Lithologic Reservoirs

Ordos Basin is a large Mesozoic inland depressed basin with rich oil and gas resources. Triassic Yanchang Formation is the main oil-bearing formation , where a set of lacustrine-delta facies deposits is developed. The reservoir is a typical lithologic reservoir with poor reservoir conditions and high reservoir heterogeneity. The forming of the reservoir is mainly under the control of high quality of source rocks and favorable reservoir sand bodies. The late constructive diageneses and tectonisms are closely related to the improvement of the reservoir. The overpressure of Chang 7 is the main driving force for the hydrocarbon migration and accumulation. Effected by the aspects of depositional environment , reservoir features , source rocks and the combination of the reservoir and seal , NE meandering river and SW braided river delta depositional patterns are developed. The delta front subsea distributary channel and mouth bar are the most favorable sedimentary facies belt for the generation of Yanchang Formation reservoirs.

The significance of cementation in porosity preservation in deep-buried sandstones

HUANG Sijing,HUANG Peipei,WANG Qingdong,LIU Haonian,WU Meng,ZOU Mingliang

2007, Vol.19(3): 7–13 Abstract ( 1395 ) PDF (945 KB) ( 817 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.002

Cementation in sandstone is very important retention processes in reservoir evolution , which enables porosity in deepburied sandstones to preserve. Based on the studies of occurrences of dolomite (ankerite) cement , quartz cement and clay cement and the timing and mechanism of cementation from Paleogene sandstone of East China Sea Basin , Upper Paleozoic and Triassic sandstone of Ordos Basin and Triassic sandstone of Sichuan Basin , a suggestion that large part of cementations occur at the early stage of diagenesis before effective compaction is presented here. Some of these cementations are related to tectonic uplift during earlier burial , and some to early acid fluid in coalbed. Partial and early cementation could enhance the mechanical strength of rocks and the resistance to porosity loss with depth and compaction by change of the porosity depth curve during shallow to deepburial diagenesis , which takes a significant part in reservoir quality prediction.

Research on the heterogeneous distribution of petroleum( Ⅱ)

LIN Chengyan,TAN Lijuan,YU Cuiling

2007, Vol.19(3): 14–22 Abstract ( 450 ) PDF (1317 KB) ( 513 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.003

On the basis of the current research on the hydrocarbon accumulation theory and hydrocarbon dist ribution rules , the theory of hydrocarbon heterogeneous distribution was definitely put forward. Taking the lithologic hydrocarbon reservoirs in the middle section of the third member of Shahejie Formation (Es32 ) in Niuzhuang Depression as the main example , the effect factors and the forming mechanisms for the hydrocarbon heterogeneous distribution have been discussed in detail. The heterogeneous distribution of hydrocarbon has several levels , of which the main affecting factors are different. In subdepressions , oil source and trap conditions were the main factors controlling heterogeneous distribution of petroleum macroscopically. In the secondary block , the heterogeneous distribution is controlled by oil source , structural conditions , in addition to the reservoir heterogeneity. The heterogeneous distribution of single sand body or the interior reservoir was resulted from reservoir heterogeneity. The idea that reservoir heterogeneity affects the hydrocarbon accumulation and leads to heterogeneous hydrocarbon distribution was stressed here. The phenomenon that hydrocarbons distribute heterogeneously in different scale is universal and objective , and it is even obvious in the subtle and complex reservoirs , including lithologic reservoirs and buriedhill reservoirs and so on. The presentation about the theory of hydrocarbon heterogeneous distribution takes a significant part in the exploration of lithologic reservoirs and complex reservoirs , and the fine exploration and development in highdegree exploratory areas , and it will play a great role in the reservoir evaluation , hydrocarbon reserves calculation , well deployment and so on.

“Multi-factor controlling , four-factor entrapping and key-factor enrichment”of stratigraphic-lithologic reservoirs and exploration practice in Erlian Basin ( Ⅱ) ———“Four-factor entrapping” mechanism

JIN Fengming,ZHAO Xianzheng,ZOU Weihong,LU Xuejun,SHI Yuanpeng,CAO Lanzhu,LU Lifei

2007, Vol.19(3): 23–27 Abstract ( 433 ) PDF (656 KB) ( 449 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.004

Based on the analysis of the hydrocarbon accumulation conditions for stratigraphiclithologic reservoirs in different sags in Erlian Basin , the accumulation of the stratigraphic-lithologic traps is considered to be controlled by four factors. On the premise of traps and oil sources , favorable migration pathway is the background for the forming of the reservoirs ; the features of fluid dynamics are closely related to the distribution of the reservoirs ; the res-ervoir critical property is the deciding factor for the hydrocarbon injection ; the sand body sealing is the key factor for the accumulation.

