Lithologic Reservoirs

Since the 1990’s, petroleumexploration in China has come to a stage of lithologic reservoirs. Nevertheless, during the course of the lithologic reservoir exploration, some new and puzzling problems emerged. The relationship between the pseudo line-ups events and isochronous sediment surface is discussed. It is put forward that acoustic impedance inversion must be taken seriously for lithologic reservoir exploration when you were tracing the deeper sand bodies. The acoustic impedance interpretation of calcareous compacted sandstone is also discussed.

Resear ch status of dolomite genesis and its problems in Sichuan Basin

LIU Shugen, HUANGWenming, ZHANG Changjun, ZHAO Xiafei, DAI Sulan,ZHANG Zhijing, QIN Chuan

2008, Vol.20(2): 6–15 Abstract ( 645 ) PDF (614 KB) ( 1041 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.002

The formations from the Upper Sinian toMiddle Triassic in Sichuan Basin are marine deposits and mainly composed of carbonate rocks. Through 50 years petroleum exploration, fifteen carbonate gas-bearing beds have been found in the basin. Among them, carbonate rocks of Upper Sinian and Cambrian have been completely dolomitized, and the others also have dolomitization more or less. There are various explanations for the genetic model of dolomite in marine carbonate reservoir in Sichuan Basin, mainly including: protogene, penecontemporaneous, reflux, meteoric-seawater mixing water, burial, hydrothermal fluid, leaching of basalt and biogenesis. Dolomite reservoir is regarded as one of the most important carbonate reservoir, and the dolomitization is the prerequisite for the development of high-quality carbonate reservoirs in Sichuan Basin. The burial dolomitization and meteoric-seawater mixing dolomitization of marine carbonate rocks have been widely queried, and there are two taphrogenesis events and related extensive fluid activities in marine carbonate rocks in Sichaun Basin, so hydrothermal dolomitization could be more widespread than previously thought in Sichuan Basin.

Quer ies about Helan aulacogen

DI Lingjun, XIE Guangcheng

2008, Vol.20(2): 16–21 Abstract ( 543 ) PDF (525 KB) ( 813 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.003

Since the plate tectonic theory was introduced into China in 1970’s, aulacogen has been considered in the area of Helan Mountain in Ordos Basin by some geologists. It is believed that Helan Mountain, Qinling and northern Qilian area were at the stage of rifting development fromMid-Neoproterozoic to Early-Mid Cambrian, and that Qinling, northern Qilian, Helan Mountain formed a trifurcate rift valley system. This viewpoint was quickly accepted and quoted by many geologists in China. The concept of aulacogen was extended and developed by some scholars. This paper raises the queries about the aulacogen in Helan Mountain. Through consulting a large amount of documents and data about aulacogen both at home and abroad, researching the shapes and sedimentary features of Qinling-Qilian- Helan Mountain area, and carefully verifying seismic, gravity, magnetic and electric profiles of the so-called aulacogens that cross the Mid-Lower Proterozoic, the authors think that the evidence of aulacogen in Helan Mountain is insufficient, and it is quite different from the aulacogen defined at home and abroad in the aspects of sedimentation and structure. So it is believed that aulacogen does not exist in Helan Mountain area.

Delta depositional system and sandbody distr ibution of the second member of Shanxi Formation in Changbei Gasfield, Ordos Basin

WANG Hua, ZHENG Rongcai, ZHOU Qi, LI Fengjie, WEI Qinlian

2008, Vol.20(2): 22–28 Abstract ( 621 ) PDF (508 KB) ( 524 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.004

Changbei Gasfield is located in the northeast of Shanbei Slope in Ordos Basin. Shanxi Formation of Lower Permian is a series of clastic deposits, and it can be divided into two lithologic segments (P1s1 and P1s2) , between which the second member of Shanxi Formation (P1s2) is the principal producing formation. Based on core description, mineral analysis and well logging data, Shan 2 member is considered as marine braided river delta deposit. Delta plain subfacies developed well in Changbei Gasfield, of which the widely developed distributary channel sandbodies are favorable for the hydrocarbon accumulation. The method of sequence-lithofacies paleogeographymapping is adopted to describe the sandbody distribution characteristics of Shan 2 member, which could offer reliable reference for reservoir prediction.

