Study On The Structural And Characteristics Of Karst Collapse In Fractured&Cave Carbonate Reservoir

Carbonate reservoir in Tahe Oilfield Ordovician is complex. The type of the reservoir is the cave which is very irregular. When the cave system is becoming large-scaled, it causes the overlying strata to collapse. Because of the collapsed cave is not completely filled, it is still a large storage space, and it has the development potential of a very large scale. Through the observation of the theory of cave callapse, investigation of field geological and the Tahe oilfield geological coring, conventional imaging logging, and combined with the structure of the Tahe Oilfield forming period, the ancient river systems, summary the phenomena of karst collapse in Tahe Oilfield local distribution, the reasons of the cave collapse, the seismic facies characteristics. The main research findings of this paper include the following aspects:(1) Study of Ordovician of Tahe Oilfield field geological, and summarizes the karst genesis. Crack is the basis for the karstification. The original early fractures control the direction and distribution of karst. Karstification intensity is related to paleocurrent and stratigraphic tendency.(2) Study of karst collapse reservoir and background of Tahe Oilfield karst, summarize the identification characteristics of collapse reservoir on core, conventional logging, logging, and the earthquake.(3)The cave collapse of Tahe oilfield is not only the results of the single role of a karst factors, but also the product of the multiple factors.Controlling factors including the tectonic movement of karst collapse, the gravity of the strata overlying, the dissolution of the crack expanded role in the transformation of the role of hydro (water), and other factors.(4) According to the period of cave collapse, divided into two types:early collapse and late stages of collapse. According to the formation mechanism，divided into four types:Fracture-related collapse, Load collapse,Gully and its lateral cave collapse load collapse and Tectonic deformation(5) Comprehensive utilization of imaging well logging, seismic, conventional logging, well testing, cores,flakes,production of dynamic information, binding to the existence of karst collapse well as the center, identify the collapse phase with the seismic profile and0-40ms amplitude change rate plan following the combination of extract of T74,fracture distribution and the curvature of the T74construct, depicts the distribution characteristics of collapse facies in the plane.