The classification and evaluation criterion of low permeability reservoir : An example from Ordos Basin

ZHAO Jingzhou,WU Shaobo,WU Fuli

2007, Vol.19(3): 28–31，53 Abstract ( 470 ) PDF (304 KB) ( 938 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.004

Based on the mercury penetration analysis of more than 300 samples and analysis result s of more than 260 casts and more than 100 image pores , and referred to the classification criterion about clastic reservoir , especially low permeability reservoir , the low permeability sandstone reservoirs in Ordos Basin were divided into four types and four sub-types. The four types include low permeability reservoir ( I) , extra-low permeability reservoir ( II) , super-low permeability reservoir ( III) and tight reservoir ( IV) . Among them extra-low permeability reservoir and super-low permeability reservoir are the main reservoir types of Triassic Yanchang Formation in Ordos Basin. According to t he characteristics of t he pore structure and petrophysics and the classification criterion of the reservoir thickness , they are divided into two sub-types respectively.

Petroleum migration and accumulation of Yanchang Formation in Jiyuan area , Ordos Basin

YAO Jingli, WANG Ke, SONG Jianghai,PANG Jinlian

2007, Vol.19(3): 32–37 Abstract ( 531 ) PDF (939 KB) ( 566 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.006

Based on the analysis of source rocks , reservoir , dynamics and migration pat hways of Yanchang Formation in J iyuan area , Ordos Basin , the rule of pet roleum migration and accumulation is analyzed. Dark mudstones were developed in t he maximum lake flooding period of Chang 7 , which are t he main source rocks. Most of the reservoir s are extra-low permeability reservoirs. The intergranular pore is t he main space for reservoir , and the pore throat types are mainly thin-pore with micro-throat and micro-pore with micro-throat . Anomalous pressure is the main dynamic for the hydrocarbon migration , and it is closely related to the depth of the duck mudstone. Connected sand bodies are the main migration pathway , in which high permeability in accumulation stage takes an important part . The reservoir distribution of Yan-chang Formation is partly controlled by micro-fractures. Two types of accumulation patterns including “source rocks-connected sand bodies-reservoir”and“source rocks - micro-fractures-reservoir”are finally summarized.

Diagenesis of Chang 3 reservoir of Yanchang Formation in Jiyuan area , Ordos Basin

DU Haifeng,YU Xinghe

2007, Vol.19(3): 38–43 Abstract ( 440 ) PDF (963 KB) ( 441 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.007

The Chang 3 sandstone reservoir of Yanchang Formation in Jiyuan area is lithologic reservoir , which belongs to continental delta deposits. The framework sand body is delta front subsea distributary channel . The reservoir lithology is arkose and syrosem arkose , with the low maturity of lithologic composition and good texture maturity. The reservoir is typical low porosity and low permeability reservoir with average porosity of 12. 62 % and average permeability of 0 . 8 ×10- 3 μm2 . Based on the data of SEM , cast slice cathodeluminescence and X diffraction etc. , the diagenesis of the study area was analyzed. The result showed that the third member of Yanchang Formation is now in the transition period from the early diagenetic stage B to late diagenetic stage A. In the early diagenetic stage , the stratum water circulating environment is a relative opened type of weak acid , and in the late diagenetic stage , it is a relative closed type of weak acid , which provide good conditions for denudation. The mechanical compaction , cementation and displacement result in the poor physical property of Chang 3 reservoir , and t he denudation is infavor of the reservoir.

Controlling factors for lithologic hydrocarbon reservoirs and petroleum prospecting target in Xiaocaohu area , Taibei Sag

LIU Juntian,JIN Zhenjia,LI Zaiguang,TAN Xinping,GUO Lin,WANG Bo,LIU Yuxiang

2007, Vol.19(3): 44–47 Abstract ( 436 ) PDF (588 KB) ( 516 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.008

Xiaocaohu area is rich in hydrocarbon resources with low degree of exploration and high potential . With the exploration increasing, structural reservoirs become rare, while the difficulty of the stratigraphic-lithologic reservoirs increase. According to the research on the accumulation conditions of the natural gas in Xiaocaohu area, Taibei Sag, the accumulation mode was discussed. The result showed that the reservoirs are cont rolled by structure, lithology and fault, among which lithology and fault are the key factors controlling the accumulation. On the basis of the exploration of lithologic reservoirs in two nose-shaped uplifts and sag, extending periphery block was carried out to develop fine gas reservoir description. The drilling of lower channel sand bodies along the ridge of the nose-shaped uplift is successful, making Ge 7 to Hongtai 2 a continuous oil/ gasbearing area.

