| Shiwu has become one of the most important oil fields after years of explorationin Songliao basin.The structural belts of W19and W20blocks locate in centralstructural belt. W19block is now the focus of the exploration area in Shiwu oil filed.Nongan reservoir of K1q2is the major oil bearing series in W19block, the burieddepth between500-600m. With the deepening of the oil and gas exploration anddevelopment of W19block, many basic geological problems become veryoutstanding, These problems are now affecting production and sustainabledevelopment. Many old wells of W19block obtained commercial hydrocarbon flowby oil production test in K1q2. No further geological research has been done for a longtime. Characteristics understanding and development potential of the reservoir and isnot clear. So that, the research of stratigraphic correlation, sedimentary micro-facies,litho-electricity correlation of reservoir and structural trap et al are necessary. Basedon these research, favorable region prediction of oil and gas reservoir is done to lay agood foundation for further development.1. Method of the ResearchThrough the comparison and analysis of the characteristics of seismic reflectionand lithology, lithofacies and Well logging change of stratigraphic interfaces, thestrata interface characteristics are analysed. With Quantou formation contrast mainindex beds and assistant index beds are defined, the research of stratigraphicclassification and correlation, stratum thickness, sandstone percent are made.Combined with cycle analysis, the analysis of well logging facies, the interfacefeatures (lithology, well logging and seismic features) and the comparative analysis ofthe well drilling and seismic characteristics, the single well of sedimentarymicrofacies division is made. On the basis of stratigraphic classification and contrastand single well of sedimentary microfacies research, the planiform character ofsedimentary microfacies is made with the sand formation and main small layer as theunit. Through the research of the relationship of the four properties, the reservoirlithology, physical properties, oil content and electrical properties, by use of thephysical properties calculated by the logging data and the combination of oil-bearingparameters and core property and oil-bearing material, and it realized the planedistribution of the reservoir physical property and oil-bearing properties, and the planedistribution rule is researched. Through combination of the seismic section and theexisting structure maps, draw a structure diagram of the top of sand formation, andanalyzes the structural trap features of each small layer. Based on the above work,study the favorable reservoir area and make favorable area forecast. 2.Stratigraphic division and correlation and MicrofaciesStratigraphic division and correlation of K1q2of W19Block in Shiwu oilfield,Made K1q2to devided into5sand group, The sand groups of N1and N2and N3weredivided into four small layers, The overlay thickness of three sand groups is thickenedfrom east to West and from north to south. Every sand group and small layer has. Astable inter layer of mudstone Each layer has a phenomenon of0sand body (sandbody wedge out).Due to the development of mudstone in the sand group of Nong I,small layers has more phenomenons of0sand body. Sand body features is not stablethickness and stable extensions. On the secetion each small layer Shows goodconnectivity in the sand groups of N2and N3. The main Characteristics ofsedimentary facies of K1q2are fluvial facies. The sand groups of Nong I Shows fourmicrofacies. They include Meandering river, point bars, natural levees,crevasse-splays flood plain. The sand groups of N2and N3Shows braided stream.They Show three micro facies arebraided streamand Heart beach and flood plain. N2and N3sand group during the development of braided river braided river plain to themeandering river of transition stage The whole Extension direction is NE-SW In theresearch area range. The source of Sediment. The source of Sediment May be comesfrom Northeast of uplift or Southwest of the uplift.3. Application of four reservoir correlationsCrude siltstone and fine sandstone is the main sandstone in K1q2. The N1formation consists dominantly of mudstone. The N2formation consists dominantlysandstone in the lower part and mudstone in the middle-upper part. The N3formationconsists dominantly sandstone in the lower part and mudstone in the upper part. TheN4formation consists dominantly sandstone in the middle-lower part and mudstonein the upper part. The N5formation are composed of sandstones and mudstone. TheNong’an oil reservoir belong to the medium porosity and low permeability ones,being of porosities of15%～25％and permeabilities of10md～500md in general.The Nong’an gas reservoir belong to the medium porosity and low permeability ones,being of porosities of15%～25％and permeabilities of10md～500md in general.The corresponding relation between the abnormal porosity and permeability ofNong’an reservoir are preferably well. on its longitudinal section porosities showedlittle change and permeabilities move northwards from the bottom up. Oil saturationin reservoir more than40%of zone have increasing trend from N5toN4, that haveincreasing trend significantly from N3to N2. Oil saturation in reservoir more than40%of N2and N3,wide and well oil-bearing reservoir, are main oil layer.4. Research of structural trapsNong’an oil layer of W19Well area in Lishu faulted depression is Shallow oiland gas reservoir. It is mainly affected by the dense development region ShallowFracture Network during neotectonic period. Oil and gas accumulation in the shallowlayer usually depends on whether there are deep main faults for linking reservoir. Inthe later structure activity, the deep main faults at the open state are the major channelfor hydrocarbon migration. Suitable trap can aggregate to form oil and gas reservoirs when it migration up along faults. Deep normal faults have F1、F4、F8、F9、F14inthe study area. There are two high anticlines which locate in the southwest andnortheast of study area respectively. The regional faults are developed which for thedistribution of reservoir has obvious control function. The control factors of traps arestructure and lithology. The structure is the main factor which for the reservoirprovides an enclosed space. The lithology plays an indispensable role of hydrocarbonmigration, storage, traps and the distribution of reservoir. Sand thickness, reservoirphysical property, sedimentary facies distribution and lithologic pinch out influence ofoil and gas reservoir too.5. Favorable area predictionUse the characteristics of reservoir, least resistivity method combiningsedimentary facies, four-property of oil reservior and structural traps, for predictionfavorable areas. As the main reservoir of sand group N2and N3are better than N4and N4. Sand group N2is better than N3. The southwest and central of favorable areais better than the northeast. |
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