epigenic karst and obvious vertical distribution and it can be divided into the weathering crust palaeosol,vertical vadose karst zone and horizontal underflow karst zone from the top to the bottom. The vertical vadose karst zone is dominated by high angle dissolved enlarged fractures,while horizontal underflow karst zone is dominated by low angle dissolved enlarged fractures and unfilled caverns. This study result is helpful for guiding fine description of carbonate karst reservoirs and searching for favorable carbonate karst reservoirs.

Lithofacies characteristics and identification methods of Mesozoic volcanic rocks in Bohai Sea

CAI Dongmei, YE Tao, LU Fengting, GAO Kunshun, REN Yunpeng

2018, Vol.30(1): 112–120 Abstract ( 480 ) PDF (1839 KB) ( 786 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2018.01.011

With great control effects on volcanic reservoir forming, volcanic facies identification is an effective way to reduce the exploratory risk. Based on the geologic and drilling data,the types of volcanic facies were defined, and the lithofacies characteristics of Mesozoic volcanic rocks in Bohai Sea were analyzed through electrofacies analysis,seismic facies identification and seismic attribute analysis,and the identification methods for different types of lithofacies were studied. The results show that the Bohai Sea area is dominated by intermediate basic volcanic eruption,and the volcanic facies include eruptive facies,effusive facies,volcanic vent facies and volcanic sedimentary facies,dominated by effusive facies. The effusive facies has the characteristics of high resistance,low acoustic time difference,and the basic effusive facies has lower gamma ray value compared with neutral effusive facies. The eruptive facies is characterized by high acoustic time difference and low resistance,and the density of volcanic breccia is greater than that of tuff. From 3D seismic data,the eruptive facies and volcanic vent facies are mainly clutter reflection,with low frequency and medium amplitude,while Effusive facies are characterized by continuous and strong amplitude and low frequency,and volcanic sedimentary facies has the characteristics of continuous medium frequency and weak amplitude reflection. The eruptive facies and neutral effusive facies are favorable reservoir rocks in the study area.

Shale lithofacies identification and classification by using logging data: a case of Wufeng-Longmaxi Formation in Fuling Gas Field,Sichuan Basin

CHE Shiqi

2018, Vol.30(1): 121–132 Abstract ( 417 ) PDF (1697 KB) ( 273 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2018.01.012

With the development of Fuling shale gas field production,the marine shale reservoirs in Fuling Gas Field show obvious heterogeneity and complex lithology. Based on the comprehensive and accurate ECS(Elemental Capture Spectroscopy Sonde)special well logging data of Wufeng-Longmaxi Formation shale,the siliceous component sources were analyzed,and according to the ECS special well logging data and thin section,combined with the different sources of siliceous components,the ternary diagram of shale mineral component was established to accurately divide shale lithofacies. The log response characteristics of different shale lithofacies were analyzed by using conventional logging data,and uranium-free gamma ray and density logging which are sensitive to shale lithofacies were selected to establish shale lithofacies identification logging plate. The result shows that the shale facies identified by conventional logging data is in accordance with the recognition results by ECS special logging data. When the TOC mass fraction of Wufeng-Longmaxi Formation shale is greater than 2%,the source of siliceous components is dominated by biogenic factors,when the TOC mass fraction is less than 2%, the source is mainly terrigenous debris. Eight kinds of lithofacies of Wufeng-Longmaxi Formation shales were identified,including siliceous shale,mixed siliceous shale,clay-rich siliceous shale,carbonate-rich siliceous shale,mixed shale,argillaceous-silty mixed shale,clay-rich silty shale and silty-rich argillaceous shale. The most favorable shale lithofacies was defined as the siliceous shale and mixed siliceous shale with high siliceous content and high TOC content. The result could effectively improve the accuracy and practicability of shale lithofacies classification and it is significant for the efficient development of shale gas resources.

