The dryness of superheated steam is 100% and it exists in the form of pure steam whose properties are like ideal gas. When the steam has a large degree of superheat, it may take a relatively long time to cool, during which time the steam is releasing very little energy and transmitted long distances. The heating radius of superheated steam in the formation is 5-10m larger than saturated steam. In the heating area of superheated steam, the comprehensive effects by superheated steam (crude oil viscosity reduction, improved flow environment, changes in rock wettability and improved oil displacement efficiency, etc.) is much higher than that of saturated steam. Superheated steam stimulation in Kenkyak high water cut heavy oil reservoir pilot test results showed that the average daily oil production of single well by superheated steam stimulation was 2-4 times than that of saturated steam stimulation. Superheated steam is more effective to heat water-invaded oil reservoir than saturated steam.

The selection of profile control layers is based on the decision made by single factor at present. Fuzzy cluster analysis based on transitive closure is introduced to establish an evaluation model of profile control layers' selection. Firstly, combining the static geological data and dynamic development data, the evaluation indexes which affect the selection of profile control layers are screened to form the evaluation index system; secondly, according to fuzzy cluster analysis theory, the evaluation index matrix related to profile control layers' selection is dynamically clustered, and the profile control layers are selected on the basis of each category's characteristics of geological and development; finally, the results of profile control layers' selection are examined by the comparison of water injection profile. In addition, the evaluation model is put into practice in a testing well group, and the application shows that the profile control layers selected by the model is reasonable and reliable.

Production of superheated steam huff and puff wells is affected by reservoir geological characteristics (effective thickness, net gross ratio), the state of development (recovery degree, integrated water-cut) and steam injection parameters (intensity of steam injection, steam injection rate, temperature and degree of superheat. etc.). On the basis of analysis of each factor, All factors set were established by a new specified model and the weight of each factor was determined by the functional correlation between the factors and production of each well. The integrated measured value of all factors was calculated by dimensionless value of each factor through integrated evaluation methods. Statistics results showed that the oil production of each well has perfect proportional relationship with the integrated measured value of all factors, there is the higher the integrated measured value of all factors, the higher the oil production of each well. According to this good correspondence, the integrated evaluation template was formed, and the total coincidence reached 96% with high reliability in the practical application in the Kenkiyak Oilfield, Kazakhstan.

The Darcy linear equation has been widely used to describe the fluid flow in porous media. It is inaccurately used to describe the flow through preferential flowing paths which exert important influence on the performance of waterflooding reservoir. In this paper, the following two problems have been studied: (1) flow law in preferential flowing paths generated by water flooding; (2) sound nonlinear mathematical model considering special internal and external boundary conditions. The greater the permeability in porous medium becomes, the easier fluid can flow. Meanwhile the flow mechanism would change correspondingly as well. Exact solution of the nonlinear model is obtained analytically by integration. It is shown that in preferential flowing channels the flow velocity and the pressure gradient are a nonlinear relationship which is different from the traditional Darcy theory described as a straight line. Finally, the seepage characteristics of nonlinear flow and its influence are determined by analyzing the pressure gradient curve and velocity distribution between the observation point and the target well. Keywords: Preferential flowing paths; Non-linear model; Forchheimer equation; Integration method; Pressure gradient.

Following the criterion of zero pollution for non-target layer, an optimization model for multi-layer reservoir profile control was established by reservoir engineering method. Combining the selective injection mechanism of profile control agent, the whole injection process of profile control agent was simulated by the iteration calculation method of time step splitting. Firstly, the activated range of profile control layer was judged by means of threshold pressure of each formation; secondly, the flow rate of profile control agent was distributed by the water absorption index of each layer; finally, the wellhead injection pressure was calculated base on the pressure equilibrium mechanism. The model not only can be used to optimize the injection displacement and total injection volume of profile control, but also to predict the grading pressure during the process of profile control. In addition, the sensitivity of parameters in this model was analyzed, such as injection displacement, viscosity and resistance factor. Ultimately, the optimal design of injection parameters of profile control for an actual well group was put into practice.