Lithologic Reservoirs

Under the guidance of sequence stratigrapy and sedimentology, Wenchang Formation in Panyu 4 depression is subdivided into six third-order sequences based on the features of seismic reflection termination, and the distribution of sequence is significantly controlled by fault activity. The seismic facies, including high-amplitude and high-continuity wedge facies, hummocky facies, progradation facies, have been recognized based on the seismic internal reflection configuration and external shape. Controlled by basin texture and fault activity of Panyu 4 depression, wedge-seismic facies is mainly distributed in the downthrow side of boundary fault in the eastern depression, and progradation-seismic facies is mainly distributed in the gentle slope of the western depression. The distribution of seismic facies of Wenchang Formation is asymmetry in the plane and stongly inherited in the vertival profile. Large-scale coarse-grained nearshore subaqueous fans developed in the downthrow side of boundary fault of the eastern Panyu 4 depression were supplied by Dongsha uplift, and the medium-small scale and multi-type deltas came fromthe west and southside of western gentle slope．

Study on sequence models and controlling factors of Paleogene Dainan Formation in Gaoyou Sag, northern Jiangsu Basin

JI Youliang， WANG Yong， LI Qingshan， HU Bin

2014, Vol.26(4): 9–15 Abstract ( 521 ) PDF (796 KB) ( 475 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.04.002

According to core, drilling, seismic data and laboratory analysis, this paper carried out a comprehensive study on sequence stratigraphy of Paleogene Dainan Formation in Gaoyou Sag. The sequences were divided into three third-order sequences and eight fourth-order sequences accorded to the identifying mark of sequence boundary, and the sequence strtigraphy framework was established. Two kinds of sequence models were established. One is a completed lacustrine sequence model, and it is composed of lowstand system tract, transgressive system tract and highstand system tract. Another is an uncompleted lacustrine sequence model, and it is composed of lowstand system tract and transgressive system tract. At last, the controlling factors to the sequence development were analyzed. It is considered that the tectonic subsidence is the main controlling factors for the third-order sequence structure, and that the lake level change caused by the climate and the rate of sediments supplying are the main controlling factors for the fourth-order sequence in this area.

Skin factor of horizontal wells

LI Chuanliang， ZHU Suyang

2014, Vol.26(4): 16–21 Abstract ( 642 ) PDF (576 KB) ( 830 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.04.003

Horizontal wells have advantages to vertical wells in developing low quality petroleum resource. However, the conventional production rate equations of horizontal wells seldom take into account the skin factor of wells, with which production rates of horizontal wells cannot be well predicted. Based on the equivalent flow resistance theory, a new production rate equation of horizontal wells was derived in this paper with the skin factor. Two skin factors are introduced into the new equation, which are formation damage skin factor and formation improvement skin factor. The formation damage skin factor is resulted from mud intrusion in drilling and completion of wells, while the formation improvement skin factor is resulted from stimulations of wells such as acidizing and fracturing. The two factors have different effects on production rates of horizontal wells. The formation damage skin factor affects production rate of horizontal wells to a quite small extent, however the formation improvement skin factor to a quite great extent. So, the formation protection in drilling and completion of horizontal wells are not necessary, while the stimulations are effective methods to enhance the productivity of horizontal wells.

Depositional system evolution and provenance orientation in the eastern Maichen Sag, Beibu Gulf Basin

HU Hao， LU Yao， TANG Qunying，WANG Min

2014, Vol.26(4): 22–27 Abstract ( 753 ) PDF (1082 KB) ( 503 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.04.004

Based on the data of rock slice, cast thin section, scanning electronic microscope, fractional and reservoir physical properties analysis, this paper summarized reservoir space and pore structure of Xujiahe Formation in northeast Sichuan Basin, analyzed the diagenesis types, and quantitatively calculated the pore evolution process. The research reveals that the reservoir of Xujiahe Formation is in the middle diagenetic B phase. The diagenesis includes compaction, cementation, dissolution and tectonic fracturing. The average original porosity is 31.1%. 45.74% pores are lost for compaction, and 22.51% pores are filled by cementation. However, the porosity was added to 6.4% because of dissolution and tectonic fracturing, which improved the reservoir quality in some degree. The result of calculated porosity is in accord with actual porosity, which shows the feasibility of this method, and it contributes directive meanings in the evaluation of diagenetic evolution.

