, Volume 30 Issue 3
    

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    济阳坳陷古近系沉积体系与油气运
  • The present research status and progress of petroleum exploration in the Jiyang Depression
    LI Pilong; JIN Zhijun; ZHANG Shanwen; PANG Xiongqi; XIAO Huanqin and JIANG Zaixing
    , 2003, 30(3): 299-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Since commercial oil being gained in 1962, 70 fields, 40.1×108t oil reserves and 361.41×108m3 natural gas reserves have been found in the Jiyang Depression. The resources proved degree has reached up to 56.97%, which shows the depression is at medium to high exploration degrees. The total residual resources are 46.72×108t in the Jiyang Depression, suggesting there is still a good exploration potential. However, there are three problems to the exploration at present: ① there is magnitude discovery every year in some sags with high exploration degree whereas low exploration effect in some sags with low exploration degree, which indicates that resources potential should be reappraised or petroleum distribution pattern should be further summarized; ② efficient forecast theory and method are short of in the exploration of subtle traps (especially lithological reservoirs), and the ratio of the subtle oil-gas pool in the newly found pools has been increased year after year, foreshowing a new exploration potential domain; ③ accumulation mechanism of lithological reservoirs is still unknown. The threshold controlling petroleum research shows that in Jiyang Depression, 7 of 26 accumulation systems have not reached accumulation threshold, and large-scale exploration should not carried through, whereas 19 of 26 have reached accumulation threshold with residual resources potential from 1.42×108t to 6.31×108t. Based on the ternary accumulation theory, three conditions must be met in the formation of oil accumulation in lithological reservoir: favorable sedimentary environment and sand body type, favorable generation and expulsion conditions of source rock, and physical property of sand body reached certain critical condition.
  • Identification of growth fault by fault fall analysis
    ZHAO Yong and DAI Junsheng
    , 2003, 30(3): 300-0.
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    Growth fault fall is defined as the layer thickness difference between two walls, and paleo-fall of certain moment is defined as the sedimentary thickness difference of this moment, which can be measured and calculated directly by structural evolvement section or geologic section and top and bottom contour maps. Also, it can be measured and computed through time-deep transform on seismic profile. Compared with the fault growth index analysis, fault fall analysis can be used no matter whether some layers are short of on the upthrow side; secondly, it isn′t influenced by the depth of basin subsidence; then it has a clear geologic meaning and can easily identify the fault active intensity. The fault fall analysis is a simple method and can be easily mastered and operated. Using this method, 45 faults in lower part of the Es-3 member of the Eocene Shahejie Formation in Dongying Sag were analyzed, which were in obvious movement at that time, and the conclusions are as follows: the deepest tract of fault subsidence was located within the western part of Chennan fault, the middle part of Shengyong fault and the central major fault.
  • Undiscovered pool sizes prediction of higher exploration degree area
    XIE Guojun; JIN Zhijun; XIAO Huanqin and PANG Xiongqi
    , 2003, 30(3): 301-0.
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    The discovery process can be viewed as sampling with varied probability without replacement and the assumption that the pool population obeys Pareto law. The pool population can be estimated with the information of discovered pool sizes and their discovery times by sampling theories. The method is used in Wangjiagang-Bamianhe petroleum accumulation system, which lies in the south slope of Dongying Sag and has a higher exploration degree, for predicting its pool population and undiscovered pool sizes. The result indicates that 42,000 reserves units are accumulated in pools, size more than 50 reserves unit, and 17,000 undiscovered reserves units mainly in the pools that their size,are less than 500 reserves unit.
  • Framework of high-resolution sequence strati-graphy for Well Yi 3-7-7 in Bonan Oil Field
    JIANG Zaixing; WANG Weihong and YU Hongzhong
    , 2003, 30(3): 302-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    High-resolution sequence stratigraphy has become an important way for oil exploration. The lithological oil-gas reservoirs well developed in the Bonan Oil Field of Zhanhua Sag. Taking Well Yi 3-7-7 as an example in the Bonan oil field, by analyzing sedimentary facies and high resolution sequence stratigraphical framework, 3 sedimentary facies, 7 sub-facies and 15 microfacies were recognized, and 4 third-level sequences, 9 system tracts and 44 para-sequence sets were divided. The differences of combination of different micro-facies and physical property characteristics affected the oil-gas distributions in parasequences. By studying the relationship between oil-gas distribution and para-sequences of the typical braid delta and underwater fan, and by analyzing the different combination types and physical characteristics, the braid delta, underwater fan and multi-developed braided channel are all thought to be the most favorable oil and gas reservoirs
  • Relationship between sequence stratigraphy and hydrocarbon accumulation in Es3-Es1 of the Shahejie Formation， Dongying Sag
    ZHANG Zonglin; CAO Yingchang; GAO Yongjin and JIANG Zaixing
    , 2003, 30(3): 303-0.
