Quantitative Fault Seal Characterization And Risk Assessment Of Fault Trap Of Clastic Rock

Studying on the fault sealing has important significance in oil and gas exploration and development. In order to recognize the law of fault sealing in clastic rock, this paper selected Bozhong 34-2/4 oilfield as the study area. Based on the domestic and foreign literature research and oilfield data, the formation and reservoir characteristics of the area were analyzed, and the scale and activity period of fault development were statisticsed. Through the combination of multi attribute, multi section display and encryption and other means to carry out the fault fine interpretation and based on the quantitative criteria for the growth of fault segment, the reliability of the model is verified. According to the results of the correction, the fault system is divided and the number, distribution and range of the fault traps were carried out. Based on the fault capillary sealing mechanism and sealing type, a quantitative evaluation model of fault sealing in clastic rock formation was summarized. On the basis of this model, with comprehensive consideration of anatomical results and fault surface properties, the quantitative characterization formula of fault sealing ability for Huanghekou sag was established and the risk of faults in Shahejie Formation in BZ34-2/4 Oilfield was assessed.Shahejie formation in BZ34-2/4 Oilfield, whose rock of reservoir develops poor properties, belonging to the low porosity and low permeability of ultra-low permeability reservoir, is typical of the clastic strata. The structure performances the trap which is cutted by faults, of which throw distributes between 45~100m. Based on a variety of methods, 8 new faults were interpreted, 1 fault was eliminated and 1 fault was corrected in study area, and F5 and F35 should be in the soft connection stage. On this basis, finally the 8 fault traps of I oil group were implemented, with totally area of 20.0km2, 9 fault traps of II oil group were implemented, with totally area of 24.0km2. Under the oil group and small layer framework, the North and Middle of NO.2 Block should be divided in a set of oil-water unit, the South of NO.2 Block should be divided in 2 sets of oil-water unit and NO.4 Block should be divided in 3 sets of oil-water unit. According to the fault sealing mechanism and sealing type in clastic strat, evaluation parameters, methods and models of fault lateral sealing for clastic rock were established and based on fluid pressure difference on both sides of the fault and clay/shale content in the fault zone, the quantitative characterization formula of fault sealing ability was established: AFPD=0.0683×SGR-1.3562. Then the risk of the control trap faults of North, East, Northwest of NO.4 Block was assessed, predicting the new fault-control oil area to reach 4.71km2.