Sedimentary and reservoir characteristics of glutenite in Yan 18-Yong 921 area, steep slope of Dongying Sag

XIAN Benzhong， LU Zhiyong， SHE Yuanqi， WANG Xin， WANG Lu， HUANG Handong

2014, Vol.26(4): 28–35 Abstract ( 547 ) PDF (1029 KB) ( 604 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.04.005

Steep slope of rift basins with strong faults activities is characterized by deep water gravity flow sandstone and conglomerate and high-quality source rocks in the same layer. As a result, reservoir properties became the key factor for hydrocarbon exploration in this area. In this paper, strata division, sedimentary facies and reservoir characteristics were studied to well understand the forming rules of high-quality reservoir of the lower third member of Shahejie Formation（E2 s3x）and the upper fourth member of Shahejie Formation （E2 s4s ）in steep slope in Yan 18-Yong 921 area, Dongying Sag. Geological-seismic integrated sedimentary facies study shows that basin filling processes and sedimentary facies composition were mainly controlled by the evolution of boundary faults, and sedimentary system evolution from bottom to top included three stages as follows: fan delta with shallow water, deep water near shore subaqueous fan to flooding lacustrine basin fan and deep water near shore subaqueous fan to slump lacustrine basin fan. The reservoir spaces mainly come from pore, with less fractures. Sedimentation is the key controlling factor of reservoir properties when the buried depth is less than 2 600 m. However, dissolution increased when the buried depth is more than 2 600 m and the reservoir entered into the late diagenetic stage. According to the analyses of reservoir controlling factors, we proposed that high quality reservoirs come from mid-fan of near shore subaqueous fan in E2 s3x and sand group Ⅰ-Ⅳ of E2 s4s ,flooding lacustrine basin fan in sand group Ⅴ and Ⅵ of E2 s4s and fan delta front in sand group Ⅶ and Ⅷ of E2 s4s .

Characteristics and origin of low porosity and low permeability sandstone reservoir of Wenchang Formation in HZ25-7 structural belt of Huizhou Depression

GE Jiawang， QIN Chenggang， ZHU Xiaomin， CHEN Shuhui， L IU Yinghui， ZHANG Xin

2014, Vol.26(4): 36–43 Abstract ( 673 ) PDF (1127 KB) ( 590 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.04.006

Huizhou Depression is an important oil and gas-rich region of Pearl River Mouth Basin. HZ25-7 structural belt is an important area designed for seeking oil and gas of Wenchang Formation in Huizhou Depression. The research of reservoir characteristics and mechanism of Wenchang Formation is the foundation of oil exploration breakthrough. Based on comprehensive analysis of various data such as drilling, casting thin sections, scanning electronic microscope, physical properties analysis and mercury penetration test, this paper analyzed the reservoir characteristics and mechanism of Wenchang Formation of HZ25-7 structural belt. The results show that sandstones are mostly litharenite and feldspathic litharenite, and are generally immature both texturally and compositionally. The average porosity and permeability of the sandstones are 12% and 7.1 mD respectively, and it is emphatically defined as the low porosity and low permeability reservoir. Pore types are mainly intragranular dissolved pores and primary intergranular pores, and its micro-pore structure is typical medium-micro pore and fine throat, with poor pore connectivity. Such low porosity and permeability reservoir of Wenchang Formation is controlled by depositional conditions and diagenesis. Braided fluvial deltaic depositional environment characterized by near provenance determined the large quantity of ductile grains in detrital composition and the infilling of part of primary pores by resulting matrix. Strong compaction results in primary porosity loss significantly. Due to low content in soluble grains, the improvement of physical properties mediated by organic acid is not obvious. Clay and carbonate cementations lead to continued worsening of reservoir properties and tightening, but abnormal overpressure is constructive to the preservation of reservoir porosity.