Oil-gas geological features and its exploration potential in South Turgay Basin , Kazakhstan

KONG Xiangyu,YIN Jinyin,ZHANG Faqiang

2007, Vol.19(3): 48–53 Abstract ( 741 ) PDF (702 KB) ( 1097 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.009

South Turgay Basin is an important oil-bearing basin in central south Kazakhstan, which is a rift basin of Mesozoic. The struct ure character is grabens separating horsts. Aryskum Trough in the south is the main depression and oil kitchen , including four NW-SE direction grabens from west to east. The oil fields found are located in the arches and slopes. The main genetic unit is Jurassic-Cretaceous series , and several regional unconformities exist through the sediments. Lower-Middle Jurassic mudstones are mainly source rocks, the principal reservoirs are the clastics of the Middle-Upper Jurassic and the Lower Cretaceous Formation, and early Cretaceous mudstone is regional seal. Although during more than 20 years exploration course, most large-size reserves have been found , there are many exploration potential fields. Except for the structure traps, the stratigraphic traps of Jurassic-Cretaceous Formations at the graben flanks and the basement weathered crust of Paleozoic are the future exploration directions.

Sand control effect of reversed slop break:A case study from the third member of Shahejie Formation in Chenjia Depression

YUAN Shukun,WANG Yingmin,CHEN Zhenyan,WEI Shuijian,L IU Wenchao

2007, Vol.19(3): 54–58 Abstract ( 609 ) PDF (1408 KB) ( 452 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.010

The theory of slope break is a new achievement of sequence stratigraphy applied in continental basins. The former research showed that the slope breaks along source area direction are favorable for the generation of stratigraphic lithological t raps because of that the lowstand system tracts are easily developed in this area. The research on Chenjia Depression shows that mutual grade slope breaks are developed in the lower third member of Shahejie Formation. The controlling pat terns of the slope breaks in different depositional stages are different. Based on the slope breaks identification and the analysis of the relationship between the slope breaks and the favorable target traps, the controlling effect of the slope breaks opposing source area direction on sandstone distribution is proposed , especially in the middle and small faulted lake basins with rapid filling.

Advances of strontium isotope in sedimentology

LIU Haonian,HUANG Sijing,HU Zuowei,WU Meng,WANG Qingdong

2007, Vol.19(3): 59–65 Abstract ( 658 ) PDF (261 KB) ( 1166 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.011

The studies on strontium isotope have received rapid development s in all fields of sedimentology, with the continuous development of dissolution technology for strontium isotope samples of marine carbonate, testing method for diagenetic alteration and strontium isotope database of marine sediment s in the period of geologic history. Strontium isotope is applied to carry out the researches in the aspect s of the provenance analysis, dating marine sediments, paleoclimate and paleoenvironment analysis, water-rock interaction and hydrogeochemistry. The latest progress and development t rends in these fields are discussed.

Sedimentary microfacies of the second member of Hetaoyuan Formation in Xia’ermen Oilfield , Biyang Sag , Nanxiang Basin

LI Qi,CHEN Zhenlin,TIAN Jianfeng,GUO Qiling,GUO Guangfei,SHU Kedong

2007, Vol.19(3): 66–72 Abstract ( 462 ) PDF (1366 KB) ( 685 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.012

The reservoir heterogeneity of the second member of Hetaoyuan Formation in Xia’ermen Oilfield is strong and the adjacent well productivity is greatly different. On the basis of the data of core, well logging and grain size, the division and characteristics analysis of sedimentary microfacies of the second member of Hetaoyuan Formation are carried out, and the shape and distribution of the reservoir sand body and the mode of sand body superposition are analyzed. The result showed that Ⅱ—Ⅴoil2bearing layer of the second member of Hetaoyuan Formation developed braided river delta front subfacies deposit , which can be divided into five sizes of sedimentary microfacies and creeping turbidite sand body. The sedimentary microfacies include subsea distributary channel, mouth bar, distal bar, front sheet sand and distributary interchannel, among which the subsea distributary channel and mouth bar are the favorable facies belt s of the study area.