Deep crust structur al featur es and new targets of petroleum explor ation in Qaidam Basin

ZHANG Jinglian, SHI Lanting, CHEN Qilin, ZHANG Huquan, WEI Pingsheng

2008, Vol.20(2): 29–36 Abstract ( 529 ) PDF (496 KB) ( 698 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.005

Three oil-gas bearing regions have been proved in Qaidam Basin since the 1950’s, including Tertiary oil filed in west, Jurassic oil field in north and the Quaternary gas field in east. It is a problemconcerned by the petroleum geologists where the new targets are for the further exploration. The discoveries of eclogite, ultramafite and gold mine in the periphery of the basin and gypsum-salt, dolomite, illite and strontiummine in the basin indicate the existence of mantle fluid activity. The seismic sounding result shows that low velocity-high conductive layers widely developed in the mid-crust of Qaidam Baisn. The analyses of the relationships between the low velocity-high conductive layers and discordogenic fault, between the fault and the unconformity and between the shallow fault and the reservoir take a significant part in looking for large oil and gas fields. The research shows that the further exploration should be stressed in deep granite and weathered crust in Chaixi area, and the deep of Sanhu area is the favorable target for looking for large gas fields.

Sedimentary characteristics and evolution of Badaowan Formation of Lower Jurassic in northwest margin of Junggar Basin

WANG Changyong, ZHENG Rongcai, WANG Jianguo, CAO Shaofang, Xiao Mingguo

2008, Vol.20(2): 37–42 Abstract ( 441 ) PDF (444 KB) ( 433 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.006

The sedimentation of Badaowan Formation in the 8th block in northwest margin of Junggar Basin is regarded as braided river facies. Based on the analysis of the rock type, features and sedimentary facies marks, it is believed that Badaowan Formation is braided river delta and lacustrine sedimentation. The sedimentary distribution and evolution of Badaowan Formation are systematically studied. The result shows that the lake level descended since Late Triassic and swamp deposit widely developed in Badaowan Formation by the extinction of the lake basin, with the inputting of alluvium and the shrinking of swamp, strata overlapped from east to west and braided river developed; shallowlacustrine and braided river delta developed well with the ascending of the lake level in sub-stage of J1b51; the lake level descended swiftly since the sub-stage of J1b4, which resulted in the extinction of the shallow lacustrine in the study area; during the sub-stage of J1b 2+3, lake transgression emerged once more, and it was characterized by a large scale of shallow lacustrine; the lake level descended again since the sub-stage of J1b1, shale increased with the attenuation of fluviation, and swamp widely developed at the last stage of Badaowan Formation.

Influencing factor s of low permeability r eservoir proper ty of Yanchang Formation in Changqing Oilfield

QU Chunxia, YANG Qiulian, LIU Dengfei, LIU Xu, LI Aiqin, CUI Panfeng

2008, Vol.20(2): 43–47 Abstract ( 547 ) PDF (323 KB) ( 588 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.007

With the development of the petroleum exploration in Changqing Oilfield, the reservoir permeability gradually becomes poor, so fine geologic research is necessary for the further development. The reservoir properties are mainly affected by depositional settings, cement content and micro-pore structure, etc. To definite the main influencing factors for the reservoir property could take a significant part in guiding the exploration and development in Changqing Oilfield.

Heterogeneity models and hydrocarbon distr ibution in Chang 6 member of Yanchang Formation in Gongdatan ar ea, Ganguyi Oilfield

WANG Hui, WANG Fengqin

2008, Vol.20(2): 48–53 Abstract ( 432 ) PDF (418 KB) ( 538 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.008

Based on the geology, logging and the data of core analysis and production test, three macro-heterogeneity models of inner layer, interlayer and horizon in the reservoirs are established for Chang 6 member in Gongdatan area, Ganguyi Oilfield. The relationship between the hydrocarbon distribution rule and the reservoir heterogeneity is studied. The research shows that the macro-heterogeneity of Chang 6 member is strong. The hydrocarbons of inner layer, horizon and interlayer mainly distribute respectively in the lower part of positive rhythm sand bodies and the upper part of the reverse rhythm sand bodies, in the delta plain and front distributary channel and in the first sand group of Chang 6 member which has good physical property and weak heterogeneity. It is shown that the macro-heterogeneity of Chang 6 member controls the lateral and vertical petroleumformation and distribution.

