Study On Productivity And Dynamic Characteristics Of Fractured Horizontal Well In Low Permeability And Dense Gas Reservoir

Low permeability and tight gas reservoir account for a very large percentage in gas resources of China. With the conflicts between the supply and demand of global natural gas accelerating day by day. unconventional low permeability and tight gas reservoir is drawing increasing attention due to its abundant potential resources and bright developmental prospects. These gas reservoirs are featured with low porosity, low permeability, high water saturation and bad connectivity, so the development and exploitation of low permeable reservoirs often triggers threshold pressure and stress sensitivity. Compared with the conventional reservoirs, Non-Darcy phenomenon will increase the difficulty of such a tight gas reservoir. In recent years, the most efficient approach is the horizontal well multistage fracturing for such a gas reservoir. We should continue to make an in-depth study in productive performance of horizontal well, the elements influencing productivities and the design of fractured horizontal well, which because the development of horizontal well for low permeability tight gas reservoirs have relatively brief durationThis article comprehensively applies multidisciplinary theories and methods of fluids flow in gas reservoir mechanics, numerical simulation, gas reservoir engineering and production dynamic analysis to make a thorough and in-depth research about the productivity and dynamics of fractured horizontal well in low permeability gas reservoir. This research has made the fllowing contributions concerning the JS2reservoir in Xin-chang gas reservoir:1) Based on the filtration mechanism of horizontal well in low permeability gas reservoir, this paper bulid a new model for forcasting productivities of fractured horizontal well in low permeability and tight gas reservoir,with the impact of threshold pressure gradient (TPG), the length of horizontal well, and fracturing parameter respectively considered.2) Analyzing the geological features and the exploitation of Xin-chang gas field JS2reservoir, and describing the major problem and reason is facing for this tight gas reservoir.3) A model of tight gas reservoir with low permeability is set up, by combining the geological model of JS2reservoir as well as by using numerical simulation methods. The elements influencing productivities are studied and researched from the following aspects:the location of horizontal section, the length of horizontal section, well network between vertical and horizontal well, fracturing parameter and reservoir parameter which includes net pay thickness, reservoir heterogeneity and stress sensitivity.4) Based on the productive dynamic data of the already developed horizontal, the paper researchs the productive dynamic and factors influencing productivities. Single well control reserves and radius are calculated by using traditional production decline equations, Blasingame, flowing material balance and history matching, and selecting the best method adapted to horizontal section in tight gas reservoir. Then, analyse the effect evaluation of horizontal wells by comparing with vertical wells, which based on the control reserves, stable production capacity and production decline.Main results about this research are introduced.1) A model for forcasting productivities of fractured horizontal well in low permeability and tight gas reservoir is bulided, which is suitable to sensitivity analysis of productivities. The results show that productivity of horizontal wells decreases with start-up pressure gradient at a linear.2) A model of tight gas reservoir with low permeability is set up, which could be used to comprehendively study the elements influencing productivities.3) Stable production capacity of horizontal well is batter than the vertical.4) By various calculation methods of control reserves, Blasingame and history matching have been chosen as the research method of gas control reserves and drainage radius in this thesis.On the whole, this research results have important directive to effectively develop low permeability and tight gas reservoir with fractured horizontal well. At the same time, it is also useful to horizontal well development of unconventional tight gas reservoir and gas shale.