Salt movement and the types of related traps in Pre-Caspian Basin

SHI Danni,YANG Shuang

2007, Vol.19(3): 73–79 Abstract ( 588 ) PDF (1413 KB) ( 676 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.013

Pre-Caspian Basin is one of the famous oil/ gas-bearing basin with the deepest subsidence and the thickest sedimentation in the world ,which is located in the southeastern East Europe Platform. The salt rock stratum in Kungurian of Lower Permian and the traps generated by salt movement are the main factors for post-salt reservoir accumulation and enrichment . The salt distribution , shape characteristics and the evolution of salt movement are studied ,and the types of hydrocarbon traps and genetic features are analyzed ,which provide scientific reference for the optimization of the exploration targets in post-salt strata.

Study on seismic impedance inversion

WANG Xiwen,SHI Lanting,YONG Xueshan,YNAG Wuyang

2007, Vol.19(3): 80–88 Abstract ( 566 ) PDF (2012 KB) ( 1149 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.014

There are many methods for seismic impedance inversion. Aiming at the methods of generalized linear inversion , the key techniques are discussed here , such as iterative impedance inversion , regularization method , resolution of impedance inversion , the statistic and mean square deviation used to control the inversion quality , secondary smooth filtering and the constrained impedance inversion. And a great of modeling computation are carried out . Referred to the methods of recurrence impedance inversion , the main techniques are analyzed in the aspects of the wavelet and reversed wavelet extraction , the effect of noise on reversed wavelet extraction and so on.

Hydrocarbon saturation determined by dual-TE logging

HE Zongbin,NI Jing,WU Dong,LI Yong,LIU Liqiong,TAI Huaizhong

2007, Vol.19(3): 89–92 Abstract ( 506 ) PDF (781 KB) ( 481 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.015

According to dual-TE logging , intrinsic relaxation time T2int and t he T2int deviation between hydrocarbon and water can be obtained , which can be used to discriminate the formation fluid property and evaluate the hydrocarbon saturation. It is using T2int deviation to obtain volumes of the movable hydrocarbon and movable water , and using cutoff value to determine the volume of capillary bound water . The hydrocarbon saturation could be obtained after these volumes were calibrated by hydrocarbon index. This method has been compiled to FLAN module for oil and gas identification and evaluation by nuclear magnetic resonance log. The real data of many wells are processed by this module. The result proves a good effect .

Prestack seismic data spl icing techniques based on shaping operator derived from poststack record

FENG Xinyuan,WANG Yuchao,HU Ziduo,LI Fei,SHAO Xichun

2007, Vol.19(3): 93–96 Abstract ( 414 ) PDF (1010 KB) ( 543 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.016

In order to overcome the disadvantages in the conventional prestack seismic data splicing processing , the post stack record was used to obtain shaping operators. Then the shaping matched filtering is perormed. This technique makes the seismic data with different characteristics consistent on frequency , phase and mplitude ,and carries out the prestack seismic data splicing. The practical application of the technique showed that it could provide high quality prestack gathers for subsequent processing , by which the shaping operators obtained are stable and easy to perform , and that it is assuredly a good choice for block-tie processing.

Water saturation evaluation of low resistivity reservoir in southern Tahe Oilfield

ZHAO Yi,ZHANG Chenguang,FAN Zhenjun, LIU J iahua

2007, Vol.19(3): 97–100 Abstract ( 459 ) PDF (786 KB) ( 658 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.017

Water saturation is one of t he key parameters to evaluate hydrocarbon reservoir . Based on t he core analysis result s and the bound water saturation derived rom the nuclear magnetic resonance (NMR) test results for several wells of Triassic low resistivity reservoir in southern Tahe Oilfield , the comparison of the evaluation results of water saturation derived from Archie equation and Waxman-Smits model respectively is carried out . The result shows that using Waxman-Smits model to evaluate water saturation in this area is more advisable.

Research and appl ication of amplitude-preserved split-step Fourier prestack depth migration

LV Bin,WANG Yuchao,LI Fei

2007, Vol.19(3): 101–105 Abstract ( 419 ) PDF (835 KB) ( 589 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.018

Both the travel-time information and amplitude information are required to be contained in the prestack depth migration imaging results in the lithology analysis. Based on one-way wave equation , split step Fourier prestack depth migration method is fast and steady. It is carried out by phase shift processing in frequency-wave number domain and time shift processing in f requency-space domain according to the idea of velocity field split . The disadvantages of conventional one-way wave equation in amplitude preserved migration restrict the application of this method in lithology imaging. So split-step Fourier amplit ude-preserved migration operator was put forward. It carries out the amplitude-preserved migration with the phase shift amplitude-preserved correction operator in frequency-wave number domain and time shift amplitude-preserved correction operator in f requency-space domain. The comparison of the shot illumination analysis result s and the prestack depth migration imaging results aiming at Marmousi model indicated the validity and effectiveness of this method.

