Study Of Fault System And Reservoir-controlling Mechanism In Tanan Depression, Haita Basin

This paper thoroughly analyze the geometry features of faults on the basis of 3D seismic data of Tanan depression and draw two sets of fault systems with the interface of Damoguaihe group exist in vertical and the combination modes of lower system are mainly domino offect, shovel-fan, graben and multistep, reflecting stretching degroup of faults, while those of upper system are usually V-type, y-type or inversion y-type. Combination modes of the two systems are mainly flower type and partially y or inversion-y type. General fault strike is NNE-NE and fault combinationa of main strike-slip faults are echelon and parallel while those between main and secondary faults are pinniform, comb, brush and braided, and those of secondary faults are usually parallel.The four phases of evolution of faults in Tanan depression are phase of stretching deformation from Tongbomiao group to naner member, relative rest from damoguaihe group to yiyi member, tensile-sheering deformation during yier and yisan member, compressive-sheering inversion deformation from late yimin group to qingyuangang group. In addition, the four fault systems are system of fault stretching in the early, tensile-sheering in the middle, stretching in the early while tensile-sheering in the middle, stretching in the early while tensile-sheering in the middle and inversing in the late, and the last two fault systems are long-developing faults linking the fist two systems.Reservoir type can be divided into three categories and seven sub-categories, from analysis of oil distribution and reservoir types in Tanan depression utilizing fault-system analysis and data of 400 wells, including tectonic reservoirs: reservoirs of antithetic faults blocking, synthetic fault blocks and paleo burial hill, of which the oil-bearing layers are Tongbomiao group and bedrock burial hills and mainly distributed fault-burial hill zones, sub-depression in the middle and burial-hill fault zones in the west; tectonic-lithology compound reservoirs: reservoirs of fault-lithology, tectonic-lithology, fault-unconformity blocking, of which the main oil-containing layers are Nantun and Tongbomiao group and mainly distributed in sun-depression in the east and the west and burial-hill fault zones in the west; lithology reservoirs distributed in sun-depression in the east with Nantun group as its oil-bearing layer.Analysis of fault-controlling-reservoir mechanism, based on division of faults systems and reservoir types and distribution, there are two types and five sub-types of fault traps. They are: fault traps composed of single fault, complicate fault traps composed of crisscross faults, and of lateral echelon faults and sealing-fault traps composed of Multilateral faults and compound fault traps belong to fault-lithology traps. Early stretching fault system is not active in key period of oil accumulation, of which the main function is lateral blocking; though system of fault stretching in the early while tensile-sheering in the middle is active in key period of oil accumulation, is still in blocking action for the sealing of overlapping mudstone; system of fault stretching in the early while tensile-sheering in the middle and inversing in the late is active after the key period of oil accumulation,devastating to the reservoirs of Tongbomiao group and nantun group, and help the secondary formation of reservoirs. Interface of water and oil in Tongbomiao group is dominated by lateral blockness of faults, of which minimum d value is 16 and interfaces predicated is smaller than the area of proved reserves.There are two types and three sun-types of reservoir-controlling modes, on the basis of mechanism of fault controlling reservoir, migration pathways and modes and oil-source rock correlation in Tanan depression: oil migrating along unconformity and blocked by faults, source rocks and reservoirs in the same layer while blocked by faults and vertically migrating and blocked by faults.