| At present, most of the gas reservoirs found in China are low permeability tight multilayer gas reservoir. For its complex geological characteristics, if the single layer mining method being used, the single well productivity and stable production capacity are also very limited even after sand fracturing. And it’s difficult to form a large part of the industrial gas stream. It is proved by practice that the gas well productivity can be effectively improved by using multilayer combined mining. The multilayer mining method is widely used in gas wells in low permeability gas reservoirs.On the basis of investigation and research on the present situation of tight gas reservoir exploration and development at home and abroad, we summarized the characteristics of the development of tight gas reservoir, which is based on the origin of tight gas reservoir, reservoir characteristics and seepage mechanism. We evaluate the production capacity of the multilayer reconstruction of tight gas reservoir form two aspects, vertical well productivity evaluation method and fracturing vertical well productivity evaluation method. There is a difference between the physical property and the pressure failure in each layer after the operation of straight multilayer well fracturing, which led to the interlayer channeling, wellbore intrusion. That traditional vertical well monolayer capacity evaluation method no longer meet will lead to the error of gas well productivity evaluation、reserves producing degree、scope of use、 the establishment of the rational production system、the late adjustment measure between the layers. Therefore, for the multilayer fracturing of vertical wells (according to poor physical property, low permeability and low abundance gas multilayer reservoir), we establish interlayer channeling flow layer geological model, with consideration of pressure sensitive and non-Darcy effect numerical simulation method respectively from the single factor and orthogonal factor analysis method, analyzes the main factors of effect in Sulige gas field, gas well productivity. On the basis of numerical simulation results, we introduce the commingling production with dimensionless processing method, showing the output of every layer dimensionless variation. In order to intuitively analyze the effect of evaluation parameters on multilayer fracturing gas well productivity, we established a set of multi-layer fracturing straight wells standard chart. Firstly, the relationship between formation coefficient, reservoir capacity coefficient and cumulative yield was analyzed. And a method of multilayer merging and splitting is proposed. We established the standard chart with the mathematical method and experimental design method (DOE method) to form a set of system of multilayer fracturing vertical well productivity evaluation method. The data that based on the numerical simulation results (different fracture half length, pressure coefficient, reserve capacity factor ratio, permeability under the condition of layered production and wellhead production data) has been used to the application of yield accumulation method calculated reservoir hierarchical dynamic reserves and to determine hierarchical discouraged radius. We use a large number of data (based on numerical simulation results) and MATLAB software to perform linear interpolation on the corresponding data and get quantitative relationship of hierarchical discouraged radius, reserves ratio and permeability difference under the different fracture half-length and the condition of pressure coefficient. By compiling the software for the prediction of the delamination and predict the radius of the different parameters.Through this study, obtained the main factors affecting gas production capacity, forming a multi-fractured vertical wells yield contribution standard chart, forming a system of multi-fractured vertical well productivity evaluation method, it provides a new method for the yield evaluation of multi-fractured vertical wells. |
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