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    On the integrated analyses of the seismic, well logging and well drilling data, Es3-Es1 in the Shahejie Formation of Dongying Sag can be divided into four 3rd order sequences. Sequence 1 (the lower part of Es3) and Sequence 2 (the middle part of Es3) are T-R sequences, which are composed of lacustrine transgressive system tract (LTST) and lacustrine regressive system tract (LRST). Sequence 3 (the upper part of Es3 to the lower part of Es2) and Sequence 4 (the upper part of Es2 to Es1) can be divided into four tracts, such as LST, TST, HST and FSST. The sandbodies of LRST in a T-R sequence were not only developed well, but also were easy to form reservoirs. The sandbodies of LTST developed poorly, but they were easy to form lithologic reservoirs. The sandbodies nearby the four tracts mentioned above developed well, but they have little possibility of forming reservoir because of the poor trapping conditions.
  • Petroleum accumulation and occurrence in the Dongying and the Huimin Sags
    TAN Lijuan; JIANG Youlu; LIU Hua and FAN Cuntang
    , 2003, 30(3): 304-0.
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    The conditions and characteristics of petroleum accumulations in the Dongying and the Huimin Sags in the south of the Jiyang Depression have certain resemblances, but still have a great difference. The lithology and geological ages of the major source rocks and reservoir rocks are basically uniform, and the types of traps and reservoirs are also similar in these two sags. Petroleum accumulation has two stages, and the later stage is the dominant one.The oil and gas are rich in each of the two sags of the central uplift belt. There is great difference in the petroleum richness for the two sags in despite of the similar acreage, and the provon reserves in the Dongying Sag is about seven times of that in the Huimin Sag. The main factors caused this big difference and greatly affected the maturity of organic matter are the different evolution processes in the sub-sags. In Huimin Sag, only the development of the Linnan Sub-sag is successional, and the others subsided slowly in the later Paleogene period. The subsidence history of the sags has not only controlled the maturation of organic matter of the hydrocarbon source rocks, but also influenced the reservoir and capping conditions greatly.
  • AHP applied in the research of main controlling factors for studying formation of sand lens reservoir
    JIANG Zhenxue; CHEN Dongxia; QIU Guiqiang; PANG Xiongqi; ZENG Jianhui and QIU Nansheng
    , 2003, 30(3): 305-0.
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    The main controlling factors on the formation of sand lens reservoir are of typical arrangement characteristics. AHP is a particularly effective method for quantitatively analyzing non-quantitative matter in the research of sand lens reservoirs. In the analysis process of main controlling factors of formation of the Paleogene petroliferous sand lens in the Jiyang Depression, arrangement structure model and contrast judging matrix were constructed, and AHP calculation method was applied to find out main controlling factors. The research shows that many factors, such as sedimentary microfacies of sandbody, physical property of reservoir, depth and diagenesis extent of source rock and reservoir, organic matter abundance and hydrocarbon generation potential of source rock and efficiency of hydrocarbon expulsion, are the main controlling factors of sand lens reservoirs, and the former five factors make up more than 75 per cent contributions to the formation of this kind of reservoir. On the basis of constructing the evaluation standard of every factor, the synthetical evaluation model of lens reservoir is constructed . By applying AHP to quantitatively evaluate some typical lens reservoirs in the Jiyang Depression, the quantitative results have good coherence to those of the practical statistics.
  • Inversion modeling of the hydrocarbon amount destroyed by tectonic event in the Jiyang Depression
    PANG Xiongqi; ZUO Shengjie; JIN Zhijun; XIE Guojun and JIANG Zhenxue
    , 2003, 30(3): 306-0.
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    The rational determination of the destroyed hydrocarbon amount caused by tectonic event is the key for geologist to evaluate petroleum resources, recognize the process of hydrocarbon accumulation and guide the exploration, especially for the rift basins and the superimposed basins located in eastern and western China, respectively, which have experienced multi-stages of tectonic events. Based on the theory of thresholds controlling hydrocarbons, the destroyed hydrocarbon amounts due to tectonic events of 19 pool-forming systems with higher exploration degree in Jiyang Depression have been inversly modeled. The results indicate that the above amounts are usually in a range of 2-4 billion tons, and different poor-forming systems have varying amounts. By establishing the quantitative relationship between the destroyed hydrocarbon amount due to tectonic event and the geological influencing factors, some parameters are determined to be the main controlling factors such as hydrocarbon expulsion intensity, the ratio of sand to formation thickness, the net reservoir thickness, the number of tectonic event, the dip angle of target bed and the fault density.
  • Relationship between source rock and oil accumulation in Dongying Sag
    ZHANG Linye; JIANG Youlu; LIU Hua; TAN Lijuan and ZHANG Le
    , 2003, 30(3): 307-0.