Char acter istics and geological significance of seismites of Paleogene in Yangxin Subsag of J iyang Depr ession

WANG Ke1 LIU Xianyang, ZHAO Weiwei, SONG Jianghai, SHI Zhenfeng, XIANG Hui

2008, Vol.20(2): 54–59 Abstract ( 449 ) PDF (350 KB) ( 934 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.009

Seismite is a type of catastrophic deposits with recognizable evidence for seismic activities and sequence. According to core observation and description, many deformation structures with seismite characteristics are recognized within sandstone and shale sedimentary strata of Paleogene continental faulted basin in Yangxin Subsag, such as micro-faults, earthquake fissures, liquefaction sandstone veins, water-escape structure, vibrational liquefaction deformation structure, seismic pillow structure and associated structure, etc. The vertical sequence of seismites in Yangxin Subsag, in ascending order, is underlying unshocked layer, micro-faults layer, autoclastic shattered breccia layer, vibrational liquefaction deformation structure layer, seismic pillow structure and associated structure layer, liquefied homogeneous layer and overlying unshocked layer, which corresponds to different earthquake intensity respectively. The discovery of seismites can be used to analyze the intensive activity stages of basincontrolling boundary fault, and seismite itself is a kind of potential reservoir, so it has important geological significance for studying earthquake event deposit.

Structural-sedimentary evolution char acter istics of Paleogene in Liaohe Depr ession

SUN Hongbin, ZHANG Fenglian

2008, Vol.20(2): 60–65 Abstract ( 462 ) PDF (457 KB) ( 580 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.010

Liaohe Depression is a Cenozoic oil-bearing depression which overlaps Mesozoic basin. The rift characteristics are very obvious at the early stage of Paleogene, but in the later period, the depression characteristics are marked. The evolution of Liaohe Depression could be divided into three periods, including Sha 4 and Sha 3 rift period, Sha 1+2 rift-depression period and Dongying depression period. Fan delta and sublacustrine fan facies developed during rift period of Sha 4 and Sha3; fan delta facies and alluvial facies chiefly developed during rift-depression period of Sha 1+2; delta facies and flood plain facies mainly developed during the depression period of Dongying stage.

Sedimentary facies of Guan 162 fault block in Dagang Oilfield

PENG Xuehong, HE Zhenming, LIU Xuefeng

2008, Vol.20(2): 66–73 Abstract ( 461 ) PDF (621 KB) ( 468 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.011

Based on the coring and logging data, the sedimentary facies in ZaoⅡand Ⅲ reservoirs of Guan 162 fault block in Dagang Oilfield are analyzed. The result indicates that Guan 162 fault block is mainly composed of braided river facies. The main microfacies are braided channel, interchannel beach, fluviatile flood-plain and flood plain. The plane distribution and evolution of the sedimentary microfacies are studied. Combining with the statistical analysis of the petrophysical data, it is considered that the braided channel sand body is the favorable facies belt in the study area.

Paleogene sequence configur ation in Baxian Sag

XIE Xiaojun, DENG Hongwen

2008, Vol.20(2): 74–77 Abstract ( 441 ) PDF (310 KB) ( 584 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.012

The inner architecture and sequence configuration of the Paleogene in Baxian Sag are analyzed. Niudong fault and the related E-W zonation and S-N segmentation divide Baxian Sag into three structure-geomorphic units ( the south, north and middle segment) . The sequence configuration, development degree of provenance system, the depositional system and the genetic type of sand bodies, and the allocation type between the sand bodies and the structure-geomorphy of each segment are apparently different.

Technology of duplex wave migr ation and its application

WANG Su

2008, Vol.20(2): 78–82 Abstract ( 410 ) PDF (443 KB) ( 394 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.013

According to the forward modeling technique of wave equation, the duplex wave features of the vertical boundaries are indicated. The duplex wave migration imaging technique is studied. The results of the forward modeling and the application of this technique show that duplex wave migration enables the identification of all types of vertical boundaries including salt walls, subtle vertical faults within the reservoir, vertical zones that exist above the oil to water contacts etc, which is a beneficial supplement for the conventional seismic processing. This technique takes a significant part in recognizing the geologic information related to the fault system and discovering the high production oil/gas zones controlled by fault and the remaining oil controlled bymicrofault.

