Lithologic Reservoirs

The seismic vertical resolution of sand shale interbed is very important to the exploration of lithologic reservoirs. Band limited seismic wavelet and its resolution are discussed. The theoretical model of sand shale interbed shows that the definition of !/4 vertical resolution is not reasonable while!!/8 vertical resolution is much more reasonable. The exploration practices of lithologic reservoirs showthat the vertical resolution may be !/16 when there is a big set of shale which includes thin sandstone. The research result provides theory foundation for the lithologic reservoir exploration of sand shale interbed.

Development status of exploration of subtle hydrocarbon traps

YANG Guochen，YU Bingsong

2008, Vol.20(3): 6–11 Abstract ( 413 ) PDF (277 KB) ( 632 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.03.002

The discovered subtle traps are divided into three genetic types, including stratigraphic#lithologic trap, complex subtle structural trap and combination trap. According to the main controlling factors for the trap forming, each of these types includes nine simple$factor controlling subtle traps and one complex%factor controlling subtle trap. The nine simple factors include reservoir body, reservoir space, sealing condition, migration and filling&up condition, trap shape and framework, trap position, dynamic condition of trap forming, reservoir fluid property and preservation condition. The current basic theories and techniques of the exploration for subtle traps are summarized, and the combination ofmultiple techniques is stressed to be the foundation of subtle trap exploration.

Beach body types and reservoir property of Feixianguan Formation in nor thwestern Sichuan

ZHANG Jinyou, WANG Xingzhi, ZHANG Fan, ZENG Deming, WANG Baoquan,JIANG Zhibin, LI Yaogang, ZHU Yonggang

2008, Vol.20(3): 64–68 Abstract ( 399 ) PDF (392 KB) ( 590 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.03.013

The beach body of Lower Triassic Feixianguan Formation in northwestern Sichuan can be divided into platform marginal oolitic beach and intraplatform point beach. The water is relatively deeper at the forming of most of platformmarginal oolitic beach which is not transformed by the diagenesis of fresh water and mixed water and has poor reservoir properties. However, a part of oolitic beach formed under shallowwater environment, and it is transformed by the diagenesis of fresh water and mixed water and well dolomitized, which can form excellent reservoir. The intraplatform point beach experienced good dolomitization and has good reservoir properties, with little development and thin thickness. Beach facies is only the basic condition for reservoir development. The forming of effective reservoir in the beach body depends on the later diagenesis. The beach body is dolomitized when it exposes above the water, which is favorable for the later buried denudation and forming of good reservoir.

Characteristics of sedimentary microfacies of Upper Triassic Chang 6 reservoir in Weibei area of Ordos Basin

YANGWei, TIAN Jingchun, XIA Qingsong, WANG Feng

2008, Vol.20(3): 69–73 Abstract ( 516 ) PDF (347 KB) ( 670 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.03.014

Chang 6 reservoir of Yanchang Formation in Weibei area is mainly composed of gray fine sandstone and siltstone. Based on core observation, single well facies and logging data analysis, the characteristics of sedimentary microfacies and the distribution ofmicrofacies in each sublayer ofUpper Jurassic are systematically studied. The results show that braided river delta front and turbidite are the main deposits in Chang 6 reservoir in Weibei area. The subaqueous distributary channel, mouth bar, distal bar, sand sheet and interdistributary bay are the main sedimentary microfacies of the braided river delta front. The study results settle a strong base for the prediction of favorable reservoir facies belts and the further exploration.

Seismic wave field characteristics and frequency distributionin fluid-saturated media

BIAN Lien, HE Zhenhua, HUANG Deji

2008, Vol.20(3): 74–78 Abstract ( 524 ) PDF (328 KB) ( 710 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.03.015

When the seismic wave propagates in fluid-saturated stratum, its wave field changes compared with the case of none fluid, because of the influence of resistance such as the viscosity and diffusion of the fluid. Based on the onedimensional diffusive and viscous wave equation, two-dimensional diffusive and viscous wave equation is derived. The characteristics and rule of the change of seismic wave field are analyzed by numerical simulation, which provide guidance and criterion for the reservoir identification and prediction. The result shows that viscosity coefficient mainly affects the frequency distribution of seismic wave, and diffusion coefficient mainly controls the attenuation of seismic wave with no influence on the frequency distribution.

Application of tomographic static correction in northern margin of Qaidam Basin

WU Jie, SU Qin, WANG Jianhua

2008, Vol.20(3): 79–82 Abstract ( 464 ) PDF (214 KB) ( 595 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.03.016

Since seismic exploration in the northern margin of Qaidam Basin is mainly carried out in mountainous region, foothill belt, gobi and desert, where the variation of lowvelocity layer is rapid, so static correction has become a bottleneck restricting the effect of exploration. Tomographic static correction technology of Greenmountain is a nonlinear inversion method, which inverses the near surface velocity structure by means of first break time and ray path gained by ray-tracingmethod, calculates the statics, eliminates the effect of static correction and improves the resolution of seismic section. The application in the northern margin of QaidamBasin shows that this method improves the statics precision and resolves the statics problemsuccessfully.