Characteristics and genesis of clastic reservoir with low porosity and low permeability of Lower Cretaceous in Tanzhuang Sag

ZHANG Qin， ZHU Xiaomin， LIU Chang， JI Hancheng，CHEN Xiang

2014, Vol.26(4): 44–49 Abstract ( 586 ) PDF (777 KB) ( 671 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.04.007

The average porosity and average permeability of clastic reservoir of Lower Cretaceous in Tanzhuang Sag are respectively 6.1% and 10.5 mD based on the data of cores, thin section, and scanning electron microscope, which means that the reservoir belongs to low porosity and low permeability reservoir. Porosity and permeability decrease from Shangshui Formation to Bacun Formation with depth getting deeper except in Ba 1 well. The reservoir properties of the Lower Cretaceous are mainly influenced by depositional conditions, diagenesis and tectonization. Low textural and compositional maturity, strong compaction and cementation and weak dissolution are composed of the essential and significant factors for the low porosity and low permeability, while fractures caused by tectonization mostly are filled by minerals as a result of little improvement of the reservoir properties.

Characteristics and main controlling factors of Chang 4+5 oil reservoir set in Longdong area, Ordos Basin

L I Panpan， ZHU Xiaomin， ZHU Shifa， L IANG Xiaowei， NIU Xiaobing， ZHENG Qinghua

2014, Vol.26(4): 50–56 Abstract ( 651 ) PDF (1007 KB) ( 501 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.04.008

The Chang 4+5 oil reservoir set of Triassic Yanchang Formation in Longdong area developed delta and lacustrine facies. The reservoir rock types are mainly lithic arkose,feldspathic litharenite and litharenite. The reservoir is typical low porosity and low permeability reservoir with the average porosity of 11.02% and average permeability of 0.37 mD. The main pore types are intergranular pores and intragranular dissolved pores. The pore structure is tiny pore and micro throat with poor sorting and connectivity. In profile, the reservoir properties of Chang 4+51 sublayer are better than that of Chang 4+52 sublayer, and the reservoir properties in the southwest are better than that in the northeast. The clastic rocks experienced compaction, cementation and dissolution. Diagenesis is the basis for the reservoir tightening, while diagenesis is the key factor for forming thigh reservoir. The strong compaction and cementation are the main diagenesis for influencing reservoir properties. The underwater distributary channel and the mouth bar sand body in delta front are favorable reservoirs, and the reservoir properties in the central part of the sand body are the best.

Characteristics of major gas-bearing reservoirs in western Sulige Gas Field

XIE Qingbin, TAN Xinyu， GAO Xia， LIANG Xinping， LAI Changjie， WANG Zhifang

2014, Vol.26(4): 57–65 Abstract ( 683 ) PDF (1167 KB) ( 592 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.04.009

In western Sulige Gas Field, the eighth member of Shihezi Formation and the first member of Shanxi Formation are the major gas-bearing reservoirs. Shan 1 member developed anastomosing river deposit, and He 8 member developed braided river deposit, in which the facies transited from braided river to meandering and anastomosing river from bottom to top. The rock types of the main gas-bearing reservoirs are lithic sandstone and lithic quartz sandstone, with little quartz sandstone, and they are characterized by low compositional maturity. Pore spaces always occur as the combination form, the pore types are mainly composed of debris dissolved pores and intercrystal pores, and little primary intergranular pores. The pore structure has features of small pore-narrow throat, high displacement pressure and narrow main contribution throat. The average porosity is 6.23%, while the average permeability is 0.4 mD, so the reservoir is characterized by low porosity and low permeability. On the basis of diagenesis analysis, the reservoir is in the middle diagenetic phase B. The reservoir properties are mainly controlled by sedimentary microfacies and diagenesis, and the heterogeneity is strong.