Determination of satur ation exponent in shaly formation

LI Xianpeng

2008, Vol.20(2): 83–85 Abstract ( 433 ) PDF (172 KB) ( 640 )

Archie formula is important for calculatingwater saturation of the reservoir, but it is only applicable to pure sandstone reservoirs. In the shaly formation, it is nonlinear relationship between the logarithm of the resistivity index and the logarithm of water saturation. The saturation exponent changes with resistivity index, with different changes under different pore structure and shale conditions. According to capillary tube theory, statistical theory, integration principle and volume model method, the relationship among saturation exponent, shale content, the parameters of pore structure and the resistivity index in shaly formation is derived, and the saturation exponent of shaly formation under different condition is determined.

Application of log data in reef flat reservoir description in Tazhong No.1 slope break

ZHAO Jun, HAI Chuan, ZHANG Chengsen

2008, Vol.20(2): 86–90 Abstract ( 492 ) PDF (393 KB) ( 538 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.015

The lithology of reef flat reservoir of Upper Ordovician in Tazhong No.1 slope break is mainly composed of carbonate. Because the reservoir space is various and complicated in the quantitative evaluation of well logging, there are a series of difficulties to evaluate carbonate with well logging data. The well logging data combining with core, experiment and well test are applied to divide the space and types of reservoirs, establish different response characteristics and models for different types of reservoirs, and build the division criterion of reef flat reservoir. According to the relationships between porosity and penetration of different types of reservoirs, the interpretation charts and criteria for different classified reef flat reservoirs are established, which provide dependable criteria for the reservoir evaluation and the choice of interval in well testing.

New development of logging techniques in open hole

ZHANG Xianglin, LIU Xinru

2008, Vol.20(2): 91–96 Abstract ( 647 ) PDF (172 KB) ( 980 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.014

For the requirement of petroleum exploration, logging techniques develop rapidly. Several logging techniques are analyzed. High resolution array induction, microresistivity image well logging, three component induction resistivity logging and cross dipole acoustic logging tool are favorable for the research on formation heterogeneity and anisotropy. Nuclear magnetic resonance logging, cable formation test and sidewall coring improve the recognition of formation fluid. Recently, new logging technique of electrokinetic logging is proposed. The measuring principle and apparatus composition of new techniques from Schlumberger, Halliburton, Atlas, Computalog and Russia are introduced, which is helpful for the development of our current scientific research and production. The current status and difference of the logging technologies in China are discussed, and the developing direction is pointed out.

Application of ar r ay acoustic wave data in well logging interpr etation

HU Hong, LUO Ning, LI Lianxin

2008, Vol.20(2): 97–101 Abstract ( 505 ) PDF (460 KB) ( 755 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.017

Array acoustic wave data are widely applied in well logging evaluation due to its abundant stratigraphic information. In addition to being used to evaluate reservoir property, array acoustic wave data also can be used to recognize the fracture around well bore, identify reservoir fluid property, predict and determine the height of hydraulic fracture, etc. Its practical application in some fields proves good effect.

Application of NMR logging technology in J iangsu Oilfield

YIN Junqiang, ZHU Juyi

2008, Vol.20(2): 102–107 Abstract ( 407 ) PDF (528 KB) ( 575 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.018

Parameters obtained from NMR logging technology can be used to evaluate the porosity, permeability,movable fluid, mobile water saturation and bound water saturation of the reservoir. The obtained reservoir parameters can be applied to evaluate the oil/water layer. NMR logging technology has special effects on evaluating oil layer with high bound water and low resistivity, water flooded layer, questionable layer for interpretation, the oil/water boundary and heavy oil layer.