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    The Dongying Sag, which has two sets of source rocks including the fourth member (Es4) and the third member (Es3) of Shahejie Formation, is abundant in hydrocarbon. By analyzing the geochemical features, the oil sources of all oil pools in the sag are investigated, and divided into three types of sources: the Es3 type, the Es4 type and the mixed type，suggesting that the crude oils in the south slope mainly generated from the Es4 source rocks, those in the central and the northern pools mainly generated from the Es3 or from the mixture of the Es3 and the Es4 source rocks, those in the central area mainly belong to the Es3 type, and those in the marginal pools distributed annularly around the sag mainly generated from the upper sub-member of Es4 source rocks. The hydrocarbons derived from the sub-sags migrated and accumulated nearby, and are distributed round the sub-sags.
  • The characteristics and distribution of abnormal pressure in the Paleogene source rocks of Dongying Sag
    QIU Guiqiang; LING Yun and FAN Honghai
    , 2003, 30(3): 308-0.
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    There are abnormally high pressures in the 3rd and 4th member of Shahejie Formation (Es3 and Es4) of the Paleogene over all the Dongying Sag, which are proved by the tested pressure data from 1307 wells and the data of drilling fluid density from 831 wells. Abnormally high pressure (coefficient of pressure is between 1.1-1.5) mainly occurs in the depth ranging from 2100 to 3500m, and the strong abnormally high pressure (coefficient of pressure over 1.5) exists in the interval between 2800m and 3500m deep. Abnormally high pressures strata are distributed in the central sag, the fault belt and the central anticline belt. The coefficient of pressure is higher in the northern slope belt than that in the southern slope belt. The highest pressure is distributed in the central sag and decreases forward to the slopes around the sag margins. The abnormal pressure distribution is well identical with under-compaction formations.
  • The sealing of Xiakou fault and its model of controlling on the petroleum accumulation
    GAO Xianzhi; DU Yumin and ZHANG Baoshou
    , 2003, 30(3): 309-0.
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    Linnan Sub-sag, located in the west of Huimin Sag, is the main hydrocarbon generation center of the sag. The sealing of Xiakou fault in the southern sag controlled the migration of hydrocarbon and the reservoirs distribution. The sealing of the Xiakou fault is related to its activity, status of fault surface and the shale gouge ratio. Based on the fault section figures and the calculation of shale smear factor of the Xiakou fault, its sealing was evaluated, which shows that the sealing condition of the fault is better in the east and the west then in the medium, and is better in the east than in the west of the fault. The formation of Linnan oilfield depends on that the fault obstructed the oil to migrate to Linnan slope. However, the Qudi oilfield formed because of the fault's unsealing, and the fault became migration pathway for oil from Linnan Sub-sag to the upper side of the fault.
  • Different sedimentary types of clastic rocks of the Paleogene in Dongying Sag
    SUN Mengru; ZHANG Qin; ZHONG Dakang; ZHANG Li; YOU Chunying and ZHU Xiao-min
    , 2003, 30(3): 310-0.
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    The Paleogene in Dongying Sag developed different sedimentary types of petroclastic reservoir rocks at the different stages of basin evolution, forming depositional environments of alluvial fan, river, nearshore subaqueous fan, fan delta, deep water turbidite fan, delta, delta-front slump turbidite fan, and bar shore-shallow lake. The reservoir rocks consisted of conglomerate, pebbly sandstone, medium-arenose sandstone, fine sandstone and siltstone. Different sedimentary types of reservoir rocks have the different componential and textural maturities, of which delta-front mouth bar and bar shore-shallow lake reservoir sands have the highest componential and textural maturities. The reservoir rocks deposited in fluvial environment, (fan) delta-front subaqueous distributary channel and mouth bar have the most effective reservoir properties, (fan) delta-front mat-shipped and bar shore-shallow lake sands are in the second, and nearshore subaqueous fan and turbidite fan sands have the poorest reservoir properties.
  • Correlation of the Paleogene sandstone reservoirs in different areas of Dongying Sag
    Lü Xixue; ZHONG Dakang; ZHU Xiaomin; XIE Zhonghuai; HAO Yun-qing and LIU Baojun
    , 2003, 30(3): 311-0.
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    Dongying Sag is divided into the northern steep slope zone, the central uplift zone and the southern gentle slope zone. Because of their geological background differences, these reservoirs of the Paleogene have different characteristics. In the north, the reservoir rocks are mainly sandstones and conglomerates that entered the later diagenesis earlier at the shallower depth. The secondary pores developed moderately and are mainly distributed from 1650m to 2450m. In the interval of 3200-3500m exists another secondary pore zone. The dissolution and cementation of carbonates occurred alternatively in vertical profile. In the central uplift, the reservoir rocks are mainly turbidites, the faults developed well and acid water was active in the geological history. Therefore, the reservoirs entered the later diagenesis stage in the earlier time. In the uplift, the secondary pores developed best and widely spread from 1800m to 3500m. The carbonate cements are poor, and the reservoirs are the best in quality. In the south, the reservoir rocks are mainly shore-shallow lacustrine sandstones and get into the later diagenesis lately. The secondary pores in the south developed poorly and the reservoir quality is relatively poor compared to those in the north and south zones.
