Research On The Well Spacing Technology Of Cluster Well Groups For The Development Of Multilayered Sandstone Gas Reservoirs

Tight gas resource in China is rich,and has become the most realistic unconventional gas resources to be developed.Unlike the single thick sand-bodies in the United States,tight gas reservoirs in China usually have thin and multi-layered properties.The Shenmu gas field in Ordos Basin is a typical tight gas reservoir with thin multi-layers in the longitudinal direction.This reservoir is very tight and heterogeneous.The production rate of each layer is very low and different.Additionally,the superposition rate of coal resource with natural gas resource in Shenmu gas field is 100%,and the mineral rights conflict should be taken into account when spacing the gas wells on the ground.Therefore,the key to realize the efficient development of this kind of gas reservoir is to layout a set of reasonable well patterns.In order to realize the efficient development of multi-layered tight-gas reservoirs,taking Shenmu gas field as an example,we studied the well spacing technology of cluster well groups.This not only solved the problem of how to match the mode of well spacing with the complicated geological conditions for multi-layered tight-gas reservoirs,but also avoided the conflict of mineral rights with the coal resources.Around the well spacing technology of cluster well groups for the development of multi-layered tight-gas reservoirs,the following main research works were done:Taking Shenmu gas field as an example,many characteristics and properties of multi-layered tight-gas reservoirs were analyzed,such as the typical geological characteristics,sedimentary facies,facies distribution characteristics and physical properties.This work laid a geological foundation for the study of well spacing technology.Based on the evaluation of the advantageous area of a single layer and the analysis of the main geological influence factors on single-well productivity,the normalized optimization method of advantageous area for multi-layered reseroirs was studied and then successfully applied to Shenmu gas field.We studied the method to identify the superimposition mode of sand bodies,mainly including the vertical mode,the lateral mode and the composite mode and also including 3 sub style of the vertical mode,the multi-layers style,single-layer style and double-layer style.Based on different superimposition modes,we obtained the optimal well type for each superimposition mode by researching on the development boundaries and adaptability of different well types.According to different geological conditions,we optimized the direction of placing a horizontal well,the length of horizontal section and the main fracture parameters.We ascertained the reasonable range of well spacing of Shenmu gas field using the analogy of sand body size,the analysis method of drainage radius,the interference probability method of inter-wells and the numerical simulation method.Based on dynamic reserves abundance,we especially studied the optimum design method of well numbers of a cluster well group and put forward 4 differential well patterns of cluster well groups under different geological conditions.Under the above research works,a set of well spacing technology of large cluster well groups considering the regional differentiation of tight sandstone gas reservoirs with multilayers was formed.And the optimization of well spacing in Shenmu gas field was thoroughly carried out.The research results,which have been effectively applied to the development of Shenmu gas field,could be of important reference value to the development of the other similar gas reservoirs at home and abroad.