Research On Wellbore Pressure And Flow Profile Of Complex Structure Gas Wells

In the present, low permeability gas accounts for over half of the known field reserve. The efficient and effective exploitation of low permeability gas reservoir plays a key role in the environment protection and economy growth. To counter the high technology and economic difficulties low permeability natural reservoir presents, complex structure wells are selected to improve exploitation efficiency. The necessary of studying productivity emerges.As the subject of pure gas well with complex structure, this paper studies single-phase steady seepage in formation and flowing in wellbore, and obtains single-phase flow model, three-dimensional steady seepage model, gas reservoir-wellbore coupling model and its sloving method, the pressure and flow rate profile in complex structure gas well based on sufficient investigation and absorbing research about productivity of complex structure well, variable mass flowing in horizontal wellbore and reservoir-wellbore coupling model The main achievements and cognition have been achieved as follow:(1) The establishment of horizontal wellbore single phase pressure drop model and multi-branched wellbore converging pressure drop model is done based on laws of momentum, the conservation of mass and energy. In addition, influence factors of converging pressure drop are analyzed.(2) By diffusing wellbore into multi stage well factions, based on steady gas seepage law, mirror inflection and superposition principle, establishment of such three dimension models as infinite boundary model, top sealing model, bottom sealing model, edge water reservoir model and bottom water reservoir model have been achieved.(3) Reservoir-wellbore semi-analytical coupling model is established based on different complex structure well three dimension steady seepage models, material balance principle and well bore pressure drop models. The computer program for solving the model is written.(4) Degrade complex structure horizontal well coupling model into horizontal well coupling model, and comparison between the theoretical figure calculated from well test data and the actual figure is done to validate the effectiveness of the established model.(5) Wellbore pressure, wellbore axial inflow and wellbore radial inflow profile is calculated in plane radial multi-branched well and herringbone multi-branched well based on coupling model and formation parameter. Wellbore radial inflow profile is approximately an asymmetrical U-shape curve, wellbore pressure drop is primarily due to friction, which is low and can be ignored when the production of the gas well is low.(6) Research shows wellbore length, number of branches, angle between branches and position of branches play a key role in affecting the multi-branched horizontal well productivity. Well structure should be optimized to reduce interference between different branches and between the branch and the main wellbore, improving the radial inflow efficiency and raise well productivity.