  • Probability cumulative grain size curves in terrigenous depositional environments of the Paleogene in Huimin Sag
    YUAN Jing; DU Yumin and LI Yunnan
    , 2003, 30(3): 312-0.
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    A large number of probability cumulative grain size curves were plotted, and the probability cumulative grain size curves in the main sedimentary environments of the Paleogene in Huimin sag were summarized on the basis of observation of cores. The distributary channels in delta plane subfacies are of typical bi-segment pattern and tri-segment pattern, those of the distributary channels in delta front subfacies of “1 bouncing population-1 suspension population-transitional zone” pattern and “low slope multi-segments” pattern. The river mouth bars in the delta front have two patterns too, i.e. the “high slope 2 bouncing populations-1 suspension population - transitional zone” pattern and “1 bouncing population-1 suspension population-transitional zone” pattern. The fan delta plane subfacies have uphill arched arc, typical bi-segment pattern or tri-segment pattern and “excessive suspension population” pattern. The characteristics of the braid channels in fan delta front subfacies are changeable. The river mouth bars in fan delta front subfacies have three kinds of curves: “low slope tri-segments” pattern, “high slope multi-bouncing population-1 suspension population” pattern and “high slope 1 bouncing population-1 suspension population-transitional zone” pattern. The total characteristics of beach and bar's probability cumulative grain size curves are of “high slope and multi-bouncing population” pattern. The tempestites have “high slope multi-bouncing population-1 suspension population” pattern, multi-segments and “high slope 1 segment” pattern. The braid channels in mid-sublacustrine fan have “low slope 1 segment” pattern or uphill arched arc and “low slope multi-segments” pattern.
  • Reservoir and controlling factors of sandbodies of the Shahejie Formation in Wuhaozhuang-Changdi Region
    ZHAO Yongsheng; MA Yuxin; JI Youliang; WANG Yongshi and ZHUANG Wenshan
    , 2003, 30(3): 313-0.
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    The sandbodies of the Shahejie Formation are one of the most important oil-bearing systems in Wuhaozhuang-Changdi Region in the eastern part of Zhanhua Sag. The Sha-3 and the Sha-2 members of the Shahejie Formation are the main reservoir beds. Based on the integrated analyses of geological, logging, seismic and chemical data, there are 3 types of sedimentary system developed in this area with the Sha-3 and the Sha-2 members, and they are turbidity fan, subsurface alluvial fan, and beach and dam. The subsurface alluvial fan and turbidity fan can be further divided into 3 types of sub-facieses, i.e., root-fan, middle-fan and fan edge by conglomerate distribution, etc. The middle-fan can be further divided into 3 micro-facieses-braided channels, spaces between channels, and front-edge zone. Reservoir physical properties of the braided channel sandbody and front-edge sandbody of the middle-fan are good because the primary pores and secondary pores developed well. Reservoir physical properties of sandbody in root-fan, fan edge and space between braided channels are poor in this area. The reservoir properties were controlled by lithology, sedimentary microfacies and diagenesis during the reservoir development. The reservoir of the Shahejie Formation can be divided into 3 types of good, medium and poor reservoirs.
  • 3-D modeling of sedimentary facies of steep-slope fan reservoir
    WU Shenghe; WU Junchang; CHU Yong; XIAO Huanqin and ZHANG Jianlin
    , 2003, 30(3): 314-0.
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    This paper deals with the effect evaluation of reservoir facies modeling and forecasting using stochastic modeling methods and multi-disciplinary information (well and seismic data). Taking the steep-slope fan reservoirs in the Paleogene of Yong 921 area of Jiyang Depression as an example, 3-D facies modeling was completed by using the information from all the 37 wells, the half number of wells and the only 5 wells, respectively, as well as combining with the seismic data. The results show that, if good probability correlation relation exists between acoustic impedance and sedimentary facies, excellent effect of 3-D facies modeling and prediction can be achieved by using Stochastic Modeling such as Marked Point Processes method, even if there are only a few wells used. It is of great practical significance in reservoir prediction at petroleum exploration or early development stage when there are only a few wells in study area.
  • Prediction of lithologic traps using stochastic simulation
    ZHANG Jianlin; WU Shenghe; WU Junchang; XIAO Huanqin and HUANG Qizhi
    , 2003, 30(3): 315-0.
