Research On Seepage Flow Patterns Of Fine Controlled Fractured Thin And Poor Reservoir In Xingnan Development Aera

The main mining object of water flooding change from thick oil layers with high permeability to thin and poor reservoir as Daqing Oilfield is at ultra-high water cut stage.Thin and poor reservoir is referring to layers with thin thickness and poor properties.Production wells of secondary and tertiary infilled well patterns in xingnan development aera has low individual production with high water content,the utilization condition of thin and poor reservoir is still poor,the injection-production system of single sandbody is not suitable,the control degree of water flooding and the thickness useage is low.Fine controlled fracturing technique can improve the useage while the limited entry fracturing is not suitable for thin and poor reservoir,the effective period of fine controlled fracturing is short at present,the decline rate of production capacity is high,and the fracturing effect become poorer even failure.It is necessary to clarify the percolation mechanism of thin and poor reservoir with fine controlled horizontal fractures so as to study further on the seepage flow patterns of fine controlled fractured thin and poor reservoir.The thesis describes the distribution and properties of thin and poor reservoir,evaluates the utilization condition of thin and poor reservoir,analyzes the causes of poor producing condition,and find out current problem of fine controlled fractureing of thin and poor reservoir.Horizontal fracture model of fine controlled fracturing is founded and simplified,flow equations of thin and poor reservoir with horizontal fractures are derived,and then the mathematical model of fine controled fracturing could be obtained through the utilization association conditions,boundary conditions and initial conditions.The equations and forms of numerical model could be solved with reasonable difference equations and established boundary conditions.The seepage flow patterns of fine controlled fractured thin and poor reservoir could be numerical simulated by using self-developed "Numerical Simulation Software for Fine Controlled Fracturing of Thin and Poor Reservoir" according to the base data of fine controlled fracturing well group.Then hydroelectric simulation and artificial core plate model physical simulation experiments can be carried out to study on the flow characteristics of five-spot patterns or injection-production units.Studies in the thesis show that the seepage flow of fine controlled fractured thin and poor reservoir in xingnan development area is equivalent to the seepage flow of heterogeneity thin reservoir with low permeability and horizontal fractures.The seepage area of thin and poor reservoir is divided into non-flow zone,non-linear seepage zone and quasilinear seepage zone.Flow field and potential field can be qualitative characterized through distribution of saturation and pressure,as the change and distribution of saturation and pressure of thin and poor reservoir is the dynamic reflect of fluid flow.Generally the isobar and pressure gradient contour map around the injection well and production well assumes approximation circular center on the wellbore,the convex or concave shape of pressure gradient contour distribution is effected by the injection-production wells.The pressure consumption near wellbore area is large,pressure gradient is high,the pressure gradient of the midpoint between injection-production wells is lower,and there is still some non-flow zone.Horizontal fractures created by fine controlled fracturing make a huge impact on seepage field,high pressure gradient is concentrated along the horizontal fracture border.The distribution of isobar and pressure gradient become more intense,pressure gradient increase,pressure transmission expand.Low pressure gradient zones are greatly reduced,non-flow zone will disappear under the influence of certain radius horizontal fractures.The seepage flow pattern of fine controlled fractured thin and poor reservoir change a lot under various development factors with different reservoir properties and fracture parameters.Pressure contour distribution between injection and production wells is more intensive,pressure diffusion area is larger and pressure gradient of the same region have increased as the number of injectionproduction wells increase,well spacing decrease and injection-production pressure increase.The start pressure gradient decrease as higher permeability reservoir with stronger ability allowing fluid to pass through,pressure drop around the wellbores is reduced,and the region of low pressure gradient is significantly smaller.The pressure gradient range is enlarged,and the pressure range becomes larger with larger distribution scale and higher conductivity of horizontal fractures.The area of the low pressure gradient is greatly reduced after fine controled fracturing,while there are still some certain areas with zero water saturation in the well pattern because of unablity to start.