Study on fault sealing in Fang 169 block of Zhaozhou Oilfield

CUI Yanmin, LU Zhengyuan, ZHONG Wei

2008, Vol.20(3): 83–88 Abstract ( 434 ) PDF (504 KB) ( 535 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.03.017

Based on the existing exploration and production data of Fang 169 block in Zhaozhou Oilfield, the Shale Gouge Ratio (SGR) algorithmdefined byYielding et al in 1997 is adopted to carry out the preliminary quantitative calculation on two selected typical faults. The result shows that the quantitative analysis results are consistent with the conclusion obtained fromproduction dynamic data analysis. It indicates that this SGR algorithmcan be applied to other similar faults in the study area.

Application of dual laterolog interpretation of fracture parameters in Ar an Field, Iran

XIAN Wei, WU Weihang, LI Xiaogang, XIA Ming

2008, Vol.20(3): 89–94 Abstract ( 390 ) PDF (406 KB) ( 524 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.03.018

The Tertiary Qom Formation of the Aran Field, located in the Kashan Block of Central Iran Basin, is a set of fractured carbonate reservoir with lowmatrix porosity and permeability. For the study of fractured reservoir, the drill core and imaging logging data are the most straightforward and credible means to discern the development situation of natural fracture in the reservoir, but these are expensive. In the traditional logging methods, the Dual Lateral Logging (DLL) is of stronger competence of convergence, it is very useful to recognize the fractures in the resistive formation. On the basis of previous studies on the numerical model and inversion methodology of dual laterolog response, we establish an interpretation model of fractured reservoir parameters to estimate the fracture parameters of sub-member C4 of the Qom Formation in this block, and then compare the results with the core, imaging logging data and well testing data. The result indicates that this method can exactly evaluate the fractured reservoir in this area.

Development of new logging technology in cased hole

ZHANG Xianglin, LIU Xinru

2008, Vol.20(3): 95–98 Abstract ( 408 ) PDF (143 KB) ( 868 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.03.019

For the requirement of petroleum exploration, logging technologies develop rapidly. Almost all logging methods for obtaining log data can be applied in cased hole in any time to determine the production status and the oil saturation in oil layer, to carry out old well evaluation and production performance monitoring, and to evaluate cementation and well service life. The measuring principle of foreign newlogging technologies is introduced, which is helpful for guiding our research and production. The current status and gap of logging technologies in China are discussed and the developing direction is pointed out.

Methods of calculating porosity without logging porosity data

WANG Xiaoguang, KUANG Hongwei, WU Zeyun, SU Jing

2008, Vol.20(3): 99–103 Abstract ( 435 ) PDF (228 KB) ( 413 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.03.020

Aiming at the well fields without logging porosity data, we can use type log data to establish porosity interpretation model through core scaling method. There are two common porosity models which are established by SP reduction factor and apparent resistivity. After comparing these twomodels with the model established by shale content parameters, we found that porosity calculated by shale content porosity model is relatively more coincided with the porosity that calculated by core analysis and its mean absolute deviation is 0.162, while the mean relative deviation is 5.934%. So it is believed that applying shale content porosity interpretation model to calculate reservoir porosity is relativelymore accurate in the study area. Thereby, a feasible method is supplied to evaluate reservoir and quantitatively calculate reservoir parameters by using type log data.

Geological modeling for point bar of meander ing r iver and its application in hor izontal well

SI Li

2008, Vol.20(3): 104–108 Abstract ( 434 ) PDF (381 KB) ( 744 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.03.021

Based on the accurate description of point bar, the researches on improving the accuracy of geological structural model, lithology model and modeling method of lateral accretion interbed in point bar are carried out. A geological modeling for horizontal well in point bar is proposed. The application of this method shows that the error of structural model is within 0.45 metres and the coincidence rate of the lateral accretion interbed is 85%. It is favorable for guiding the design of the horizontal well.

Experimental simulation for the influence of fault property and dip angle on petroleum migration and accumulation in Jiyang Depression

MA Zhongliang,ZENG Jianhui,ZHAO Leqiang,WU Yue,XU Xiaosong,LI Dan

2008, Vol.20(3): 109–113 Abstract ( 489 ) PDF (353 KB) ( 378 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.03.022

Based on the 2D simulation experiment, the influences of fault property and the change of dip angle on petroleummigration and accumulation in JiyangDepression are discussed. The results showthat: ① The capillary pressure difference between sands and faults changes with the variational fault property, so fault property affects the petroleum migration. When the fault property is poor, the capillary pressure difference is favorable for the petroleum migration.When the property is better, the capillary pressure difference is unfavorable for the migration; ② The change of dip angle causes the buoyancy in sands to change, so it takes a significant part in the petroleum migration.When there is a small dip angle, the buoyancy is favorable for the oil filling in sands, however, when the dip angle is large, the buoyancy is favorable for the oil migrating upward along the fault; ③ There is a complementarity of the fault property and dip angle for the oil migration and accumulation. The better the property is and the larger the dip angle is, the more favorable they are for the petroleum migrating in the upper sands; while the poor property and small dip angle are favorable for the petroleummigrating in all the sands.