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    Probability correlative relation exists between acoustic impedance (AI) and lithology. The relation can be applied to make an effective prediction of lithologic traps by synthetically using the stochastic modeling method and multi-disciplinary information. The general processes of this study include: lithology interpreting within the wells, as the constraining data of 3-D lithology modeling; well-logging constrained seismic inversion, obtaining high frequency 3-D AI data; probability relation analysis between AI and lithology; selecting the methods of stochastic modeling based on facies type and then making the analysis of geologically statistical characteristics; 3-D stochastic modeling based on 3-D structural model, obtaining various alterative simulation realizations; then making assessment on multi-explanations of lithologic trap forecasting realization. A case study of lithologic traps of turbidite fan deposits in Ying 11 district of Dongying Sag, Jiyang Depression, Bohai Bay Basin is carried out to show the general process of this research.
  • Seismic inversion for granule gravel reservoir
    LIU Shuhui; Zhang Fanchang; YIN Xingyao and ZHANG Guangzhi
    , 2003, 30(3): 322-0.
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    The geology situation of project T719 is complicated. Its dominant reservoir is granulite or conglomerate reservoir. Drilling data indicate that the sands have much difference in their thickness and have rapid change horizontally. For detailed study and prediction of reservoir,impedance inversion is realized in such a way: firstly, build a fine impedance model using neural networks, constrained by well log information; then, adjust this model exquisitely. Finally, an inversion section with broad frequency width can be obtained.
  • Finite element simulation of the present ground stress field of Sha-4 Member in the Chun-41 fault block
    LIU Xiantai; DAI Junsheng; XU Jianchun and WANG Bifeng
    , 2003, 30(3): 323-0.
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    Chun-41 fault block of the Liangjialou oil field, whose main oil and gas producing intervals are Sha-4 member, is located in the southwest of the Dongying Sag. The present ground stress has important effect in the exploitation of oil field. The horizontal principal stress orientations were established by core acoustic velocity and well drift statistics; the maximal horizontal principal stresses were measured by acoustic emission and the minimal horizontal principal stresses of key wells were calculated by hydraulic fracturing. Taking ground stress results of key wells as constraint condition, the present ground stress field of Sha-4 member is simulated with elastic plane finite element in this fault block. The results are as follows: the maximal horizontal principal stress is 52-74MPa, and the direction is close to east-west within the fault block and mainly northwest within the faulted zone; minimal horizontal principal stress is 41-52MPa, and the direction is close to south-north in this fault block and mainly northeast within the faulted zone.
  • Characteristics and diagenetic environments of source rocks by cathodoluminescence
    ZHANG Benqi; YU Hongzhong; JIANG Zaixing; WANG Yujing and WANG Weihong
    , 2003, 30(3): 326-0.
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    To provide the useful scientific materials for the exploration and development of hydrocarbons in the Zhanhua Sag of Jiyang Depression, 182 slices of core have been observed and analyzed with cathodoluminescene method, which came from the Well Yi 3-7-7 in Bonan oil field in Jiyang Depression, and most of the cores are fine sandstones or inequigranular sandstones. The different luminous and cementation types are classified based on the luminous characters of continental minerals and authigenic cements, such as quartz and feldspar. With the help of the microscope, the characteristics of minerals were deduced and their sources were estimated based on different lithological types; the diagenesis of different segments was studied, and the diagenetic environments were restored. By comparing the characteristics of cathodoluminescence with the source minerals, the mineral source was thought to be from the Gudao arch in the southeast. On the basis of structural and light mineral maturation, the topography of source area was thought to be rather high, with strong denudation and fast burial.
  • Application of artificial neural network pattern recognition technology to the study of well-logging sedimentology
    ZHANG Fuming; LI Hongqi; SHAO Cairui and ZHAO Xiaoyan
    , 2003, 30(3): 327-0.
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    Application of the Artificial Neural Network (ANN) to identify sedimentary microfacies from well logging data can complete the series auto-interpreting. The application can improve the auto-interpreting accuracy and make us get more satisfied results. Ten parameters from the well logging curves are selected for to describing their shape characteristics when the deposition patterns of 8 key wells in Chezheng Sag, Jiyang Depression are studied. Effective parameters were selected on the basis of cores and local experiences, and based on artificial neural network pattern recognition technique, the sedimentary microfacies of well cross section were auto-interpreted. About 40 wells and the results were interpreted by using the software. The software will be fit for the researchers who have the experiences of geological interpretation and some backgrounds of local geology.
  • Searching subtle traps using the theory of slope break
    ZHANG Shanwen; WANG Yingmin and LI Qun
    , 2003, 30(3): 328-0.
