Abstract:

Fractures of carbonate reservoirs are complex in Tazhong area and are critical to the poroperm characteristics of the reservoirs,hydrocarbon migration and accumulation,and productivity of wells.Taking into consideration the characteristics of fractures in the Ordovician carbonates in the Tazhong area,this paper presents three fracture prediction technologies,including coherence processing,strain analysis,and numerical simulation. High coherence facies indicates dense formation and low coherence facies may mean the existence of karst cavities or fractures,while extreme low coherence facies reflects faults of different grades.Strain analysis predicts the density of fractures caused by multi-phase tectonic movements,through drilling calibration and taking into consideration the parameters such as strata thickness,lithology,and fracture orientation.Constrained by strain magnitude,curvature,and other seismic attributes,the numerical simulation determines plane distribution and development of fractures through probabilistic simulation.According to the cutting relationship,filling components and filling orders of fractures observed in core samples,this paper predicted the fractured zones in the Ordovician carbonate reservoirs in Tazhong 16 -Tazhong 30 wellbloek by combining logging data,fracture prediction results of the foregoing three technologies,and analysis of regional tectonic stress field.The prediction results are consistent with the statistics of fracture parameters of the cores taken from the Ordovician carbonate reservoirs in the field,showing that these technologies are practical and effective in predicting fractured zones in carbonates.

Key words: coherent processing, strain capacity analysis, numerical simulation, fracture, carbonate rock prediction, Tazhong area