| Yi Ning depression has high degree of prospecting and research in Yi Li basin. Research of field outcrops and well drillings show that there are several sets of hydrocarbon source rock in Yi Ning depression. Well Ning1 and Ning4 had separately achieved low industry oil flow and gas flow in Badaowan formation, Jussiac and Cangfanggou formation, Triassic. While it has not get high industry oil flow by now, it possibly due to tectonic movement destroyed the primary reservoir, or possibly due to the trap forming time had mismatched migration and accumulation time, or possibly due to the reservoir has poor quality. for all, It is worthness to carry out the reseach of the tectonic evolution of Yi Ning depression after Permian, the research of the depositional characteristic of hydrocarbon source rock and reservoir. and the research of the prepecting of favorable oil and gas accumuliation place.Based on the theory of petroleum geology, reservoir geology, tectonic geology, using the technique of comprehensive analysis of sediments, forword model analysis technique and seismic inversion technique, made a systerm research of the hydrocarbon oil source and reservoir of Permian to Jurrassic. Using the technical means of erosion thickness restoration, the author carried out systerm research of the tectonic features and evolution of Yi Ning depression since Permian, and then predict the favervorable oil-gas accumulation belts and traps. The main point is as follow:Yining depression can be divided into six current tectonic structural units, that is the northeast sub-depression belt, northwest sub-depression belt, central sub-depression belt, eastern sub-uplift belt, and south slope belt. Yining depression developed nearly vertical fault, and fault strike are mainly NNE direct, NWW direct, nearly EW direct and SN direct. The relationship of different strike fractures reflects Yining depression had been in tensile tectonic condition. There are three significant erosion surfaces, and they respectively correspond with the Permian eroding events, the upper Jurassic eroding events and paleogene eroding events. the Permian denudation mainly took place around Yining depression. Upper Jurassic denudation and paleogene denudation nearly developed in western part and middle part near Huimingzhuang district in Yining depression. The Jurassic erosion amount reachs to more than one thousand meters in the middle part of Yining depression. Yingning depression has inheritance paleostructure during Permian to Jurassic period, the northern part is low and the southern part is high. The whole sedimentary center migrated from north to northeastern part. Yining depression developments lacustrine facies, alluvial fan facies, fan delta facies, swamp facies, fluvial sediments, and volcanic facies, From Permian to Jurassic, the environment experienced longitudinal evolution from lacustrine to delta environment, alluvial plain environment, lacustrine and swamp to fluvial environment of Yining depression. The main sandbody types are including channel sand of meandering river, channel sand of alluvial fan, distributary channel sand of delta, shoals sand of shallow lacustrine, et al. The sand body of Tiemulike formation of Permian mainly developed in line from Yining country to Yining city in north Yining depression, and the district near Well Ning2 in east Yingning depression. The accumulated sandstone thickness is 100 to 200 meters. The sand body of Xiaoquangou formation of Triassic distributed along the four river way in nearly north to south trend, the accumulated sandstone thickness can reach more than 120m. The sand body of Shuixigou formation of lower-middle Jurassic is thick in north and thin in south overall, the accumulated sandstone thickness reaches 120 to 200 meters. The reservoir characteristics of Yining depression is influenced by sedimentary micro-facies and diagenesis together. The reservoir with high porosity of Tiemulike formation extent in northeast to southwest direct, distribute in the eare closed by Well Ningl, Huiminzhuang, Well Ning6, Jagesitai, Yingtamu. The reservoir with high porosity of Xiaoquangou formation extent in northeast to southwest direct, distribute in the line form Chabuchaer to Huiminzhuang.Yining depression developed three sets of petroleum systems, they are respectively Tiemulike formation petroleum system, Xiaoquangou formation petroleum system, and Badaowan formation petroleum systerm. The former two are better. Using the method of hydrocarbon yield rato curves, the hydrocarbon generation quantity and resources quantity of Tiemulike formation and Xiaoquangou formation has been calculated. The total hydrocarbon generation amount to (3.81～49.29)×108t, resources amount to (0.15～1.97)×108t. hydrocarbon resouces quantity is 0.64×108 t in fifty pecent probability.The sub-uplift belt in the middle of Yining depression is uplifting in long term since its forming in early Trissic. The area along the line from Huiminzhuang to Well Ning6 is hydrocarbon migration common orientation zone of Tiemulike formation and Xiaoquangouqun formation, meanwhile this eare is closed to the hydrocarbon source rock, the reservoir and trap are also favorable, it is the most advanagous district for oil and gas exploration. The southern slope of Yining depression inheritancely developed since Permian. The area alone the line from Well Ning6 to Jiagesitai in southern slope is in the direction for several period of oil and gas migration. This area is farther to hydrocarbon souce rock, It has favorable reservoir and trap, can be divided into better district for oil and gas exploration. The favorable reservoir of Shuixigou formation extends in the middle part of Yining depression in northeastern direction.Well Ning4 and Ning3 drilled in the broken blocks traps in middle sub-depression. Both traps formed early, and trap scale are large. While the top of those trap developed small faults, that may destroy oil migration.2-D seismic network density in northeastern sub-depression can not accurately identify the description of traps. Well Ningl dosen’t locate in the structural pitfalls. Well Ning6 and Ning2 drilled in the south slope belt in Yining depression failed, that may owing to the traps are far away from the hydrocarbon source rocks, or they are drilled in uncertain structure locations. By making structural maps of main target strata and analysis of oil migration, it can be conclude that Hui mingzhuang fault nose trap is the most favoralble target for oil and gas exploration. This trap located in the middle sub-luplift belts in Yining depression. It formed in later Permian, since then it ineritencely developed. It has favorable reservoir and cap rock, it is also the common area for the oil and gas’s migration and gathering. The fault nose trap on the west of Well Yi2 and the Jigesitai fault nose trap are in the effective distance for oil migration, meanwhile it is in the range of favorable reservoir. They can be treated as the better trap for oil and gas exploration. |
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