Multi-layer Hydraulic Fracturing To Extend The Research And Application Of Mathematical Models

A specific character in the oil and gas field in our country is that the scale of low permeability oil and gas field is great. Especially in recent years, the scale of low permeability oil and gas field act like uptrend year after year. In low permeability reservoir, pay zones tend to anisotropic, multilayered, and the distance of layers is far. One pay zone output can not meet economic exploitation requirement. In order to exploit these reserve volume and get preferable economic benefit, a efficiency method is apply hydraulic fracturing. In order to get the maximum reservoir recovery ratio as well as take fracturing charges least, we expect to use multiple fracturing technology to breakdown all pay zones at the same time.Multiple fractures propagation simulation is the core of multilayer fracture. Error will appear if we use the conventional hydraulic fracture simulation method of homogeneous, thick reservoir in the multiple zones fracture. It is necessary to research on the hydraulic fracture simulation technique of multiple fractures system, and to establish a mathematical model which can simulate the simultaneous propagation of multiple fractures in different zones. The research in this respect yet lay in blank inland at present, and scholars overseas have done some research but their research is faultiness.Multilayer fracture model usually make up of flow distribution model and single fracture extension model. In the existing multilayer fracture model, flow distribution model distribute the liquid only at specific time, whereas left out of account in the whole construction work; and the model to simulate single fracture extension is two-dimension fracture propagation model. Base on the investigation foundation of predecessor, this article distribute the flow at the beginning and during the fracturing, and couple with the three-dimensional single fracture extension model to simulate the multiple fractures propagation in the hydraulic fracture course.The main job of the article is:1.to investigate the correlation literature of multilayer hydraulic fracture abroad, especially the correlation literature about fracture propagation of multilayer fracture;2. to derive and built the mathematical model of the flow distribution in multilayer fracture, which make up of primary partition and real time reassign according to the feature of multiple fractures;3. to derive and built the three-dimensional mathematical model of single fracture extension ,and give out the solution method of model base on the correlation literary both here and abroad;4. to compile the analogue computing programme with the Visual Basic 6.0, and to carry out simulation computing and analyze the result;5. to derive and built a new mathematical model to simulate multiple fractures propagation combining the 2D model and 3D analysis method, and study the influencing factor of fracture dimension;6. to compute and analyze an example well using the simulation calculate programme.