Model-based multi-par ameter s non-linear inver sion method in pr estack domain

WANG Hui, ZHANG Yufen

2008, Vol.20(2): 108–113 Abstract ( 426 ) PDF (355 KB) ( 501 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.019

A multi-parameters inversion method in prestack domain is proposed. A lithology model near well is established, of which the parameters include layers time, P-wave velocity, S-wave velocity and density. Under the guidance of Gassmann fluid substitution theory, the permeable layers could be distinguished from impermeable layers. According to the characteristics of the study area, the rock-physics regression relation and prior model of each layer are established. In the basis of Bayes principle, the linearized Zoeppritz equation and convolution model are applied to obtain the posterior probability density of the lithologymodel. The results of the testing byMarmousi2 model show that we could obtain not only accurate inversion result, but also the sensitivity information indicating the existence of oil and gas of each parameter, which could reduce the risk of final exploration.

Quantitative pr ediction of fullness degr ee of lithologic trap in West Sag of Liaohe Depr ession

ZHANG Fengqi, PANG Xiongqi, LENG Jigao

2008, Vol.20(2): 114–118 Abstract ( 443 ) PDF (266 KB) ( 512 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.020

In order to determine whether the trap is oil-bearing or not and how much is the fullness degree of lithologic trap in West Sag of Liaohe Depression, the geostatistic analysis and R-model principal factor analysis are carried out to 117 lithologic traps. The results showthat the main controlling factors of the fullness degree of lithologic trap are the distance between lithologic trap and the center of hydrocarbon expulsion, the fluid potential, the sand content of target stratum and the sand thickness. Based on the correlation analysis and multiple regression analysis, the quantitative prediction models between the fullness degree and each of the controlling factors are established. The validation results of these prediction models indicate that more than 80%predicted fullness degree values of lithologic trap are consistent to the factual values, which implies that this prediction method is practicable.

Resear ch and application of carbonate r eservoir prediction method in YH ar ea

TENG Tuanyu, YU Jianping, CUI Haifeng, ZHANG Ninachun

2008, Vol.20(2): 119–123 Abstract ( 417 ) PDF (434 KB) ( 554 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.021

The carbonate reservoirs in YH area are characterized by deep burial depth, complex lithology, unobvious seismic response and strong anisotropy. The techniques of fracture prediction, seismic attribute analysis and impedance inversion are applied to predict the carbonate reservoir. A set of reservoir prediction method suitable for this area is put forward, which could improve the precision of reservoir prediction.

Can uplift r esult in abnormal high pr essur e in formation?

LI Chuanliang

2008, Vol.20(2): 124–126 Abstract ( 446 ) PDF (102 KB) ( 643 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.022

In order to make clear the cause of abnormal high pressure in formation, a study is carried out on the probability that uplift of formation can result in abnormal high pressure. The result shows that due to the high ratio of thermal expansion coefficient to compressibility of water, uplift can not cause abnormal high pressure in formation.The abnormal high pressure in oil and gas reservoirs requires a large height of uplift, which is unpractical generally.So the main cause of abnormal high pressures is still the invasion of external liquid into closed formations.

Identification and inter -well pr ediction of interbeds in thick oil layer

YAN Yaozu, DUAN Tianxiang

2008, Vol.20(2): 127–131 Abstract ( 595 ) PDF (366 KB) ( 564 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.023

At the early stage of the oilfield development, it only used density and frequency to describe the interbeds. The quantitative description method, especially the inter-well prediction method for interbeds becomes significant in the later period. Taking the thick sandstone reservoir in Ordos Basin as an example, the recognition method for interbeds is analyzed. The stochastic modeling techniques combining with lithology and logging are applied to establish a 3D interbed model. This model takes a significant part in guiding the potential excavation and increasing oil recovery.

Calculation method of contaminated ar ea homing and its application

QU Yongchun, WANG Zhuwen

2008, Vol.20(2): 132–136 Abstract ( 380 ) PDF (347 KB) ( 416 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2008.02.024

The contamination has a great impact on the precision of measurement in isotope logging. The contamination type and contamination correction coefficient are introduced briefly. The interpretation result was not influenced before the isotopes distributed in the formation; the proportional relationship among formation injection quantity, the filtration production content and the radioactivity intensity was destroyed by contamination after isotopes had distributed in the formation; and the interpretation accuracy for the amount of stratified relative water injection was affected. According to these characteristics, the contamination area homing model and calculation method for contamination correction are proposed, and good results have been achieved.