波动压力约束条件下套管与井眼之间环空间隙的研究

利用一维不稳定流动的基本方程，对套管与井眼环空间隙不同时的波动压力进行了计算，绘出了环空间隙与最大井底波动压力之间的关系曲线。根据此曲线及地层破裂压力的最大极限值，可以确定某种尺寸套管与并眼之间间隙的最小值。研究结果表明，在套管与并眼间隙相同的条件下，套管尺寸越大，井底最大波动压力也越大。从控制井底最大波动压力的角度考虑，在确定套管与井眼之间的环空间隙时，大尺寸套管应采用较大的间隙。从波动压力因素方面考虑，由浅井条件所确定的套管与井眼之间的环空间隙同样适合于深井条件。

DETERMINATION OF ANNULUS CLEARANCE BETWEEN CASING STRING AND BOREHOLE UNDER THE CONDITION OF LIMITED SURGE PRESSURES

The annulus clearance between casing string and borehole in the constraint of surge pressure and formation fracture pressure is studied. The minimum clearance between a casing string and borehole can be determined by establishing the relation curves of the clearances and the maximum surge pressure at bottom hole in consideration of the limitation of formation fracture pressures. The maximum surge pressure in bottom hole increases with the increasing of casing diameter for the same clearance. In order to control the maximum surge pressure at bottom hole, the clearance of casing string with large diameter should be larger than that of the small casing in casing program design. The clearances determined according to the condition.s of conventional wells can be adapted to deep wells while only considering surge pressure.