Application of 3D seismic survey in loess tableland

SHANG Changliang, FU Shouxian

2007, Vol.19(3): 106–110 Abstract ( 495 ) PDF (1405 KB) ( 628 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.019

It is a real challenge to carry out seismic survey in loess tableland. Due to its particular geologic features, we always adopt the method of 2D seismic survey with crooked lines in valleys and straight lines in this area, which is limited for the exploration. The technology of reticulate 3D seismic survey in loess tableland is put forward here. The characteristics of the primary sources and the related processing techniques are discussed. The application effects on processing and geology are analyzed. The results show that the techniques of reticulate 3D seismic survey are significant for the oil-gas exploration in the loess tableland.

Identification of the shallow gas reservoir in Shanle area,Tuha Basin

YUAN Shengxue,WANG Jiang

2007, Vol.19(3): 111–113 Abstract ( 490 ) PDF (395 KB) ( 523 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.020

The exploration of shallow layer gas is at the initial stage in Tuha Basin. The shallow gas reservoir discovered in Shanle, Hongtai and Santanghu area are characterized by complex lithologies, poor physical property, unobvious response of logging, obvious productivity difference and sharp lateral variations of stratum etc. The identification method was discussed on the basis of the analysis of lithologies,physical property, electrical property, stratum and logging. The good results have been achieved.

Prediction method for marl fractured reservoir———An example from Shulu Sag

WANG Menghua,CUI Yongqian,ZHANG Ruifeng,LU Yonghe,WANG Sicheng,LU Lifei

2007, Vol.19(3): 114–119 Abstract ( 528 ) PDF (925 KB) ( 711 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.021

Due to the anisotropy and heterogeneity of the marl fractured reservoir,it is difficult to predict the fracture accurately with conventional methods.Based on the theories of tectonic stress field,seismic wave frequency attenuation and fracture detection,the pseudo2acoustic inversion,digital simulation analysis of tectonic stress field, forward modeling of rock physical model and anisotropy and attenuation attributes analysis combining with the available data of geology, drilling, well logging and the prestack and poststack seismic data are applied to analyze the marl fractured reservoir in Shulu Sag. The relations among the marl fracture development and stratigraphic lithologies,stress distribution and tectonic development are made clear, and the distribution range of the favorable reservoir was finally predicted. The application result of the real data proves the effectiveness and reliability of this method in the reservoir prediction.

Horizontal wells are not suitable for bottom water reservoir development

LI Chuanliang

2007, Vol.19(3): 120–122 Abstract ( 494 ) PDF (259 KB) ( 525 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.022

The adaptability of horizontal wells for bottom water reservoirs is analyzed in order to develop reservoir more efficiently. The result shows that the effect of horizontal well on curb water coning is limited , the limit recovery efficiency of it is lower than that of vertical well , and the stimulation treatments for it are difficult to be carried out . It concludes that horizontal wells are not suitable for bottom water reservoir development , but advantageous for edge water reservoirs with thin layer , low permeability and heavy oil .

Productivity analysis of horizontal well with non-Newtonian power law fluid

SHUAI Yuanyuan,WANG Xiaodong,SUN Ting,ZHOU Congcong

2007, Vol.19(3): 123–125 Abstract ( 543 ) PDF (210 KB) ( 570 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.023

Productivity analysis of horizontal well wit h non-Newtonian power law fluid is helpful to carry out rational development and evaluation of heavy oil reservoirs. The steady seepage flow model of non-Newtonian power law fluid is firstly presented and solved , and then the formula is modified referred to the characteristics of horizontal well . The productivity formula is finally obtained. The effect s of the characeristics of various fluids on the productivity of horizontal well are analyzed by case studies.

Discussion on lithologic seismic exploration

SHI Songqun,WANG Yuchao

2007, Vol.19(3): 131–134 Abstract ( 431 ) PDF (201 KB) ( 818 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2007.03.025

Many previous geophysical problems need to be relocated and rethought referred to the lithologic seismic exploration for subtle reservoirs. According to the experience of seismic prospecting work for many years, some basic ideas and thought s about how to carry out t rue lithologic seismic exploration are proposed here. Based on the analysis of the concept of seismic exploration resolution and its application, the problems how to improve seismic exploration resolution by using seismic attributes in lithologic seismic prediction of the thin reservoir are put forward and discussed.