The Charactersitics Of Cenozoic Transtensional Structures And Their Controlling Effects On The Hydrocarbon Accumulation In The Dongying Sag

Supported by the exploration theory of subtle reservoirs,Oil and gas exploration in Dongying sag has achieved a long and stable development.However,with the influence of low oil and gas prices and the high mature exploration area,how to change ideas and improve exploration benefits become the new topic.For a long time,A series of exploration achievements have been obtained benefit from the viewpoint and concept of extensional structure in Dongying sag.But with the development of exploration,transtensional tectonic has been playing an important role in hydrocarbon accumulation process gradually.Taking the Cenozoic transtensional tectonic for research objects,on the base of the previous study,comprehensive geological,logging,seismic and other data,using balanced profile,physical modeling and other technology,Combining qualitative and quantitative,dynamic and static methods,the static characteristics of transtensional tectonic are deeply researched,different types of transtensional structural styles are summarized,the identification mark of transtensional structure is established,the plane distribution law of transtensional structure is clarified.Based on these studies,a quantitative evaluation method for fault activity of transtensional structures is proposed,characteristics of different types of transtensional tectonic fault activity were specified,the evolution characteristics of transtensional structure have been carried out,three kinds of transtensional tectonic evolution model are established.Physical simulation experiment is carried out,which combines the dynamic evolution characteristics of the transtensional structure to define the genetic mechanism of the transtensional structure.Comprehensive the static characteristics,dynamic evolution and mechanisms of transtensional tectonic,combined with sedimentary reservoirs and trap conditions in the work area,the reservoir-controlling law of transtensional structure is clarified and the reservoir-controlling mode of transtensional structure is established.The results show that in the Cenozoic of Dongying sag,11 transtensional tectonic belts including Wangjiagang,Bamianhe,Gaoqing,Qingxi and Haoxin are developed.Typical features of the transtensional structure are the stratigraphic deformation characteristics and the combination of faults.There are three types of stratigraphic deformation patterns: towing,dislocation and associated fault.Drag structures are common in broom-like structural styles,reflecting relatively strong horizontal movements,The dislocation deformation is common in the echelon transtensional structure,which can be divided into strata dislocation and fault dislocation.The associated fault pattern refers to the characteristics of secondary fault development on the active plate,and it is also commonly associated with towing deformation structure,which is commonly seen in the echelon and lateral torsional structure.There are three types of fault plane combinations,such as “broom” type,en echelon,and side joint type,there are three negative flower-like structural styles in the section.The “broom” type structural styles are distributed in the steep slope zone of Dongying sag,The pattern of the en echelon is distributed in the slope zone of the sag,the side joint type structural styles are distributed in the middle of the sag.Study on the activity of transtensional faults requires comprehensive consideration of the characteristics of the faults in both vertical and horizontal directions.The comprehensive evaluation table of the activity of transtensional faults can better characterize the characteristics of the activity of transtensional faults.The stress field of “broom” type transtensional structure shows the characteristics of early extension late strike-slipping.The stress field of “side joint” type transtensional structure shows the characteristics of early strike-slipping late extension.The stress field of “en echelon” type transtensional structure shows that strike-slip and tension occur simultaneously.The closure and opening of transtensional faults are coupled.At the same time,when one side opens,the other side is closed.Controlled by tectonic styles,there are three types of reservoir-controlling modes of transtensional faults.The “broom” type transtensional structure forms a two-stage reservoir-controlling model.The stress release at the divergent side and the reservoirs developed,these factors are beneficial to the lateral migration of oil and gas.Stress concentrated at the convergent side of the“broom” type transtensional structure,and the fault plane is closed tightly,which are conducive to hydrocarbon accumulation.The echelon torsional structure forms a segmented hydrocarbon accumulation model,the development of reservoir is controlled by the side of transtensional valley,and the released stress is beneficial to hydrocarbon migration.On the side of the transtensional ridge,the stress is relatively concentrated and the fault sealing is good,which is beneficial to the accumulation of oil and gas.The “side joint” type transtensional structure controls the development of turbidites and other types of reservoirs in the middle of the sag,forming a lithologic reservoir model.