Explorative Target Evaluation On Feixianguan Formation In The Triassic Series, East Sichuan

Based on stratigraphy and petrology, applied means of electric property, Feixianguan formation has been divided and contrasted in this dissertation. Guided by the theory of carbonate sedimentary, the characteristics of rocks, paleobiology and background of paleo-environment have been analyzed. Sedimentary facies and microfacies have been studied and divided. Model of, sedimentary facies has been established. Applied theory and method of carbonate reservoir geology, the characteristics of diagenesis and evolution of pores have been researched in detail. We pointed out that diagenetic difference is the basic cause, which results in the difference of reservoir characteristics of Feixianguan formation on the eastern and western side of trough in east Sichuan. By means of mercury, mold, SEM and image analysis, the characteristics of reservoir and microscopic pore texture have been studied and described in detail. Based on special disposed to the seismic material, reflected characteristics of oolitic beach reservoir in routine seismic section have been analyzed, and distribution of oolitic beach reservoir has been established. On the basis of the characteristics of gas pool and research of sedimentary facies, reservoir and resource sequent, many traps have been reselected in queuing. Combimed with the results of seismic forecasting to oolitic beach reservoir, sixteen recent drill targets have been put forward. Some targets have been adopted by the Southwest Petroleum Company, and good economic effects have been acquired.The main conclusions of this dissertation are as follows:Feixianguan formation can be divided and contrasted in northeast of Kaijiang-Liangping trough. The carbonate platform in Feixianguan formation of east Sichuan can be classified three sediment areas: open platform, platform trough and platform tidal flat. There are three typical diagenetic pattern in Feixianguan formation, that are deepening-upward pattern, tidle flat dolomite pattern and shallowing-upward pattern. Specific paleogeography framework in period of Feixianguan caused that the types of dolomitization are different in each side of the trough. In northeast side of the trough there are not only mixed water dolomitization, but also reflux dolomitization of high concentration sea-water. As a result, large areas and thick Oolitic dolomite reservoir has been formed In northeast side. Development of reservoir in Feixianguan formation of east Sichuan is controlled by favorable sedimentary facies. If it is wide-area oolitic beachs reservoir and concentrated and developed in some sections in the trap, gas pool observe differential principle of upper-gas and sub-water, and scale of gas pool is controlled by structure. Gas pools in Feixianguan formation are not single lithologytraps, or only controlled by structure. Most gas pools assume the compound characteristics of lithology-structure or structure-lithology. Because of different sedimentary environment (from marginal platform oolitic beachs to gypsum dolomite flat in upper tidle flat), the anomalous reflected characteristics of oolitic beach reservoirs in seismic sections are different. This makes seismic forecast of oolitic beach reservoirs possible. This new discovery provides strong foundation of assessing traps and selecting exploration target.Based on assessing traps, two traps of type I , seven traps of type II and fourteen traps of type III have been selected dominantly. Total areas of traps are 395.63 km2. Gas pool exploration in Feixianguan formation of east Sichuan should be based on sedimentary facies and combined with forecasting method of seismic information. In premise of assessing traps, gas exploration in each of structure belts should be synthetically assessing exploration and prospecting exploration, that is the exploration should be taken as a whole and systematic engineering. At the same time we should pay attention to other hidden traps except compound lithology-structure traps. Marginal oolitic beachs and lower intertidal zones in east side of the trough are the first areas for...