Prediction for fractured tight sandstone reservoir of Xu 4 member in eastern Yuanba area,northeastern Sichuan Basin

ZHANG Hui, GUAN Da, XIANG Xuemei, CHEN Yong

2018, Vol.30(1): 133–139 Abstract ( 369 ) PDF (1531 KB) ( 462 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2018.01.013

The tight-fracture reservoir is an important reservoir type of Triassic Xujiahe Formation in Sichuan Basin. Since the reservoir has low porosity,low permeability and strong heterogeneity characteristics,the accurate prediction of properties of Xujiahe Formation is the key and difficult point of oil and gas exploration and development in northeastern Sichuan Basin. Facing with these problems,We proposed a theoretical workflow of reservoir prediction. The main idea of our workflow is to define sand in face and define fracture in sand. Firstly,the distribution of favorable sand was predicted by seismic attributes and seismic inversion on the basis of facies-controlled techniques;then using pre-stack and post-stack technology to predict multi-scale fractures,at the same time,based on the method of relation of fault-fracture and difference of reservoir-cap to evaluate effective faultfracture system;Finally,considering the prediction result of sand and fractures point out the favorable exploration target area. The reliability of our method has been testified by comparing with drilling data,and we believe our method can be used to predict others tight sandy reservoir.

Distribution characteristics and influencing factors of movable fluid in tight sandstone reservoirs: a case study of Lucaogou Formation in Jimsar Sag,NW China

LI Min, WANG Hao, CHEN Meng

2018, Vol.30(1): 140–149 Abstract ( 435 ) PDF (1625 KB) ( 526 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2018.01.014

Determining the content,distribution and influencing factors of movable fluid is the basis for effective evaluation of the development potential of tight reservoir. 21 samples of tight sandstone reservoirs of Lucaogou Formation in Junggar Basin were selected to measure the NMR T2 spectrum at different degrees of water saturation by using NMR T2 spectrum analysis and centrifuge tests,and the influencing factors of the differences in the movable fluid were analyzed by cast thin section and scanning electron microscopy. The results show that the T2 spectrum of reservoir rocks is mainly manifested by five forms,and the complexity of reservoir micro-characteristics and pore throat structure are the main reasons for the various types of NMR T2 spectrum. The best centrifugal force for tight oil reservoir to make bound water state is 400-450 psi,the saturation of movable fluid is 29.44%-68.92%,and the average value is 46.69%. The content and distribution of the movable fluid in different rock samples are obviously different,and the minimum of pore throat radius of the movable fluid distribution is about 50 nm,and the mainstream throat radius is 70-200 nm. The relationship between movable fluid content and physical property shows that for the reservoirs with poor physical properties,the permeability is the main controlling factors,but for the reservoirs with better physical properties,the impact of permeability on the movable fluid content is small. The pore type,shape and surface roughness all affect the content and distribution of the bound water. The development and distribution of secondary pores,the size of pore throat and its connectivity,the filling degree and occurrence of clay minerals and the development of cracks,are the influencing factors of movable fluid content. These results can provide a basis for evaluating the development potential of tight reservoirs.

Classification of Fuyang oil reservoir with ultra-low permeability around placanticline of Daqing Oilfield

YIN Daiyin, XIANG Junhui, WANG Dongqi

2018, Vol.30(1): 150–154 Abstract ( 374 ) PDF (1147 KB) ( 454 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2018.01.015

In order to meet the demand of fine waterflooding of Fuyang oil reservoir with ultra-low permeability around placanticline of Daqing Oilfield,the method of reservoir classification limit is usually used to realize the reasonable classifications on ultra-low permeability reservoir blocks at early stage of production. However,for some ultra-low permeability blocks,different classification parameters fall into different classification results, which exacerbates the non-determinacy of results. To solve this problem,on the basis of existed achievements of classification limits for Fuyang oil reservoirs with ultra-low permeability,the method combined multi-parameter cluster analysis,dynamic and static consistency test with comprehensive evaluation was established. The classification evaluation criteria for two groups and four sub-groups were determined,and the classification results of each block were verified. The results show that this method solves the problem of classification difficulty caused by different classification parameters of individual blocks falling into different classification results,and realizes the reasonable classifications of 63 developed ultra-low permeability blocks. In addition,it has the characteristics of simple calculation and high accuracy,which provides a powerful basis for efficient and fine classifications of ultra-low permeability blocks in Daqing Oilfield.