Characteristics of tight oil reservoirs of the Permian Fengcheng Formation in Wu-Xia area, Junggar Basin

L IU Yinghui， ZHU Xiaomin， ZHU Mao， L IAO Zongbao， WANG Xiaojun， WANG Junhuai

2014, Vol.26(4): 66–72 Abstract ( 631 ) PDF (1214 KB) ( 709 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.04.010

Tight oil reservoirs have become popular targets in petroleum exploration both at home and abroad in recent years. This paper studied the rock types, reservoir space, physical properties and main influencing factors for “sweet spots” of tight oil reservoirs of Permian Fengcheng Formation in Wu-Xia area by using petrography, SEM, cathodoluminescence and core analysis. The result shows that the reservoir of Fengcheng Formation consists of dolomitic rock, tuff, siltstone, mudstone and salt beds, with the first present predominantly in the reservoirs. The main reservoir spaces are fractures, dissolved pores, intracrystalline pores and intergranular pores. Fracture and dissolved porosity in the reservoirs are around 53% and 35% respectively. The porosity is 1%～10%, with an average porosity of 3.86%. The average permeability is 0.17 mD, and the samples that the permeability is less than 2 mD account for more than 85%. The reservoir belongs to low porosity and low permeability reservoir. The “sweet spots” of the tight oil reservoir is mainly influenced by dolomitization, fracturing and dissolution.

Advancement on formation mechanism of deep effective clastic reservoir

PAN Rong， ZHU Xiaomin， WANG Xingxing， ZHANG Jianfeng

2014, Vol.26(4): 73–80 Abstract ( 610 ) PDF (901 KB) ( 1369 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.04.011

As petroleum exploration goes into a more and more mature stage, deep clastic reservoir is becoming an important new area for exploration in the oil-gas basins. The research of deep petroleum exploration is focusing on the mechanism of the clastic reservoir evolution. The formation mechanism of the deep effective clastic reservoir is complex and closely connected to the sedimentation, diagenesis and tectonism. Sedimentary environment is the prerequisite and foundation for forming effective reservoir. Secondary pore produced by the main constructive digenesis vastly improves reservoir physical properties. Depositional environment and diagenetic conditions that can prevent or slow down diagenesis effectively is conductive to the reservoir physical properties, including low geotemperature, rapid burial history, abnormal pressure, gypsum-salt bed effect, hydrocarbon inject, grain coats and fluid activity, etc. During the evolution of deep reservoirs, tectonic compaction reduces the pore volume, while the structural fractures improve the seepage ability of the reservoir porosity, forming effective fractured reservoir. Thus, the reservoir forming mechanism was suggested with the deposition, dissolution and tectonism being fundamental, key and occasion respectively. Through using modern technology, conducting the diagenesis modeling experiments and using new methods with the inter-discipline knowledge, have already become the main development trends of the research of the forming mechanism of the deep effective clastic reservoir.

Characteristics and controlling factors of low porosity and low permeability reservoir of the second member of Jialingjiang Formation in southern Sichuan Basin

Y ANG Zhe， ZHONG Dakang， DU Benqiang， L I Qirong， ZHU Haihua， ZHOU Yuzhe

2014, Vol.26(4): 81–87 Abstract ( 525 ) PDF (1095 KB) ( 522 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.04.012

Based on core observation, casting thin sections, physical properties and logging data, this paper studied the petrologic characteristics, diagenesis, reservoir space types, physical properties and controlling factors of the reservoir of the second member of Jialingjiang Formation in southern Sichuan Basin. The results show that high-quality reservoir is mainly developed in dolomite, especially in oolitic dolomite and micritic dolomite. The formation of oolitic dolomite is related to early dolomitization, and that of micritic dolomite is due to the dolomitization of micrite along with burial. Reservoir spaces of oolitic dolomite include intragranular dissolved pore, and the main pore types of micritic dolomite are dissolved pores and intracrystalline dissolved pores. The reservoir has the properties of low porosity and low permeability. Reservoir qualities are affected by palaeohigh, sedimentary facies and diagenesis. The restricted platform dolomite in the southeastern palaeohigh and grain beaches are favorable reservoirs.

