Thin-layer Multi-layer Fracturing Stress Profile And The Form Of Fracturing Study

Zhongyuan Oilfield is a typical representative of complicated reservoirs with multiple layers which are thin and different in in-situ stress,and which tend to anisotropic, multilayered, and the distance of layers is far. Usually the productivity of a single sand layer is limited,one pay zone output can not meet economic exploitation. To improve the production of a single well and the recovery rate of a gas or oil reservoir ,and to decrease the operation times and down-hole service cost,it is necessary to conduct separate layer fracturing at the same time. The engineering which can settle this fracturing problem of multiple zone condition named multiple fracturing technology.Today,it is an usual and useful methold to get all kinds of petrophysical paramers from full-wave acoustic logging.And these paramers are bases of in-situ stress and fracture pressure ,the research,contrast,analysis of which are parts of the contents of this paper. The paper studies the calculating models of fracture pressure of barewell, perforated completion well,vertical well,inclined well.To the inclined wells,this paper uses the rock's linear elasticity theory, considers some influencing factors such as the treatment conditions > the fracturing fluid filtration effect,porosity, pore pressure,the orientation of perforating,the inclined angle and so on to study the stress field around the wellbore ,the breakdown mechanism of rack and the breakdown pressure in the way of barewell and perforated completion respectively. So it provides the theory principle for successfully fracturing for these wells.After getting the continous rock mechanics parameter,we can use the fuzzy cluster analysis method of fuzzy mathematics to get independly layers quickly.Many study has been conducted in the fracturing technique of reservoirs with multiple layers,but the emphase is separate layer injecting and fracturing. Error will appear if we use the conventional hydraulic fracturing simulation method of homogeneous, thick reservoir in the multiple zones fracturing. It compels us to research the hydraulic fracturing 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 content of this paper is base on the predecessor research ,the main work include combining the multilayer injection profiles model and the multiple fracturing simulation model, determining the injection ratios at the beginning and during the fracturing, and unite the single fracture propagation model(two-dimensional and pseudo-three-dimensional) to simulate the whole fracturing process.The multilayer injection profiles of two-dimension model lies on the magnitude of perforating friction,the least in-situ stress ,the injecting height,the elasticity module,efficiency and so on,which is different from conventionality limited-entry techniques .If the mechanics character of one layer is weak ,the increasing in height of which can make great effect on crack geometry of pseudo-three-dimensional .At last ,based on theresearches of predecessors ,this paper establishes a two-dimensional model to calculate three dimensional crack geometry.