Study On The Characteristics Of Paleokarst Collapse Of Ordovician Carbonate Rocks In Tahe Oilfieldd

There are three types of reservoir storage space in Ordovician carbonate fractures and caves in Tahe Oilfield,Tarim Basin: karst caves,karst pores and fractures,of which karst caves are the main reservoir space.Carbonate rocks that are easily eroded are subjected to a combination of surface weathering and atmospheric precipitation during the karst period to form a large number of karst caves.Later karst caves were buried deep and collapsed due to various factors.Although the karst collapse body is filled with collapsed breccia,it still has a large storage space.By studying the distribution characteristics,formation time,and control factors of the karst collapse body,the genetic types are divided.Combined with the statistics of the abundance of production wells in the karst collapse body,the development potential is evaluated to provide direction and basis for later development.The main research results of this article are as follows:(1)The boundary of the negative structure in the study area was determined by the structural curvature method and the datum method,and the distribution map of the negative structure was drawn.Further,by distinguishing the morphological differences of different negative structures on the seismic profile and the presence or absence of "beaded" reflection characteristics,three types of negative structures,karst collapse,gully and syncline,were divided,and the distribution characteristics of karst collapse were determined.The area distribution and filling of karst collapse bodies are counted,including unfilled,mechanically filled and collapsed filled.(2)By quantitatively analyzing the morphological characteristics of karst collapses,using the growth index(G),vertical elevation change(?z)and width(w)and other parameters to quantitatively evaluate the formation time of ancient karst collapses,the karst collapses in this area were determined.The formation period was mainly formed during the deposition period of the Bachu Formation,and reached the peak of collapse during the deposition period of the mudstone of the Lower Bachu Formation.(3)By analyzing the influence of different geological factors on the formation of karst collapse bodies,it is believed that the formation of karst collapse bodies in the study area is mainly related to deep and large faults,karstification and the load effect of overlying strata;Combining the differences in morphology,seismic profile characteristics and genesis of karst collapse bodies,the collapse bodies in the study area are divided into three types: fracture-related collapse,load collapse,and gully lateral collapse.(4)By analyzing and comparing the relationship between the type of single well collapse structure and seismic response,and calculating the production abundance of different types of collapse,it is considered that the proportion of high-yield wells in the lateral direction of the gullies is the largest,and the proportion of high-yield wells related to fractures is the second,which is beneficial Zone.The development potential of the subsidence zone was evaluated by the parameters of production well yield,vent loss,fault density,seismic reflection law and amplitude change rate in the subsidence zone,and the production characteristics of some subsidence zones in the Type I development zone were described.There are three types of storage space in Ordovician carbonate fractures and caves in Tahe Oilfield,Tarim Basin: karst caves,karst pores and fractures.Among them,karst caves are the main reservoir spaces.Carbonate rocks that are easily eroded are subjected to a combination of surface weathering and atmospheric precipitation during the karst period to form a large number of karst caves.Later karst caves were buried deep and collapsed due to various factors.Although the karst collapse body is filled with collapsed breccia,it still has a large storage space.By studying the distribution characteristics,formation time,and control factors of the karst collapse body,the genetic types are divided and combined with statistics of the production wells in the karst collapse body The evaluation of the development potential of the abundance provides a direction and basis for later development.