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    Based on sequence stratigraphy principles, an exploration method for the subtle traps in lake basin slope break of land facies was put forward by using the theory of slope break. By analyzing and summarizing the formation mechanisms and characteristics of structural slope break, sedimentary slope break and erosional slope break in the areas of torsion slope break belt in north of the central uplift, the erosional slope break belt in south of Chenjiazhuang salient, and the sedimentary slope break belt of the Dongying delta in the Dongying Sag, it was suggested that the lake basin slope break zone of land facies was the developed area of lowstand system tracts and subtle traps, and the subtle traps directed by the theory of slope break in the exploring areas with high-level exploration could be found. The system tract of grade four can concretely control the location and scale of sandstone bodies, and it is satisfactory for oil exploration.
  • Geometry, kinematics and mechanism interpre-tation of the major boundary faults in Dongying Sag
    QI Jiafu; XIAO Huanqin and ZHANG Weigang
    , 2003, 30(3): 329-0.
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    Dongying Sag is an Eocene multiple-graben controlled by extensional faults along the northwest and north margins. The structural contour map of fault surface depicted the diverse-attitude of the major boundary fault. Regionally, the fault-strike extended towards northeast in the west segment, towards east-southeast in the middle segment and towards southeast in the east segment. In a map-scale, the 3-D geometry of the major boundary fault was a sinuate listricfault with some lateral and oblique ramp. The faults with various tending were synchronously of normal fault displacements during the Eocene so that the structural pattern was an extensional structure with two-direction. The distribution and migration of the depoaxes in the hanging-wall of major boundary fault showed that the dominating extension seemed to take in NW-SE during the Eocene and in S-N during the Oligocene. The extension deformation field with two-direction could be interpreted by a model which the local S-N extension derived from right-lateral-slip movement of NNE deep fractures (e.g. Tanlu deep fracture) superposed on regional NW-SE extension derived from mantle uplifting during the Eocene.
  • The basic equation of sedimentation and its application in rift lake basin
    LU Hongyou; CAO Yingchang and JIANG Zaixing
    , 2003, 30(3): 330-0.
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    Sedimentation of lake basin is controlled by the following factors: climate, structure, sediment supply, sea level change and so on. Change of water depth and subsidence amount of the lake basin basement, change of the absolute lake level and sedimentary thickness are considered into a simple equation (called as the basic equation of sedimentation), and every parameter stands for the change value during the period of Δt. Combining with the discussion of the sedimentary basic equation and the signification of every parameter, the forming mechanism of sequence boundary and the principles of lake regression and lake transgression were interpreted. The formation of the sequence boundary was controlled by climate changing, structural lifting and differential vibratory movement which are the three forming mechanisms of the sequence boundary. Based on the forming mechanisms, the lake regression can be further divided into two types: normal lake regression and forced lake regression. The normal lake regression was caused by excessive filling of sediment, and forced lake regression by falling of relative lake level.
  • Division of system tract of different sequence units and its implication in petroleum explo-ration
    LI Qun; WANG Yingmin; QIU Yigang; MA Hong and ZHAO Hui
    , 2003, 30(3): 331-0.
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    Generally, explorationists are interested in lowstand system tract in the exploration of subtle traps. However, system tracts of different levels and their formation need to be further studied in exploration practice. The formation of system tracts, their combination characteristics and application in hydrocarbon exploration, as well as the case studies of the Bohai Bay Basin, were studied in this paper. From the results, it was obtained that system tracts were the products of datum plane variation, and system tracts developed in sequences of different grades. The system tract units of Grade Three are corresponding to oil-gas-bearing layers. However, oil-gas is actually accumulated in system tracts of Grade Four.
  • Oil-bearing degree of different-scale sequence boundaries and system tracks
    SONG Guoqi; JI Youliang and ZHAO Junqing
    , 2003, 30(3): 332-0.
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    On comparison of the found oil and gas reserves with the different-scale sequence boundaries and reservoirs in system tracks in the Jiyang Depression, it is found that the reserves of oil and gas in glutenite reservoirs of low frequency sequence are real huge, and those in glutenite reservoirs of medium frequency sequence are in the medium, and those in glutenite reservoirs of high frequency sequence are minimum. In transgresssive system tracks, oil and gas reservoirs developed not well, and the oil and gas reserves in them are very small. In fluvial highstand system tracks, the shape of the reservoirs is lenticular, with good sealing conditions, so the reserves of oil and gas in this kind of reservoir are great. In lacustrine highstand system tracks, the effects of progradational parasequence sets and para-sequence boundaries of delta facies on the trapping of oil and gas depend on subsequent tectonic movements. The subsequent tectonic movements did not influence the oil-bearing degree of reservoirs in lowstand tracks, but could strongly increase sealing capability of reservoir in highstand tracks through changing original geometric configuration and trend of sequence strata, and then improved oil-bearing degree.
  • Evolution of sedimentary facies of the Paleogene in Binnan-Lijin areas， Dongying Sag
    CHEN Shiyue; YAN Jihua and YUAN Wenfang
    , 2003, 30(3): 333-0.