Estimating method of braided channel bar under sparse well net: a case from Su X block in Sulige Gas Field

CUI Lianke, SHAN Jingfu, LI Fuping, CUI Lu, CHONG Jian

2018, Vol.30(1): 155–164 Abstract ( 374 ) PDF (1679 KB) ( 483 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2018.01.016

In the braided river sedimentary environment,braided channel bars are more important reservoir sand body for oil and gas accumulation. How to identify braided channel bars by drilling well data,and then combine in plate,moreover,predict the distribution of channel bars,is the foundation for correctly understanding braided river deposits. The fine geological study of fine subzone division and correlation and sedimentary microfacies distribution in Su X block of Sulige Gas Field is insufficient,and single well yield and ultimate recovery are low. Based on the data of logging,field outcrop and modern satellite images,combined with fine stratum classification,sand thickness center line connecting method,braided bar logging phase separation method,radar map of braided bar and braided bar prediction technology,were used to identify and characterize single channel and braided bar,compile the radar map of braided bar and predict the braided bar. The results show that the layer of 1-1 and 1-2 of the lower He 8 member both developed three channels. The braided bar is given a length to thickness ratio of 60:1-80:1,a width to thickness ratio of 30:1-40:1,and a length to width ratio of 2:1-3:1, while the length is 300-1 100 m and the width is 150-550 m. The single channel sand thickness is inversely proportional to the number of braided bar. The results of infill wells show that the radar map of braided bar and prediction technology both have high credibility. The above methods can improve the drilling ratio of braided bar, provide a better condition for the arrangement of infill wells and horizontal wells and improve oil and gas recovery efficiency,and provide reference for the study of sand body distribution and space superposition in the block with similar stratum structure and well density.

Fracturing technology for thin layer in tight sandstone reservoir and its application

LIU Jiankun, JIANG Tingxue, WAN Youyu, WU Chunfang, LIU Shihua

2018, Vol.30(1): 165–172 Abstract ( 556 ) PDF (1147 KB) ( 908 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2018.01.017

In order to solve the fracturing problems in the thin layer of tight sandstone reservoir,such as difficulty of controlling fracture height,low stimulated reservoir volume, low proppant supporting efficiency,the maintaining of flow conductivity etc.,the difficulties of fracturing in such reservoir were analyzed by the means of simulating how different kinds of fracturing fluid under different fracturing construction parameters affect the fracturing parameters,and the main controlling factors were obtained. On this basis,a fracturing technological method for controlling fracture height and improving fracture supporting efficiency was formed. The result shows that the main factors affecting the expansion and extension of the fracture are the viscosity of fracturing fluid,followed by the construction displacement and the liquid quantity. The thin layer fracturing should be based on the controlling of fracture height,make full use of the natural fracture,and improve the construction volume and the supporting efficiency. Low viscosity fracturing fluid is suitable for thin layer volume fracturing for it can take into account the role of controlling fracture height and making long fracture length in thin layer fracturing,which is beneficial for opening and expanding natural fractures,and further reducing reservoir damage. The combination of multi-viscosity fracturing fluid system at different stages of pump construction can not only expand the effective fracture volume and form multi-scale fracture system,but also take into account the requirement for controlling fracture height in the front fluid stage and carrying proppant in the carrying stage. Variable density proppant combined with multi-scale proppant adding method can match different size proppant with different scale fracture system, and improve the supporting efficiency of multi-scale fracture system and fractures in far well zone. The research result was successfully used in many wells in Longfengshan thin layer gas reservoir and Jiangling thin layer oil reservoir. According to the testing result,the production was far better than that of conventional fracturing method and the stable production period was improved effectively. This method improved the effectiveness of thin layer fracturing.