| The weak deformation tectonic belt is a tectonic belt with a low degree of deformation caused by the regional stress field or the basement fault activity,which has no uniform fracture surface.The results show that the weak deformation tectonic belt is widespread in the sedimentary basin,and is closely related to oil and gas accumulation.The Quantou Formation of San Zhao depression in Songliao basin has many small structures which show en echelon or braided weak deformation belt,at the same time,these structures have a certain relationship with the accumulation and distribution of oil and gas.With the analysis of the development characteristics and evolution mechanism of Fuyang reservoir of oil and gas accumulation,the structure has an important guiding significance to clear exploration direction of the next step in the Fuyang reservoir of oil.According to the geological and seismic data,coherent body slice data distribution,the basement fault characteristics and the plane distribution of oil and gas pools of Fuyang reservoir,we identified 9 weak deformation tectonic belts in the hydrocarbon reservoir,respectively 2 NNW-trending Zhaozhou weak deformation tectonicbelts,2NNW-trending Weixing weak tectonic deformation belts,1 NNE-trending Shengping weak deformation tectonic belt,1 NNE-trending Yuxi weak tectonic deformation belt,3 SN-trending weak tectonic deformation belts in Xujiaweizi area.These weak deformation belts show en echelon type and braids structural style in the plan.In the section,concealed fault zones are characterized by flower structure,negative flower structure or "Y"-shaped structure.The paralleled fault zone and the mixed fault zone are developed in the Fuyang reservoir.In the plane,the paralleled fault zone is SN-trending.In the section,it characterized by "Y"-shaped structure and "V"-shaped structure.The mixed fault zone formed with faults of different directions in the plane.In the profile,it characterized by the compositegraben tectonic style.Based on the analysis of tectonic evolution characteristics in Fuyang reservoir of San Zhao depression and combined with structural physical simulation experiments,we can conclude that the NNE-trending weak deformation tectonic belt and NNW-trending weak deformation tectonic belt with the en-echelon structure were formed by Xuxi basement fault under 45°-60°degree oblique tension effect.The SN-trending braided weak deformation belt formed with the strike-slip movement of Xuzhong basement fault and it formed in the la ter stage of strike-slip movement.The SN-trending paralleled fault zone was formed by the EW-trending transtentional activities,at this time,basal fracture and tensile stress in the east-west direction the angle between basement fault and EW-trending transtentional stress is 75°-90°.The mixed fault zone was formed in the process of the above three types of faults.In the junction at different directions,forming the "break point".At this point different range of fault zones formed.The significance in hydrocarbon accumulation of concealed fault zones in Fuyang reservoir of San zhao depression in 4 aspects: First,it provides a large amount of heat for the development of hydrocarbon source rocks.Second,improve the porosity and permeability of reservoir.Third,improve the migration path.Four,plenty of structural traps and lithologic traps and micro amplitude structures and arcuate fault blocks are formed,which provided sufficient space for hydrocarbon accumulation.The weak deformation belt has a certain impact on the accumulation and distribution of oil and gas accumulation belt with three rules: The oil and gas reservoirs are mainly distributed in both sides of the weak deformation tectonic belt;At the cross section of the weak deformation belt,the oil was enrichment;The SN-trending weak deformation tectonic belt controlled the oil by the characteristic of segmentation. |
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