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    There were many sedimentary facies in Binnan-Lijin areas of the Dongying Sag in the Paleogene, such as fan delta, inshore submerged fan, shallow lake, semi-deep lake and deep lake. From bottom to upper sections, the sedimentary facies vertically evolved in such order: fan delta-semi-deep lake, deep-lake-fan delta, inshore submerged fan-shallow lake-semi-deep lake-shallow lake. Based on lithologic statistics in over eighty wells, it is suggested that the main periods of supplying sediments are the Sha-4 and the later Sha-3 sedimentation episodes. Except for Sha-4, in the other periods of the Paleogene, the Chenjiazhuang salient provided more sediments than the Binxian salient.
  • Controlling model of permeability difference on the hydrocarbon accumulation of sand lens reservoirs
    QIU Nansheng; WAN Xiaolong; JIN Zhijun; ZENG Jianhui; ZHANG Shanwen and JIANG Zhenxue
    , 2003, 30(3): 336-0.
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    Analyses of the oil fullness degree of Niu-35 Sands in the Dongying Sag, and its controlling factors, combining with the experimental results of four simulations, indicate that permeability difference is the most important controlling factor to oil fullness degree of sands. The heterogeneity of porosity and permeability of sands has critical effect on distribution of oil and water within the sands and their fullness degree. A model has been built up, in which the heterogeneity within the reservoir controls the oil accumulation in a confined sand body. Oil migrates and accumulates in sands with the middle permeability in vertical direction firstly, and the sand body's fullness degree is the highest ones. The sands with largest permeability can also become favorable accumulation rooms if oil source is of abundance. However, oil will accumulate firstly in the sands with largest permeability if the permeability difference is large enough, then accumulates in sands with middle permeability. The formation pressure difference, not buoyancy, may be the main dynamics for hydrocarbon accumulation in lithological reservoirs.
  • Characterization of the effective source rocks in the Shahejie Formation of the Jiyang Depression
    WANG Yongshi; JIN Qiang; ZHU Guangyou and Guo Changchun
    , 2003, 30(3): 337-0.
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    Concept of effective source rock needs to be confirmed in petroleum exploration. It is a very good case study to apply this concept in the Jiyang Depression, as there is great quantity of geological and geochemical data of effective source rocks from this depression after 40 years exploration. Based on previous materials and the geochemical investigations, the oil shales and calcareous shales in the upper part of Es4 and in the lower part of Es3 should be the major oil source rocks in the depression. Generally these shales have TOC generally over 2% and contain sapropelic organic matter. The shales of the upper Es4 were formed in hypersaline (salt-lake) to saline-lake environments and those of the lower Es3 were sediments in saline-lake to brackish-lake. As the anoxic environments were frequently suspended or disturbed by tectonic activities and turbidity currents, the effective source rocks were characterized by great heterogeneities both in their TOC contents and in regional distributions. In order to describe the particular features of the effective source rocks, a new method to evaluate the source rocks is used, in which evaluated units by system tracts and classified the source rocks are divided into 5 levels according to TOC content.
  • Lacustrine palaeo-productivity in the Third Member of the Shahejie Formation in Dongying Sag
    LIU Huimin; LI Shoujun; ZHENG Deshun and LI Xueyan
    , 2003, 30(3): 342-0.
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    Productivity is the quantity of organic matter produced by organisms per unit area and unit time. Hydrocarbon source rocks can be usually formed in the regions where palaeo-productivity values are large in a paleo-lake, and it is contrary in the regions where palaeo-productivity values are small and preservation conditions are poor. By using the method of calculating palaeo-productivity derived from paleo-oceanography, the sedimentary and biological data from Dianchi, Erhai and Fuxian Lakes in Yunnan, the formula that palaeo-productivity in a lake can be calculated is obtained from the data of 18 sampling positions. Then, the values of palaeo-productivity for hundreds of wells drilled into the Third Member of the Shahejie Formation of Dongying Sag were calculated by this formula, and the plan views of contour lines were drawn. The results show that the palaeoproductivity values of semi-deep lacustrine facies or facies between semi-deep lacustrine and deep lacustrine are high, while those of the lake margins (delta facies or lacustrine offshore facies) are much less than the values for lacustrine facies.
  • Characteristics of geotemperature and geopre- ssure fields in the Jiyang Depression and their significance of petroleum geology
    XIAO Huanqin; LIU Zhen; ZHAO Yang; DAI Lichang and XU Xiaoming
    , 2003, 30(3): 343-0.
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    The lateral and vertical characteristics of geotem-perature and geopressure fields and their coupling characteristics in the Jiyang Depression were summarized. And the relationship between geothermal-geopressure fields and hydrocarbon distribution was also analyzed. The study shows that the Dongying Sag and Zhanhua Sag have the characteristics of overpressure T-P system, while the Huimin Sag shows sub-pressure T-P system. Different T-P systems controlled the formation and distribution of oil reservoirs in different sags.