Controlling factors and development periods of fracture of Da’anzhai member in Fuling area, eastern Sichuan Basin

HE Long， ZHENG Rongcai， L IANG Xiwen， X U Wenli

2014, Vol.26(4): 88–96 Abstract ( 608 ) PDF (1332 KB) ( 772 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.04.013

The reservoir of Da’anzhai member in Fuling area, eastern Sichuan Basin, is characterized by low porosity, low permeability and strong heterogeneity, and fracture is the main reservoir space. According to outdoor surface occurrence, core observation, thin section analysis, scanning electronic microscope and image logging, this paper divided fractures into three types by genetic mechanism: structural fracture, diagenetic fracture and dissolved fracture, and fractures are characterized by low inclination, long length and high density. The main controlling factors for each type of fractures are lithology, tectonism and diagenesis. Based on the fracture characteristics, isotope analysis of fracture fillings and the acoustic emission experiment of rocks, it is indicated that the fractures can be divided into three stages at least: the late Yanshanian, the early and late Himalayan respectively.

High resolution sequence stratigraphy of the fourth member of Xujiahe Formation in central fault-fold belt of Yuanba area, Sichuan Basin

WANG Mingfei， QU Dapeng， XIAO Wei， LING Tao， CHEN Lingjun

2014, Vol.26(4): 97–102 Abstract ( 604 ) PDF (1170 KB) ( 508 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.04.014

On the basis of formation development characteristics, this paper studied the high-resolution sequence stratigraphy division of the fourth member of Xujiahe Formation in central fault-fold belt of Yuanba area. Firstly, based on the sedimentary characteristics of modern braided river and braided river delta, we clarified the braided river sedimentary system and braided river delta sedimentary system. Through the drilling and logging data, we defined that the study area developed braided river facies and braided river delta facies. And then, according to the principle of high resolution sequence stratigraphy, we identified two types of braided channel which have sequence stratigraphy significance, including high accommodation vertical superimposed braided channel and low accommodation lateral superposed braided channel, which can be used to judge the transformation position of base level cycle for single well high resolution sequence division. It was considered that the fourth member of Xujiahe Formation can be divided into two fourth-order cycles and three sub-members. Finally, combined with the seismic sequence interpretation of the fourth member of Xujiahe Formation, we established regional sequence stratigraphic framework, which provides foundation for the further study on sedimentary facies distribution in sequence stratigraphic framework.

Quantitative research on the effect of diagenesis on porosity evolution of Xujiahe Formation in northeastern Sichuang Basin

HU Hao， L U Yao， TANG Qunying，WANG Min

2014, Vol.26(4): 103–108 Abstract ( 494 ) PDF (933 KB) ( 481 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.04.015

Organic geochemistry characteristics of source rocks in Liaohe Depression

L IANG Mingliang， WANG Zuodong， ZHENG Jianjing， L I Xiaoguang， WANG Xiaofeng， QIAN Yu

2014, Vol.26(4): 110–116 Abstract ( 532 ) PDF (922 KB) ( 529 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.04.016

In order to study the characteristics of source rocks for the hydrocarbon formation between western and eastern sags in Liaohe Depression, this paper studied the organic geochemistry characteristics of source rocks of Shahejie Formation by using Rock-Eval and GC-MS detection on saturated hydrocarbons. The GC-MS analysis and biomarker analysis of organic matter saturated hydrocarbon of 18 blocks of source rocks show the different biomarker characteristics of the same formation, and abietanes and methylsteranes compounds were detected in mass chromatogram at m/z 191 and m/z 231 respectively in the eastern and western sags. The results show that there are significant differences in the depositional environment and precursor input between the western and eastern sags in Liaohe Depression, and those might be important reasons for the differences of source rocks and hydrocarbon accumulation between western and eastern sags in Liaohe Depression.

