水平气井靶点高差对排液的影响

随着川西低渗透致密气藏不断加大水平井开发力度,水平井气井逐渐增多,水平井井筒积液成为气藏水平井开发普遍存在的难题.如果井筒内产生积液,井底回压增大,井口压力下降,产量递减较快,气井携液能力减弱,将导致井筒附近储层的含水饱和度升高,气相渗透率下降,气井难以开采,甚至最终水淹停产.应用水平井筒内流体由分层流向非分层流转变判别式,对影响水平段井筒携液的因素进行分析表明:水平段井筒倾角越大、积液高度越高,水平井筒中气液两相流型更易从层流转向非层流,水平段中的液体也就更易被气流带出.虽然井筒倾角对气体临界流速的影响较小,但井筒倾角越大,井筒内A靶点附近的积液高度越高,液体就更易被气流携带出水平段.通过实例分析也证明,水平井A、B靶点高差对气井排液有影响,B靶点比A靶点越高,越有利于井底积液从水平段排出.

Influence of Height Difference between Target Points for Horizontal Gas Wells on Liquid Drainage

With the degree of horizontal wells development increasing in the low-permeability and tight gas reservoirs in western Sichuan Basin,horizontal gas wells are increasing and liquid loading in the horizontal wells is a common development difficulty.The liquid loading will result in back pressure in bottom hole increasing,well head pressure droping,fast production decline rate,and carrying fluid capacity weakening in the gas wells.The ultimate result is: the gas wells are difficult to be produced and even closed in production after water flooding at the conditions of higher water saturation and lower gas permeability of the reservoirs around wellbore.The factors of effecting liquid loading in the horizontal well are analyzed by using the discriminant that estimate fluid flow pattern from laminar into non-laminar.The result shows that bigger angle of inclination and higher hydrops height of the horizontal segment,fluid flow pattern is easier to become non-laminar from laminar and the fluid is easier to be carried out by the air current from horizontal wells.The angle of inclination of the horizontal segment has little influence on gas critical flow rate,but the bigger angle of inclination of the horizontal segment will bring higher hydrops height of target A and the fluid is easier to be carried out by the air current from the horizontal wells.Example proves that the height difference between target A and target B has influence on liquid drainage of the gas wells.If target B is higher than target A,the fluid is easier to be carried out from the horizontal wells.