The Songliao Basin, China Petrochemical Newly Registered Blocks Of Petroleum Geological Characteristics And Exploration Direction

This paper is the main achievements of the pilot project by the name of Evaluation ofexploration potentials in Sinopec's new registered areas in Songliao basin, which is fromOilfield Exploration & Production Department, Sinopec. The project was finished byManagement Department of Eastern New Exploration Areas and Exploration & ProductionResearch Institute, Sinopec.At present, there are twenty two new registered exploration areas belonging to Sinopecin Songliao basin, which is located in the edges of the basin with low exploration degree andnon-systematic data. The formers considered that the exploration potentials of these areaswere limited because they are far away from the main petroleum generative depression,characterized by high structural uplift, large erosion thickness and thinner strata. However, aseries of fault subsidences and depressions were found by recent exploration in these areaswhich indicates that there are some prospects. The main intentions of the paper include theresearches of the regional tectonic framework, tectonic unit division, structural evolutionfeatures and tectonic deformation styles of the new registered areas in the north and south ofSongliao basin, which are guided by basic petroleum geology theory and petroleum systemtheory; the researches of source rock features, assemblage of reservoir and seal; trap styles;analysis and systematic evaluation of exploration potentials of new registered areas from theangle of view of basin formation and hydrocarbon generation and pool formation; optimizingof exploration areas, scientific decision, optimizing deployments, reasonable use ofexploration investment and realization of the hydrocarbon breakthrough of the new registeredareas in Songliao basin at an early date.Basing on the systematic collection and regularization and digestion of the seismic,geologic, geochemical, well drilling and source rock sample analysis data, the project teamreprocessed the old seismic data, merged and interpreted the new and old seismic data andthen drew unified map, analyzed the source rock samples of the region of interest, and gotprofound understanding of the structural features, strata and sedimentary features, source rockconditions, features of reservoir and seal assemblage, trap conditions and pool formationconditions, thus obtained following achievements:1.There are great differences of the structural styles and structural deformation featuresin the south and north of Songliao basinThere are great differences of the structural styles and deformation in the south and northof Songliao basin. The fault traps generally develop in the south, but the anticlinal traps develop in the north even though in the layer system of fault depression. The deformation isdominated by anticline traps in the north of Songliao basin, but dominated by differentialadjustment in the south of Songliao basin, which directly influences the possibility ofhydrocarbon remigration to form secondary hydrocarbon reservoir.2. The distribution of the fault depression groups of Songliao basin is characterized bypartition and zonationThe longitudinal central fault depression zone made up ofYian-Lindian-Anda-Xujiaweizi fault depressions is characterized by large scale, elongatedshape, extreme orientation, complete fault depression layer system and large burial depth. Thefault depression zone west to the central fault depression mainly strikes NNE, which ischaracterized by extreme orientation, small sale, elongated shape, complete fault depressionstrata and shallow burial. The fault depression area east to the central fault depression is smallwith complicated features. The fault depressions in the central part west to Haerbin distributein group, but generally strike in NNW and NW, which indicates that the formation period ofthe fault depression in new registered areas in the north of Songliao basin is a little later thanin the middle and west areas and the cause of formation is more complicated. In the south ofthe basin, the south Tong-liao fault depressions distribute extensively and generally strike inNNW and SN and NNE.3. Negative structure is obviously characterized by inherited features in the newregistered areas of Songliao basinThe depressions of the depression layer mostly superimpose with the fault depressions inSongliao basin, obviously such as Binxian depression, Suihua depression, Zhezhongdepression and Changtu depression. At the stage of conversion of fault depression todepression, the basin were uniformly in the stage of lake basin deposition.4. The depression layers of the new registered areas of north Songliao basin werecontrolled by the main body of the basin so that the depth gets thinner in the boundary ofbasin but gets thicker in the inner of basin. There are several depositional center in thedepression of the new registered areas of Songliao basin.The new registered areas are mainly located in the boundary of Songliao basin, so thedepth of the depression layers were thin (100～2000 m), which is consistent with generalchanges of depression layers of Songliao basin. The strata depth and distribution of thedepression layers in the south of Songliao basin were controlled by the early fault depressionsor fault depression group and resulted in the depression layers in Kailu and Zhangwu andTieling areas are relatively thick. Although generally in the background of uplift, there are differences among the three blocks. The depth of the depression layers reduce gradually to theboundary of basin.5. The tectonic units were redivided according to the study of the structural features ofSongliao basin.The Songliao basin was divided into six primary tectonic units such as central depression,northeast uplift, southeast uplift, north pitching area, southwest uplift and west slope. It wasfurther divided into forth five secondary tectonic units.6. Source rocks develop in the new registered areas of Songliao basin.The high qualified source rock was uncovered by the drilling of the Tunan-1 well inManghan fault depression of south Songliao basin, which obviously enhanced the evaluationof the potential of the Manghan depression and drove the understanding of the explorationpotential of the fault depressions of south Songliao basin.7. The assemblages of generation and reservoir and cap of the new registered areas ofSongliao basin can generally be divided to two types, namely "self-generation andself-storage" and "lower-generation and upper storage".There are two types of assemblages of generation and reservation and cap in the faultdepression layers of the new registered areas of north Songliao basin. The assemblages of thestructural layer of the fault depression of the new registered areas of north Songlaio basin canbe divided into two types, namely self-generation and self-storage in the deep section (deepreservoir forming assemblage) and lower-generation and upper storage in the middle section(middle reservoir forming assemblage), the latter is dominant. The generation and reservationassemblage of the structural layers of fault depression in the new registered areas of southSongliao basin is dominated by self-generation and self-storage, but dominated byself-generation and self-storage in the new registered areas of north Songliao basin.8. The evaluation module was built and implied in the comprehensive evaluation of thenew registered areas of Songliao basin, which is built on the base of integrated analysis of thegeologic conditions of the new registered areas of Songliao basin and Pdsys evaluationsystem. The results of the evaluation is as follows, four type-Ⅰ, four type-Ⅱ, six type-Ⅲandeight type-Ⅳblocks. Based on the evaluation results, the blocks of Taimanqi, Mulan-Binxian,Suihua and Changtu-Tieling were thought to be the type-Ⅰblocks. They are the blocks withconsiderable hydrocarbon exploration potentials and are the major blocks of the newregistered areas of Songliao basin.