Geological modeling in initial stage of development of fluvial r eservoir

SU Jinchang, ZHANG Lan, MA Xinfu

2008, Vol.20(3): 114–118 Abstract ( 411 ) PDF (477 KB) ( 579 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.03.023

Aimed at the complicated geological characteristics of fluvial reservoir in Bohai Bay and the limited well logging data in the initial stage of the reservoir development, a method of fluvial reservoir modeling is proposed. Well drilling and logging data combiningwith geological modeling techniques are applied to performthe geological modeling of fluvial reservoir under the impedance constrained inversion. Taking the geologic modeling in BZ3-2 Oilfield in Bohai Bay as an example, the result shows that the quantitative geologic modeling of fluvial reservoir established under the guidance of this method provides a reasonable geology criterion for the exploration of fluvial reservoir and decreases the development risk.

Efficient development and benefit evaluation in Yulin Gasfield

WANG Yongqiang, LIU Zhanliang, HONG Hong, HAO Yuhong, QIAO Yabin,ZHANG Lin, MA Yunfeng, LIU Xiaojiang

2008, Vol.20(3): 119–123 Abstract ( 430 ) PDF (159 KB) ( 602 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.03.024

Yulin Gasfield is a typical lithologic gas reservoir with low permeability. Based on the thought of efficient development, dynamic analyses of gas field development are proposed for the purpose of scientific development of the low-yield wells, mainly including well productivity verification and classification management. Gas reservoir engineering method is applied to simplify the dynamic monitoring workload, which is based on the theoretical calculation of formation pressure and bottomhole flowing pressure. This method has been proved to save a large amount of testing cost. The research of benefit classification and criterion and the trend analysis of benefit bymultiple evaluation indexes could settle a strong base for the benefit evaluation of gas field development and carry out the efficient development ofYulin Gasfield.

Experiment research on water locking damage in low-permeability sand gas reservoirs

LEI Ru, REN Xiaojuan

2008, Vol.20(3): 124–127 Abstract ( 399 ) PDF (220 KB) ( 506 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.03.025

Based on the lab experimental research, the comparison is performed among the three types ofwater locking damage of low-permeability sand gas reservoirs. The research shows that water locking damage happens widely and seriously in low-permeability sand gas reservoirs. Among these three types of water locking damage, the water locking under underpressure condition has the minimal damage, the damage under overpressure condition is relatively maximal, and the damage under normal pressure is relatively medial. We should not use water base working fluid, if have to, we should make it in the underpressure condition.

Strategies of development technology for ultra-low permeability reservoir

LI Shuheng, ZHAO Jiyong, CUI Panfeng, YANG Jinlong, Chen Wenlong

2008, Vol.20(3): 128–131 Abstract ( 494 ) PDF (362 KB) ( 856 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.03.026

Ultra-low permeability reservoir in Ordos Basin has large oil resource, but it has poor physical properties and high starting pressure gradient, so it is hard to be exploited. According to these characteristics, the development strategies of “advanced water injection, well space shortening, rising injection-to-production-well ratio, increasing artificial fracture length and fluid diversion capacity”are proposed, and good result has been achieved in the pilot tracey in Zhuang 9 wellblock, Xifeng Oilfield. The development design settles a strong base for the efficient development of ultra-lowpermeability reservoir and broadens the prospects of oil and gas exploration and development in Ordos Basin.

Study on the production rate decline of fractured and cavernous carbonate reservoir in Tahe Oilfield

LI Bolin, TU Xingan, LI Chuanliang

2008, Vol.20(3): 132–134 Abstract ( 444 ) PDF (261 KB) ( 568 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.03.027

Tahe Oilfield is a carbonate bottom-water reservoir with fractures and caves. The producing wells penetrate only part of the pay-zone. So the formation under the penetration can not be recognized clearly. In order to understand the geology of the whole reservoir, the production data are used and analyzed. Based on the characteristics of the production rate decline, the wells in Tahe Oilfield are classified into three types: rapidly declined well, medially declined well and slowly declined well. The cave system also can be classified into three types correspondingly, including closed cave system, semi-closed cave systemand open cave system. Closed cave systemis lack of natural drive energy, while open cave system has abundant natural drive energy, and semi-closed cave system behaves between the closed cave system and open cave system. According to the closure property of cave system, production procedures of oilfield can be directed properly.