  • Hydrocarbon filling and chemical diagenesis evolution of the clastic reservoir of the Paleogene in Dongying Sag
    CAI Jingong; ZHANG Zhihuan; ZHU Xiaomin; XIE Zhonghuai; LI Yanxia; LIU Hongjun and YUAN Dongshan
    , 2003, 30(3): 354-0.
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    The micro-characterstics of minerals in clastic reservoir, their assemblage features and the distribution features of clastic grains from different formations, cements and clay minerals in sedimentary profile in Eocene from Dongying Sag, Jingyan Depression are presented. The primary diagenesis of clastic reservoir and its geochemical process, and discusses the geological/geochemical factors controlling diagenesis of clastic rocks are analyzed. This study shows that the geological/geochemical factors controlling diagenesis of the reservoir rocks, including lithologic features of parent rocks, reservoir petrofacies, changes of pore-water character in formation, filling of early-stage calcites and hydrocarbon in pore. The most important factor is the alteration of geochemical conditions of pore-water. The early-stage precipitation of calcites, corrasion of feldspars and calcites, the geological/geochemical condictions for the formation and conversion of clay minerals, and the controlling roles that petroleum inflow plays in the evolution of reservoir diagenesis are presented.
  • Development of carrying bed systems in the south slope of Dongying Sag
    LIU Zhen; ZHANG Shanwen; ZHAO Yang and GAO Xianzhi
    , 2003, 30(3): 355-0.
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    The south slope of Dongying Sag, Jiyang Depression, develops various kinds of carrying beds, including faults, sand bodies and unconformities, which formed the complex solid network paths. The oil reservoirs whose hydrocarbons migrated vertically along the faults often have multiple oil beds overlapped around the faults. However, the oil reservoirs whose hydrocarbons migrated mainly along the connected sand bodies mainly formed in strata nearby the source rocks. Hydrocarbons through the unconformity belts can migrate in a long distance and formed stratigraphic reservoirs. All reservoirs in the south slope of Dongying Sag were formed by migration in two or more carrying beds. The multi-match relation between fault systems, sand bodies and unconformities in time and space resulted in the complex distribution of reservoirs. The margin and the end of carrying bed systems are usually the significant target areas of oil and gas migration.
  • Controlling factors of sandstone reservoir of the Paleogene in Dongying Sag
    ZHONG Dakang; ZHU Xiaomin; ZHANG Zhihuan; CAI Jingong and XIE Zhonghuai
    , 2003, 30(3): 376-0.
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    Sandstones reservoir quality of Paleogene in the Dongying Sag is mainly controlled by compaction, carbonate cementation and dissolution and deposition environment. All controlling factors to physical characteristics of reservoirs are analyzed based on the data from analyses of mold thin section, cathodoluminescence thin section, scanning electron microscope, physical properties and carbonate contents of rocks. And the evaluation to these factors is carried out. The results show that：① The porosity decreases a lot by compaction at shallow burial depth or low diagenesis stage and the porosity decreases by 6.8% as depth increases 1000m. ②Carbonate cementation have an obvious impaction on reservoir quality. When carbonate is less than 15%, porosity in sandstones is over 20% generally. With carbonate over 15%, as depth increases 1000m, porosity will decrease about 3%. ③Dissolution plays an important role in reservoir quality. Secondary porosity from carbonate dissolution is up to 20%. However, the dissolution is mainly controlled by the regional tectonic setting and the dissolution is relative stronger nearby the faults. The sandstones with middle-fine, well-sorted and low matrix were subjected heavy dissolution. The controlling of sedimentation to reservoir quality is attributed to primary porosity, dissolution and cementation.
  • Igneous rock reservoirs of the Well Shang 741 area in Huimin Sag
    XU Gang; WANG Xingmou; QIU Longwei; JIANG Zaixing and CAO Yingchang
    , 2003, 30(3): 377-0.
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    There are 3 sets of igneous rocks in the area of Well Shang 741 in the Huimin Sag. The first set consists of volcaniclastic rock and basalt, and is distributed in the first member of Shahejie Formation (Es1). The volcaniclastic rock and basalt are distributed in coniform and stratiform occurrences, respectively. The second and third sets of igneous rocks are stratiform diabase, which developed at the later Es3, and invaded into the middle Es3 member. By integrated analyses and comparisons of exploitation well with the three dimensional seismic data, the distribution area, shape and occurrence of the igneous rocks of various periods in Well Shang 741 area are determined. The igneous rocks of Well Shang 741 area can be classified into volcanic vent filled facies, outbreak facies, overfall facies, and invasion facies, etc. The outbreak and invasion facies are further divided into sub-facies. The development features of reservoir space are different in different lithofacies belts. In a word, around volcanic vent is favorable reservoir development position.
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