New Evaluation Method of Fracture Permeability Based on Stoneley Wave Data and Electric Imaging Log in Tight Fractured Sandstone Reservoir

Abstract

Quantitative evaluation of fracture permeability is one of difficulties in log interpretation. In recent years, more and more well-logging new technology, such as electrical imaging logging and array sonic logging were widely applied in complex reservoirs evaluation, and also, provided great help in calculating frac- ture permeability. But, one of the most difficult questions in fracture permeability modeling is how to acquire physical fracture permeability samples, which would be used to calibrate the empirical model. Commonly, the physical fracture perme- ability samples can be gained from full diameter cores analysis, or interpretation results from formation testing data. But unfortunately, this kind of samples are of- ten very few because of the difficult of fractured full diameter cores analysis and the lacking of testing data focalized fractured intervals. So, this paper put forward a new idea or method to resolve this trouble, which may be called as Dual Calibra- tion method. As we know, the permeability calculated from Stoneley wave (can be called as Stoneley permeability) was total formation permeability, which consist of matrix and fracture permeability. In no fracture intervals, the Stoneley permeability should be equal to the matrix permeability, so we can calibrate the Stoneley per- meability to matrix permeability, which gained from conventional core analysis or matrix interpretation. In fractured intervals, fracture permeability can be computed from the calibrated Stoneley permeability and the matrix permeability. Generally, an empirical fracture permeability model can be established from fracture aper- ture and porosity, which often gained from electric imaging processing. So we can calibrate this model by fracture permeability acquired from above steps and make the model suit for the target areas. Namely, this idea can be simply described as: the matrix permeability calibrated Stoneley wave permeability, and Stoneley wave permeability calibrate the electric imaging fracture permeability. This method had been used in some oilfields in Western China and good results were produced. In