The Geophysical Research Of The Structure Characteristics In The Western Of The Mohe Basin.

Mohe basin is one of the auxiliary oil and gas zone in the Northeast areas. After a comprehensive analysis research, the results of following aspects have been gained.Basic characteristics of the potential field anomalies for the area around Mohe basin. The characters of Buger gravity anomalies are: the overall trend is "two highness clipping one lowness",which namely from north of the line of Hewan-Longhe in north survey areas and the zone of the high gravity values near Qianshao-Xilinji-Yuying in south, the middle zone of the Jingou-Linhai-Changying is the low gravity values.The high gravity value areas are mostly exposed basement or basement hunch, the low gravity value areas are in mostly the distribution area of Jurassic sedimentary strata. The characteristics of the magnetic anomalies ofâ–³T are that: the distribution of the line of Gulianhe-Hewan is the zone of low positive magnetic anomaly values, the distribution of the line of Jintao-Changqing and from south of Changying is the calm negative magnetic anomaly zone, the distribution of the Longhe-Yilin-Hailuyashan is the magnetic anomaly zone of high frequency cluttered. And the second kind of the corresponding magnetic anomaly is non-magnetic or weakly magnetic Jurassic sedimentary strata and non-magnetic rock. The geological interpretations of seismic reflection layers are : TO5 is nearly equivalent to the reflection top surface of the up-Shangkuli group; T2 is roughly equivalent to the reflection of top surface the Ershierzhan group; T3 is nearly equivalent to the reflection top surface of the Xiufeng group; T4 is roughly equivalent to the up-Jurassic's top surface reflection ;T5 is broadly equivalent to the reflection of top surface of the basement. Through several profiles, we compare and analyze the characteristics of wave group of the different reflection layers. The reflection layer of TO5 is west-shallow and east-deep on the whole, the deepest position is about -720m; the reflective layer of T2 changes deep from south to north, the deepest position is about -2600m; the reflection layer of T3 is south- shallow and north-deep, the biggest depth reaches -4380m; the reflection layer of T4 changes deep from south to north, the greatest depth is about -6250m; the reflection layer of T5 is to smooth in EW, the depth changes great in SN, the greatest depth is about -8000m.Faults. From seismic data we find that there is two types of faults of detachment faults and negative thrust faults, negative thrust fault from the fault section features can separate two types of straight section and slope-level model. From the potential field data we gain that this basin developes the four main faults of EW,NW,NE and NNE; includes which the faults of 7, 12, 16 and 9 items, 44 items are all bedrock postive faults, fault formation periods from the old to the new order are : EN to SN,NE and NW . Constructure unit division. The main basis is the distributions and combination characteristics of positive faults across the basement with SN and EW correction controlling the first tectonic units, as well as the tectonic pattern and the distribution characteristics of median-down Jurassic normal sedimentary layers. Mohe basin is divided into four first-tectonic units, namely near-Heilongjiang hunch, Gulianhe hunch, Tahe hunch and central depression. The west part of basin constitutes overall the tectonic pattern of the "two hunches clipping one concave". Analysis of major tectonic style. The major tectonic patterns are a series of negative thrust faults and associated structures in the space combination formed by the regional stress settings, which Includes the imbricate negative thrust structure, the double structure, passive double structure, fault-bend fold strucure, and corresponding thrust structure. Covering strata stratigraphic sequence. Layer sequence of T5-T4 is a set of pre-Jurassic strata, which may be a certain opposite relation to the D-C ocean facies clastic rocks and carbonate rock of the adjacent areas in Russia; Layer sequence of T4-T3 is equivalent to Xiufeng group of the middle Jurassic, we conclude that the set of strata directing north may be transition to the semi-deep lake facies to deep lake facies sediment; Layer sequence of T3-T2 is equivalent to the Ershierzhan group of middle Jurassic, its settlement centers move to north comparing to the Xiufeng group.The formation and evolution of Mohe basin. The heat-hunch tension crack stage since Carboniferous ; up to the early Jurassic, the Crust was intermittent tension, formed nearly east-west and north-south trending basement fault of controlling the depression stage of Mohe Basin ; since Moho interface hunching brings tension stress field, which caused basin fault sustained time not long, successively basin subsided whole, the fault was translated to depression, deposition centers moved northward, and Mohe Basin entered its heyday; shrinking phase, in the early pre-Cretaceous sedimentary center moved eastward, the basin gradually narrowed the scope , after the Paleogene, Neogene tectonic movements, large depression declined. The petroleum Analysis of Mohe Basin. Three sets of growing oil layers of the middle-down Jurassic in the western Basin provided the better hydrocarbon source rocks; it had better reservoir and cover layers conditions ,in addition, the faults developed, which provided favorable conditions of the migration and storage; late folding function formed a compound syncline, with many local anticline belts in the folds and depression, which provide trap conditions for the gathering oil and gas.In the large scope of the southern basin , under a middle Jurassic strata existed early Cretaceous volcanic layers, growth, storage and cover conditions were better than the western basin.