Study On The Characteristics Of Fault Accommodation Zones And Its Oil-controlling Effect In Palaeogene Of Dongxin Area

The Dongxin area is located in the eastern section of the central uplift of the Dongying Sag and is the main development zone of Dongxin Oilfield.Under the control of complex torsion and diapir,the fault-regulating belts of different types of faults develop in parallel developmental sections,overlapping zones,close proximity areas,and the transition ends and tail ends of a single main fault.The exploration and development process of more than 50 years shows that the combination pattern and activity characteristics between the main fault and the regulation fault of the adjustment zone not only control the reservoir type and crude oil distribution characteristics of the second member of the Shahejie Formation in the Dongxin area,but also the injection well network.The coordination affects the distribution characteristics of the remaining oil in the area.Aiming at the problem that the classification of fault adjustment belts in Dongxin area is not uniform,the anatomy of structural style is not specific,and the oil control characteristics are not clear,the well-seismic combination is used to identify the fault adjustment belts in the Dongxin area,and the structure of different types of fault adjustment belts is clarified.Features and corresponding identification marks are established.Through the combination of physical simulation and numerical simulation,the evolution mode of the regulation zone was established.Finally,through the analysis of the coupling relationship between the activity of the fault adjustment zone and the accumulation period of the crude oil,the oil control effect of the fault adjustment zone was clarified,and the remaining oil was characterized.The distribution characteristics provided a geological basis for the adjustment of the development plan of Dongxin Oilfield,and achieved the following results and understanding:The Sha 2 Member of the Dongxin area is a set of river-braided river delta sedimentary system.The development characteristics of the strata are greatly affected by the secondary faults in the area.Most of the wells in the well are damaged to varying degrees.The faults caused by the faults in the faults are obvious,and most or all of the strata in the second member of the Shahejie Formation can be lost.The third-order faults can also cause large-scale faults in the second member of the Upper Shahejie Formation.The faults below the fourth level can only cause individual faults.Loss of the sand layer group or thinning of the thickness.According to the number and shape of the main faults and the pattern of the faults,the 10 small fault adjustment zones identified in the Dongxin area are classified into 5 types and 7types.Among them,multiple fault control types include parallel-opposite type,parallel-tosynchronous type,superimposed isotropic type,superimposed opposite type and approaching type,and single fault control type includes inverting type of fault turning end and divergence of fault tip end type.The modulating fault of the parallel fault adjustment zone is parallel to the main fault in the plane.In the cross section,the parallel collateral type is in the reverse or the same direction,and the parallel directional structure is the complex mantle structure;the superimposed fault The adjustment fault of the adjustment zone is obliquely intersected with the main fault on the plane,and is flower-like or ponytail-like on the profile;the adjustment fault of the approachtype adjustment zone appears on the plane as one end converges on the central axis fault.The fan shape of the near-parallel spread at the other end is a composite flower shape on the cross section;the adjustment fault of the divergent fault adjustment zone converges on the plane in the phoenix tail of the main fault,and is comb-shaped on the upper part of the section,and the upper part is It is a cabbage-like shape;the regulating fault of the intrinsic fault-regulating zone converges on the plane in a meandering manner on the main fault,and in the cross-section,it appears as a comb-tooth with a high angle oblique to the main fault.The divergent fault adjustment belt has a small area,a large fault density,a complex and variable fault pattern,and a difficult seismic identification.It is necessary to combine the spatial position and comprehensively utilize the structural style along the layer coherence and the different direction sections for multi-directional determination.The superimposed fault adjustment zone has a great similarity with the seismic profile characteristics of the approaching fault adjustment zone.It is necessary to combine the cross-layer coherence to compare the profiles in different directions for comprehensive judgment.The structural features of the parallel fault adjustment belt and the intrinsic fault adjustment belt are relatively simple,and can be identified by analyzing the characteristics of the stratigraphic and typical seismic sections along the layer.The parallel fault adjustment belt is mainly located in the parallel fault system of Xinzhen in the east,and the main faults on both sides are mostly oil source faults;the fault fault adjustment belt is mainly located in the overlapping area of faults distributed in the side of the Dongying structure.The faults on both sides are also oil source faults;the approaching fault adjustment zone is developed at the junction of the Dongying structure and the Xinzhen structure,and the four oil source faults are formed by a three-type inverted "Yi" pattern;The fault adjustment zone is developed at the transition end of the fault in the northwestern part of the Dongying structure,which is related to the release of the stress of the arc fault.The divergent fault adjustment zone is developed at the fault end of the western part of the Xinzhen structure and is formed by the release of the tip end stress of the main fault.The superimposed and parallel fault zone of the Dongxin fault zone is the earliest,and the disappearance is also the earliest,followed by the approaching fault adjustment zone;the introverted and divergent fault zone are the lateest and disappear the latest.It is controlled by the coupling development zone of the belt and the coupling relationship between the activity of the belt and the activity of the oil source fault.The superimposed and parallel adjustment zones are the most favorable target areas for oil and gas development.