Research On High-resolution Sequence Stratigraphy And Oil&Water Distribution Rules Of Heidimiao Layer In Yingtai Area

Yingtai area is located in the south of Qijia-Gulong sag, part of central sag area in thenorth of the Songliao Basin which is in the northeast of China. It is surrounded by a series ofnose-type structures, Yingtai nose-type structure mainly in the west, Puxi nose-type structurein the northeast and Xiaomiaozi anticline structure in the south. Within this area fault zonesare well developed in north-north-east （NNE） trends. Due to the dependence relationshipbetween nose-type structures and fault zones, fault zones with a crosscutting nose-typestructure are always developed in Yingtai and Puxi nose structures. Similarly, crosscuttingfaults are found in the south of Xiaomiaozi. The favorable combination of these structuresand faults has provided advantageous structural environment for the forming of oil and gasreservoirs. Heidimiao oil layer belongs to the petroliferous assemblage of central SongliaoBasin, including the strata of Nen2, Nen3and Nen4of Nenjiang group in which oil layersembedding deeply, the source layer distributing widely and cap-rock developing well. Thereare lithological reservoirs and lithology-structure reservoirs in Heidimiao oil layer and thereis considerable potential oil and gas resource. Great progress of basin degree about Heidimiaooil layer has been achieved recent years. And Yingtai area in Gulong sag is considered as themost favorable area.This paper takes Nen3group （H2） of Yingtai area as the main study layer to establish thesymbols of sand layers, study the distribution characteristic of sand layer, divide the oilreservoir types, and analyze its characteristics of oil and water distribution of Heidimiao oillayer based on its lithological characteristics, which will provide fundamental geological datafor fine exploration deployment in this area. First determine interface symbols of differentgrades of sedimentary cycle by combining logging data and seismic data under the directionof sedimentology theory and high-resolution sequence stratigraphy theory. Then based onthe division and correlation of sand groups in Heidimiao, synthesizing the information of3Dseism data, drilling data, logging data and core data, well ties profile, sandstone contrastdiagram and oil reservoir profile are drawn. Furthermore, spatial distribution rules of sandlayer in Heidimiao oil layer are expected to be analyzed in this article through the data ofstratum thickness, sandstone thickness, the thickness ratio of sandstone to stratum, andporosity isogram. Finally, study the types of oil reservoir and rules of oil-water distributionby synthesizing T07structure diagram, core data, logging data, oil reservoir profile and testdata. The rules are described as: the Heidimiao oil layer is thick in east and north but thin in thewest and south as a whole. Little sandstone is found in H3（Nen2） but that is highlydeveloped in H2（Nen3） and H1（Nen4） in which lenticular sandlayer can also be found.Sandstones in each oil group are developed with varying thickness, great depth difference andcomplex lateral connectivity. What’s more, sandstones in the research area manifest a declinein layers and thickness from east to west. The thinner and smaller-scale sandstones in thewest have weak lateral connectivity but strong control of oil and water distribution, whichresults in the formation of concealed lithological reservoir uncontrolled by geologicalstructure. The reservoir lithology of Heidimiao oil layer is siltstone-oriented with poorphysical property. Lithology is the main controlling factor of oil-water distribution, followedby the structure. Heidimiao oil layer mainly includes three types, lithological oil reservoir,lithological-structural oil reservoir and structural oil reservoir, among which lithologicalreservoir plays a dominant role. Oil usually distributes inH₂²and H₂¹sand group longitudinally,and mainly inH₂². When faults act as the pathways for the longitudinal migration of oil andgas, oil mainly stores inH12sand group andH₂²presents oil-water layer or water layer. In thesame sand layer, there sometimes shows oil-water inverse inH₂²because of lowerpermeability even if there is no faults shelter from in the profile. This research could providereliable geological basis for further detailed prospecting, the research of old wellre-examination, favorable area evaluation and horizontal well drilling design.