Carbon and oxygen isotope analysis method for dolomite formation mechanism: A case study from Proterozoic dolomite in Yanshan area

LI Qianw en， JIN Zhenkui， JIANG Fujie

2014, Vol.26(4): 117–122 Abstract ( 569 ) PDF (835 KB) ( 878 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.04.017

Dolomites are well developed in Gaoyuzhuang Formation to Wumishan Formation in Yanshan area, Beijing. However, the understanding of dolomite genesis in this area is still unclear. This paper used carbon and oxygen isotope analysis to carry out reconstruction of ancient salinity and ancient temperature of the dolomite samples selected from Gaoyuzhuang Formation, Yangzhuang Formation and Wumishan Formation in the Ming Tombs area. The result shows that in Gaoyuzhuang Formation, the mean of δ13C is -1.13‰, the mean of δ18O is -7.87‰ , the mean of Z is 122.188 5, and the average diagenetic temperature is 51.85 ℃; in the Yangzhuang Formation, the mean of δ13C is -0.93‰, the mean of δ18O is -6.11‰ , the mean of Z is 122.434 8, and the average diagenetic temperature is 47.82 ℃; in Wumishan Formation, the mean of δ13C is 0.13‰, the mean of δ18O is -4.60‰ , the mean of Z is 125.370 7, and the average diagenetic temperature is 39.48 ℃. According to the analysis of the above results, we concluded that most dolomites of Wumishan Formation were mainly resulted from penecontemporaneous dolomitization, and dolomites of Yangzhuang Formation were resulted from dorag dolomitization. The dolomite genesis of Gaoyuzhuang Formation is more complicated, which includes not only seepage reflux dolomitization but also dorag dolomitization.

Prediction and accumulation conditions of dolomite reservoir in Xingang area

ZHANG Liping， WANG Changli， ZHAO Tongze， HAN Shumin

2014, Vol.26(4): 123–129 Abstract ( 475 ) PDF (1210 KB) ( 380 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.04.018

Clastic rocks and dolomite are the main two reservoir types in Xingang area. The previous deep and wide exploration research is only for clastic reservoir. Research on dolomite reservoir characteristics and distribution is seldom, which restricts the dolomite reservoir exploration in this area. Through core analysis, logging and seismic data, based on the analysis of structure, deposition, source rock evaluation and single well reservoir, combined with data volume fusion technology, this paper carried out the prediction of dolomite reservoir distribution, and studied the oil and gas accumulation conditions of Es3, and then made clear the dolomite reservoir exploration potential of Es3 in Xingang area. The result shows that high-quality hydrocarbon source rocks developed in Es3 in Xingang area, oil and gas reservoir type belongs to primary self-storage, and the distribution area is large. A lot of fractures and dissolved pores are developed in the dolomite reservoir of Es35 , which provides favorable places for oil and gas enrichment. This understanding has certain reference value for the study of the same type of dolomite reservoir.

Directional one-way wave field separating numerical simulation of the seismic wave equation and reverse-time migration

CHEN Keyang， CHEN Shumin， L I Lailin， WU Qingling， FAN Xingcai， LIU Zhenkuan

2014, Vol.26(4): 130–136 Abstract ( 587 ) PDF (1072 KB) ( 674 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2014.04.019

In order to further improve the knowledge of seismic wave propagation law, this paper applied Poynting vector to 2D directional one-way wave field separation numerical simulation of seismic wave equation for the first time. According to the Poynting vector wave field numerical characteristics, the seismic up-way wave, down-way wave, left-way wave and right-way wave fields are automatically recognized and separated during the seismic wave numerical simulation. Taking isotropic model, tilt layer model and Marmousi model as examples, we carried out the corresponding numerical simulation experiments. The computational results show that the presented method is correct and effective. It can get the directional one-way wave field in the snapshots of each iteration step, and finally get the numerical records with directional one-way wave field separation. The presented method is simple and easy to accomplish with small computational cost. Therefore, it has important application value in the different one-way wave identification and separation processing and in imaging stage of the practical seismic data.