Abstract:

This paper discusses the deposition of fault lakes represented by Dian-chi and Erhai Lakes,the system,feature,facies,distribution model ofdelta deposition,and the significance for petroleum exploration.The research shows that:1.The configuration and water system oflake basin are controlled by tectonic framework.The sizes of deltas areusually small with an area of about 10 to decades km².The deltas formedalong main fault trend are larger.Therefore,to find deltaic oil-gas pools,we should concentrate our efforts to the ends of elongation direction inthe basin.In a asymmetric basin,median and small sized deltaic oil-gaspools can be found in the gentle slope side.2.Different morphotyped del-tas exist in the same basin.The distribution and evolution of the deltasare controlled by interaction between jet flow of river mouth and longshorecurrent.Main reservoirs are channel sands,river mouth bar sands andfront sheets in fluvial-dominated deltas.The bars that parallel with shore-line are favourable for the formation of oil-gas pools with litho-stratigraphictrap in lacustrine dominated deltas.3.In the early stage of the develop-ment of fault lake or the stage of strong tectonic movement,the sedimentwere eharacterized by debris flow due to the great depth of lake basin waterand steep shore slope.In the latter stage or stable stage,the delta sedimentswere the main type of filling lake basins.In stratigraphic sequences,deltaic oil-gas pools formed in the late stage of every tectonic cycle shouldbe the main objeetives for petroleum exploration.4.The delta sedimentsoften have transitive features between traction current and gravity.The se-diments are composed of the mixture of coarse and fine materials in grainsize and mud content is very high,causing unhomogeneity of sand bodies.Therefore,correspondent method should be adopted to deal with the featuresso as to increase oil production.